Colonic and Rectal Diseases: Diverticulosis and Ischemic Colitis
- Diverticuli represent protrusions of the colonic mucosa through areas weakened by the penetration of the vasa recta into the colonic wall.
- The prevalence of diverticulosis increases with age, rising from 30% at age 60 years, to 70% by 80 years of age.
- Diverticulosis is usually asymptomatic but complications include infection (diverticulitis) in 20% of patients, and bleeding in 5% of patients. Segmental inflammation of the sigmoid colon with resulting fibrosis and stricturing may occur.
- When stool obstructs the lumen of a diverticulum, an increase in the diverticular pressure ensues leading to decreased blood supply and necrosis. Diverticulitis is a contained perforation of a diverticulum with the formation of a pericolonic abscess. When the perforation is large it can lead to peritonitis and a life-threatening presentation.
- The typical presentation includes left lower quadrant pain, fever, and leukocytosis. Physical examination reveals left lower quadrant tenderness and occasionally a palpable mass. Peritoneal signs can be seen in severe cases.
- The diagnosis of diverticulitis is based on clinical evidence without the need for imaging. If the diagnosis is in doubt or there is a need to rule out complicated presentations, CT can be performed and is more than 80% sensitive. Flexible sigmoidoscopy should be avoided.
- Treatment of acute diverticulitis is achieved by hydration and a 10-day course of antibiotics. The route of administration can either be oral or intravenous depending on the severity of the presentation. Antibiotics should target both gram-negative bacilli and anaerobes. Large abscesses should be drained percutaneously, while surgery is indicated in cases of overt perforation and peritonitis.
- Contrary to common belief, dietary modifications such as avoiding seeds have no proven benefit in the prevention of diverticulitis.
• Diverticular bleeding
- 5% of patients with diverticulosis suffer a significant gastrointestinal bleeding.
- Up to 50% of patients hospitalized for lower gastrointestinal bleeding have a bleeding diverticulum.
- Diverticular bleeding is typically painless and self-limited.
- Since the risk of recurrent diverticular bleeding is approximately 25% after the first episode and 50% after a second episode, surgery to remove the affected segment of the colon should be entertained after a second bleed from the same segment. The use of endoscopy to pinpoint the bleeding source is complicated by the fact that diverticular bleeding often stops spontaneously before colonoscopy is done. Therefore, early colonoscopy after a quick bowel purge is preferred.
• Ischemic colitis is characterized by segmental inflammation and ulceration of the colonic mucosa as a result of a decrease in blood flow. In most cases the decreased blood flow is caused by a transient drop in blood pressure. Ischemic colitis usually afflicts older individuals with atherosclerotic disease.
• Ischemic colitis presents as bloody diarrhea with mild crampy abdominal pain.
• Plain abdominal radiographs may reveal submucosal edema described as thumb printing. Colon wall thickening can be seen on computed tomography. Endoscopy reveals segmental patchy erythema with ulceration of the affected area, but endoscopy is only indicated to exclude other possible causes of colitis.
• Treatment is usually supportive by ensuring adequate hydration, adequate perfusion pressure, and broad spectrum antibiotics.