Approximately one in four people with diverticulitis develop serious, sometimes life-threatening health problems.

If you have diverticulitis and experience any of these symptoms, you may have developed a complication:

  • Fever over 100 degrees Fahrenheit (38 degrees Celsius)
  • Worsening or severe abdominal pain
  • Inability to tolerate fluids
  • Low blood pressure

Some of the complications of diverticulitis include:

  • Abscess
  • Fistula
  • Peritonitis
  • Rectal bleeding
  • Intestinal obstruction

Diverticulitis and Abscesses

An abscess is a walled-off collection of white blood cells and bacteria — commonly known as pus — that forms inside your body.

Abscesses are typically accompanied by swelling and inflammation, and can cause abdominal tenderness and severe abdominal pain.

Diverticular abscesses form when the infection from a diverticulum spreads from your large intestine to other areas of your body — most often in the pelvic area or in the mesentery, the tissue that connects your intestines to the back wall of your abdomen.

Only about 15 percent of people with diverticulitis develop abscesses.

Some small abscesses (less than two centimeters in diameter) may resolve on their own with the help of antibiotics. Larger abscesses may need to be drained using a thin plastic catheter inserted through the skin.

Your doctor may also recommend surgery to create an opening in the skin, called a stoma, from which the abscess can be drained.

Diverticulitis and Peritonitis

Peritonitis is an infection of the peritoneum, the silk-like membrane that lines the inside of your abdomen.

Diverticular peritonitis occurs when the infection from a diverticulum spreads outward from a perforation or hole in the wall of the colon into the abdominal cavity.

Symptoms include:

  • Severe abdominal pain
  • Fever and chills
  • Nausea
  • Vomiting
  • Bloating

Because the bacteria that cause peritonitis can spread throughout the entire body, peritonitis is considered life-threatening and should be treated immediately.

Patients who experience diverticular peritonitis usually undergo emergency surgery to remove the infected part of the colon. A second surgery is then necessary to rejoin healthy sections of the colon.

Diverticulitis and Fistula

A fistula is an abnormal passageway that can develop between two hollow organs, such as the colon and the bladder, or between an organ and the inner wall of the body.

A diverticular fistula can form if an infected diverticulum is touching or in close proximity to another organ. If the diverticulum ruptures, the infection can spread to the other organ, forming a passage between the two organs.

Fistulas are more common in men.

However, women who have had a hysterectomy are at a higher risk of developing this complication because the uterus, which normally separates the large intestine from the bladder, has been removed.

Diverticular fistulas commonly form between the colon and the bladder and can lead to a bladder infection or a urinary tract infection (UTI). Fistulas may also form between the colon and other organs, including the:

  • Small intestine
  • Uterus
  • Vagina
  • Abdominal wall
  • Thigh

Diverticular Bleeding

Diverticular bleeding occurs when small arteries inside a diverticulum erode, causing blood to leak into the colon. People who experience diverticular bleeding may notice maroon or bright red blood in their stool.

In most cases, this problem will resolve on its own. However, rectal bleeding can also be a symptom of other health issues, such as colon cancer.

Therefore, if you experience this complication, you should see your doctor.

Rarely, a serious condition called diverticular hemorrhaging can also occur. This complication, which usually affects elderly patients, causes weakness or lightheadedness and the appearance of large amounts of blood in the stool.

In some cases, people may require a blood transfusion, as well as surgery to remove the segment of the colon containing the bleeding diverticulum.

Bowel Obstruction and Diverticulitis

Inflammation from diverticulitis can narrow the intestinal cavity, making it difficult for waste to pass through the body. This narrowing of the bowel is known as a stricture.

If a stricture is the result of inflammation, it will usually resolve on its own once inflammation subsides. However, strictures can also be the result of recurrent episodes of diverticulitis.

Over time, diverticular inflammation can lead to scarring inside the intestine, causing the intestinal passageway to become narrower. The resulting complication is known as a non-inflammatory stricture and may require surgery to correct.

If the bowels become completely blocked by scarring, this is known as intestinal blockage or bowel obstruction. These complications are life-threatening, as they can lead to a ruptured intestine and peritonitis.

Complete blockage of the bowels requires emergency surgery to correct. People with this condition will often feel extreme abdominal pain and nausea and won't be able to pass gas or have bowel movements.

Irritable Bowel Syndrome (IBS) and Diverticulitis

A 2013 study published in the journal Clinical Gastroenterology and Hepatology suggests that patients with diverticulitis may be at a higher risk of developing irritable bowel syndrome (IBS).