Radiating Hope: Radiology Department Blog


Pyloric Stenosis, What does that mean?

Post Date: July 13, 2021
Pyloric Stenosis, What does that mean?

Abnormal, thick pylorus-Distended Stomach?

What is the pylorus?

The pylorus is the lower portion of the stomach that connects the stomach to the small bowel (duodenum). Normally food passes from the stomach to the small bowel through the pylorus without any problem.

So what happens in pyloric stenosis? 

Normal pylorus-Abnormal thick pylorus preventing passage of food
Normal pylorus (green arrow)?. Abnormal thick pylorus preventing passage of food (pink arrow)

In pyloric stenosis, the muscles in this part of the stomach enlarge, narrowing the opening of the pylorus and eventually preventing food from moving from the stomach to the intestine leading to forceful vomiting and dehydration. Vomiting might be mild at first and gradually become more severe as the pylorus opening narrows.?Babies who have pyloric stenosis often want to eat soon after vomiting.

Symptoms present between three and five weeks of age and very rarely occur after 12 weeks of age. Pyloric stenosis is more common in male babies, in preterm babies and in firstborn children.

Why does it happen?

We don’t know, but it is likely due to multiple causes involving genetic and environmental causes.

Environmental factors such as:

  • Smoking: ?Studies showed a 1.5 to 2-fold increased risk of pyloric stenosis among babies of pregnant women (1).
  • Bottle feeding: One study showed that bottle-fed infants experienced a 4.6-fold higher risk of pyloric stenosis compared with infants who were not bottle-fed (2).
  • Medication: The use of some antibiotics particularly when administered to infants younger than two weeks of age?increased the risk of developing pyloric stenosis (3).


How is the diagnosis done? 

In addition to the history and the physical examination, the doctor will request an ultrasound. Ultrasound is the main imaging modality used to diagnose pyloric stenosis. It helps us to see the pylorus, evaluate its size and look for fluid passing through the pylorus into the small bowel.

Abnormal, thick pylorus-Distended Stomach?
Abnormal, thick pylorus (green arrows)?. Distended Stomach (pink arrow)?

Normal pylorus-Normal, non distended stomach
Normal pylorus (green arrows)?. Normal, non-distended stomach (pink arrow)

How is pyloric stenosis treated? 

Usually, pyloric stenosis is treated with surgery to widen the pylorus so that food can pass through it into the intestines.


Abu Ata template

Dr. Nadeen K Abu Ata, author; Glenn Miñano, BFA, editor; Meredith Towbin, copy editor



  1. Svenningsson A, Svensson T, Akre O, Nordenskjöld A. Maternal and pregnancy characteristics and risk of infantile hypertrophic pyloric stenosis. J Pediatr Surg. 2014 Aug;49(8):1226-31. doi: 10.1016/j.jpedsurg.2014.01.053. Epub 2014 Feb 10. PMID: 25092081. 
  2. Krogh C, Biggar RJ, Fischer TK, Lindholm M, Wohlfahrt J, Melbye M. Bottle-feeding and the Risk of Pyloric Stenosis. Pediatrics. 2012 Oct;130(4):e943-9. doi: 10.1542/peds.2011-2785. Epub 2012 Sep 3. PMID: 22945411; PMCID: PMC3457615. 
  3. Honein MA, Paulozzi LJ, Himelright IM, Lee B, Cragan JD, Patterson L, Correa A, Hall S, Erickson JD. Infantile hypertrophic pyloric stenosis after pertussis prophylaxis with erythromcyin: a case review and cohort study. Lancet. 1999 Dec 18-25;354(9196):2101-5. doi: 10.1016/s0140-6736(99)10073-4. Erratum in: Lancet 2000 Feb 26;355(9205):758. PMID: 10609814. 


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About the author: Glenn Miñano

Glenn Miñano is a media specialist in the Department of Radiology, providing graphic design, photography, printing, video services, and administration of the department’s online properties. His works have been published in several medical articles, such as the American Journal of Radiology and the American Institute of Ultrasound. He has been providing these services to the Radiology Department since 1996.