Best differentiating feature between ulcerative colitis and Crohn's disease is?

Ans. is 'a' i.e., Distribution of pseudopolyps * Pseudopolyps (inflammatory polyps) can be seen in both crohn's disease and ulcerative colitis "Pseudopolyps (inflammatory pseudopolyps) can be seen both in ulcerative colitis and crohns disease". - Clinical pathology.* In ulcerative colitis the distribution of these pseudopolyps can be diffuse but in crohn's disease the distribution cannot be diffuse because a classic feature of crohn's disease is the sharp demarcation of diseased bowel segments from the adjacent uninvolved bowel. When multiple bowel segments are involved the intervening bowel is essentially normal (skip lesions).* Establishing the distribution and extent of disease is essential in differentiating Crohn's disease from ulcerative colitis, in guiding therapeutic decisions, and in assigning colorectal cancer risk. Biopsies must be obtained even from normal-appearing areas to evaluate for any histologic evidence of disease activity, because this approach is more sensitive than macroscopic evaluation for inflammation.