What is diverticulitis?

What is Diverticulitis?

Diverticulitis is an inflammatory condition that occurs when diverticula (small pouches or outpouchings that form in the wall of the colon) become inflamed and/or infected. 1

Pathophysiology and Epidemiology

Diverticulitis develops from diverticulosis, which is the presence of diverticula without inflammation. Key facts about diverticulitis include:

• Diverticula form from herniation of colonic mucosa and submucosa through defects in the circular muscle layers, often at sites of penetrating blood vessels 2
• Only 5-10% of patients with diverticulosis develop acute diverticulitis 3
• Annual incidence in the US is approximately 180 per 100,000 people 2
• Results in approximately 200,000 hospital admissions annually with healthcare costs exceeding $6.3 billion per year 2
• Prevalence increases with age: <10% in those under 40 years, to 50-66% in those over 80 years 3

Risk Factors

Several factors increase the risk of developing diverticular disease:

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

Classification of Diverticulitis

According to the World Society of Emergency Surgery (WSES), diverticulitis is classified into:

1. Uncomplicated diverticulitis:

   • Inflammation limited to the colon without extension to the peritoneum
   • Characterized by diverticula, wall thickening, and increased density of pericolic fat

2. Complicated diverticulitis:

   • 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 and signs include:

• Left lower quadrant abdominal pain (most common symptom)
• Nausea and vomiting
• Fever
• Altered bowel habits (constipation or diarrhea)
• Leukocytosis (elevated white blood cell count) 1, 2

Diagnosis

The American College of Physicians recommends:

• CT imaging with contrast for patients with suspected acute left-sided colonic diverticulitis 1
• CT has a sensitivity of 98-99% and specificity of 99-100% 2
• CT findings include colonic wall thickening, pericolic fat stranding, and possible complications (abscess, perforation) 1

Clinical diagnosis alone lacks accuracy, with positive predictive value of only 0.65, compared to 0.95 with additional cross-sectional imaging 1

Management

Treatment depends on the severity of diverticulitis:

Uncomplicated Diverticulitis:

• Outpatient management is appropriate for most patients 1
• Selective use of antibiotics rather than routine use 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: oral amoxicillin/clavulanic acid or cefalexin with metronidazole 2

Complicated Diverticulitis:

• Intravenous antibiotics (ceftriaxone plus metronidazole or piperacillin-tazobactam)
• Percutaneous drainage for abscesses
• Surgical intervention for peritonitis, large abscesses, obstruction, or fistula formation 2

Prevention of Recurrence

To reduce risk of recurrence:

• High-quality diet with adequate fiber
• Maintaining normal body mass index
• Regular physical activity
• Smoking cessation
• Avoiding NSAIDs (except aspirin for cardiovascular prevention) 1

Complications

Potential complications of diverticulitis include:

• Abscess formation
• Perforation leading to peritonitis
• Fistula formation
• Obstruction
• Strictures
• Bleeding 1, 2

Prognosis

• Approximately 12% of diverticulitis cases are complicated 1
• Recurrence rate after an index episode is approximately 22% at 10 years 1
• Mortality is 0.5% for elective colon resection and 10.6% for emergent colon resection 2

It's important to note that the risk of complicated diverticulitis is highest with the first presentation, and decisions regarding elective surgery should be personalized rather than based solely on the number of episodes 1.