Clostridioides difficile colitis

Clostridioides difficile colitis, also known as pseudomembranous colitis and previously known as Clostridium difficile colitis ¹⁰, is a common cause of antibiotic-associated diarrhea, and increasingly encountered in sick hospitalized patients. If undiagnosed and untreated, it continues to have high mortality. It may be classified as a form of infectious colitis.

Epidemiology

C. difficile infection is usually preceded by antibiotic use or chemotherapy and is therefore usually encountered in unwell, hospitalized patients with significant comorbidity. 

Clinical presentation

Typically, patients present with diarrhea, fever, raised white cell count, and abdominal pain with distension. 

Pathology

Clostridioides difficile (formerly Clostridium difficile ¹⁰) is a Gram-positive anaerobic bacterium that does not normally inhabit the bowel but can colonize it following disruption of normal colonic flora, commonly due to antibiotic use or chemotherapy within six weeks of onset ¹. C. difficile produces two toxins, A and B, both of which exert cytotoxic and enterotoxic effects on the bowel, with clinical manifestations primarily attributed to toxin B ⁴.

A pseudomembrane on the colonic mucosa, consisting of fibrin, white cells, and cellular debris, is characteristic of the condition ¹. Definitive diagnosis is achieved by isolating C. difficile toxin from the stool sample.

Radiographic features

Plain radiograph

Early in the disease, few findings may be evident on abdominal radiographs. Bowel dilatation, mural thickening and thumbprinting (due to thickening of the haustral folds) are seen later. Eventually, in untreated or fulminant cases, appearances will be those of toxic megacolon ³, with subsequent perforation and free intraperitoneal gas.

Ultrasound

The primary characteristic is a marked increase in the wall thickness of the affected colon segment, commonly the rectosigmoid region, with variable proximal extension. The mucosa often appears discontinuous and redundant, indicating ulceration and pseudo-membranous debris. Luminal collapse may occur. Doppler interrogation reveals preserved vascularity of the bowel wall. Haustral folds are present and may appear unusually thick and prominent. Free fluid between bowel loops typically exhibits a complex, heterogeneous echogenicity ⁹.

Fluoroscopy

Barium studies demonstrate the same findings as plain radiography. Additionally, the pseudomembrane may be visible on double contrast studies. The role of barium enema has significantly reduced in its use for the diagnosis of this entity due to the availability of CT and the risk of perforation ².

CT

Findings include ²:

• bowel wall thickening (most common)

• thumbprinting

• accordion sign

• shaggy mucosal outline

• pericolic stranding: is present but minimal as it is mainly a mucosal disease

• peritoneal free fluid (ascites) is seen in up to 40% of cases ⁸

• typically involves the whole colon ¹¹

  • limited involvement of the right colon is seen in 30-40% of cases

  • isolated involvement of segments of the colon or rectum alone is possible, but uncommon

• rectal involvement in the vast majority of cases (90-95%) ²

Treatment and prognosis

Treatment involves supportive therapy (fluid and electrolyte replacement) and eradication of C. difficile with antibiotics (usually vancomycin or metronidazole) ⁵. 

A novel treatment option is that of fecal transplant, whereby 'healthy' fecal matter is either administered via nasogastric tube or directly into the colon, after having been donated by a family member ⁵.

Untreated pseudomembranous colitis carries a high mortality from the sequelae of toxic megacolon and perforation.

Differential diagnosis

Other causes of toxic megacolon and colitis include:

• neutropenic colitis

  • can affect any portion of the small or large bowel, but is usually limited to the cecum ¹¹

  • less prominent wall thickening than in C. difficile colitis ¹¹

• inflammatory bowel disease

  • ulcerative colitis

  • Crohn disease

• ischemic colitis

• radiation-induced colitis

• colonic lymphoma: also causes thumbprinting

If there is a history of bone marrow transplantation and the bowel involvement is not limited to the colon, consider:

• gastrointestinal graft-versus-host disease ⁷

  • GvHD usually shows a discontinuous pattern of bowel involvement and frequently affects the small bowel ¹¹

  • less prominent wall thickening ¹¹