Imaging after Total Hip Arthroplasty PCAs.  Introduction/Background It has been approximately 60 years since Sir John Charnley introduced the modern era of hip replacement surgery [1]. Approximately 370,000 primary total hip arthroplasties (THAs) were performed in the United States in 2014 [2]. Sloan et al [2] estimated that the volume of primary THAs would increase to 635,000 procedures annually by 2030. Over the years, modifications have been made to attempt to decrease complications such as loosening and wear with additional fixation techniques (eg, osseointegration) and articular surfaces (eg, metal on highly cross-linked polyethylene, antioxidant doped polyethylene liners, metal-on-metal [MoM], ceramic on polyethylene, and ceramic on ceramic articulations) [3-5]. The most common causes for surgical revision of THA from 2012 to 2019 as reported in the American Academy of Orthopaedic Surgeons American Joint Replacement Registry were infection and inflammatory reaction (19.3%), instability (17.4%), and aseptic loosening (15.8%) [15-17]. Wear or osteolysis was the cause for revision in 7.5%. The imaging studies used to follow uncomplicated primary hip prostheses and to assess several prosthesis-related complications are reviewed. Separate discussions pertinent to imaging of MoM prostheses are included. Special Imaging Considerations Ultrasound (US): US has been used for assessment of soft tissues adjacent to hip arthroplasties and, in contrast to MRI and CT, is not affected by prosthetic artifacts. US may be limited in its ability to assess deep soft tissues. Metal artifact reduction sequences (MARS)-MRI: MARS-MRI enable soft tissues around the prosthetic hip such as the pseudocapsule, tendons, and neurovascular structures to be assessed. Reviews of some MARS-MRI techniques are available in the literature [18-21]. Metal artifact reduction (MAR)-CT: Metallic hip prostheses, particularly cobalt chrome components, produce artifacts on CT scanning that can obscure adjacent structures.


Imaging after Total Hip Arthroplasty PCAs. As reviewed by Roth et al [22], these artifacts are related to both the prosthesis (eg, type of metal and geometry) and the scanning parameters. Several techniques have been used to reduce these artifacts (termed MAR) [22,23]. Fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT Skull Base to Mid-Thigh and Fluoride PET/CT Skull Base To Mid-Thigh: PET studies (using either FDG or fluoride) may be tailored to focus imaging of the area of interest, Reprint requests to: publications@acr.org Imaging After Total Hip Arthroplasty such as the hip, rather than including the entire region of the skull base to mid-thigh. Many of the investigations included in this document were performed before the widespread availability of PET/CT, and consequently, they were performed as PET studies without CT. Bone Scan Hip Periprosthetic uptake can be present for a year or more after prosthetic insertion [25-27]. Therefore, bone scintigraphy of the hip for routine surveillance of asymptomatic hip arthroplasties is not supported. Bone Scan with SPECT or SPECT/CT Hip Data on the normal evolution of periprosthetic uptake on single-photon emission computed tomography (SPECT) or SPECT/CT of the hip following hip arthroplasty are lacking [28]. However, on planar bone scintigraphy, persistent periprosthetic uptake can be present for more than 1 year following implantation [25-27]. Consequently, bone scintigraphy with SPECT or SPECT/CT is not supported for routine surveillance of asymptomatic hip arthroplasties. CT Hip There are no recent studies advocating routine CT scanning of the hip for asymptomatic patients with conventional or MoM prostheses. Fluoride PET/CT Skull Base to Mid-Thigh It can take a year or more for periprosthetic uptake to normalize around a hip prosthesis [29,30]. Therefore, fluoride PET/CT skull base to mid-thigh is not supported for routine surveillance of asymptomatic hip arthroplasties.


Imaging after Total Hip Arthroplasty PCAs. MRI Hip MRI for asymptomatic non-MoM hips: MRI is generally not indicated in routine follow-up of asymptomatic patients with non-MoM prostheses. However, the MRI findings in asymptomatic patients are being investigated [19,31-33]. MARS-MRI for asymptomatic MoM prostheses: Pseudotumors consistent with ARMD have been reported on MRI in patients without pain following MoM arthroplasties [6,33-38]. Thus, MRI may be beneficial in this group. In a series of MoM hip resurfacing arthroplasties, clinical outcomes and radiographic screening underestimated the presence of pseudotumors and supported the use of MRI for screening [38]. Similarly, Koff et al [33] performed 4 yearly MRI examinations of patients with surface replacement prostheses and found evidence of ALTRs in high- functioning individuals without pain. They concluded that MRI should be considered as part of the routine patient follow-up protocol to allow early detection and follow-up of ALTRs. In 2 series, comparison of MRI results to histologic findings showed the sensitivity of MRI for pseudotumors to be 85% and 71%, respectively, and the specificity to be 59% and 87%, respectively [39,40]. Sensitivity was greater when the MRI examination was performed within 3 months of the revision surgery (88%) [39]. Imaging After Total Hip Arthroplasty Combined US and MARS-MRI studies: Comparison to surgical results suggests combining US and MARS-MRI improves accuracy. Small numbers of lesions detected on US are not visible on MRI, and some lesions seen on MRI are not apparent on US [35,36,41]. Radiography Hip Follow-up radiographs for asymptomatic non-MoM total hip prostheses: Radiographs have been the imaging mainstay for following THA [42]. Review of serial radiographs is useful for identifying subtle changes, emphasizing the need for baseline radiographs.


Imaging after Total Hip Arthroplasty PCAs. However, Hart et al [43] followed postoperative patients with THAs undergoing routine follow-up, excluding patients with complications of fracture, dislocation, or infection or who had died. Of the 423 patients studied, 414 had radiographs at 6 to 12 weeks and 276 had follow-up radiographs at 1 year. No THA case was identified in which clinical management was changed by the radiographic examination in this time period. This suggested to the authors that, in asymptomatic patients, some follow-up radiographs might be omitted. Radiographs for follow-up of asymptomatic MoM total hip prostheses: The FDA recommends routine long-term follow-up of patients with MoM hip implants, typically to occur every 1 to 2 years [44]. This includes appropriate radiographs. Serial radiographs are helpful to assess subtle changes [42]. Radiographs can be used to assess component position, component loosening, bone quality, osteolysis, fracture, dislocation or subluxation, femoral neck narrowing, and medial femoral calcar erosion [36,45]. The latter may be an indicator of ARMD, warranting cross-sectional imaging (positive predicative value [PPV] 0.83) [45]. US Hip US for follow-up of asymptomatic non-MoM total hip prostheses: A few studies have investigated US to assess asymptomatic patients with metal-on-polyethylene (MoP) bearings [41,46]. Nishii et al [41] concluded that US seemed a promising noninvasive tool for detection of ARMD pseudotumors. However, there are no recent studies indicating the use of US for routine surveillance of nonmetal on metal prostheses. US for follow-up of asymptomatic MoM total hip prostheses: US may be beneficial as asymptomatic patients may show imaging changes of or associated with ARMD [46]. US can be used to detect pseudotumors (solid or cystic) and other findings seen with ARMD such as joint effusions, bursal collections, and synovitis [36,47-49].


Imaging after Total Hip Arthroplasty PCAs. Williams et al [46] proposed high-resolution US surveillance of all asymptomatic patients with a MoM implant that is known to result in high serum metal ion levels. Low et al [50] prospectively followed 152 asymptomatic MoM hip resurfacing arthroplasties at a mean of 4.3 years using US. Progression of findings occurred in 19%, and new pseudotumors developed in 10%. No asymptomatic hip resurfacing arthroplasty patient with both a normal initial US and low blood metal ions (<2 ug/L) developed pseudotumors within 5 years of initial assessment, and, therefore, they concluded this patient subgroup did not require repeat follow-up within 5 years [50]. Comparison of US with MRI: A summary of studies comparing US to MARS-MRI as the reference standard for detecting ARMD shows sensitivities for US of 69% to 100% and specificities of 83% to 96% [36]. Kwon et al [52] found that US was valid and useful for detecting interval changes in lesion size and grade in comparison with MARS-MRI. Combined US and MARS-MRI studies: Comparison to surgical results suggests combining US and MARS-MRI improves accuracy. Small numbers of lesions detected on US are not visible on MRI and some lesions seen on MRI are not apparent on US [36,41,52]. Variant 2: Symptomatic patient with hip prosthesis. Initial imaging. Bone Scan Hip There is insufficient evidence to support the use of bone scan of the hip as the initial imaging procedure in the evaluation of the symptomatic hip arthroplasty. Bone Scan with SPECT or SPECT/CT Hip There is insufficient evidence to support the use of bone scans with SPECT or SPECT/CT of the hip as the initial imaging procedure in the evaluation of the symptomatic hip arthroplasty. Imaging After Total Hip Arthroplasty CT Hip There is insufficient evidence to support the use of CT of the hip as the initial imaging procedure in the evaluation of the symptomatic hip arthroplasty.


Imaging after Total Hip Arthroplasty PCAs. A possible exception might be for detection of a ceramic acetabular liner fracture where case reports suggest CT to be more sensitive than radiographs [53]. Fluoride PET/CT Skull Base to Mid-Thigh There is insufficient evidence to support the use of fluoride PET/CT skull base to mid-thigh as the initial imaging procedure in the evaluation of the symptomatic hip arthroplasty. Image-Guided Aspiration Hip There is no relevant literature to support the use of image-guided aspiration of the hip as the initial imaging procedure in the evaluation of the symptomatic hip arthroplasty. MRI Hip Non-MoM hip prostheses: There is insufficient evidence to support the use of MRI of the hip as the initial imaging modality for the patient with a symptomatic non-MoM arthroplasty. MoM hip prostheses: Because radiographs may be normal in patients with symptomatic pseudotumors [54], advanced imaging has been supported. Based on literature review, Petscavage-Thomas and Ha [49] suggested MARS-MRI as the first-line of imaging for detection of ARMD. Radiography Hip Radiographs are usually the first imaging modality for assessment of a patient with a symptomatic hip prosthesis. Non-MoM hip prostheses: The literature indicates that radiographs are usually the first imaging modality for assessment of a patient with a symptomatic hip prosthesis. Comparison radiographs are useful; however, an assessment of stem loosening on comparison studies may be suboptimal due to variables such as differences in hip flexion or rotation [55]. Some radiographic features such as increased femoral head and stem offset suggest the need for additional imaging for ARMD due to trunnionosis [56]. Metallosis may be identified around nonmetal on metal prostheses due to trunnionosis or following severe liner wear and/or liner dislocation or fracture [14,57-59].


