<prompt> Which of the following is the earliest change in intestine which occurs in Crohns disease?Cobblestone appearanceAphthous ulcerPerforationStricture  <response>: Ans. b. Aphthous ulcerRef: Robbins and Cotran Pathologic Basis of Disease 9th Ed; Page No- 797 Crohns diseaseUlcerative colitisLocationTerminal ileum and colonSegmental with skip lesions, rectal sparingRectum; sigmoid colon, continuous colonic lesionsGross Morphology. Transmural inflammation noncaseating granuloma formation with lymphoid aggregates in mucosa. Cobblestone mucosa, creeping fat, bowel wall thickening string sign on barium swallow X-ray, linear ulcers, fissures. Fibrosis commonly seen. Mucosal and submucosal inflammation only. Friable mucosa with superficial andor deep ulcerations compare normal with diseased. Fibrosis is rareMicroscopic Morphology. It is chronic noncaseating granulomas. Associated with HLA-DR-1. Thl mediated.. TH17 cells may also be contributory.. IL-23 receptor polymorphisms is protective. Crypt abscesses and ulcers, bleeding, no granulomas.. Associated with HLA-DR-2. Th2 mediated. IL-10 gene polymorphism is associated with UC. s Crohns diseaseUlcerative colitisComplications. Malabsorptionmalnutrition, colorectal cancer increases risk with pancolitis. Fistulas e.g. enterovesical fistulae, which can cause recurrent UTI and pneumaturia, phlegmon abscess, strictures causing obstruction, perianal disease. Hosepipe appearance. Fulminant colitis,. Toxic megacolon present. Perforation is rare. Loss of haustra - lead pipe appearance on imaging. Garden-hose appearanceIntestinal Manifestation Diarrhea that may or may not be bloody Bloody diarrheaExtra intestinal Manifestations. Rash pyoderma gangrenosum, erythema nodosum, eye inflammation episcleritis, uveitis, oral ulcerations aphthous stomatitis, arthritis peripheral, spondylitis. Kidney stones usually calcium oxalate, gallstones. May be ? for anti-Saccharomyces cerevisiae antibodies ASCA. 1deg sclerosing cholangitis.. Associated with p-ANCATreatmentCorticosteroids, azathioprine, antibiotics e.g. ciprofloxacin, metronidazole, infliximab, adalimumab5-aminosalicylic preparationse.g. mesalamine, 6-mercaptopurine, infliximab,colectomy Crohns diseaseUlcerative colitis 