Pyloric stenosis

Written by: Dr. Faria Rahman

Edited by: Dr. Joann Hsu

The case

5 week old male sent by pediatrician for vomiting after feeding for 2 weeks. Mom states that the baby has been vomiting after every feed, occasionally projectile in nature. 

Exam: Sunken anterior fontanelle, small area of fullness in the epigastric area, tender to palpation of the epigastric abdomen.

High on the differential is pyloric stenosis, especially with the fullness in the epigastrium and projectile vomiting. So how do we use ultrasound to assess for pyloric stenosis?

Ultrasound technique

  • You want to have the baby lying supine but also comfortable, preferably in the parent’s arms or in the carrier.

  • You use a linear probe and scan transverse in the RUQ region, looking for the liver and gallbladder. The pylorus will be just medial to the gallbladder. Sometimes you can rotate the probe counterclockwise to catch the pylorus.

  • Typically, a normal pyloric sphincter will not be visible on ultrasound, so if you see a muscular structure in the RUQ by the GB and the stomach, it most likely indicates pathology. 

Here you can see a muscular structure between the stomach and the gallbladder, which is the pylorus. In this view, the pylorus appears like a hamburger, with the muscles on either end resembling the bun of the burger.

In this view, the pylorus appears like a circular ring or a donut shape. 

Here are the images from our patient:

You can see the stomach on the right of the screen, liver on the left, and the pylorus in the middle, shaped like a hamburger

Short axis view

Ultrasound findings here show a thickened muscular structure connecting between the stomach and the small intestine. 

  • To assess for pyloric stenosis, you measure the muscular layer of the pyloric sphincter in both longitudinal and transverse views. 

  • A wall thickness of >3mm raises concern for hypertrophy. If the pyloric canal is >14mm, there is concern for pyloric stenosis. (Think rule of 𝜋, 3.14. >3mm thick and >14mm long= pyloric stenosis)

Typically, the sonographer will evaluate the pylorus while feeding as well.

  • Patients are asked to not feed for about 20-30 minutes prior to the examination, and while under ultrasound evaluation, the baby is given milk in real time.

  • In these images you can see hyperechoic ingested material in the stomach (milk) that is not passing through the pylorus, raising further suspicion for pyloric stenosis.


Happy scanning!

References: 

Sivitz AB, Tejani C, Cohen SG. Evaluation of hypertrophic pyloric stenosis by pediatric emergency physician sonography. Academic emergency medicine. 20(7):646-51. 2013

Zhu J, Zhu T, Lin Z, Qu Y, Mu D. Perinatal risk factors for infantile hypertrophic pyloric stenosis: A meta-analysis. J Pediatr Surg. 2017;52(9):1389-1397. doi:10.1016/j.jpedsurg.2017.02.017

Teele RL, Smith EH. Ultrasound in the diagnosis of idiopathic hypertrophic pyloric stenosis. N Engl J Med. 1977 May 19. 296(20):1149-50.

Rohrschneider WK, Mittnacht H, Darge K, Tröger J. Pyloric muscle in asymptomatic infants: sonographic evaluation and discrimination from idiopathic hypertrophic pyloric stenosis. Pediatr Radiol. 1998 Jun;28(6):429-34

Costa Dias S, Swinson S, Torrão H, et al. Hypertrophic pyloric stenosis: tips and tricks for ultrasound diagnosis. Insights Imaging. 2012;3(3):247-250. doi:10.1007/s13244-012-0168-x

Booth EM