What is diverticulitis?

What is Diverticulitis?

Diverticulitis is an inflammatory condition that occurs when small pouches (diverticula) that form in the wall of the colon become infected or inflamed. 1 It represents a common complication of diverticulosis, which is the presence of multiple diverticula in the colon.

Pathophysiology and Classification

Diverticulitis develops when diverticula, which are outpouchings of the intestinal wall, become inflamed or infected. These diverticula form when the mucosa and submucosa herniate through weak points in the colonic wall, often at sites where blood vessels penetrate the muscle layer 2.

Diverticulitis is classified into two main categories:

1. Uncomplicated Diverticulitis:

   • Inflammation confined to the colon
   • No extension beyond the colon wall
   • Presents with diverticula, wall thickening, and increased density of pericolic fat 1

2. Complicated Diverticulitis:

   • Inflammation extends beyond the colon
   • Further classified based on severity:
     • Stage 1A: Pericolic air bubbles or small amount of pericolic fluid without abscess
     • Stage 1B: Abscess ≤ 4 cm
     • Stage 2A: Abscess > 4 cm
     • Stage 2B: Distant gas (> 5 cm from inflamed bowel segment)
     • Stage 3: Diffuse fluid without distant free gas
     • Stage 4: Diffuse fluid with distant free gas 1

Clinical Presentation

Typical symptoms of diverticulitis include:

• Acute pain or tenderness in the left lower quadrant
• Fever
• Nausea and vomiting
• Altered bowel habits (constipation or diarrhea)
• Increased inflammatory markers (elevated C-reactive protein and white blood cell count) 1, 2

Diagnosis

Diagnosis of diverticulitis requires a comprehensive approach:

• Clinical assessment: Left lower quadrant pain, fever, and leukocytosis are suggestive but not sufficient for diagnosis 1

• Imaging: Contrast-enhanced CT scan of the abdomen and pelvis is the gold standard diagnostic test with 98-99% sensitivity and 99-100% specificity 2

• Laboratory tests: Elevated white blood cell count and C-reactive protein levels support the diagnosis 1

Risk Factors

Several factors increase the risk of developing diverticulitis:

• Age over 65 years
• Obesity (BMI ≥ 30)
• Low-fiber diet
• Physical inactivity
• Smoking
• Use of medications such as NSAIDs, opioids, and steroids
• Genetic factors (variants in the TNFSF15 gene)
• Connective tissue diseases (polycystic kidney disease, Marfan syndrome, Ehlers-Danlos syndrome)
• Hypertension and type 2 diabetes 2

Management

Treatment depends on the severity of diverticulitis:

Uncomplicated Diverticulitis:

• Observation with pain management (typically acetaminophen)
• Dietary modification (clear liquid diet initially)
• Selective antibiotic use rather than routine administration in immunocompetent patients 1, 2

Antibiotics should be reserved for patients with:

• Systemic symptoms (persistent fever, chills)
• Increasing leukocytosis
• Age > 80 years
• Pregnancy
• Immunocompromised status
• Chronic medical conditions (cirrhosis, chronic kidney disease, heart failure, poorly controlled diabetes) 2

First-line antibiotics include:

• Oral: amoxicillin/clavulanic acid or cefalexin with metronidazole
• IV (if unable to tolerate oral intake): cefuroxime or ceftriaxone plus metronidazole, or ampicillin/sulbactam 2

Complicated Diverticulitis:

• Intravenous antibiotics: ceftriaxone plus metronidazole or piperacillin-tazobactam
• Percutaneous drainage for abscesses
• Surgical intervention for peritonitis, obstruction, fistula, or persistent symptoms 1, 2

Prevention of Recurrence

To reduce the risk of recurrence, patients should:

• Consume a high-quality, high-fiber diet
• Maintain normal body mass index
• Be physically active
• Avoid smoking
• Avoid NSAIDs (except aspirin prescribed for cardiovascular disease prevention) 1

Prognosis

• Mortality is low (approximately 1%) with medical therapy
• Mortality increases to about 4% for those requiring surgery
• Recurrence rates after medical management range from 13% to 36% 3
• The risk of complicated diverticulitis is highest with the first presentation 1

Important Caveats

1. Don't confuse with bladder diverticulitis: While we discussed colonic diverticulitis, bladder diverticulitis is an extremely rare condition affecting bladder diverticula 4.

2. Colonoscopy timing: After an episode of diverticulitis, the need for colonoscopy depends on the patient's history, most recent colonoscopy, and disease severity 1.

3. Surgical decisions: Elective segmental resection should not be based solely on the number of episodes but should be personalized considering disease severity, patient preferences, and risk-benefit assessment 1.