Investigation and diagnosis of hypertrophic pyloric stenosis.

Forty-nine infants who underwent investigation or surgery for hypertrophic pyloric stenosis (HPS) over a 30-month period were reviewed. Significant weight loss was present in 18 infants, of whom 16 had HPS. A test feed was performed in 46 infants with 1 of 27 false positive and 6 of 29 false negatives. An ultrasound examination was performed in 34 infants with 4 of 23 false positives and 1 of 11 false negatives. It is recommended that if the test feed is positive then surgery should be performed, otherwise an ultrasound examination can be used as a screening test but a positive result should be confirmed by other means before surgery.