Diverticulitis

Diverticulitis of the colon is a potential complication of diverticulosis – a condition in which the mucosa and submucosa protrude through weak points in the intestinal wall, forming small pouches. These outpouchings most often develop in the sigmoid colon, the S-shaped segment of the large intestine, and typically occur in areas where blood vessels penetrate the muscular layer of the bowel¹. Traditionally, diverticulosis was considered an age-related disorder affecting mainly individuals over 50 years, but recent studies show a rising incidence among younger adults² ³.

Diverticulosis is usually asymptomatic, but acute diverticulitis can cause severe symptoms and, in some cases, become life-threatening. Earlier, it was estimated that 10–25% of individuals with diverticula would develop diverticulitis⁴. However, more recent data from colonoscopy and CT imaging suggest the true risk is likely below 5%⁵.

Epidemiology

Diverticulitis is more prevalent in Western countries compared to Asian regions, although recent data indicate a rising incidence in Asia, with a 0.5% annual increase⁵. In the United States, more than half of individuals over the age of 60 have diverticulosis, making it a widespread condition despite advances in diagnostics. Although prevalence increases with age, there has been a marked rise in younger patients: between 1980 and 2007, cases among people aged 40–49 years increased by 132%⁵.

Ethnic differences have also been observed. Hospital admission rates are highest among White individuals (62 per 100,000), followed by African Americans and Hispanics (around 30 per 100,000), with the lowest rates reported in Asians (10 per 100,000)⁵. Interestingly, immigrants from non-Western countries have lower risk upon arrival, but their risk increases the longer they live in Western societies. This pattern suggests that lifestyle factors play a significant role in the development of the disease⁵ ⁷.

Causes and Pathophysiology

Diverticula form through a combination of structural weakness in the bowel wall, increased intraluminal pressure, and low dietary fiber intake⁸. When the opening of a diverticulum becomes blocked, often by fecal material, local inflammation and bacterial overgrowth can occur. This process may lead to perforation, abscess formation, and, in severe cases, peritonitis.

The disease progression can be outlined as follows:

• Formation of diverticula: Small pouches develop in the bowel wall, usually in areas of high pressure and low fiber intake.

• Inflammation and infection: Obstruction of a diverticulum fosters bacterial growth, resulting in inflammation and localized infection.

• Altered gut flora: Ongoing inflammation may cause micro- or macroperforations, potentially leading to abscesses or generalized intra-abdominal infection.

• Immune response: The body attempts to control the infection, but this may also contribute to fibrosis and stricture formation.

• Complications: Severe inflammation can cause rupture, abscess formation, fistula, intestinal bleeding, or strictures leading to obstruction⁵.

Risk Factors

Several factors are associated with the development of diverticulitis⁹:

• Increasing age

• Chronic constipation

• Sedentary lifestyle

• Overweight, particularly abdominal obesity

• Smoking

• Use of NSAIDs

• Diet high in red meat, processed foods, and fat¹⁰

• Genetic predisposition¹¹

  
  

Symptoms and Clinical Presentation

Symptoms of diverticulitis vary widely in both intensity and duration. The most common include¹²:

• Acute abdominal pain, typically in the lower left quadrant (in about 49% of patients)

• Elevated temperature and increased inflammatory markers

• Palpable tender mass in the abdomen

• Altered bowel habits, including constipation or diarrhea

• Reduced or absent bowel sounds

• Bloating and excessive gas

• Fever

• Nausea and/or vomiting

• Hematochezia (blood in stool)

• Increased urinary frequency¹⁰ ³

Possible complications:

• Bowel perforation

• Abscess formation (in approximately 17%)¹³

• Fistula development

• Gastrointestinal bleeding

• Intestinal obstruction

• Perforated peritonitis (in 1–2%)¹⁴

Diagnosis

Diverticulitis is most often diagnosed during an acute episode, presenting with significant abdominal pain and systemic symptoms such as fever. The diagnosis is based on a combination of clinical findings, laboratory tests showing leukocytosis, and imaging studies¹². Because abdominal pain has many differential causes, several tests are used to confirm diverticulitis and exclude other pathologies.

• Ultrasound: A useful tool for detecting uncomplicated cases, allowing visualization of bowel wall inflammation and localized fluid collections.

• CT scan (computed tomography): The gold standard for diagnosing and staging diverticulitis. It provides precise information on the extent of inflammation, the presence of abscesses, perforation, or free air in the abdominal cavity³. Disease severity is commonly classified based on CT findings.

• Endoscopic evaluation: Reserved for selected cases, such as when biopsies are needed or when another diagnosis is suspected. Colonoscopy is generally contraindicated during acute diverticulitis due to the risk of perforation. After the acute episode has resolved, flexible sigmoidoscopy may be considered, as diverticula are most often located in the sigmoid colon¹⁶.

CT-Based Classification³

Grade	CT Findings
Mild	Bowel wall thickening, pericolic fat stranding
Moderate	Bowel wall >3 mm, phlegmon, or small abscess
Severe	Bowel wall >5 mm, perforation with free air, abscess >5 cm

Treatment

Management depends on the severity of disease, the patient’s overall condition, and the presence of complications. In mild cases, conservative treatment is often sufficient, while surgery may be required in severe or recurrent disease.

Uncomplicated diverticulitis (localized disease):

• Treatment generally involves rest, intravenous fluid therapy, and antibiotics.

• Antibiotic regimens should cover both aerobic and anaerobic bacteria, as recommended by the American Gastroenterology Association¹¹ ¹⁷.

Complicated disease or special considerations:

• Surgery is considered in cases with abscess formation, fistulas, bowel obstruction, or recurrent attacks in immunocompromised patients.

• Surgical intervention can be elective or emergent.

• Current practice emphasizes an individualized approach rather than simply counting the number of episodes, weighing disease severity, patient preferences, and risk–benefit of surgery¹¹.

Hartmann’s procedure:

• Common in severe disease.

• Involves removal of the diseased segment of the colon (typically sigmoid) with creation of a temporary colostomy, where the bowel is brought through the abdominal wall³.

Prevention

Preventing diverticulitis is closely linked to lifestyle and dietary habits. Measures shown to reduce risk include⁵ ¹⁰:

• High-fiber diet (vegetables, fruits, whole grains)

• Reduced intake of red and processed meats

• Adequate fluid intake and regular bowel habits

• Regular physical activity

• Smoking cessation

• Weight reduction in overweight individuals

Sources:

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17. Sartelli M, Weber DG, Kluger Y, et al. 2020 update of the WSES guidelines for the management of acute colonic diverticulitis in the emergency setting. World Journal of Emergency Surgery. 2020 Dec;15:1–8.

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