Ultrasonographic features of normalization of the pylorus after pyloromyotomy for hypertrophic pyloric stenosis.

PURPOSE: The purpose of this study was to describe the time course, early postoperative changes, and morphologic features of normalization of the pylorus after pyloromyotomy for hypertrophic pyloric stenosis.

METHODS

The subjects were 17 infants (9 boys, 8 girls) who underwent umbilical incision Ramstedt pyloromyotomy. The pyloric muscle mass was measured immediately before the operation and then at intervals from 3 days to 6 months after the operation using a 7.5-MHz ultrasound probe.

RESULTS

In longitudinal section, the dorsal part of the pyloric muscle thickened transiently and then thinned to normal values by 5 months after the operation. It was 5.1 +/- 0.8 mm (mean +/- SD) preoperatively, increased to 6.0 +/- 0.3 mm by day 3 after the operation (P <.05), and thinned to 2.8 +/- 0.2 mm by 5 months after the operation. Concomitantly, the length of the pylorus gradually decreased (from 20.1 +/- 2.9 mm preoperatively to 16.9 +/- 2.7 mm by 3 days postoperatively [P <.05] and to less than 15 mm, by 4 months). In transverse section, the muscle normalized as in the longitudinal section. At the site of the incision it was 4.3 +/- 0.4 mm thick preoperatively, thickened to 4.6 +/- 0.4 mm by 3 days after the operation (P <.05), thinned to 2.1 +/- 0.9 mm by 7 days (P <.05), and then increased slightly, but always was less than 3.0 mm. Morphologically, in transverse section, the incised area looked like a wedge by 3 days after the operation.

CONCLUSIONS

After pyloromyotomy for hypertrophic pyloric stenosis, there is an early transient increase in muscle thickness within the first few postoperative days followed by a slow decrease that reaches normal thickness (<3 mm) by 5 months. This decrease in thickness is accompanied by a gradual decrease in length to 75% of the preoperative value by 5 months. The morphologic features in this normalization are first a wedge (day 3), then a flat tire (days 7 and 14), and finally an elongated ring (5 months). J Pediatr Surg 36:582-586.