Sigmoid diverticulitis complicated by intramural abscess

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 Sigmoid diverticulitis

Sigmoid diverticulitis complicated by an intramural abscess is a severe form of diverticulitis, where inflammation and infection of the diverticula (pouches in the wall of the colon) progress to form an abscess within the colon wall. This is a complex and potentially dangerous condition requiring prompt diagnosis and treatment.

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1. Cause:

The primary cause of sigmoid diverticulitis is the inflammation and infection of diverticula in the sigmoid colon. Diverticula are small pouches that can form in weakened areas of the colonic wall, often due to increased intraluminal pressure. When one or more of these diverticula become inflamed and infected, diverticulitis occurs. If untreated, diverticulitis can lead to complications like perforation, fistula formation, or abscesses.

An intramural abscess refers to a collection of pus within the colon's wall. This complication is typically due to localized infection and inflammation spreading into the surrounding tissues of the bowel wall, leading to the formation of an abscess within the muscular or submucosal layers.

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2. Etiology:

  • Diverticulosis is the precursor condition. Most cases of diverticulitis are caused by long-term diverticulosis.
  • Infection: Most cases of diverticulitis are associated with the overgrowth of colonic bacteria (such as Bacteroides, E. coli, and other anaerobes) within the diverticula. This leads to localized inflammation and infection.
  • Dietary factors: A low-fiber diet, which increases intracolonic pressure, is a major risk factor.
  • Age and genetics: Diverticulosis becomes more common with age, particularly after the age of 50. There may also be a genetic predisposition in some individuals.

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3. Pathophysiology:

The pathophysiology of diverticulitis complicated by an intramural abscess involves several stages:

  • Diverticula formation: The formation of diverticula occurs due to chronic increased pressure within the colon, which pushes the mucosal and submucosal layers through weak areas of the colonic wall, typically at the site of blood vessel penetration.
  • Inflammation and infection: In diverticulitis, the diverticula become inflamed, often due to bacterial infection. The inflammation can lead to swelling, erythema, and necrosis of the bowel wall.
  • Abscess formation: If the infection progresses and is not controlled, the abscess may form in the colon wall. This is an intramural abscess, which is confined to the wall of the colon, unlike a free perforation that involves the peritoneal cavity.
  • Complications: If untreated, this may lead to further complications like perforation, peritonitis, or fistula formation.

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4. Epidemiology:

  • Prevalence: Diverticulosis is common in Western populations, particularly among those over 40 years of age. The incidence of diverticulitis increases with age, and around 10-25% of people with diverticulosis develop diverticulitis.
  • Complications: Diverticulitis complicated by an intramural abscess is a relatively rare but serious complication, occurring more commonly in older patients or those with recurrent or severe cases of diverticulitis.
  • Risk factors:
    • Age > 50 years
    • Obesity
    • Low-fiber diet
    • Smoking
    • Sedentary lifestyle

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5. Clinical Presentation:

The clinical presentation of sigmoid diverticulitis complicated by an intramural abscess often includes the following features:

  • Abdominal pain: Typically located in the lower left quadrant, which is characteristic of sigmoid diverticulitis.
  • Fever and chills: Signs of systemic infection.
  • Nausea and vomiting: Due to bowel obstruction or irritation.
  • Altered bowel habits: Diarrhea or constipation can occur, with some patients experiencing obstructive symptoms.
  • Tenderness: Localized tenderness or a palpable mass in the lower left abdomen (indicative of an abscess or inflammation).
  • Signs of sepsis: In more severe cases, patients may present with tachycardia, hypotension, and altered mental status due to systemic infection.

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6. Imaging Features:

Imaging plays a crucial role in diagnosing diverticulitis and identifying complications like intramural abscesses:

·         CT scan (contrast-enhanced): The gold standard for diagnosing complicated diverticulitis.


 CT findings of an intramural abscess include:

o    Thickened colonic wall in the sigmoid colon.

o    Presence of an abscess within the colonic wall or pericolonic area.

o    Bowel wall enhancement on contrast imaging.

o    In severe cases, the presence of free air if perforation has occurred.

·         Ultrasound: May show a localized collection of fluid, although it is less sensitive than CT.


·         Barium enema



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7. Treatment:

The treatment of sigmoid diverticulitis complicated by an intramural abscess typically involves a combination of medical and surgical management:

  • Medical management:
    • Antibiotics: Broad-spectrum antibiotics targeting anaerobes and Gram-negative bacteria (e.g., metronidazole plus ciprofloxacin or piperacillin-tazobactam).
    • Bowel rest: Patients are typically advised to avoid oral intake to rest the bowel.
    • Fluid resuscitation: IV fluids for hydration and correction of electrolyte imbalances, especially if the patient is febrile or septic.
    • Drainage: In cases of large abscesses, percutaneous drainage may be considered. This is typically guided by imaging (usually CT).
  • Surgical management:
    • Surgery may be required if there is a large or inaccessible abscess, signs of perforation, or if the patient does not improve with conservative measures. Surgical options may include:
      • Resection of the affected colon: This may involve removing the affected segment of the colon (typically a sigmoid colectomy).

Colostomy: In severe cases, a temporary colostomy may be needed to divert fecal material while the colon heals.

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8. Prognosis:

The prognosis for sigmoid diverticulitis complicated by an intramural abscess depends on the severity of the disease and the timeliness of treatment:

  • Mild to moderate cases can usually be managed with antibiotics and percutaneous drainage, and most patients recover without long-term issues.
  • Severe cases with large abscesses, perforation, or peritonitis may have a poorer prognosis and require more aggressive surgical intervention. Complications like sepsis or persistent infection can lead to prolonged recovery times and higher mortality rates.
  • Recurrence: Some patients may experience recurrent episodes of diverticulitis, increasing the need for surgical intervention in the future.

In summary, sigmoid diverticulitis complicated by intramural abscess is a serious condition that requires timely and effective treatment. Imaging, particularly CT, plays a crucial role in diagnosis and management, and appropriate medical and/or surgical interventions are key to improving outcomes.

 

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