Differential diagnosis of pseudomembranes
• Pseudomembranous colitis is a complication of antibiotic-associated colitis caused by C. difficile . Not all C. difficile infections produce pseudomembranous colitis. Grossly, discrete gray-white patches of pseudomembranes are identified. The histologic features include loosely adherent fibrinopurulent exudate on the luminal surface (pseudomembrane) with associated superficial mucosal necrosis.
• Features of Ischemic colitis damage include mucosal necrosis, hemorrhage with congestion in the lamina propria, hyalinization of lamina propria, occasional fibrin thrombi, and pseudomembrane (neutrophilic-fibrinous exudate) formation. In longstanding ischemic bowel, mucin depletion, regenerative change, lymphoplasmacytic infiltrate, hemosiderin pigment, and fibrosis of lamina propria are seen. Systemic vasculitis should be considered in the differential diagnosis in these cases.