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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 :) +  
pg32  Yeah, recall that the midgut rotates AROUND THE SMA in development. If you can recognize that the ligament of Treitz is on the wrong side (right) then you know you have a malrotation issue. Then you recall the midgut rotates around the SMA and you pick that answer out of pure association recall and get it right. Nice. +  




 +2  upvote downvote
submitted by alexb(25),

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 +  
carmustine  UWorld question ID 318 +  




 +1  upvote downvote
submitted by moloko270(43),

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 yotsubato(416),

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(154),

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