Imaging after Total Hip Arthroplasty PCAs. However, Chang et al [14] found that in more than half of patients with surgically proven metallosis, radiographs did not show metal density in the soft tissues preoperatively. Radiographs are neither sensitive nor specific for infection. Normal radiographs do not exclude infection; half of the patients in a series of 20 infected hip prostheses reviewed by Tigges et al were normal [60]. Lucencies suggesting aseptic loosening or focal osteolysis may be present in infected hips [60]. Progression of lucency may be rapid in cases of infection. Periostitis was seen in 2 cases. Stumpe et al [61] reviewed radiographs of 35 patients with painful total hip replacements: 9 with septic, 21 with aseptic prosthetic loosening, and 5 without loosening. Rapid progression of osteolysis, rapid component migration, and/or irregular periprosthetic osteolysis were used to diagnose infection. For 2 readers, a sensitivity of 89% and 78%, specificity of 50% and 65%, and accuracy of 60% and 69% were found. In a review, Fritz et al [18] noted that radiographs are usually the first imaging modality for patients with postoperative lateral hip pain. Radiographs help assess the presence of periprosthetic fractures, avulsions of the greater trochanter, and heterotopic ossification [18]. Radiographs showing >2 mm surface irregularities of the greater trochanter have been reported with abductor tendon abnormalities and peritendinous edema on MRI [62]. However, a review of 38 cases of greater trochanter pain syndrome and 100 controls showed the findings of trochanteric surface irregularities including spurs protruding 2 mm were associated with a 24.7% PPV, 64.0% sensitivity, 25.7% specificity, 74.3% false-positive rate, 36.0% false-negative rate, and 65.3% negative predicative value (NPV) for clinical greater trochanteric pain syndrome [63].


Imaging after Total Hip Arthroplasty PCAs. MoM hip prostheses: The FDA notes that in the symptomatic patient following insertion of a MoM prosthesis, radiographs in conjunction with nonimaging information, may disclose the need for revision [44]. Metallosis resulting from severe wear of a metal on metal articulation may occasionally be identified on radiographs [64]. Component position can be assessed [65]. Matharu et al [54] found hips with resurfacing arthroplasties and symptomatic pseudotumors were more likely than those without pseudotumors to have abnormal radiographs (80.0% compared with 63.4%). Radiographic features Imaging After Total Hip Arthroplasty that predicted revision for pseudotumors included high inclination, acetabular or femoral osteolysis, and acetabular loosening. In that study, 20% of hip resurfacing prostheses with pseudotumors at revision surgery had normal radiographic features [54]. Based on these findings, Matharu et al [54] concluded that radiographs were important and useful in all follow-up protocols to assess MoM hip resurfacing prostheses. Petscavage-Thomas and Ha [49] concluded on literature review that cross-sectional imaging, particularly MRI, is still beneficial even in the presence of normal radiographs. US Hip Non-MoM hip prostheses: There is insufficient evidence to support the use of US of the hip as the initial imaging modality for the patient with a symptomatic non-MoM prosthesis. US for MoM hip prostheses: In a series of 82 hips (82 patients) undergoing revision of MoM prostheses, Lainiala et al [51] found the sensitivity of US examination to be 83% with a specificity of 92% for pseudotumors in the trochanteric region and a sensitivity of 79% and a specificity of 94% for identifying pseudotumors in the iliopsoas region. Matharu et al [66] studied a series of 40 MoM hip resurfacing arthroplasties (39 patients) undergoing revision surgery who had preoperative imaging with both US and MARS-MRI.


Imaging after Total Hip Arthroplasty PCAs. Comparison with operatively identified pseudotumors showed US to have a sensitivity of 90.9% and a specificity of 42.9% compared with an MRI sensitivity of 93.9% and a specificity 57.1%. The PPV was similar (88.2% US, 91.2% MRI) but the NPV was higher for MRI (66.7% on MRI, 50.0% for US) [66]. Variant 3: Symptomatic hip arthroplasty patient, history of acute injury. Additional imaging following radiographs. If a fracture is suspected clinically but is not demonstrated or not fully characterized on radiographs, additional imaging may be necessary. Fracture location, component stability (stable versus loose), and femoral bone stock are features that can influence management and that can be assessed on imaging [67-70]. Bone Scan and Gallium Scan Hip There is insufficient evidence to support the use of combined bone and gallium scan of the hip in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. Bone Scan and Gallium Scan With SPECT or SPECT/CT Hip There is insufficient evidence to support the use of combined bone and gallium scan with SPECT or SPECT/CT hip in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. Bone Scan Hip There is insufficient evidence to support the use of the bone scan of the hip in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. Bone Scan with SPECT or SPECT/CT Hip There is insufficient evidence to support the use of the bone scan with SPECT or SPECT/CT of the hip in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. CT Hip Nonenhanced multidetector CT of the hip has been suggested for fracture detection when radiographs are negative or equivocal and there is high suspicion for periprosthetic fracture or when additional fracture characterization is needed for treatment planning [22,70].


Imaging after Total Hip Arthroplasty PCAs. There is no relevant literature documenting additional benefit of CT with IV contrast, relative to noncontrast CT for fracture detection/assessment. Contrast may be helpful if there is a question of vascular injury [23]. The reported efficacy of CT to provide information regarding component loosening (for treatment planning) when a fracture is present is inconsistent [68,71]. Case reports suggest CT to be more sensitive than radiographs for detecting fracture of a ceramic liner [53]. FDG-PET/CT Skull Base to Mid-Thigh There is insufficient evidence to support the use of FDG-PET/CT skull base to mid-thigh in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. Imaging After Total Hip Arthroplasty Fluoride PET/CT Skull Base To Mid-Thigh There is insufficient evidence to support the use of fluoride PET/CT skull base to mid-thigh in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. Image-Guided Aspiration Hip There is insufficient evidence to support the use of image-guided aspiration of the hip in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. MRI Hip MRI can demonstrate femoral periprosthetic fractures and stress reactions [18]. However, a nondisplaced fracture may be difficult to see on MRI if there is only mild associated marrow edema, and susceptibility artifact from the prosthesis may obscure the pertinent findings [72]. Pelvic fractures can be demonstrated. There is no relevant literature documenting the additional benefit of MRI with IV contrast, relative to noncontrast MRI, for fracture detection. US Hip US is limited in its ability to detect periprosthetic fracture [73]. WBC Scan and Sulfur Colloid Scan Hip There is insufficient evidence to support the use of white blood cell (WBC) and sulfur colloid of the hip imaging in the evaluation of the symptomatic hip prosthesis in the setting of acute injury. Variant 4: Symptomatic hip arthroplasty patient, infection not excluded.


Imaging after Total Hip Arthroplasty PCAs. Additional imaging following radiographs. Ong et al [74] found the incidence of infection after THA in the Medicare population for 1997 and 2006 to be 1.63% within 2 years and 0.59% between 2 and 10 years. The identification of periprosthetic infection is critical to choosing appropriate treatment but diagnosis can be challenging [75]. Guidelines for patient evaluation have been developed [76]. A definition of periprosthetic infection has been proposed by the musculoskeletal infection society that includes major and minor criteria but not specifically imaging criteria [75]. Bone Scan and Gallium Scan Hip The most recent data on bone and gallium scans for diagnosing periprosthetic hip infection are more than 25 years old because this test has been largely replaced by labeled leukocyte and marrow imaging and FDG-PET [77-79]. Bone Scan and Gallium Scan with SPECT or SPECT/CT Hip There is no relevant literature to support the use of bone and gallium scan with SPECT or SPECT/CT of the hip as these tests have been replaced by leukocyte and bone marrow imaging and FDG-PET for diagnosing periprosthetic hip infection. Bone Scan Hip Bone scan of the hip is sensitive but not specific for periprosthetic hip infection. Performing the test as a 3-phase bone scan does not improve accuracy, with reported sensitivity and specificity ranging from 29% to 88% and 50% to 92%, respectively [61,80-82]. Bone Scan with SPECT or SPECT/CT Hip Schweizer et al [83] retrospectively studied 58 total hip prostheses, including 31 symptomatic and 27 asymptomatic prostheses, with bone scan with SPECT/CT. SPECT/CT identified the cause of pain in 19 (61%) of the 31 symptomatic devices. No pathology-specific uptake pattern was observed. Although periprosthetic uptake was significantly higher in symptomatic individuals than in asymptomatic individuals, a normal result did not exclude pathology.


Imaging after Total Hip Arthroplasty PCAs. CT Hip In a 2002 study, Cyteval et al [84] prospectively reviewed helical noncontrast CT scans of 65 painful prosthetic hips with diagnosis confirmed by surgery. Infection was present in 12. Fluid collections in muscles and perimuscular fat demonstrated a 41% sensitivity and a 100% specificity for infection (PPV 100%, NPV 88%, accuracy 89%). Joint distension was 83% sensitive and 96% specific with a PPV of 83%, NPV of 96%, and accuracy of 94%. Thus, fluid collections in muscles and perimuscular fat had a 100% PPV, and absence of joint distention had a 96% NPV for infection. In the same study, periostitis was 100% specific but only 16% sensitive for infection. (PPV 100%, NPV 84%, accuracy 85%) [84]. A more recent study by Isern-Kebschull et al [85] confirmed that findings on Imaging After Total Hip Arthroplasty noncontrast multidetector CT could differentiate delayed periprosthetic joint infection from aseptic loosening or granulomas. Intravenous (IV) contrast may be of help in defining abscess [23]. FDG-PET/CT Skull Base to Mid-Thigh Reported results for diagnosing periprosthetic hip infection have been inconsistent. In some investigations, the test has been both sensitive (81%-95%) and specific (89%-94%) for infection [82,86-90]. The results of other investigations; however, have been less satisfactory, with sensitivity and specificity ranging from 64% to 100% and 38% to 68% [91-93]. Delank et al [94] reported that although a negative FDG-PET excludes infection, a positive result could not accurately differentiate infection from aseptic inflammation. Kiran et al [92] performed preoperative FDG-PET/CT on 130 painful cemented hip arthroplasties and reported a sensitivity of 95% and a specificity of 38% for periprosthetic infection. In this investigation, the false-positive rate of FDG PET/CT compared with culture alone was 77%. Comparisons of FDG-PET with conventional nuclear medicine studies have been contradictory.


