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Kidney Stones

A very large 7mm kidney stone

One in 10 people are diagnosed with kidney stones during their lifetime.  The peak incidence occurs between the ages of 30 to 45.  Patients will often present with sudden onset of severe intermittent pain and nausea.  Treatment depends upon stone size, location, composition and comorbidities.  Stones less than 4 mm usually pass spontaneously while stones greater than 4 mm usually require intervention.  Stones that are unable to pass are generally treated on an outpatient basis at a urological ambulatory surgery center.  A urology-focused ambulatory surgery center offers cutting-edge minimally invasive technology necessary to treat all types of stones.  For example, a holmium laser can provide a focused beam of light to fragment stones with pinpoint accuracy.  Latest-generation shockwave lithotripsy machines (ESWL) offer exceptional radiographic imaging necessary to maximize success.  These machines work by focusing high-energy shockwaves on the stone while minimizing trauma to surrounding tissue.  A urology-specific surgical center will also have the full array of endoscopic equipment such as miniature ureteroscopes, which can be placed through the urethra and advanced all the way up in to the kidney itself to visualize stones for fragmentation.  When stones are larger, more invasive procedures are generally necessary, such as a percutaneous nephrolithotomy (PCNL), where the stone is fragmented and removed through a small puncture made through the flank.


Unfortunately, many stones formers do not receive the appropriate prevention after the acute stone crisis has resolved.  With correct preventive dietary counseling and selective medical therapy, a stone remission rate of 90% can be achieved.  Risk factors for recurrent stone formation includes young age, gender (male), race (Caucasian), family history of stones, recurrent urinary tract infections, gout and osteoporosis.  The cornerstone of prevention involves a chemical stone analysis, basic blood work and a 24-hour urine collection.  The two most common stones are composed of calcium oxalate (82%) or uric acid (8%).  A careful dietary history and review of all over-the-counter and prescription medications should also be completed.


Low-to moderate-risk stone formers will have an excellent result with dietary and fluid management alone.  All stone formers should increase their urine output to greater than 2,500 cc.  Calcium oxalate stone formers should avoid foods high in oxalate such as chocolate, nuts, black pepper and spinach.  If patients have a history of osteoporosis or osteopenia they should stay on calcium supplementation with calcium citrate.  If not, then calcium supplements should be avoided unless a screening bone density test later reveals problems with low bone density.  A low-salt diet will further reduce the risk of future stones.  Increasing dietary citrate with fresh lemon, lime, orange or pineapple juice will also inhibit stone formation.
People who form uric-acid stones should follow a low-purine diet and minimize intake of beef, fowl and shellfish.  Uric-acid stone formers often require urinary alkalization with medications such as potassium citrate.  The goal of alkalization is a urinary pH between 6.5 to 7.0.  Uric-acid stones often cannot be visualized on routine X-rays and therefore require diagnosis by CT or ultrasound.  Unlike the more common calcium-based stones, uric-acid stones can often be dissolved with medical management without the need for surgical intervention.


All patients with kidney stones should be referred to a urologist for management and prevention.  High-risk stone formers generally placed on long-term medical therapy and dietary restrictions.  These patients are followed up on an annual basis for routine X-rays, urinalysis and repeat 24-hour urine collections.


Kidney stones can be a very painful and often recurrent problem.  Sudden onset of severe pain often occurs at the worst possible times.  Kidney stones often are caused by underlying metabolic disorders and proper evaluation is essential for stone prevention.