Pyloric Stenosis

1 month male old with vomiting • Xray of the Week

Figure 1. What is the important finding on this ultrasound of a 1 month old male?

Figure 2: Ultrasound of pylorus. A. Target sign on the short axis view with the thickness measuring 0.60 cm (N<0.30 cm). B. The longitudinal plane shows an elongated pylorus measuring 2.23 cm (N<1.60 cm) with thickened pyloric muscle, also known as the cervix sign. The pyloric mucosa protrudes into the gastric antrum which is the antral nipple sign (red arrows)

Introduction:

Hypertrophic pyloric stenosis (HPS) is seen in infants causing gastric outlet obstruction from a thickened pylorus muscle. The incidence is around 2-5 in 1000 live births every year. Infants from 2-6 weeks old present characteristically as projectile non-bilious vomiting which can be severe enough to cause hypochloremic, hypokalemic metabolic alkalosis and dehydration (1, 2). Risk factors include but are not limited to, smoking during pregnancy, preterm delivery, first-born infants, and exposure to macrolides such as erythromycin (3).

Discussion:

The gold standard imaging technique for diagnosing HPS is ultrasound with high specificity and sensitivity. Sonographic signs of HPS include (4): -Target/Donut sign- Echogenic mucosa surrounding thickened pyloric hypoechoic muscle (Figs. 1A, 2A).

-Cervix sign- showing thickened pylorus on longitudinal view (Figs.1B, 2B)

-Antral nipple sign- pyloric mucosa protruding into the gastric antrum (Fig. 2B)

Sonographic measurements of the pyloric wall >0.30 cm and pyloric length of >1.5 cm (Fig. 1,2) indicate HPS (1, 2). Some authors even suggest that the numerical values are less important compared to the morphology of the antropyloric canal in real-time on ultrasound (2).

There also may be a lack of gastric emptying which can be seen on upper GI series if ultrasound is non-diagnostic. Endoscopy can also be a diagnostic tool but is rarely used due to its invasive and cost-ineffective nature (1).

Treatment:

Once the infant is rehydrated, surgical pyloromyotomy is curative with excellent outcomes (5).

References:

1. Hernanz-Schulman M. Infantile hypertrophic pyloric stenosis. Radiology. 2003;227(2):319-331. doi:10.1148/radiol.2272011329

2. Niedzielski J, Kobielski A, Sokal J, Krakós M. Accuracy of sonographic criteria in the decision for surgical treatment in infantile hypertrophic pyloric stenosis. Arch Med Sci. 2011;7(3):508-511. doi:10.5114/aoms.2011.23419

3. Galea R, Said E. Infantile Hypertrophic Pyloric Stenosis: An Epidemiological Review. Neonatal Netw. 2018;37(4):197-204. doi:10.1891/0730-0832.37.4.197

4. Indiran V, Selvaraj V. The cervix sign and other sonographic signs of hypertrophic pyloric stenosis. Abdom Radiol (NY). 2016;41(10):2085-2086. doi:10.1007/s00261-016-0809-5

5. Aspelund G, Langer JC. Current management of hypertrophic pyloric stenosis. Semin Pediatr Surg. 2007;16(1):27-33. doi:10.1053/j.sempedsurg.2006.10.004

Neal Joshi is a medical student and aspiring diagnostic radiologist at Rowan University School of Osteopathic Medicine in New Jersey. Prior to medical school, he did research with mouse models for Parkinson’s disease and L-DOPA induced dyskinesias. He also did an internship at Kessler Institute for Rehabilitation in a stroke lab analyzing MR images in ischemic stroke patients with hemispatial neglect. During his time at Rowan, he did research with animal models for traumatic brain injury with an emphasis on electrophysiology of neurons. He graduated from William Paterson University where he completed his studies in biology and biopsychology. Apart from medical school, Neal loves to read, skateboard, go on hikes, and spend time with his friends.

Update July 2022: Dr. Joshi is a Radiology Resident at Thomas Jefferson University in Philadelphia.

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Kevin M. Rice, MD is the president of Global Radiology CME and is a radiologist with Cape Radiology Group. He has held several leadership positions including Board Member and Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator. He was once again a semifinalist for a "Minnie" for 2021's Most Effective Radiology Educator by AuntMinnie.com. He has continued to teach by mentoring medical students interested in radiology. Everyone who Dr. Rice has mentored has been accepted into top programs across the country including Harvard, UC San Diego, Northwestern, Vanderbilt, and Thomas Jefferson.

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