Imaging after Total Hip Arthroplasty PCAs. Some investigators have reported that FDG-PET is more accurate than bone scintigraphy and labeled leukocyte and marrow imaging, whereas other investigators have reported the opposite results [61,82,87,88,95,96]. Fluoride PET/CT Skull Base To Mid-Thigh Based on the available data, fluoride PET/CT does not appear to offer any advantages over FDG-PET/CT or 3- phase bone scintigraphy for diagnosing periprosthetic hip infection [97-100]. Image-Guided Aspiration Hip Although both false-positive and false-negative results may occur, joint aspiration with synovial fluid analysis remains probably the most useful test for confirming the presence or absence of infection and identifying the causative organism [101]. A meta-analysis by Carli et al [102] yielded a mean sensitivity of 68.6% and a specificity of 96.4% for joint aspiration culture. Hip aspiration can be performed using fluoroscopic, US, or CT guidance or without image guidance [103-105]. Contrast injection has been described for CT arthrography following joint aspiration [106]. Specific tests of retrieved synovial fluid such as alpha-defensin and polymerase chain reaction for bacteria and leukocyte esterase are beyond the scope of this review [107]. MRI Hip MRI can demonstrate soft tissue and bone features associated with periprosthetic infection, including inflammatory synovitis that may have a lamellated appearance [108], soft tissue edema, lymphadenopathy, fluid collections, bone marrow edema, and periosteal reaction [72,109-112]. IV contrast can be used to differentiate phlegmon from abscess and to define sinus tracts and communicating fluid collections [72]. However, IV contrast is generally not necessary to make the diagnosis of infection [72]. Evaluation of 19 patients suspected of having infection showed noncontrast MRI to be highly reproducible in the detection, localization, quantification, and characterization of fluid collections [113].


Imaging after Total Hip Arthroplasty PCAs. Galley et al [110] used optimized MRI sequences and found irregular soft tissue mass, soft tissue edema, bone destruction, and fistulas to be significant features of periprosthetic infection, with sensitivities of 47.4% to 100% and specificities of 73.1% to 100.0%. Albano et al [109] found lymph node assessment (of the affected compared to the unaffected hip) identified infected implants with high accuracies (up to 93.1%). Galley et al [110] found periosteal reaction, capsular edema, and intramuscular edema after THA at 1.5T MRI with MAR to have high accuracy in the evaluation of periprosthetic joint infection (86%-91% accuracy). Schwaiger et al [112] were able to distinguish patients with infection from those with loosening using MRI features. Soft tissue edema (sensitivity, 86.7% and specificity, >73.3%), abnormalities at both acetabular and femoral components (sensitivity/specificity, 66.7%/93.3%-100%), and enlarged lymph nodes (80%/86.7%) enabled this differentiation. Radiographic Arthrography Hip There is no recent literature to support the current use of conventional arthrography of the hip in the evaluation of periprosthetic infection. US Hip Detection of joint effusion, fluid collections, and sinus tracts is possible with US, and, therefore, this modality is helpful in identifying infection [47]. Some discrepancy regarding the reliability and threshold for detecting effusion on US has been noted [47,114]. van Holsbeeck et al [115] used US to evaluate 15 asymptomatic patients with total Imaging After Total Hip Arthroplasty hip replacements and 33 patients who had pain in the hip after arthroplasty and radiologic findings consistent with component loosening (6 of whom had infection). All patients with intraarticular effusion and extraarticular extension had infection (100% specificity). WBC Scan and Sulfur Colloid Scan Hip The role of combined leukocyte and marrow imaging for diagnosing periprosthetic hip infection has been studied by several investigators.


Imaging after Total Hip Arthroplasty PCAs. Specificity has consistently been high, ranging from 88% to 100%. Sensitivity has been more variable, ranging from 33% to 100% [88,95,96,116,117]. Variant 5: Symptomatic hip arthroplasty patient, infection excluded. Additional imaging following radiographs. This variant includes wear, loosening, and osteolysis. Bone Scan with SPECT or SPECT/CT Hip In 37 painful hip arthroplasties, the results of the bone scan with SPECT/CT were comparable to those of MRI for detecting polyethylene wear, periprosthetic fracture, infection, and aseptic loosening. MRI detected 21 soft tissue abnormalities, 14 tendon lesions (12 tendonopathies, 2 tears), 6 bursitis, and 1 pseudotumor. In contrast, bone scan with SPECT/CT found 1 soft tissue abnormality: iliopsoas tendinopathy, which also was identified on MRI [120]. CT Arthrography Hip Arthrography of the hip may be combined with CT [106]. However, most CT examinations of prostheses are not routinely performed with either IV or intraarticular contrast, particularly now that MAR algorithms for CT have been introduced [22,23]. CT Hip Liner wear: Liner wear may be detected on CT as thinning of the liner contour, development of a gap between a ceramic head and liner [22], shift of femoral head position within the acetabulum, and, in severe cases, metallic deposits in the soft tissues from contact between the femoral head and acetabular metal backing [122,123]. Loosening: Gillet et al [124] compared radiographs and CT with MAR (CT-MAR) for the diagnosis of component loosening. The sensitivity of CT for acetabular or femoral loosening was higher than for radiographs (33.3% and 51.5% for 2 readers for radiographs and 84.85 % for CT). The specificity of both radiographic and CT examinations was high and similar (96.9% and 100% for 2 readers for radiographs and 96.9% and 95.4% for CT). An advantage of CT is its ability to define the amount of the acetabular ingrowth surface that is in contact with bone [22].


Imaging after Total Hip Arthroplasty PCAs. Osteolysis: Osteolysis due to wear typically results in expansile well-defined lucent lesions. Helical CT with metal- artifact reduction is more sensitive than radiographs for identifying and quantifying osteolysis after THA [125]. Walde et al [126] confirmed CT to be more sensitive than radiographs for periacetabular lesion detection in a cadaver model (74.7% sensitivity for CT, 51.7% sensitivity for radiographs). Comparison of CT and MRI Imaging After Total Hip Arthroplasty demonstrated that for lesions of all sizes, CT was less sensitive than MRI (CT, 74.7% sensitive and MRI, 95.4% sensitive) [126]. Most CT examinations of prostheses are not routinely performed with either IV or intraarticular contrast, particularly now that MAR algorithms for CT have been introduced [22,23]. Fluoride PET/CT Skull Base To Mid-Thigh Although most investigations have focused on the ability of fluoride PET/CT to differentiate between aseptic loosening and periprosthetic infection, normal asymptomatic controls were included in several of them. Kobayashi et al [98] reported that increased periprosthetic uptake was present in all cases of loosening and infection but in only 1 (3.7%) of 27 controls. Kumar et al [99] reported that 10 of 12 (83.3%) asymptomatic hip prostheses demonstrated no periprosthetic uptake, whereas periprosthetic uptake was present around all 28 aseptically loosened and all 16 infected devices. Choe at al [97] reported that 3 of 17 (17.6%) control hip prostheses demonstrated minor periprosthetic uptake and the mean SUVmax (4) was significantly less than that of aseptic loosening (7) and infection (11); P < . 01 and P < . 001, respectively. Image-Guided Anesthetic Injection of Hip Intraarticular anesthetic has been used to evaluate painful THAs, primarily to differentiate referred pain (especially from the spine) from pain originating in the hip [127]. Significant pain relief after intraarticular anesthetic injection suggests an intraarticular cause [128,129].


Imaging after Total Hip Arthroplasty PCAs. Lack of improvement is thought to be unhelpful and warrants follow-up [129,130]. MRI Hip Wear: MRI is thought to be the most helpful tool for assessing the severity of intracapsular wear-induced synovitis [131]. On MRI, polyethylene wear-induced synovitis appears as low to intermediate signal intensity material that may distend the joint and extend into adjacent bursae [18]. Loosening: Burge et al [132] compared MRI with MAR techniques to radiographs with findings assessed at revision surgery. MRI was shown to be more sensitive than radiography for assessment of component loosening. For acetabular component loosening, MRI showed a sensitivity of 83% and a specificity of 98% compared with radiographs (sensitivity of 26% and specificity of 100%). For femoral component loosening, the sensitivity of MRI was 75% and the specificity 100%, whereas radiographs showed a sensitivity of 20% and a specificity of 100%. Backer et al [120] evaluated MRI and SPECT/CT for assessing loosening and found the sensitivity, specificity, PPV, and NPV of MRI were 86%, 88%, 60%, and 100% and of SPECT/CT were 93%, 97%, 90%, and 100%, respectively. Osteolysis: There is some discrepancy in the literature regarding whether CT or MRI is the optimal study for detecting osteolysis. This may be related to technical factors. Potter et al [133] compared MRI appearances and surgical findings in 15 hips. In all operated cases, osteolysis found on MRI was confirmed at surgery. Walde et al [126] evaluated CT and MRI for the detection of osteolytic lesions in a cadaver model. For lesions of all sizes, CT was 74.7% sensitive and MRI was 95.4% sensitive. The sensitivity of radiographs was only 51.7%. However, Robinson et al [134] demonstrated a reduced sensitivity (27%) and specificity (1%) of MARS-MRI in comparison with CT-MAR for detecting osteolysis associated with painful MoM hip prostheses.


Imaging after Total Hip Arthroplasty PCAs. There is insufficient literature documenting an additional benefit of MRI with IV contrast, relative to noncontrast MRI, in this population. Radiographic Arthrography Hip Loosening: There is no recent relevant literature regarding the use of arthrography of the hip in the evaluation of component loosening. Older studies had suggested a selective role for arthrography for further analysis when there was hip pain and a question of loosening and negative or equivocal radiographs [135,136]. However, this examination appears to be little used currently. Variant 6: Evaluation of symptomatic hip arthroplasty patient with metal-on-metal prosthesis or findings suggesting trunnionosis. Question of adverse reaction to metal debris. Additional imaging following radiographs. Changes due to ARMD may occur months or years after surgery and can be symptomatic or asymptomatic [7,137]. The results of revision surgery may be poor, and early identification of soft tissue changes of ARMD is thought to be important to improve outcome [7,138]. Investigators have sought to identify clinical, laboratory (eg, cobalt and Imaging After Total Hip Arthroplasty chrome ion levels in the blood), and patient features that could identify patients with or likely to develop ARMD so that revision or close follow-up could be performed. These are outside the scope of this document. Imaging remains a critical resource although its optimal utilization is still being clarified. CT Hip Overall, CT is less able than MRI to detect changes associated with ARMD. Noncontrast CT may be considered following other imaging modalities to assess osteolysis. Robinson et al [134] found a sensitivity of 44% for CT in comparison with MARS-MRI for ARMD pseudotumor detection in patients with unexplained painful MoM prostheses. Also, the detected pseudotumors could not be classified as to structure using CT.


