Diverticular Disease

Diverticulosis is "a condition that occurs when small pouches, or sacs, form and push outward through weak spots in the wall of your colon." "These pouches form mostly in the lower part of your colon, called the sigmoid colon." In the United States and Western Europe the disease is "predominantly in the left colon, with up to 90% of cases exclusively in the sigmoid colon," while in Asia it "often occurs in younger people and predominantly occurs in the right colon." It is extremely common with age: "More than 30% of U.S. adults between the ages of 50 and 59 and more than 70% of those older than age 80 have diverticulosis."

The weak spot is where a blood vessel passes through the muscle. "A diverticulum can form at a point of natural weakness where the vasa recta penetrates the colonic wall to supply blood to the mucosa and submucosa." "Dysregulation of colonic peristalsis results in nonpropulsive segments with high intraluminal pressure, leading to herniation through the muscularis layer." The old explanation is now uncertain: "Increased pressure from straining and constipation was once thought to be the initiating factor resulting in this colonic wall herniation. However, this theory is currently under question," and the current view is "an interaction among connective tissue degradation, lifestyle factors, and genetic predisposition." About 50% of the risk for diverticulitis is attributed to genetic factors.

Most people never know they have it. "Most people who have diverticula in their colon do not have symptoms or problems," and "Less than 5% of people with diverticulosis develop diverticulitis." Diverticular disease means the pouches are causing trouble — chronic symptoms, bleeding, or diverticulitis and its complications.

Bleeding happens without inflammation. "Diverticula are prone to bleeding due to the proximity of the vasa recta to the intestinal lumen," and "Diverticular bleeding occurs when a small blood vessel within the wall of a diverticulum pouch bursts." "Any bleeding associated with diverticulosis is painless," and it "typically occurs in the absence of diverticular inflammation or infection." It "may be severe and life-threatening": about 5% to 15% of people with diverticulosis bleed, and "A third of these patients experience massive bleeding" — though "Most bleeding associated with diverticulosis is self-limiting and does not require intervention." NIDDK’s teaching is blunt: "If you have bleeding from your rectum —even a small amount—you should see a doctor right away."

Diverticulitis is inflammation of the pouches, and its cause is less certain than textbooks once said. "The presumed cause of diverticulitis is fecal obstruction of diverticula, leading to bacterial overgrowth and subsequent mucosal inflammation and microperforations. This theory has been challenged in recent years, and some studies have shown that patients with acute uncomplicated diverticulitis may be managed without antibiotics." WSES describes uncomplicated disease as possibly "a self-limiting condition in which local host defenses can manage the inflammation without antibiotics in immunocompetent patients." In uncomplicated diverticulitis "the infection only involves the colon and does not extend to the peritoneum"; in complicated diverticulitis it has spread — an abscess, a fistula, obstruction, or a perforation with peritonitis.

The staging follows the spread (modified Hinchey). Stage 0 mild clinical diverticulitis; 1a confined pericolic inflammation; 1b confined pericolic abscess; 2 pelvic or distant intra-abdominal abscess; 3 generalized purulent peritonitis; 4 fecal peritonitis — and "patients with Hinchey III and IV lesions require surgical intervention to achieve source control." A fistula to the bladder announces itself with fecaluria and pneumaturia — stool or air in the urine. The first episode is often the worst: "complicated diverticulitis is most often the first presentation of diverticulitis. The risk of complicated diverticulitis decreases with recurrences."

Confirm with CT when the diagnosis is new or the patient is sick. "Clinical suspicion of diverticulitis alone is correct in only 40–65% of patients." "A computed tomography (CT) scan of the abdomen and pelvis with intravenous (IV) contrast is the gold standard for diagnosis, with 98% to 99% sensitivity and 99% to 100% specificity." Most uncomplicated cases are managed at home: WSES suggests "management in an outpatient setting for patients with uncomplicated ALCD and no comorbidities" with "re-evaluation within 7 days." Antibiotics are selective, not routine: the AGA advises they "can be used selectively, rather than routinely, in immunocompetent patients with mild uncomplicated diverticulitis," and are advised "in patients with uncomplicated diverticulitis who have comorbidities or are frail, who present with refractory symptoms or vomiting, or who have a CRP >140 mg/L," or a raised white cell count; StatPearls adds that "antibiotics remain strongly advised for immunocompromised patients."

The fibre paradox — opposite advice at opposite times. During a flare: "A clear liquid diet is advised during the acute phase of uncomplicated diverticulitis. Diet should advance as symptoms improve," because "fiber-rich foods should be avoided because they increase GI motility in a time when bowel rest is desired." After it: "As symptoms subside, a low-residue diet should be started. Over several weeks, fiber should be gradually increased, and a high-fiber diet should be resumed to reduce the risk of diverticulitis recurrence." And the old food ban is gone: "In the past, doctors used to recommend avoiding nuts, popcorn, and seeds. However, more recent research suggests that these foods are not harmful to people with diverticulosis or diverticular disease."

Complications are handled by size and severity, and surgery is no longer counted in episodes. For "a small (< 4–5 cm) diverticular abscess," WSES suggests "an initial trial of non-operative treatment with antibiotics alone," and "large abscesses with percutaneous drainage combined with antibiotic treatment." "Patients presenting with hemodynamic instability and signs of peritonitis are candidates for emergent surgery," often a Hartmann procedure with "creation of an end colostomy." For elective surgery, the AGA says "An elective segmental resection should not be advised based on the number of diverticulitis episodes," and WSES agrees — patient factors, not the episode count, decide. Six to eight weeks later, look inside: "After an acute episode of diverticulitis colonoscopy should be delayed by 6–8 weeks or until complete resolution of the acute symptoms, whichever is longer," because "A malignancy can be misdiagnosed as diverticulitis."