HY lecture notes:
What is IBS? –> Irritable bowel syndrome à classically constipation +/- diarrhea +/- other GI Sx like cramping pain or GERD-like Sx that are relieved with defecation –> there are many ways to Tx IBS, such as starting with psych screen, but if the USMLE asks about meds, they like lubiprostone, which is used for constipation-predominant IBS (PGE1 analogue that causes increased Cl secretion in bowel –> Na follows Cl à water follows Na –> softens stool).
Travel + self-limiting watery or brown/green diarrhea; Dx? –> Traveler diarrhea = ETEC HL or HS toxin.
Bloody diarrhea + poultry consumption –> Campylobacter jejuni or Salmonella spp.
Abx (clindamycin, beta-lactam, cephalosporin) + diarrhea –> C. difficile.
Dx of C. diff –> stool AB toxin test, not stool culture.
Fever of 104 + abdo distension in C diff –> toxic megacolon –> laparotomy.
Tx of C. diff –> vancomycin, not metronidazole (updated guidelines as of Feb 2018).
Bloody diarrhea + travel –> Entamoeba histolytica.
Tx of E. histolytica –> metronidazole + iodoquinol; can give paromomycin.
Close quarters or military barracks or cruise ship + watery diarrhea –> Norwalk virus.
Child <5 years + watery diarrhea –> rotavirus.
Few organisms causing bloody diarrhea –> Shigella.
Bloody diarrhea + appendicitis-like pain (pseudoappendicitis) in a child –>Yersinia enterocolitica.
Bloody diarrhea + reactive arthritis in an adult –> Y. enterocolitica, Campylobacter, Shigella, Salmonella.
Diarrhea + Guillain-Barre syndrome –> Campylobacter.
Vomiting a few hours after eating meat –> aureus preformed heat-stable toxin.
Vomiting (or any unusual Sx like bloody diarrhea) + eating custards, creams, potato salad –> answer = S. aureus preformed HS toxin –> the type of food in this scenario “wins” over the weird bloody diarrhea finding –> bear in mind typical bloody-diarrhea-inducing gram (-) rods like EHEC, Yersinia enterocolitica, Campylobacter, Shigella, Salmonella have ~1-3-day incubation period) –> iow, if you get sick on the scale of hours from food, S. aureus preformed toxin is likely.
25F + intermittent bloody diarrhea for 3 months + intermittent fever + weight loss –> answer IBD (Crohn or UC).
Tx for Crohn + UC –> USMLE wants oral sulfasalazine (or mesalamine) first before oral steroids; for perianal disease in Crohn, topical agents / enemas can be used; NBME won’t make you pick between oral and topical distinguish (that’s more Qbank being pedantic); surgery can be done for UC.
UC + high bilirubin + high ALP –> primary sclerosing cholangitis.
Red shins + Crohn –> erythema nodosum (type III hypersensitivity; panniculitis –> inflammation of subcutaneous fat, not a rash).
Crater with necrotic debris on forearm + UC –> pyoderma gangrenosum.
IBD + eczematoid plaque on forehead + sore joints –> psoriatic arthritis (HLA-B27 –> PAIR à Psoriasis, Ankylosing spondylitis, IBD, Reactive arthritis).
IBD + back pain –> sacroiliitis (or ankylosing spondylitis).
Biopsy in Crohn –> non-caseating granulomas; transmural; UC you don’t see these findings.
Vesicles anywhere on body (not limited for extensors) + Celiac –> dermatitis herpetiformis.
Biopsy of DH –> IgA deposition at dermal papillae.
Biopsy of small bowel in Celiac –> flattening of intestinal villi.
Dx of Celiac –> IgA anti-tissue transglutaminase, anti-gliadin (aka anti-endomysial).
After Celiac Ab positivity, what’s the next best step (no further intervention necessary or duodenal biopsy) –> answer = duodenal biopsy (sounds wrong, but it’s what USMLE wants).
Weird factoid about Celiac –> increased risk of T cell lymphoma.
Biopsy of small bowel in lactose intolerance –> normal villi.
Dx of lactose intolerance –> hydrogen breath test or decreased stool pH.
Vague vignette where it sounds like either Celiac or lactose intolerance but it’s in a young adult who’s had zero symptoms until now –> lactose intolerance (can be adult-onset).
Watery diarrhea in immunocompromised patient –> Cryptosporidium parvum.
How is Giardia transmitted (is the answer “water-borne” or “fecal-oral”?); answer –> water-borne.
Steatorrhea in guy who went swimming or scuba diving –> Giardia.
Tx for Giardia –> metronidazole.
Fever + periorbital edema + muscle aches + went to a BBQ; Dx? –> Trichinella spiralis –> this is a classic triad seen in trichinosis.
How do you get trichinosis? –> bear meat (yes, Alaska is still in the United States and people hunt polar bear) or pork (pork nematode, not cestode).
What is nematode vs cestode vs trematode? –> nematode is roundworm; cestode tapeworm; trematodes are flukes.
Nematode from pork –> Trichinella spiralis.
Cestode (tapeworm) from pork –> Taenia solium.
What does T. solium cause? –> cysticersosis (muscle cysts) or neurocysticercosis (brain cysts).
“Swiss cheese appearance” of brain in someone who traveled abroad –> neurocysticercosis.
Single cystic lesion seen on brain CT in someone who went to Mexico –> neurocysticercosis.
Tx for cysticersosis / neurocysticercosis –> praziquantel or albendazole (the USMLE will never give you both and make you choose between them; for anti-helminth drugs questions, the correct answer will be the only anti-helminth drug listed).
