Diverticulosis is a condition where herniations (diverticula) form in the large intestine.
When these diverticula get infected, the condition caused is called diverticulitis.

Diverticulitis causes

Diverticulitis causes

The causes of both diverticulosis and diverticulitis remain unsure.

One suspected cause of diverticulosis is a diet low in fiber. A lack of fiber may cause the stool to harden. Hard stool stays in the bowel longer, causing slower stool (congestion or constipation). Hard stool causes elevated pressure in the intestine which can lead to diverticula forming in weaker parts of the intestine.

Likewise, it remains unclear what causes diverticulitis. It is known that bacteria in the diverticula multiply, causing infections.


Risk factors for diverticulitis are:

  • A low-fiber diet
  • Diverticulosis running in the (approximate) family
  • Long-term intake (more than four days per week for multiple years) of aspirin or non-steroid anti-inflammatory drugs (NSAIDs) such as ibuprofen (Brufen, Nurofen, …)


Diverticulitis complaints and symptoms

Diverticulitis complaints and symptoms

The symptoms for diverticulitis are:

  • Tenderness, usually in the bottom left of the abdomen, is the most common symptom. This pain can aggravate during physical activity.
  • Fever
  • Bloated feeling and gas
  • Diarrhea
  • Constipation
  • Nausea, sometimes vomiting
  • Lack of appetite
  • Blood in stool
  • Slime in stool


These symptoms can last from a few hours up to longer than a week.

Diverticulitis can cause blood loss through the anus as the result of a bleeding diverticulum. A bleeding diverticulum is caused by a very small blood vessel ripping in the diverticulum but doesn’t necessarily imply diverticulitis.

Mistreated or left untreated, diverticulitis can cause the intestine to burst where the infection is located. This condition is called intestinal perforation. Intestinal perforation is very dangerous because it may allow stool to enter the abdominal cavity, leading to peritonitis. Intestinal perforation and/or peritonitis causes acute, intense pain, usually combined with high fever.

Diagnosis diverticulitis

Diverticulitis diagnosis

The following tests may be required to diagnose diverticulitis:

  • Blood analysis, such as a differential blood cell count. An elevated amount of white blood cells may indicate an infection, while a low red blood cell count may indicate bleeding in the large intestine.
  • An ultrasound of the lower abdomen allows the doctor to examine the large intestinal wall and assess the severity of the infection. In case of severely infected diverticula, the ultrasound may be complemented by a CT scan.
  • When symptoms point to an abscess in the abdomen or a ruptured diverticulum, a CT scan is recommended.
  • Colonoscopy and sigmoidoscopy are almost solely conducted in case of ongoing complaints or to rule out other intestinal conditions. A colonoscopy allows the doctor to examine the entire large intestine, including the rectum. A sigmoidoscopy can be carried out to examine the rectum and the final section of the large intestine.
  • A urinalysis may rule out possible urinary-tract-infections (UTIs)
  • An occult blood analysis examines the stool for blood.


Diverticulitis treatment

Diverticulitis treatment

Treatment for diverticulitis depends on the severity of the symptoms. Mild cases of diverticulitis sometimes heal without treatment. A change in diet often suffices, combined with medicine if necessary. In severe cases hospitalization or surgery are required. Surgery is only an option when former treatments haven’t resulted in any improvement, or in case of sustained chronic pain, bowel obstruction, a fistula or an abscess. Less than 6 percent of diverticulitis cases require surgery.

‘Mild’ symptoms

When diverticula are severely inflamed, sometimes a fluid diet is recommended. Provided the patient’s condition has improved after a few days, they can switch to food that is easily digestible, followed by a high-fiber diet.

In case of severe inflammation and fever the doctor may prescribe antibiotics or pain killers. The patient is likely to suffer from pain in the lower abdomen after healing, which doesn’t necessarily indicate relapse.


Severe complaints or emerging complications require the patient to be hospitalized. Antibiotics are administered through an IV-drip and nutrition may be given through a feeding tube to relieve the intestines. As soon as the inflammation drops, the patient’s diet can slowly return to normal.


In some cases, diverticulitis leads to serious complications such as perforation, peritonitis or an abscess. Surgery is then necessary to remove a part of the large intestine. Another possibility is elective surgery after 1) two or more severe attacks, 2) if the patient is under 40 and 3) in case of a weakened immune system.

Partial colectomy consists of partially removing the large intestine after which the remaining ends are stitched together. Depending on the severity of the symptoms, multiple surgeries may be required. If that is indeed the case, colostomy is the most commonly used procedure. A colostomy takes the end of the large intestine out of the body via an opening in the abdomen, creating an artificial exit (stoma) through which stool can leave the body. The stoma is usually removed after a couple of months, and the intestinal ends are reattached.


Another serious complication of diverticulitis is an abscess growing in the abdomen. In most cases, though, the abscess doesn’t need to be surgically removed as a drainage procedure often proves sufficient. Drainage consists of a needle inserting a small tube into the pus-filled cavity which is then rinsed.

Dr. Yannick Nijs contact

Dr. Yannick Nijs
Colorectal surgeon

St-Michel Europe Hospitals
150 Linthoutstraat
1040 Brussels

+32 470 588 537
+32 2 614 37 20

Contact usBook a consultation