Imaging after Total Hip Arthroplasty PCAs. Thus, the authors concluded that CT would not be a suitable alternative for MARS-MRI and another study such as US may be considered. CT is also less able to detect muscle atrophy. In comparison with MARS-MRI, CT demonstrated a high rate of false-negative examinations for identifying muscle atrophy (sensitivity of 81%, specificity of 37%) [134]. Although, Walde et al [126] demonstrated in a cadaver model that MRI could detect osteolysis with greater sensitivity than CT. Robinson et al [134] demonstrated a reduced sensitivity (27%) and specificity (1%) of MARS- MRI in comparison with CT-MAR for detecting osteolysis associated with painful MoM hip prostheses. MRI Hip MARS-MRI has been used as a reference standard for imaging of the soft tissues around prosthetic hips [134,139]. ARMD Pseudotumors: MRI allows demonstration, localization, measurement, follow-up, determination of solid or cystic composition, and classification of pseudotumors associated with ARMD [36]. Invasion of adjacent soft tissues, muscle atrophy, and tendon avulsions can also be assessed [36,40,131]. Mahajan et al [140] found a difference in the appearance of pseudotumors depending on the site of corrosion. The MoP group demonstrated the highest proportion of thick-walled cystic masses (56.7% in head-neck taper corrosion MoP and 46.5% in dual taper corrosion MoP versus 28.7% in MoM), whereas the MoM group had the highest proportion of thin-walled cystic masses [140]. Weber et al [141] found no significant difference between the MRI appearances of symptomatic and asymptomatic MoP ARMD. Several studies have compared MARS-MRI with surgically proven ARMD pseudotumors. Sensitivity ranged from 71% to 93.9%. Specificity ranged from 42.9% to 87% [39,40,66].


Imaging after Total Hip Arthroplasty PCAs. Lainiala et al [39] found a higher sensitivity for detecting ARMD pseudotumors for studies performed within 3 months before revision surgery (88% sensitivity, 78% specificity), and a lower sensitivity for studies obtained >1 year before revision surgery (sensitivity 29%, specificity 97%). It was suggested that studies >1 year not be used for clinical decision making or planning revision surgery. Combined US and MARS-MRI studies: Comparison to surgical results suggests combining US and MARS-MRI improves accuracy. Small numbers of lesions detected on US are not visible on MRI, and some lesions seen on MRI are not apparent on US [41,52]. Wear: MRI is the most accurate imaging method for assessing wear induced synovitis [131]. Synovial characteristics may reflect the implant type and wear severity [9,142]. Osteolysis: As noted above, there are conflicting reports regarding the optimal study for detecting osteolysis. Walde et al [126] demonstrated in a cadaver model that MRI could detect osteolysis with greater sensitivity than CT. The sensitivity for detecting lesions was 51.7% for radiography, 74.7% for CT, and 95.4% for MRI. CT was more accurate; however, than MRI for measuring lesion volume [126]. Robinson et al [134]; however, demonstrated a reduced sensitivity (27%) and specificity (1%) of MARS-MRI in comparison with CT-MAR for detecting osteolysis associated with painful MoM hip prostheses. Morozov et al [143] evaluated 20 symptomatic patients with MoP prostheses with corrosion at the head-neck taper. Comparison of MRI and surgical findings found MRI to have limited sensitivity for either acetabular (11.1% sensitivity) or femoral (33.3% sensitivity) osteolysis [143]. There is insufficient literature documenting the additional benefit of MRI with IV contrast, relative to noncontrast MRI, in this population.


Imaging after Total Hip Arthroplasty PCAs. Imaging After Total Hip Arthroplasty US Hip US can be used to detect ARMD pseudotumors (solid or cystic) and other findings seen with ARMD such as joint effusions, bursal collections, capsular and bursal thickening, and synovitis [36]. Kwon et al [52] found that US was valid and useful for detecting interval changes in lesion size and grade in comparison with MARS-MRI. A summary of studies comparing US to MARS-MRI as the reference standard for detecting ARMD shows sensitivities for US of 69% to 100% and specificities of 83% to 96% [36]. In a series of 82 hips (82 patients) undergoing revision of MoM prostheses, Lainiala et al [51] found a sensitivity of 83% and specificity of 92% for US examination of pseudotumors in the trochanteric region and a sensitivity of 79% and specificity of 94% for identifying pseudotumors in the iliopsoas region. Matharu et al [66] studied a series of 40 MoM hip resurfacing arthroplasties in 39 patients undergoing revision surgery who had preoperative imaging with both US and MARS-MRI. Comparison with operatively identified pseudotumors showed US to have a sensitivity of 90.9% and a specificity of 42.9% compared with an MRI sensitivity of 93.9% and specificity of 57.1%. The PPV was similar (88.2% US, 91.2% MRI), but the NPV was higher for MRI (66.7% on MRI, 50.0% for US) [66]. Combined US and MARS-MRI studies: Comparison to surgical results suggests combined US and MARS-MRI improves accuracy. Small numbers of lesions detected on US are not visible on MRI, and some lesions seen on MRI are not apparent on US [41,52]. Variant 7: Hip arthroplasty patient with trochanteric pain. Suspect abductor injury, or trochanteric bursitis, or other soft tissue abnormality. Additional imaging following radiographs. Postoperative greater trochanter pain may be due to greater trochanteric bursitis, or other etiologies such as gluteus minimus or medius tendinitis, or tears or avulsion [73].


Imaging after Total Hip Arthroplasty PCAs. Trochanteric bursitis is reported to occur in up to 17% of hips after THA and may be related to the surgical approach [144,145]. CT Hip CT is less optimal than MRI for assessing soft tissues [22]. Fractures and fluid collections can be identified on CT. Image-Guided Anesthetic +/- Corticosteroid Injection Hip Joint or Surrounding Structures If trochanteric bursitis is thought to be a source of pain, Robbins et al [144] suggest the bursa may be injected with either lidocaine alone as a diagnostic test, or in combination with a corticosteroid as a therapeutic measure. MRI Hip MRI can be used to assess peritrochanteric structures including the gluteus minimus and medius muscles, abductor tendons, and the trochanteric bursa [146,147]. There is no relevant literature documenting the additional benefit of MRI with IV contrast, relative to noncontrast MRI, in this population. Pfirrmann et al [147] compared the MRI findings about the greater trochanter in 25 patients after primary THA without pain and 39 patients with trochanteric pain and abductor weakness. Although several abnormalities were seen in both symptomatic and asymptomatic groups, defects of the abductor tendons and fatty atrophy of the gluteus medius muscle and the posterior part of the gluteus minimus muscle were uncommon in asymptomatic patients. Comparison of MRI findings with findings at surgical revision in 14 patients confirmed all MRI tendon findings. Joint distension and decompression of synovitis into the greater trochanteric bursa and fluid undermining the hip abductors can be assessed on MARS-MRI [72]. Weber et al [141] noted that extracapsular disease associated with ARMD could be misinterpreted as trochanteric bursitis. Radiographic Arthrography Hip Weakness or detachment of the abductor muscles may occur after THA using an anterolateral approach [148].


Newly Diagnosed Palpable Scrotal Abnormality.  Introduction/Background Palpable scrotal abnormalities are caused by a variety of disorders, ranging from indolent benign conditions to aggressive tumors as well as infectious and vascular processes, often requiring emergent surgical intervention [1- 3]. In these patients, the diagnostic workup typically begins with a complete clinical history and physical examination, including analysis of risk factors, often followed by imaging [4,5]. Germ cell testicular tumors (GCTT) are the most frequently diagnosed cancer in young men and constitute approximately 95% of all testicular tumors [6]. It is estimated that 1 in 250 men will develop GCTT during their lifetime, most often between 20 to 34 years of age, representing 0.5% of all new malignancies [6]. GCTT histologically include seminoma and nonseminoma (52% and 48%, respectively) or mixed tumors [7]. Most patients with GCTT are diagnosed quite early and present with stage I disease, when the tumor is confined to the testicle; in these patients, inguinal orchiectomy is the first recommended maneuver that has both diagnostic and therapeutic aims [13]. Close clinical and imaging surveillance with or without short-course adjuvant chemotherapy are accepted alternatives for patients with stage I disease [6]. In patients with more advanced disease presenting with extratesticular tumor, several courses of chemotherapy followed by the judicious surgical removal of residual tumor is commonly used. High-risk patients and those with relapsing or refractory disease are referred to specialized tertiary centers for advanced high-dose chemotherapy plus autologous hematopoietic support [8]. Special Imaging Considerations Contrast-enhanced ultrasound (CEUS) and US shear-wave elastography (SWE) are gaining clinical acceptance as useful additions to first-line US examinations of the scrotum in patients with newly diagnosed palpable scrotal abnormality. aThomas Jefferson University Hospital, Philadelphia, Pennsylvania.


Newly Diagnosed Palpable Scrotal Abnormality. bPanel Chair, Northwestern University, Chicago, Illinois. cPanel Vice-Chair, UT Southwestern Medical Center, Dallas, Texas. dUT Southwestern Medical Center, Dallas, Texas. eUniversity of Cincinnati, Cincinnati, Ohio. fThe University of Texas MD Anderson Cancer Center, Houston, Texas. gDuke University Medical Center, Durham, North Carolina. hRoswell Park Cancer Institute, Jacobs School of Medicine and Biomedical Science, Buffalo, New York. iThomas Jefferson University Hospital, Philadelphia, Pennsylvania, Primary care physician. jJohns Hopkins Hospital, Baltimore, Maryland; American Urological Association. kCleveland Clinic, Cleveland, Ohio. lUniversity of Alabama at Birmingham, Birmingham, Alabama. mNew York University, New York, New York. nThe Ohio State University Wexner Medical Center, Columbus, Ohio. oSpecialty Chair, University of Alabama at Birmingham, Birmingham, Alabama. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org OR Discussion of Procedures by Variant Variant 1: Newly diagnosed palpable scrotal abnormality. History of trauma or infection. Initial imaging. CT Abdomen and Pelvis CT of the abdomen and pelvis is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients with a history of trauma or infection. There is no relevant literature regarding the use of CT of the abdomen and pelvis in these patients. CT Pelvis CT of the pelvis is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients with a history of trauma or infection.


