It is a benign disease of the colon characterized by the development of pulsion-type outpouchings. These are really false diverticula because they consist of mucosa lined only by serosa. They most often occur between the mesenteric and antimesenteric taenia coli, where the colonic blood vessels pierce the muscle. They indicate herniation of the mucosa through weak points in the colon wall. They are most common in the sigmoid and left colon but may occur anywhere in the colon.

Diverticulosis most likely develops as a result of a low-fiber diet. As food becomes more refined and processed, the amount of dietary fiber decreases. This is particularly prevalent in Western societies, which consume only one-tenth the amount of fiber consumed 100 years ago, before refined diets were so prevalent. In rural Africa and other societies not exposed to a Western diet, diverticular disease is almost nonexistent (1). Rural Africans reportedly consume 60 to 100 g of fiber a day, whereas Americans consume only 10 to 15 g per day.

Fiber increases stool weight, decreases whole gut transit time, and lowers colonic intraluminal pressure. A high-fiber diet requires less contraction by the bowel to propel the stool onward. There is less segmentation, and muscle hypertrophy does not occur.

Approximately 30 million Americans have diverticulosis. Only 1% to 2% of people younger than 30 years of age are affected; one third of Americans older than 45 years are affected. The incidence rises with age; two thirds of the population older than 85 years is affected (2). Most people are asymptomatic, but 15% to 30% eventually develop diverticulitis.

Saint’s triad is the constellation of cholelithiasis, hiatal hernia, and diverticulosis.

Acute diverticulitis with local peritonitis is the most likely diagnosis for this patient. She has had an appendectomy, which means that the most likely differential diagnoses are colon carcinoma, inflammatory bowel disease, and ischemic colitis.

Perforation (micro or macro) causing pericolic infection with formation of a phlegmon, pericolic abscess, fistula formation, and frank peritonitis are the most common complications of diverticular disease. Acute inflammation can also lead to ulceration or erosion into a colonic wall blood vessel (remember where on the bowel diverticula most commonly occur) and cause bleeding. Chronic inflammation may lead to stricture formation and colon obstruction. Small-bowel obstruction is a common but not frequently mentioned complication of acute diverticulitis. Up to 20% of patients with acute diverticulitis may have small-bowel obstruction as a result of a loop of small bowel getting snared in the inflammatory nest. This is to be distinguished from an ileus, which may develop as a result of acute diverticulitis.

A fistula may develop between the inflamed colon and any surrounding structure. Colovesical fistulas are the most common, accounting for nearly 60% of fistulas associated with diverticular disease (4). Approximately 2% of patients with acute diverticulitis develop a colovesical fistula. They are more common in men than in women, probably because in women the uterus lies between the colon and the bladder. Colocutaneous fistulas are the next most common type associated with diverticulitis. A women who has had a hysterectomy may develop a colovaginal fistula.

Dysuria (90%), pneumaturia (70%), and fecaluria (70%) are the most common symptoms. Chronic urinary tract infections may occur. There are no physical signs related to the fistula per se, although one third of patients have evidence of a systemic infection.

Barium enema, cystoscopy, or both may demonstrate the communication between the colon and bladder. Radiography of the urine after a barium enema is described. Often the fistula cannot be demonstrated and the diagnosis is made based on history. The patient may be asked to urinate while in the bathtub to see if bubbles appear in the water.

The investigation of choice at this point is computed tomography (CT) of the abdomen and pelvis with intravenous (IV) and water-soluble oral contrast. This not only helps to confirm the diagnosis but also demonstrates the extent of the disease, including any abscess collections or free intraperitoneal air or fluid. In general, the diagnosis can be made clinically with sufficient confidence to permit treatment without more definitive investigation.

Colonic wall thickening, stranding of pericolic fat, pericolic or distant abscesses, and extraluminal air are characteristics of diverticulitis seen on CT (5). Colonic diverticula seen on CT are not diagnostic of acute diverticulitis.

Mrs. Witt definitely should not have a barium enema or colonoscopy. Both procedures could worsen the situation. Colonoscopy could blow open a sealed perforation. Barium enema could provoke free perforation and lead to extravasation of barium into the peritoneal cavity, causing barium peritonitis.

The films should be reviewed with the radiologist. CT-guided percutaneous drainage is an excellent option for identifiable pericolic abscesses in patients with acute diverticulitis. The potential for CT-guided percutaneous drainage is one of the reasons CT is so attractive in patients with acute diverticulitis. Approximately 75% of peridiverticular abscesses can be drained in this way. The advantages are that it facilitates resolution of the sepsis without surgical drainage, and it permits a one-stage elective operation later. There is no evidence that Mrs. Witt has an abscess, thus there is no merit in percutaneous drainage in her case.

No. Mrs. Witt should be admitted for bowel rest, IV fluids, IV antibiotics, pain relief, and observation. In general, outpatient management is appropriate for patients who can tolerate diet, who do not have systemic symptoms, and who do not have peritoneal signs. Mrs. Witt fails to meet all of these criteria.

Approximately 1% of patients with diverticular disease eventually require surgery. Approximately 15% to 30% of patients admitted to the hospital with acute diverticulitis need surgery. Mrs. Witt is not likely to need surgery on this admission.

Mrs. Witt should be seen in the clinic in a few weeks to make sure that the acute episode has settled. At that time, full assessment of her colon, either by flexible sigmoidoscopy and barium enema or by colonoscopy, should be arranged.