USMLE step 3: uworld practice test 2 Question and Answer

3 yo M has a 8 day hx of 3-4 daily episodes of soft, *foul-smelling diarrhea*. Increased belching & Flatus, decreased appetite but drinks liquids without difficulty. 6 yr old sister has same sx. Fam went on cruise to Mexico last month so he tried new foods and went swimming at beach&in cruise ship pool. Went on wkd camping trip 3 wks ago and ate the fresh fish. After vacation, he went back to reg diet fruits, veggies 7 meats. P 108, hyperactive bowel sounds. negative stool occult blood. CAUSE of sx? - *giardia lamblia* -greasy, foul-smelling diarrhea, bloating, flatus/belching, weight loss -transmitted thru *fecal-oral route* or thru *contaminated food or water* -ingestion of unfiltered water while *camping* or hiking --drinking, swimming or consuming food from contaminated water -sx DON't present ASAP b/c takes time for cysts to mature into trophozoites in host intestines -tx: *metronidazole* norovirus - -causes viral gastroenteritis -*cruise-ship* outbreaks -BRIEF duration: resolves within days -*VOMITING more common*rota rotavirus - *watery diarrhea* in kids age 2 and under -within 1-2 DAYS of exposure -also emesis, abd pain meta-analysis - -combines results of *several studies* to *increase statistical power* thru an *increased sample size* -ideally, the results are the same as produced by single study w/larger sample size -BUT *increase in statistical power may lead to *statistically SIGNIFICANT* effect sizes that maybe *CLINICALLY IRRELEVANT*=detects a very small effect(eg risk ratio)--not practical ---also, *validity depends on the design*-metanalysis isn't always more valid than other study designs cephalohematoma vs caput succedaneum - cephalohematoma: DOESN'T cross suture lines & resolves within WEEKS, *can lead to jaundice* b/c RBC breakdown&Calcification after resolution-located UNDER periosteum Caput succedaneum: like a CAP crosses suture lines&resolves DAYS after birth-serosanuineous fluid collection above periosteum/beneath scalp subgaleal hemorrhage - -bleeding under galea aponeurotica -fatal complication of vacuum-assisted deliveries -rapidly expanding swelling leading to hypovolemic shock from blood loss 2 week old girl has *asymmetric gluteal skinfolds&increased # thigh creases on rightleft*. what else would be found? - *Apparent leg-length discrepancy* when pt lies supine w/knees flexed: affected leg looks shorter(Galeazzi test) DX: developmental dysplasia of hip -abnormal development of hip joint tht prevents femoral head from sitting properly in acetabulum -RF: *females, breech position, FH DDH, excessively tight swaddling* -instability during attempted dislocation&reduction if palpable clunk heard (Barlow and Ortolani maneuvers) who has asymmetric moro reflex? - erb palsy (seen in large for gestational age infants) who has sacral dimple? - neural tube defect (myelomeningocele) what's the next step after u/s shows dislocated right hip w/flat acetabulum and positive barlow and ortolani tests? - *Consult orthopedic surgeon* --when ID within first 6 months of life, treat by maintaining hip in *flexed&abducted position in Pavlik harness for 3 months* -when hip extension & adduction are limited, the dislocated hip is reduced and/or stabilized and normal acetabular development is promoted --monitor pavlik harness closely by orthopedic surgeon b/c associated risks( avascular necrosis, femoral nerve palsy) w/excessive hip flexion & abduction