Newly Diagnosed Palpable Scrotal Abnormality. There is no relevant literature regarding the use of CT of the pelvis in these patients. MRI Abdomen and Pelvis MRI of the abdomen and pelvis is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients with a history of trauma or infection. There is no relevant literature regarding the use of MRI of the abdomen and pelvis in these patients. MRI Pelvis (Scrotum) MRI of the pelvis is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients with a history of trauma or infection but may be used as a problem-solving tool when findings are not clear on US. There is no relevant literature regarding the use of MRI of the pelvis in these patients. Nuclear Medicine Scan Scrotum Nuclear scan of the scrotum is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients with a history of trauma or infection. There is no relevant literature regarding the use of nuclear scans of the scrotum in these patients. Newly Diagnosed Palpable Scrotal Abnormality US Duplex Doppler Scrotum The combination of grayscale and color-power Doppler US can significantly improve the specificity of B-mode US in scrotal lesion characterization [1,32]. It is very useful in diagnosis of focal inflammatory processes, such as epididymitis and testicular abscess, that can present with palpable scrotal masses in some patients [33]. Nevertheless, duplex US does not allow a definitive differentiation of malignancies from a variety of benign conditions, such as orchitis, dermoid cyst, granuloma, focal fibrosis, adrenal rest, and papillary cystadenoma. In fact, those lesions can mimic cancer, and, as a consequence, the specificity of a duplex US examination of the scrotum is lower than its sensitivity [34].


Newly Diagnosed Palpable Scrotal Abnormality. Other potential diagnoses that may be demonstrated on US include testicular hematoma, rupture (particularly in patients with a history of trauma), infarct, torsion, intratesticular varicocele, and arteriovenous malformations or angiomatosis [35]. US Scrotum A variety of infectious and traumatic processes can be accurately depicted and characterized on grayscale US [36]. Sonographically, the involved testicle may have heterogenous, hypoechoic echotexture. Additional findings in testicular trauma may include contour abnormality, disruption of the tunica albuginea, or direct visualization of a fracture line. Sonographic appearance of intratesticular hematoma depends on the time from trauma, with the hyperacute or acute hematoma appearing as a heterogeneous or isoechoic area relative to surrounding testicular parenchyma, whereas chronic hematomas are smaller in size and relatively hypoechoic to anechoic. However, scrotal US without Doppler imaging may not be able to differentiate a hematoma from a mass or evaluate for inflammation. Variant 2: Newly diagnosed palpable scrotal abnormality. No history of trauma or infection. Initial imaging. CT Abdomen and Pelvis CT of the abdomen and pelvis is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients without history of trauma or infection. There is no relevant literature regarding the use of CT of the abdomen and pelvis in these patients. CT Pelvis CT of the pelvis is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients without a history of trauma or infection. There is no relevant literature regarding the use of CT of the pelvis in these patients. MRI Abdomen and Pelvis MRI of the abdomen and pelvis is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients without a history of trauma or infection.


Newly Diagnosed Palpable Scrotal Abnormality. There is no relevant literature regarding the use of MRI of the abdomen and pelvis in these patients. MRI Pelvis (Scrotum) MRI is not routinely used as the initial examination to evaluate scrotal pathology given its uncertain clinical utility when used in addition to standard US [37,38]. In select cases, it could be help distinguish between an intratesticular and extratesticular mass when this cannot be confirmed clinically or with US [8]. MRI may aid in the diagnosis of a primary testicular mass, mostly focusing on differential diagnosis between benign and malignant testicular masses [39]. Quantitative enhancement patterns may be useful to distinguish testicular seminoma from Leydig cell tumors in direct comparison, but it is uncertain how they would perform in a routine clinical practice [40]. Nuclear Medicine Scan Scrotum Nuclear scan of the scrotum is not routinely used as an initial imaging modality for the evaluation of newly diagnosed palpable scrotal abnormality in patients without a history of trauma or infection. There is no relevant literature regarding the use of nuclear scans of the scrotum in these patients. US Duplex Doppler Scrotum The combination of grayscale and color-power Doppler US can significantly improve the specificity of B-mode US in scrotal lesion characterization [1,32]. US duplex may be able to differentiate a solid mass from a mass-like hematoma. which will be avascular (can occur without trauma). Nevertheless, duplex US does not allow a definitive differentiation of malignancies from a variety of benign conditions, such as orchitis, dermoid cyst, granuloma, focal fibrosis, adrenal rest, and papillary cystadenoma. In fact, those lesions can mimic cancer, and, as a consequence, the specificity of duplex US examination of the scrotum is lower than its sensitivity [34]. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch. acr.org/list.


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease.  Introduction/Background Gestational trophoblastic disease (GTD), or abnormal proliferation of placental trophoblastic tissue, is a rare complication of pregnancy. There is considerable variation in the worldwide distribution of GTD, with the highest frequencies reported in Asia and the Middle East and lower rates on the order of 1 per 1,000 pregnancies in Europe and North America [1,2]. Extremes of maternal age and personal history of GTD are known risk factors [1-3]. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through society representation on expert panels. Participation by representatives from collaborating societies on the expert panel does not necessarily imply individual or society endorsement of the final document. Reprint requests to: publications@acr.org Gestational Trophoblastic Disease On the whole, women with GTD have a favorable prognosis for cure with early adequate treatment, despite the presence of metastatic disease in some patients. Patients with benign but premalignant lesions are managed with uterine evacuation and enrolled in postoperative hCG surveillance [16]. Hysterectomy in patients not opting to preserve fertility does not eradicate risk of postmolar GTN [16-19]. If malignant GTN other than ETT or PSTT is suspected or has been established, further evaluation for potential metastatic lesions is initiated, clinical risk factors determined, and patients stratified into low- or high-risk groups based on the modified World Health Organization (WHO) prognostic scoring system as adapted by and combined with the international Federation of Gynecology and Obstetrics (FIGO) anatomic staging system [2,20]. This combines anatomic staging with assessment of prognostic factors: patient age, type of antecedent pregnancy, interval from gestational event to chemotherapy, hCG concentration, number and site of metastases, largest tumor mass, and previous chemotherapy.


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. Points are assigned for each variable to determine risk of resistance to single-agent chemotherapy. Scores exceeding 6 predict high-risk disease refractory to monochemotherapy, with patients maintaining good prognosis if managed with intensive combination chemotherapy [10]. Patients with brain metastases are automatically assigned a high-risk disease status, regardless of score [12]. Adjuvant surgical and/or radiation therapy can be added selectively to decrease disease burden and remove resistant lesions [21-23]. ETT and PSTT, biologically distinct tumors that are relatively refractory to chemotherapy and grow more slowly with local lymphatic rather than hematogenous metastases, are staged anatomically and primarily treated surgically [24]. Special Imaging Considerations A healthy twin live fetus may coexist alongside a partial or complete molar pregnancy. A rare phenomenon, this has been estimated to occur in 1 in 20,000 to 100,000 pregnancies [10]. The management of this entity is controversial as there is some concern that these patients may be more prone to developing GTN among other potential serious complications, such as pre-eclampsia, thyrotoxicosis, hemorrhage, trophoblastic embolism, and fetal demise [25,26]. Evidence from a series of 77 cases, however, suggests that approximately 40% of these patients may successfully deliver a healthy baby without increased incidence of malignant transformation [10,27]. Because this scenario is exceedingly rare, there is little high-quality evidence to support imaging guidelines. US Pelvis Transvaginal Transvaginal US is the accepted standard in the evaluation of early pregnancy and suspected complications. Although <50% of hydatidiform moles were prospectively identified on US in studies published >10 years ago [21,22], a more recent study reported improved sensitivity using contemporary US equipment with 86% of complete moles and 41% of partial moles diagnosed prospectively [23].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. Reported sensitivity of US detection is higher for complete mole, with its more pronounced hydropic changes of chorionic villi and absence of a gestational sac, than for partial mole [9,28]. Features suspicious for partial mole include an enlarged placenta or cystic changes within the decidual reaction in association with either an empty sac (>20 mm in diameter) or a delayed miscarriage (fetal pole with crown-rump length >6 mm but no cardiac activity) [22]. Differential diagnosis in partial molar pregnancy may include missed abortion [29] and retained products of conception. There is no substantial evidence to support a role for grayscale US features in risk stratification for future development of GTN [30,31]. Enlarged ovaries with multiple theca lutein cysts may be a helpful secondary finding in suspected GTD but are noted in <50% of patients [29,30]. Gestational Trophoblastic Disease US Pelvis Transabdominal Transvaginal US has superior sensitivity and specificity in the diagnosis of uterine masses when compared with transabdominal US, although given the rarity of GTD, literature comparing both modalities is lacking [32]. US Duplex Doppler Pelvis There is some support for a role for Doppler US in the initial diagnosis and postevacuation follow-up of patients with GTD. A lower uterine artery resistive index before molar evacuation is associated with the development of trophoblastic tumors, a potentially useful means to prospectively recognize patients who are at high risk for progression and warrant closer follow-up [33,34]. In a prospective analysis of 246 women with complete mole, Doppler pulsatility index showed potential as a predictor of subsequent development of GTN [35]. In a retrospective analysis of 189 patients with hydatidiform mole, US evidence of nodules and hypervascularization within the myometrium or endometrium 3 weeks following initial molar evacuation had a high specificity (95.5%) but low sensitivity (53.9%) for later development of GTN [33,34].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. Doppler US can also confirm the absence of vascular flow within a mass, a useful technique in patients with GTD where clot or blood products may simulate solid tissue. CT Head If physical examination and chest radiographs are normal in a patient with GTD, metastases to other sites are unlikely, and further imaging investigation is not indicated [37,43]. CT Abdomen and Pelvis If physical examination and chest radiographs are normal in a patient with GTD, metastases to other sites are unlikely, and further imaging investigation is not indicated [37,43]. Gestational Trophoblastic Disease MRI Head If physical examination and chest radiographs are normal in a patient with GTD, metastases to other sites are unlikely, and further imaging investigation is not indicated [37,43]. MRI Pelvis To our knowledge, there is no evidence to support the routine use of MRI for initial evaluation of known or suspected GTD. Evaluation of MRI in patients with hydatidiform mole is limited to small series and cases reports [44-46]. Diffusion-weighted imaging has been evaluated as a potential predictor of subsequent GTN development in a small retrospective study and was not found to be useful [46]. FDG-PET/CT Skull Base to Mid-Thigh To our knowledge, there is no evidence to support the routine use of fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET/CT for initial evaluation of known or suspected GTD. Preliminary limited data suggest a potential role for FDG-PET/CT in the identification of patients who are likely to develop GTN following initial treatment for molar pregnancy [47]. A significant difference in the standardized uptake value-max (SUVmax) of pre- evacuation intrauterine molar tissue in patients who achieved normalization of hCG versus those who progressed to GTN following dilatation and curettage was observed in this single retrospective study of 11 patients [47].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. US Pelvis Transabdominal Transvaginal US has superior sensitivity and specificity in the diagnosis of uterine masses when compared with transabdominal US, although, given the rarity of GTN, literature comparing both modalities is lacking [32]. Radiography Chest The lungs are the most common site of metastasis in GTN [7,36,60]. Chest radiographs are the primary imaging method recommended by FIGO to detect and count lung metastases for purposes of risk assessment in patients with GTN. However, approximately 30% to 40% of patients assumed to have nonmetastatic disease by radiographs may have CT evidence of micrometastases [20,38,39]. The emphasis on radiographs may in part reflect the global scope of FIGO, which provides recommendations that must apply to both industrialized countries and underresourced medical care environments. CT chest may be preferred where available because of its greater sensitivity, although controversy persists regarding the prognostic significance of tiny nodules detected by CT, as discussed below. However, the statement that chest radiographs are used for counting the number of metastases, not CT chest, was also rated as highly appropriate by a panel of 45 experts from 16 countries in association with the EOTTD [6]. CT Chest The lungs are the most common site of metastasis in GTN [7,36,60]. Approximately 30% to 40% of patients assumed to have nonmetastatic disease by radiographs may have CT evidence of micrometastases [20,38-40]. However, the clinical importance of these tiny lesions remains controversial as there is no definitive evidence of impact on long-term survival [38,41]. Assessment of the literature is complicated by the fact that suspected pulmonary micrometastases from GTN are often not confirmed histologically because they typically regress completely with treatment and biopsy is not recommended [40].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. Despite some disagreement in the literature regarding modality choice to diagnose lung metastases, patients with suspected or confirmed GTN are often initially evaluated with chest CT at many institutions. Although micrometastases are not thought to impact survival, their presence increases the likelihood of other areas of metastatic involvement and should trigger other anatomic imaging [19]. Otherwise stated, the negative predictive value of chest CT in patients with GTN is high and of substantial clinical value because hepatic or brain metastases are very unlikely in the absence of pulmonary metastases [37]. Because the lungs are the most common site of GTN metastases, the use of IV contrast is not necessary to improve lesion detection. The use of low-dose CT as a means to assess pulmonary metastases in patients with GTN was evaluated in a small study comparing standard- and low-dose CT examinations [42]. Although the number of nodules detected on the low-dose CT protocols was significantly less than the number identified on standard-dose CT examinations, the disease staging and risk score of the patients were not impacted. The EOTTD expressed a strong preference for MRI over CT for neurologic staging in a study that assessed the level of agreement among an expert panel regarding the management of patients with GTD [6]. However, in the setting of urgent neurologic findings that are due to space-occupying or hemorrhagic metastases, the ACR Gestational Trophoblastic Disease MRI Pelvis In women with GTN, pelvic MRI can delineate uterine and vaginal masses, and may provide useful detail regarding the depth of local invasion [44,46,61]. Local staging information is particularly relevant in patients with ETT or PSTT because these tumors may have extensive uterine involvement [14,15,52]. ETT and PSTT are both relatively chemoresistant, and surgical resection may have a primary role in therapy if the tumor is confined to the uterus.


