Irritable bowel syndrome, diverticulosis, and diverticulitis – etiology, pathogenesis, and clinical manifestations.
Etiology
- Exact cause unknown (multifactorial).
- Possible contributors:
- Visceral hypersensitivity (increased sensitivity to gut distension).
- Abnormal gut motility.
- Post- infectious changes (after gastroenteritis).
- Stress and psychological factors.
Pathogenesis
- Altered brain–gut axis → dysregulation of intestinal motility and pain perception.
- Episodes of abnormal contractions → alternating diarrhea and constipation.
- No structural or biochemical abnormalities (functional disorder).
Clinical manifestations
- Recurrent abdominal pain or discomfort, relieved by defecation.
- Altered bowel habits:
- Diarrhea - predominant.
- Constipation- predominant.
- Mixed.
- Bloating, excess gas.
- Mucus in stool (sometimes).
Diverticulosis
Etiology
- Low- fiber diet (most important).
- Aging (weakening of colonic wall).
- Increased intraluminal pressure (e.g., from straining).
Pathogenesis
- 1 Increased pressure in sigmoid colon → herniation of mucosa and submucosa through weak points in muscularis propria → formation of diverticula (false
diverticula).
- 2 Usually asymptomatic.
Clinical manifestations
- Mostly asymptomatic (found incidentally).
- Possible vague left lower quadrant discomfort.
- Irregular bowel habits.
Diverticulitis
Etiology
Complication of diverticulosis when a diverticulum becomes inflamed.
Pathogenesis
- Obstruction of diverticular neck by fecalith (hard stool fragment).
- Localized bacterial overgrowth → inflammation and microperforation.
- Surrounding fat and mesentery wall off infection → localized abscess possible.
Clinical manifestations
- Constant left lower quadrant pain ("left-sided appendicitis").
- Fever, chills.
- Tenderness over affected area.
- Change in bowel habits (constipation or diarrhea).
- Possible complications:
- Abscess.
- Perforation → peritonitis.
- Fistula formation (e.g., colovesical fistula → pneumaturia).
- Stricture → bowel obstruction.