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NBME 22 Answers

nbme22/Block 4/Question#1

A 2-day-old full-term female newborn suddenly ...

Superior mesenteric

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I believe this is referring to midgut malrotation. Due to improper positioning of bowel (on the right side). Ladds bands connect the large intestine to the liver.

Can lead to:

  1. Volvulus

  2. Duodenal obstruction

3. SMA Occlusion -- I'm guessing based on the answer to the question

meningitis  Yes, the question clicked for me when I realized the ligament was on the RT side instead of LT so I thought of Volvulus. Image of ligament of treitz: https://media.springernature.com/original/springer-static/image/chp:10.1007/978-3-642-13327-5_17/MediaObjects/978-3-642-13327-5_17_Fig3_HTML.gif +1  
hyperfukus  So Volvulus regardless in baby or adult is gonna cause SMA prob + Duodenal Obstruction: d/t Ladd bands im gonna go back and remember those associations :) +  




 +1  upvote downvote
submitted by moloko270(31),

just know probably that anatomically SMA runs above third part of duodenum. so if we have a ligament pulling over that side it can obstruct both duodenum (was mentioned in stem) and SMA that lies over it

in GI section they also describe SMA syndrome - when SMA obstructs the duodenum itself so its stuck between SMA and aorta. guessing from there





 +1  upvote downvote
submitted by alexb(15),

There is a decent UWorld question explaining how this works. Only reason I remembered it.

hyperfukus  i had notes from forever ago but i totally forgot lol +  




 +1  upvote downvote
submitted by yotsubato(309),

Celiac: doesnt make sense, it comes out of the root of the aorta and ends instantly. Thats not getting caught up in the volvulus alone.

Left/right colic: thats all IMA branches, thats uninvolved in the situation.

Umbilical: that getting occluded is physiologic after birth.

Whats left is SMA: which goes right above the duodenum, so i would imagine a duodenal volvulus would involve the SMA easily.





Newly born → ligament of Treitz on the wrong side → something went wrong with rotation...

In the 10th week the midgud rotates 270 degrees counterclockwise around the superior mesenteric artery (FA2019 pg352).





 +0  upvote downvote
submitted by stha123(0),

Superior mesenteric artery syndrome is a rare abnormality caused by a congenitally short suspensory muscle.





 +0  upvote downvote
submitted by nwinkelmann(111),

This is a good animation video of abnormalities of gut rotation (MUSIC IS WEIRD, lol): https://www.youtube.com/watch?v=gT85dJTT2QE and part 1 if you want to see a good animation of the normal gut rotation (also weird music, i.e. is the same, lol): https://www.youtube.com/watch?v=49awxUGZvdY