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. As such, MRI has the potential to provide important information for treatment planning. Local parametrial invasion, vaginal involvement, and pelvic extension are all better assessed with MRI than US [44]. Because the primary tumor and GTN metastases are typically vascular, IV contrast enhancement is useful to improve lesion detection. Vaginal gel may be useful to distend the vagina, optimizing the delineation of any masses or extension, if present. The majority of patients with postmolar GTN not treated with hysterectomy will have locally invasive disease [17]. Given the rare nature of ETT and PSTT, there are few consistent descriptions of imaging features, limited to small series and case reports [15,52,65]. MRI assessment of lymph node status is important to treatment planning in patients with PSTT and ETT, but other forms of GTN predominantly spread via hematogenous routes. FDG-PET/CT Skull Base to Mid-Thigh The role of FDG-PET/CT in the evaluation of patients with GTN is inconclusive and evolving given the uncommon nature of the disease. There is some evidence that FDG-PET/CT may be useful to precisely map tumor extent prior to chemotherapy, as well as to monitor tumor response and identify sites of persistent disease following therapy [66-69]. One systematic review included 19 papers totaling 81 cases of GTN, with FDG- PET/CT used in the initial staging in 59 of 81 patients and in the follow-up after initial chemotherapy in 22 of 81 patients [47]. The largest study included in this review (41 patients) showed concordance between FDG-PET or PET/CT and conventional studies that ranged from 81% to 91% with the highest discordance in chest CT, all false-negative [68].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. Among all summarized data, FDG-PET or PET/CT studies facilitated localization of persistent or unusual sites of metabolically active disease, enabled distinction of false-positive lesions on conventional studies related to areas of necrotic or hemorrhagic tissue, and identified additional or occult lesions in a small number of patients. Small lesion size, paucity of FDG-avid cells, and poorly differentiated tumors may contribute to false-negative studies. Variant 3: Surveillance of GTN, including refractory, relapsed, or quiescent GTN. GTN is highly chemosensitive and associated with excellent outcomes, but drug resistance and relapse can occur. This is more common in patients with high-volume disease at diagnosis or in those with inadequate initial therapy. Up to 12.5% of patients with high-risk disease will develop recurrence after initial remission [19]. Gestational Trophoblastic Disease US Pelvis Transabdominal Transvaginal US has improved sensitivity and specificity in the diagnosis of uterine masses when compared with transabdominal US, although given the rarity of this disorder, series that compare both modalities in patients with GTN are lacking [32]. Radiography Chest Evaluation of lung metastases in patients with relapsed or refractory disease is better accomplished with chest CT because primary prognostic scoring is no longer an issue in this patient population. CT Chest Because GTN metastases involve the lungs rather than the mediastinum, IV contrast enhancement is not necessary to improve lesion detection. Although radiographic evidence of tumor regression can lag behind a favorable biochemical response to treatment, thoracotomy with wedge resection of pulmonary lesions is sometimes performed in patients with persistent nodules. This is generally only indicated with isolated chemoresistant lesions in the absence of disease elsewhere [16,71]. Regardless, it remains the most common surgical procedure for extrauterine metastases [16,18,71].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. CT Head Although a head CT is acceptable as a means to document brain metastases (FIGO), the formalized consensus of the EOTTD favors MRI over CT in the detection of brain metastases [6]. Because GTN metastases are typically vascular, IV contrast enhancement is necessary to improve lesion detection. CT Abdomen and Pelvis CT abdomen and pelvis is useful to exclude disseminated disease in patients with high-risk or recurrent GTN who are being considered for salvage hysterectomy [16] or to evaluate for recurrence of tumors after surgical resection. In the specific context of oligometastatic disease to lung with potential for pulmonary wedge resection, CT abdomen and pelvis has particular utility for exclusion of additional disease sites [16,18]. Because GTN metastases are typically vascular, IV contrast enhancement is necessary to improve lesion detection. FDG-PET/CT Skull Base to Mid-Thigh The role of FDG-PET/CT in the evaluation of patients with refractory or recurrent GTN is incompletely defined and evolving, given the uncommon nature of the disease. FDG-PET/CT may help to identify the site of active or occult disease and facilitate planning for surgical resection and potential cure [10,66,67,69,72]. However, the evidence basis is small and retrospective. Variant 4: Assessment of complications: GTD and GTN. Patients with GTD can present with complications related to invasive mole or metastatic lesions, in large part because of the highly vascular nature of this disease process. Some of these complications can be severe and life- threatening. Hemorrhage is the most common complication and can result from tumor invading the uterus or from other sites of metastatic tumor involvement, including lungs, brain, vagina, and liver [2,16,50,73]. Selective angiographic localization and embolization can be used to identify and treat lesions with active hemorrhage as well as post-treatment sequelae, such as arteriovenous malformation [18].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. Hysterectomy may be indicated for severe uterine hemorrhage or rupture [2,18]. Although rare in the United States, patients with invasive mole may present with hemoperitoneum that is due to molar tissue penetrating the full thickness of the myometrium [20]. Finally, adnexal torsion or rupture may occasionally complicate theca lutein cysts, necessitating surgical removal [16]. Imaging evaluation in the setting of suspected GTN complications should be guided by location of clinical signs and symptoms. US Pelvis Transabdominal Transvaginal US has improved sensitivity and specificity in the diagnosis of uterine masses and abnormalities when compared to transabdominal US, although given the rarity of this disorder, series comparing both modalities in patients with GTD are lacking [32]. At some institutions, patients with GTN are not evaluated with transvaginal US due to the risk of major bleeding as a consequence of a nondetected vaginal metastasis [37]. US Duplex Doppler Pelvis GTN can be complicated by uterine vascular malformations such as arteriovenous shunts and pseudoaneurysms, described in up to 15% of cases following complete response to chemotherapy, and best delineated with Doppler US [44]. Although these findings are insignificant if asymptomatic and associated with a normal hCG, such malformations occasionally result in life-threatening vaginal or intraperitoneal hemorrhage [44]. Gestational Trophoblastic Disease Radiography Chest We are unaware of any recent formal assessment regarding the use of chest radiography to assess pulmonary complications in GTN. Lung infarct and secondary pulmonary arterial hypertension associated with trophoblastic tumor thrombus may be appreciated on chest radiography. Likewise, sequelae of endobronchial metastasis such as volume loss or airspace disease and pleural effusions that follow hemorrhage into parenchymal and intravascular metastases could potentially be visible [44,45].


