Diverticulitis

Detailed Overview

Diverticulosis (presence of uninflamed diverticula) is extremely common in older adults. Diverticulitis occurs when these pouches become obstructed or experience microperforation, leading to localized inflammation or abscess formation. Uncomplicated diverticulitis is managed conservatively, whereas complicated cases (with abscess, fistula, macroperforation, or stricture) require hospitalization and often surgical intervention.

Epidemiology & Demographics

Affects 10-25% of individuals with diverticulosis. Incidence increases with age; 50% of people over 60 have diverticulosis. While traditionally a disease of the elderly, incidence is rising in patients under 50.

Etiological Mechanism

Results from microperforation of a diverticulum, likely triggered by increased intraluminal colonic pressure and inspissated fecal material (fecalith) eroding the diverticular wall.

Primary Causes

Low-fiber diet, connective tissue weakness, altered colonic motility.

• Diet: Low dietary fiber intake and high red meat consumption.
• Medications: Regular use of NSAIDs, aspirin, or corticosteroids increases risk of bleeding and perforation.
• Obesity and physical inactivity: Higher BMI correlates with an increased risk of diverticulitis.

Years of high colonic intraluminal pressure (due to low-fiber stool requiring vigorous peristalsis) push mucosa through weak points in the colonic wall where vasa recta penetrate the circular muscle layer, forming false diverticula. A fecalith becomes lodged in the diverticular sac, causing mechanical abrasion, localized ischemia, and overgrowth of normal colonic flora (Bacteroides, E. coli). This leads to microperforation. The body walls off the perforation with pericolic fat and mesentery, forming a localized phlegmon or abscess. If the body fails to wall it off, free macroperforation and frank peritonitis occur.

Characteristic Clinical Presentation

• Abdominal pain: Constant, aching pain usually localized to the left lower quadrant (LLQ).
• Change in bowel habits: Constipation is common, but diarrhea may occur.
• Systemic symptoms: Fever, chills, and nausea/vomiting.

Physical Examination Signs

• LLQ tenderness on palpation, sometimes with a palpable tender mass (phlegmon/abscess).
• Rebound tenderness and guarding (signs of localized or generalized peritonitis).
• Fever (>38.0 C) and tachycardia.

• Abscess: Collection of pus adjacent to the inflamed diverticulum.
• Colovesical fistula: Connection between colon and bladder causing pneumaturia and recurrent UTIs.
• Colonic stricture: Repeated episodes of inflammation causing fibrosis and bowel obstruction.

Diagnostic Criteria & Guidelines

Clinical diagnosis suspected by LLQ pain, fever, and leukocytosis. Confirmed by CT scan of the abdomen/pelvis with IV and oral contrast showing bowel wall thickening (>4 mm), pericolonic fat stranding, or complications (abscess, extraluminal air).

Differential Diagnosis

• Irritable Bowel Syndrome (IBS)
• Colorectal cancer
• Ischemic colitis
• Gynecologic causes (ovarian torsion, ruptured ectopic pregnancy)

Laboratory Tests & Biomarkers

• Complete Blood Count (CBC): Leukocytosis (WBC > 10,000/microL) with a left shift.
• CRP: Elevated > 50 mg/L.
• Urinalysis: May show mild sterile pyuria due to adjacent colonic inflammation.

Imaging Modalities & Findings

• CT Abdomen/Pelvis with contrast: Thickening of the sigmoid colon wall, surrounding mesenteric fat stranding, presence of diverticula.

• Uncomplicated
  Localized colonic wall thickening and pericolonic fat stranding without abscess or perforation.
• Hinchey I
  Pericolic or mesenteric abscess.
• Hinchey II
  Walled-off pelvic abscess.
• Hinchey III/IV
  Generalized purulent (III) or feculent (IV) peritonitis due to free macroperforation.

Second-Line & Adjunctive Therapy

Moderate/Severe (Inpatient): NPO, IV hydration. IV antibiotics: Ceftriaxone 1g IV daily + Metronidazole 500 mg IV Q8H, or Piperacillin-Tazobactam 3.375g IV Q6H.

Surgical & Procedural Management

Percutaneous CT-guided drainage for abscesses > 3-4 cm. Urgent surgical intervention (Hartmann procedure: sigmoid colectomy with end colostomy) for free perforation (Hinchey III/IV). Elective sigmoidectomy offered for recurrent complicated cases or fistulas.

Recommended Lifestyle Changes

• High-fiber diet (25-35g daily) once the acute attack has resolved (do not start during acute phase).
• Adequate fluid intake to prevent constipation.
• Nuts, seeds, and popcorn are NO LONGER contraindicated.

Patient Counseling & Advice

Explain that during an acute attack, bowel rest (clear liquids) is needed, but after recovery, a high-fiber diet is crucial to prevent recurrence. A colonoscopy is required 6-8 weeks after recovery to rule out hidden colon cancer.

Follow-Up & Monitoring Schedule

Follow up 2-3 days after starting outpatient treatment to ensure clinical improvement. Schedule colonoscopy 6-8 weeks post-recovery.

Preventive Strategies

Long-term high-fiber diet, avoiding chronic NSAID use, smoking cessation, and weight loss.

Uncomplicated diverticulitis resolves in 90% of cases with medical therapy. Recurrence rate is 20-30% within 5 years.