Colonic diverticulosis and bowel obstruction

A) Colonic Diverticulosis

Diverticulum = a blind pouch that communicates with the lumen of the gut

• Congenital diverticulum: all 3 bowel layers (mucosa, submucosa, muscularis propria); distinctly uncommon
• Acquired diverticulum (most common form): lack or have attenuated muscularis propria; most common location = colon → diverticulosis

Pathomechanism

• Low fiber diet → ↓ stool bulk + ↑ difficulty in passage → abnormal ↑ intraluminal pressure → herniation of bowel wall through anatomical points of weakness
• Weakness sites: outer longitudinal muscle coat is incomplete (gathered into taenia coli); focal defects where nerves/vessels penetrate circular muscle alongside taenia
• Two key influences: (1) exaggerated peristaltic contractions + (2) focal defects

Complications

• Stool collection in diverticula → mucosal irritation → bleeding
• Diverticulitis:
  • Mild: fibrous tissue encasement → lumen narrowing
  • Severe: perforation → peritonitis or abscess formation

Clinical

• Usually asymptomatic
• Intermittent cramping, left-sided lower quadrant discomfort, sensation of incomplete rectal emptying
• Diverticulitis: tenderness + fever
• Treatment: high fiber diet to lower intraluminal pressure

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B) Bowel Obstruction

• Small bowel is most commonly affected (narrow lumen)

Consequences

• Bowels proximal to obstruction: progressive dilation; wall thinned; lumen filled with fluid and gas
• Gas-producing bacterial overgrowth in stagnating intestinal content
• Strangulation-induced bowel infarction, peritonitis
• Elevation of the diaphragm
• Clinical: colicky abdominal pain + distention, constipation without passage of wind

Causes of Bowel Obstruction

1. Hernias

• Weakness/defect in abdominal wall → protrusion of pouch-like serosa-lined sac (hernial sac)
• Common sites: inguinal + femoral canals, umbilicus, surgical scars
• Trapped viscera → pressure at neck → impaired venous drainage → stasis + edema → incarceration (permanent trapping)
• Further compromise of blood supply → strangulation → infarction

2. Intestinal Adhesions

• Surgical procedures, infections, endometriosis → peritoneal inflammation → peritonitis
• Adhesions create closed loops → intestine may slide and become trapped (internal herniation)

3. Intussusception (invagination)

• Proximal bowel segment invaginates (“telescopes”) into the distal segment
• Children: sometimes idiopathic (excessive peristaltic activity)
• Adults: often points to an intraluminal mass (tumor)
• Can cause obstruction + compromised vascular supply → infarction

4. Volvulus

• Twisting of a loop of bowel around its base of attachment → constricting venous outflow
• Mostly in the sigmoid colon
• May lead to intestinal obstruction and infarction

💡 High-yield: Diverticulosis = low-fiber diet + acquired; colon; complication = bleeding + diverticulitis + perforation. Bowel obstruction = small bowel most common. Hernia: incarceration (trapped) → strangulation (infarcted). Intussusception = telescoping; children = idiopathic; adults = tumor. Volvulus = twisting; sigmoid colon.