Gestational Trophoblastic Disease

Gestational Trophoblastic Disease. CT Chest A variety of pulmonary complications may be evaluated using chest CT [44,45], including trophoblastic tumor thrombus, associated lung infarct, and secondary pulmonary arterial hypertension. Unusual manifestations of lung metastases may be perceptible such as an endobronchial lesion with secondary obstruction and volume loss. Airspace disease and pleural effusion may follow hemorrhage into parenchymal and intravascular metastases [44,45]. Because detection of these complications may require opacification of the vessels, IV contrast enhancement is necessary to improve lesion conspicuity, although hemorrhagic complications would be visible on an unenhanced study. CT Head Craniotomy with surgical decompression is generally indicated for acute symptomatic treatment of patients with intracranial hemorrhage [16]. CT can be used to identify and localize lesions or to detect signs of increased intracranial pressure and mass effect in patients with acute neurologic symptoms and signs of deterioration. Hemorrhagic complications and structural changes related to mass effect would be visible without IV contrast, although lesion detection would be improved with IV contrast. CT Abdomen and Pelvis CT is indicated to detect metastatic disease in the staging of patients with GTN, but can also be used to identify sites of active hemorrhage or other tumor-related complications [74]. Liver metastases can be associated with catastrophic intraperitoneal hemorrhage and may require selective angiographic embolization techniques [16]. Use of CT abdomen and pelvis should be prompted by abdominopelvic location of patient symptoms in context of known GTN. Hemorrhagic complications would be evident without the use of IV contrast. IV contrast may be required to detect individual nonhemorrhagic lesions. MRI Head Craniotomy with surgical decompression is generally indicated for acute symptomatic treatment of patients with intracranial hemorrhage [16].


Staging and Surveillance of Testicular Cancer.  Malignant testicular germ-cell tumors metastasize by either the hematogenous or lymphatic route. Nodal metastases typically follow the testicular lymphatic drainage pathway alongside the testicular veins to regional lymph node groups. Tumors from the left testis will metastasize to the left para-aortic nodal group just below the left renal vein and interaortocaval group, whereas right testicular tumors will metastasize to the paracaval, precaval, and interaortocaval groups. Crossover of lymphatic involvement may occur in either right-sided or left-sided tumors; however, it is unusual to have contralateral metastasis without involvement of the ipsilateral nodes [4]. Further spread to nonregional lymph node groups, including common iliac, internal iliac, and external iliac nodes, or via the thoracic duct to the left supraclavicular nodes and subsequently to the lungs, constitutes distant metastasis [5]. Prior scrotal or inguinal surgery can alter the lymphatic drainage; therefore, external iliac and inguinal lymph nodes are considered regional in that context [6]. Staging of testicular cancer is based upon determination of extent of disease and follows the tumor, nodes, and metastases (TNM) staging system used by the American Joint Committee on Cancer [5]. TNM staging of testicular cancer is a major factor that determines treatment and prognosis in men with testicular cancer. Imaging is used to assess for expected locations of lymph node involvement and metastatic disease. Most patients with stage IA and IB pure seminoma testicular cancers are cured by orchiectomy [7]. Surveillance is strongly preferred in this group of patients; however, because 15% to 20% of men experience relapse, adjuvant therapy with one or two cycles of single-agent carboplatin or radiotherapy to decrease risk of relapse can be considered in certain high-risk patients [8-11]. Irrespective of management strategy, disease-specific survival approaches 100% [8-11].


Staging and Surveillance of Testicular Cancer. In men who relapse while on surveillance in stage I pure seminoma testicular cancer, most relapses occur in the abdominal and pelvic lymph nodes [8-11]. The 2021 National Comprehensive Cancer Network (NCCN) guidelines recommend, apart from physical examination and serum tumor markers, imaging surveillance to detect relapse for 5 years after orchiectomy [8]. In this document, clinical suspicion of tumor relapse indicates abnormal physical examination or serum markers and no clinical suspicion of tumor relapse indicates a normal physical examination and tumor markers. The management strategies and prognosis of men with stage II and higher pure seminoma testicular cancer and nonseminoma testicular cancer, as well as restaging and follow-up approaches, are beyond the scope of this document but have been described in detail by the 2021 NCCN guidelines [8]. aOttawa Hospital Research Institute and the Department of Radiology, The University of Ottawa, Ottawa, Ontario, Canada. bPanel Chair, University of Chicago, Chicago, Illinois. cPanel Vice-Chair, Duke University Medical Center, Durham, North Carolina. dMemorial Sloan Kettering Cancer Center, New York, New York. eUniversity of Minnesota, Minneapolis, Minnesota. fUrology Clinics of North Texas, Dallas, Texas; American Urological Association. gUniversity of Wisconsin, Madison, Wisconsin. hUPMC, Pittsburgh, Pennsylvania; American Urological Association. iStanford University Medical Center, Stanford, California. jEmory University Hospital, Atlanta, Georgia. kThe Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada, Primary care physician. lNational Institutes of Health, Bethesda, Maryland. mSpecialty Chair, University of Alabama at Birmingham, Birmingham, Alabama. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels.


Staging and Surveillance of Testicular Cancer. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization. Reprint requests to: publications@acr.org Staging and Surveillance of Testicular Cancer Discussion of Procedures by Variant Variant 1: Initial staging of pure seminoma testicular cancer. Diagnosed by orchiectomy. Bone Scan Whole Body Bone metastases from testicular cancer are uncommon. In one study, bone scan was able to detect metastases to the iliac bones ipsilateral to the testicular tumor before they were detectable by CT [12]. CT Abdomen and Pelvis CT is the reference standard imaging test used for assessing the retroperitoneum for the presence of metastatic lymphadenopathy. CT is rapid, reproducible, and provides excellent imaging assessment of the para-aortic and paracaval regions [13-15]. Challenges related to CT are that many young men have little retroperitoneal fat, which may be an impediment for readers interpreting the study, and that CT cannot detect metastatic disease in lymph nodes of normal size. Additionally, inflammatory lymph nodes cannot be differentiated from those that are enlarged from metastases [16]. Lymph nodes >1 cm in short axis are highly suspicious for metastatic disease, particularly if they are located in the hilar regions of the kidney or in the para-aortic or caval areas (eg, testicular cancer landing zones). Various studies have established the accuracy of CT in detecting metastatic retroperitoneal lymph nodes from testicular cancer, which ranges from 73% to 97%, sensitivity ranges from 65% to 96%, and specificity from 81% to 100% [7,17-22]. Data also indicate that the accuracy of CT declines in patients with limited disease (eg, stage N1 and stage N2) and also if the upper limit of normal lymph node size is lowered [15,17,21].


Staging and Surveillance of Testicular Cancer. Of note, most of these studies are relatively old and were performed using single-slice CT; however, limited newer data suggest similar accuracy using multi- slice CT compared with single-slice CT [23]. It is important to recognize that a significant percentage of metastatic lymph nodes will be <1 cm, up to 60% in one series [24]. For this reason, some authors suggest using a cut-off value of 0.7 cm to 0.8 cm in testicular cancer at the expense of reduced specificity [24,25]. These cut-off values are for the short-axis measurement when assessing the likelihood of nodal disease (N0 versus N1 disease); however, when assessing the nodal burden, the lymph nodes should be measured in long axis (eg, N1 versus N2 and N3 disease) [6,25]. Two studies have also evaluated the value of nodal craniocaudal length or volume as risk factors for recurrence in testicular cancer [26,27]. Another study comparing lymph node measurements performed by expert radiologists, other observers, and a semiautomated process showed excellent correlation between measurements, indicating that the task of actually measuring lymph nodes, which can be time consuming and tedious, could potentially be delegated or automated in the future [28]. The use of iodinated intravenous (IV) contrast media, as well as oral contrast media, may aid in detection of retroperitoneal lymph nodes, clarifying the adjacent normal anatomic structures including blood vessels and the duodenum [29]. CT Chest Although CT is more sensitive than radiography for detecting recurrent disease in the chest [30,31], this added sensitivity is offset by lower specificity and a higher false positive detection rate for abnormalities that are not related to testicular cancer metastases [32]. Chest CT is recommended during initial staging if chest radiograph is abnormal or when abdominal CT is abnormal [8]. Detection of mediastinal and hilar lymph nodes may be aided by the use of iodinated IV contrast media [33].


Staging and Surveillance of Testicular Cancer. FDG-PET/CT Whole Body Fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET has been used for staging and restaging patients with testicular cancer, but its incremental value in staging patients compared with CT or MRI has yet to be defined. For initial staging, PET may be slightly more sensitive than CT [34-39], but it is not recommended by the NCCN [40]. MRI Abdomen and Pelvis MRI has also been studied for staging and surveillance of testicular cancer, to identify metastatic retroperitoneal lymphadenopathy [41-46]. Limited evidence from single-institution studies indicates comparable efficacy to CT for detection of retroperitoneal lymphadenopathy, notably without the need for gadolinium-based contrast agents (GBCAs) [41,43]. A limitation of the literature regarding MRI for detection of metastatic retroperitoneal lymphadenopathy is that the studies are older and do not incorporate diffusion-weighted imaging (DWI). DWI can substantially improve identification of lymph nodes; however, it is still limited by significant overlap between benign and malignant Staging and Surveillance of Testicular Cancer lymph nodes [6]. A study published in 2020 showed comparable accuracy between MRI, which included DWI and omitted GBCAs, and CT for detection of metastatic retroperitoneal lymph nodes in testicular germ-cell tumors [47]. MRI Head MRI of the head, without and with GBCAs, is recommended during the initial staging of testicular cancer if the patient is symptomatic or has high-risk features (eg, human chorionic gonadotropin [hCG] >5000 IU/L or extensive lung metastases) [8-11]. Radiography Chest Studies have shown that chest radiography is beneficial in pure seminoma testicular cancer during the initial staging of testicular cancer to assess for the presence of pulmonary metastases [48,49]. Chest CT is recommended during initial staging if chest radiograph or abdominal CT is abnormal [8].


Staging and Surveillance of Testicular Cancer. US Abdomen and Retroperitoneum Ultrasound (US) of the abdomen and retroperitoneum to detect retroperitoneal lymph node metastases is less accurate and reproducible than CT, MRI, or PET/CT [50]. US Scrotum Scrotal US is frequently used and should always be the initial imaging modality in assessing patients with scrotal masses. Scrotal US should always be performed during the initial workup of a scrotal mass before orchiectomy to localize the tumor, plan surgery, and clear the contralateral testicle of disease [40]. After initial triage and orchiectomy, scrotal US does not have a role in the initial staging or restaging of men with testicular cancer diagnosis established by orchiectomy unless there is concern for contralateral tumor or equivocal clinical examination [8]. Variant 2: Initial staging of nonseminoma testicular cancer. Diagnosed by orchiectomy. Bone Scan Whole Body Bone metastases from testicular cancer are uncommon. In one study, bone scan was able to detect metastases to the iliac bones ipsilateral to the testicular tumor before they were detectable by CT [12]. CT Abdomen and Pelvis CT is the reference standard imaging test used for assessing the retroperitoneum for the presence of metastatic lymphadenopathy. CT is rapid, reproducible, and provides excellent imaging assessment of the para-aortic and paracaval regions [13-15]. Challenges related to CT are that many young men have little retroperitoneal fat, which may be an impediment for readers interpreting the study, and that CT cannot detect metastatic disease in lymph nodes of normal size. Additionally, inflammatory lymph nodes cannot be differentiated from those that are enlarged from metastases [16]. Lymph nodes >1 cm in short axis are highly suspicious for metastatic disease, particularly if they are located in the hilar regions of the kidney or in the para-aortic or caval areas (eg, testicular cancer landing zones).


