<prompt> Skip lesions are seen in:Ulcerative colitisCrohns diseaseTyphoidTuberculosis  <response>: Ans is b i.e. Crohns disease FeaturesUlcerative colitisCrohns ds Rectal involvement in 50 90Rectum spared Distribution of lesionsContinuousSkip lesions Mucosal appearanceFriable, diffusely involvedCobblestoneappearance Ileal diseaseRare backwash ileitisCommon Perianal abcess, fistulasRareCommon Intestinal strictures obstructionNot seenCommon Intestinal fistulasNot seenCommon Fissures RadiologicalNot seenCommon UlcersCollar-buttonLinear, cobblestone, fissures Toxic megacolonRare but more than Crohns dsVery rare Extraintestinal Manifestation - - Sclerosing pericholangitisCommonRare- Uveitis Arthritis CommonCommon- Pyoderma gangrenosumCommonRarePathological Features Depth of inflammationMucosal,superficialTransmural ,deep Creeping mesentric fatNot seenCommon Fibrous thickening of wallNot seenCommon lead pipe PseudopolypsCommonRare GranulomasNot seenCommon DysplasiaCommonRare Carcinoma10Rare 