Intestinal atresia

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Introduction0:00–0:38

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.

Duodenal atresia0:38–1:42

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 atresia1:42–2:34

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.
So for example, looking at the jejunum, if the vessels supplying it with blood are occluded then decreased perfusion leads to ischemic necrosis, which leads to segmental reabsorption and narrowing or complete destruction of the affected area.
This classically leads to an “apple peel” configuration due to it’s spiral shaped. Now, there are also some important clinical signs of duodenal atresia.

Signs, symptoms and diagnosis2:34–3:35

First, usually the developing fetus swallows and digests some amniotic fluid, but since a segment of the duodenum is narrowed or absent, the fluid has nowhere to go.
This leads to distention in both the stomach and duodenum, Which causes a “double-bubble” appearance on x-ray as a result of the inflated stomach and duodenum being separated by the muscular pyloric valve.
This distention can also be detected on a prenatal ultrasound. Also, though, since the fetus swallows less amniotic fluid, that means more fluid sticks around in the amniotic sac, which is called polyhydramnios.
Finally, the newborn might have bilious vomiting in the first few days of life, since bile’s secreted into the duodenum can’t be excreted and gets regurgitated back up with breast milk or formula, which also has no place to go.

Treatment3:35–4:08

Treatment of intestinal atresia involves gastric decompression, which is removing fluids from the stomach with a nasogastric tube, as well as making sure the newborn receives fluids intravenously.
The definitive treatment of intestinal atresia, though, is surgical removal and repair of the affected segment, which in the case of duodenal atresia is called a duodenoduodenostomy, since you’re attaching duodenum to duodenum.
Typically, prognosis following surgery is very good. Alright, as a quick recap, intestinal atresia and stenosis is where some portion of the intestine—which could be the small intestine or large intestine—is absent or narrowed.

Review4:08–4:44

Duodenal atresia is typically a result of a failure of recanalization, whereas non-duodenal atresias and stenoses are thought to be caused by ischemic injury.
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