Sonographic diagnosis of hypertrophic pyloric stenosis.

In many pediatric centers, sonography has become the primary imaging method for the diagnosis of hypertrophic pyloric stenosis, but investigators have disagreed about which dimension of the gastric outlet is most useful and accurate. We analyzed 326 consecutive sonograms in 319 infants who presented with vomiting in order to further evaluate the sonographic criteria for the diagnosis of hypertrophic pyloric stenosis. Four observers retrospectively measured three parameters: (1) the thickness of the muscle in the wall of the gastric outlet, (2) the length of that muscle, and (3) the length of the pyloric channel. In the patients with hypertrophic pyloric stenosis, muscle thickness was 4.8 +/- 0.6 mm, muscle length was 2.1 +/- 0.3 cm, and channel length was 1.8 +/- 0.3 cm. In the patients without hypertrophic pyloric stenosis, muscle thickness was 1.8 +/- 0.4 mm, muscle length was 1.3 +/- 0.3 cm, and channel length was 1.1 +/- 0.3 cm. The mean measurement for each parameter was significantly larger in patients who had hypertrophic pyloric stenosis than in those who did not (p less than .01). However, histograms of the three parameters show significant overlap in the measurements of muscle length and channel length between the patients with and those without hypertrophic pyloric stenosis. The thickness of the muscle is the most discriminating and accurate criterion for hypertrophic pyloric stenosis.