USMLE® Step 1 style questions USMLE
A 2-day-old infant girl is observed to have several episodes of bilious vomiting while in the nursery. The vomiting is triggered by feeding. She was born full-term to a 38-year-old, gravida 2 para 2, female via vaginal delivery. The pregnancy was complicated by polyhydramnios. The patient’s vitals are notable for hypotension and tachycardia. Examination of the skull reveals sunken anterior and posterior fontanelles. The patient is also observed to have upslanted palpebral fissure and prominent epicanthal folds. A single transverse palmar crease is noted on the bilateral hands. The patient has a scaphoid abdomen. Digital rectal examination reveals normal rectal tone and no expulsion of gas or stool. Which of the following best describes the pathophysiology of this patient’s condition?
Intestinal atresia exam links
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Tanner Marshall, MS
With intestinal atresia, atresia refers to a passageway that’s closed or gone completely, so intestinal atresia is when a malformation during fetal development results an absent portion of the small or large intestine.
If instead the passageway was just narrowed, then it’s referred to as intestinal stenosis—oftentimes these are both just lumped together as intestinal atresia and stenosis.
The specific type of intestinal atresia is named depending on what section of the intestines is affected.
Duodenal atresia or stenosis is where the first section—the duodenum—is affected.
The underlying cause of duodenal atresia isn’t known, although it’s commonly associated with trisomy 21, also known as Down syndrome, suggesting that it’s likely due to genetic defects affecting normal development.
Although it isn’t known why intestinal atresia develops isn’t known, it is fairly well known how it develops.
Normally, early on in development, the gut’s a hollow tube.
But by around 6 weeks gestation, the epithelium of the duodenum proliferates and it ends up plugging up the lumen making it a completely solid stick of tissue.
After that, the cells in the middle undergo apoptosis, or programmed cell death, and by 9 weeks gestation, the tube’s hollow again, called recanalization.
This entire process is called vacuolation.
In duodenal atresia, this vacuolation process fails, and the duodenum doesn’t recanalize properly, resulting in atresia or stenosis of the duodenum.
Non-duodenal intestinal atresias or stenoses, like those affecting the jejunum or ileum, or even affected the large intestine like the colon, are generally not a result of recanalization, and instead are more likely to result from ischemic injury, meaning lack of bloodflow, to the developing gut.
Now, the jejunum, ileum, and large intestine rely on blood supply from the superior mesenteric artery, while only part of the duodenum does.
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "A case of duodenal atresia with apple peel appearance: Challenging the current embryology" Journal of Clinical Neonatology (2014)
- "Duodenal atresia and stenosis: long-term follow-up over 30 years" Journal of Pediatric Surgery (2004)