Ultrasound diagnosis of infantile hypertrophic pyloric stenosis: determinants of pyloric length and the effect of prematurity.

AIM

To evaluate the determinants of sonographic measurements of pyloric length and muscle thickness in infants with hypertrophic pyloric stenosis (HPS) and to determine whether infants born prematurely have proportionately smaller measurements.

MATERIALS AND METHODS

A retrospective review was carried out of 190 infants operated on for HPS at Bristol Children's Hospital over a 5-year period. Sonographic measurements of pyloric length and muscle thickness were related to age, history of prematurity, weight, sex and family history of HPS.

RESULTS

Pyloric length in infants with HPS was significantly greater in those born at term compared to those born prematurely (18.6 mm [SD 2.2] vs 17.3 mm [SD 3.1], P = 0.043); this was explainable by body weight, with length increasing by 1.13 mm (SE 0.35) per kilogram (P = 0.002). There was no significant relationship with measured muscle thickness.

CONCLUSION

Sonographic measurement of pyloric length is strongly correlated with the weight of the infant, irrespective of other factors. The relationship of length and weight may be useful in confirming the presence of HPS in small and premature infants.