Findings: Thickening and elongation of the pyloric canal. The muscle wall thickness is 5-6 mm. The pyloric canal measures approximately 21 mm.

Diagnosis: Hypertrophic pyloric stenosis.

Discussion: When an infant presents with nonbilious vomiting, hypertrophic pyloric stenosis must be considered. Often a mass is palpated in the RUQ. Laboratory values may indicate electrolyte imbalances (alkalosis). The average age at diagnosis is 3-6 weeks old and there is a male predominance. HPS is associated with esophageal atresia, TE fistula, hiatal hernia, and chromosomal abnormalities. More recently HPS has been linked to the administration of erythromycin during the neonatal period. In addition, increased expression of growth factor genes has been found in patients with hypertrophy of the pylorus.

Ultrasound findings include a hypoechoic (circular) muscle which is increased in the thickness > 3.5 mm. The length of the pylorus exceeds 17 mm in HPS. An increased "pyloric rates", (defined as wall thickness/pyloric diameter) greater than .27 is believed by some to be a sensitive indicator of disease.

Currently, the treatment of choice is pyloromyotomy.

References:

1. Brant WE, Helms CA. Fundamentals of Diagnostic Radiology, 1994:1072-1074.

2. Honein MA, et al. Infantile Hypertrophic Pyloric Stenosis After Pertussis Prophylaxis
   with Erythromycin: A Case Review and Cohort Study. Lancet 1999 Dec 18-25; 354
   (9196): 2101-1205.

3. Lowe LH, et al. Pyloric Ratio: Efficacy in the Diagnosis of Hypertrophic Pyloric
   Stenosis. J. Ultrasound Medicine Nov 1999;(11):773-777.

4. Shim AH, Puri P. Increased Expression of Transforming Growth Factor - Alpha
   in Infantile Hypertrophic Pyloric Stenosis. Pediatric Surgery. Int 1999; 15(3-4):198-200.