Staging and Surveillance of Testicular Cancer. Various studies have established the accuracy of CT in detecting metastatic retroperitoneal lymph nodes from testicular cancer, which ranges from 73% to 97%, sensitivity ranges from 65% to 96%, and specificity from 81% to 100% [7,17-22]. Data also indicate that the accuracy of CT declines in patients with limited disease (eg, stage N1 and stage N2) and also if the upper limit of normal lymph node size is lowered [15,17,21]. Of note, most of these studies are relatively old and were performed using single-slice CT; however, limited newer data suggest similar accuracy using multi- slice CT compared with single-slice CT [23]. It is important to recognize that a significant percentage of metastatic lymph nodes will be <1 cm, up to 60% in one series [24]. For this reason, some authors suggest using a cut-off value of 0.7 cm to 0.8 cm in testicular cancer at the expense of reduced specificity [24,25]. These cut-off values are for the short-axis measurement when assessing the likelihood of nodal disease (N0 versus N1 disease); however, when assessing the nodal burden, the lymph nodes should be measured in long axis (eg, N1 versus N2 and N3 disease) [6,25]. Two studies have also evaluated the value of nodal craniocaudal length or volume as risk factors for recurrence in testicular cancer [26,27]. Another study comparing lymph node measurements performed by expert radiologists, other observers, and a semiautomated process showed excellent correlation between measurements, indicating that the task of actually measuring lymph nodes, which can be time consuming and tedious, could potentially be delegated or automated in the future [28]. The use of iodinated IV contrast media, as well as oral contrast media, may aid in detection of retroperitoneal lymph nodes, clarifying the adjacent normal anatomic structures including blood vessels and the duodenum [29].


Staging and Surveillance of Testicular Cancer. Staging and Surveillance of Testicular Cancer CT Chest Although CT is more sensitive than radiography for detecting recurrent disease in the chest [30,31], this added sensitivity is offset by lower specificity and a higher false positive detection rate for abnormalities that are not metastatic [32]. For nonseminoma testicular cancer, a slight advantage for chest CT has been noted compared with chest radiography [48,51], and chest CT is recommended during the initial staging of nonseminoma testicular cancer by the NCCN and European Association of Urology guidelines [8,9]. Detection of mediastinal and hilar lymph nodes may be aided by the use of iodinated IV contrast media [33]. FDG-PET/CT Whole Body FDG-PET has been used for staging and restaging patients with testicular cancer, but its incremental value in staging patients compared with CT or MRI has yet to be defined. For initial staging, PET may be slightly more sensitive than CT [34-39], but it is not recommended by the NCCN [40]. MRI Abdomen and Pelvis MRI has also been studied for staging and surveillance of testicular cancer to identify metastatic retroperitoneal lymphadenopathy [41-46]. Limited evidence from single-institution studies indicates comparable efficacy to CT for detection of retroperitoneal lymphadenopathy, notably without the need for GBCAs [41,43]. A limitation of the literature regarding MRI for detection of metastatic retroperitoneal lymphadenopathy is that the studies are older and do not incorporate DWI. DWI can substantially improve identification of lymph nodes; however, it is still limited by significant overlap between benign and malignant lymph nodes [6]. A study published in 2020 showed comparable accuracy between MRI, which included DWI and omitted GBCAs, and CT for detection of metastatic retroperitoneal lymph nodes in testicular germ-cell tumors [47].


Staging and Surveillance of Testicular Cancer. MRI Head MRI of the head, without and with GBCAs, is recommended during the initial staging of testicular cancer if the patient is symptomatic or has high-risk features (eg, hCG >5000 IU/L, extensive lung metastases, choriocarcinoma, nonpulmonary visceral metastases, or alpha-fetoprotein [AFP] >10,000 ng/mL) [8-11]. Radiography Chest Studies have shown that chest radiography is beneficial during the initial staging of testicular cancer, assessing for pulmonary metastases [48,49]. For nonseminoma testicular cancer, a slight advantage for chest CT has been noted compared with chest radiography [48,51], and chest CT is useful during the initial staging of nonseminoma testicular cancer by the NCCN and European Association of Urology guidelines [8,9]. US Abdomen and Retroperitoneum US of the abdomen and retroperitoneum to detect retroperitoneal lymph node metastases is less accurate and reproducible than CT, MRI, or PET/CT [50]. US Scrotum Scrotal US is frequently used and should always be the initial imaging modality in assessing patients with scrotal masses. Scrotal US should always be performed during the initial workup of a scrotal mass before orchiectomy to localize the tumor, plan surgery, and clear the contralateral testicle of disease [40]. After initial triage and orchiectomy, scrotal US does not have a role in the initial staging or restaging of men with testicular cancer diagnosis established by orchiectomy unless there is concern for contralateral tumor or equivocal clinical examination [8]. Variant 3: Surveillance of stage IA and IB pure seminoma testicular cancer. Diagnosed by orchiectomy. No clinical suspicion of recurrence. Bone Scan Whole Body Bone metastases from testicular cancer are uncommon. In one study, bone scan was able to detect metastases to the iliac bones ipsilateral to the testicular tumor before they were detectable by CT [12].


Staging and Surveillance of Testicular Cancer. Staging and Surveillance of Testicular Cancer CT Abdomen and Pelvis CT is the reference standard imaging test used for assessing the retroperitoneum for the presence of metastatic lymphadenopathy. CT is rapid, reproducible, and provides excellent imaging assessment of the para-aortic and paracaval regions [13-15]. Challenges related to CT are that many young men have little retroperitoneal fat, which may be an impediment for readers interpreting the study, and that CT cannot detect metastatic disease in lymph nodes of normal size. Additionally, inflammatory lymph nodes cannot be differentiated from those that are enlarged from metastases [16]. Lymph nodes >1 cm in short axis are highly suspicious for metastatic disease, particularly if they are located in the hilar regions of the kidney or in the para-aortic or caval areas (eg, testicular cancer landing zones). Various studies have established the accuracy of CT in detecting metastatic retroperitoneal lymph nodes from testicular cancer, which ranges from 73% to 97%, sensitivity ranges from 65% to 96%, and specificity from 81% to 100% [7,17-22]. Data also indicate that the accuracy of CT declines in patients with limited disease (eg, stage N1 and stage N2) and also if the upper limit of normal lymph node size is lowered [15,17,21]. Of note, most of these studies are relatively old and were performed using single-slice CT; however, limited newer data suggest similar accuracy using multi- slice CT compared with single-slice CT [23]. It is important to recognize that a significant percentage of metastatic lymph nodes will be <1 cm, up to 60% in one series [24]. For this reason, some authors suggest using a cut-off value of 0.7 cm to 0.8 cm in testicular cancer at the expense of reduced specificity [24,25].


Staging and Surveillance of Testicular Cancer. These cut-off values are for the short-axis measurement when assessing the likelihood of nodal disease (N0 versus N1 disease); however, when assessing the nodal burden the lymph nodes should be measured in long axis (eg, N1 versus N2 and N3 disease) [6,25]. Two studies have also evaluated the value of nodal craniocaudal length or volume as risk factors for recurrence in testicular cancer [26,27]. Another study comparing lymph node measurements performed by expert radiologists, other observers, and a semiautomated process showed excellent correlation between measurements, indicating that the task of actually measuring lymph nodes, which can be time consuming and tedious, could potentially be delegated or automated in the future [28]. The use of iodinated IV contrast media, as well as oral contrast media, may aid in detection of retroperitoneal lymph nodes, clarifying the adjacent normal anatomic structures including blood vessels and the duodenum [29]. Surveillance is strongly preferred for patients with stage I pure seminoma testicular cancer [8-11]. Surveillance protocols no longer include chest CT [30] and may eliminate pelvic CT, except in cases in which the pelvis is deemed high risk [53-55]. The number and frequency schedule of follow-up CT examinations of the abdomen and pelvis is variable [56]. Most recently, the 2021 NCCN guidelines recommends different intensity of follow-up for stage I pure seminoma testicular cancer and nonseminoma testicular cancer, which also depends on the presence or absence of risk factors for metastatic disease [8]. CT Chest Although CT is more sensitive than radiography for detecting recurrent disease in the chest [30,31], this added sensitivity is offset by lower specificity and a higher false positive detection rate for abnormalities that are not metastatic [32]. Detection of mediastinal and hilar lymph nodes may be aided by the use of iodinated IV contrast media [33].


Staging and Surveillance of Testicular Cancer. Several studies indicate that chest radiography is sufficient when compared with CT for follow-up of stage I seminomas [30,32,49,54], and the NCCN advise CT chest only be performed if the patient is symptomatic [40]. FDG-PET/CT Whole Body FDG-PET has been used for staging and restaging patients with testicular cancer, but its incremental value in staging patients compared with CT or MRI has yet to be defined. For initial staging, PET may be slightly more sensitive than CT [34-39]. The use of PET for surveillance of stage 1A and 1B pure seminoma is not well studied. MRI Abdomen and Pelvis MRI has also been studied for staging and surveillance of testicular cancer to identify metastatic retroperitoneal lymphadenopathy [41-46]. Limited evidence from single-institution studies indicates comparable efficacy to CT for detection of retroperitoneal lymphadenopathy, notably without the need for GBCAs [41,43]. A limitation of the literature regarding MRI for detection of metastatic retroperitoneal lymphadenopathy is that the studies are older and do not incorporate DWI. DWI can substantially improve identification of lymph nodes; however, it is still limited by significant overlap between benign and malignant lymph nodes [6]. A study published Staging and Surveillance of Testicular Cancer in 2020 showed comparable accuracy between MRI, which included DWI and omitted GBCAs, and CT for detection of metastatic retroperitoneal lymph nodes in testicular germ-cell tumors [47]. MRI Head MRI of the head is not recommended during the surveillance of pure seminoma testicular cancer unless the patient is symptomatic. Radiography Chest In pure seminoma testicular cancer under surveillance, studies have shown that lung relapses are rarely detected by chest radiography alone, with most relapses detected by abnormal serum markers or abdominal and pelvic CT scan [57-59], calling into question the value of chest radiography in surveillance of stage I pure seminoma testicular cancer.