USMLE GIT 9: IBD Explained! (Chron's Disease and Ulcerative Colitis) 

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/ lymed * Mistake at around 7:30: Said Chron's instead of Ulcerative Colitis
Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day.
Follow along with First Aid, or with my notes which can be found here: www.dropbox.com/sh/m55dzy5jju...
This video is going to be on some more intestinal pathology! Here, we will talk about a group of diseases called inflammatory bowel disease. The two major subtypes that you need to know is Chron's disease and ulcerative colitis. While no one is sure what exactly causes IBD, it seems to have an autoimmune component, as well as environmental factors and bacterial factors. Whatever the case may be, you need to know the two and how to differentiate the two.
Ulcerative colitis: this is a continuous inflammation that starts at the rectum and moves up the colon. Chron's skips around, causing skip lesions but most commonly affects the terminal ileum. This can lead to b12 deficiency and megaloblastic anemia! Because of this difference in location, UC more commonly causes bloody diarrhea, LLQ pain and can be resected to cure the disease.
The two also differ due to the nature of inflammation. UC usually involves the mucosa and submucosa. Chron's is usually transmural. In UC, due to it's superficial nature, it can affect the haustra and lead to straight pipe on imaging, ulcers and pseudopolyps. In Chron's due to it's transmural inflammation it can lead to fistulas and strictures, as well as perianal disease.
Now just a quick run down. There are extra-GIT manifestations of IBD. These include things like pyoderma gangrenosum, erythema nodosum, uveitis, aphthous ulcers, and ARTHRITIS! Never forget IBD is associated with HLA-B27 arthropathies! Unique complications to UC include primary sclerosing cholangitis. The main lab finding is this is that it's P-ANCA positive. Unique complications seen in Chron's is calcium oxalate stones.
Pharmacology includes things to suppress immune response. This includes corticosteroids, MABs against TNF-a, antibiotics and drugs like sulfasalazine.