This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
The pathological appearance in pseudomembranous colitis consists of - 
Select and explain. 
A. Necrosis and gangrene, B. Small ulceration with slough, C. Serositis with covered by membrane, D. Excessive ulceration in serosa
B: Small ulceration with slough
Answer: B: Small ulceration with slough 
Explanation: Pseudomembranous colitis is an acute colitis characterised by the formation of an adherent inflammatory exudate (pseudomembrane) overlying sites of mucosal injury. The mucosal injury is in the form of superficial necrosis (small ulcerations). The necrotic mucosa and exudate remain adherent to the mucosal surface as yellow plaques or membranes (slough).
Remember: The Most common cause of pseudomembranous colitis is:
C. Difficile (a normal gut commensal) (caused by exotoxins A and B).
But, pseudomembrane formation is not restricted to C. Difficile. It may also occur after any mucosal injury as in ischemic colitis. Volvulus, and with necrotizing infections such as staphylococci, shigella, candida, and necrotizing enterocolitis.