Ultrasound diagnosis of hypertrophic pyloric stenosis - Time to change the criteria

Abstract

Introduction: Ultrasound is the examination of choice for the diagnosis of hypertrophic pyloric stenosis (HPS). A correct diagnosis is dependent on the technique and measurement accuracy. However, in the world literature there is a wide range of values suggested for the diagnosis of this condition. The current minimum measurements used to diagnose HPS seem excessively large, and therefore, we set out to redefine these values.

Methods: A retrospective study was performed on 607 patients (615 scans) being investigated for HPS. The length and transverse diameter of the pyloric canal, and thickness of the pyloric muscle were measured. All results were correlated with clinical and surgical findings.

Results: In this study, the muscle thickness in the normal group was <2.0 mm than in HPS infants having a muscle thickness of 2.0-5.0 mm. All the pyloric canal lengths in the normal group were <5.0 mm than in those with HPS having a length of 10.0-24.0 mm. The transverse diameters ranged from 6.0 to 11.0 mm in the normal group compared with those with HPS having a diameter between 8.0 and 16.0 mm.

Conclusions: The current criteria for sonographic diagnosis of HPS should be redefined. The canal length is the single most important discriminator, with a clear separation between normal and abnormal. The commonly used 16.0-mm measurement is too long and should be reduced to 10.0 mm (without the risk of false positives). In many cases, the muscle thickness in those with HPS is as low as 2.0 mm, considerably less than the 3.0 mm that is currently used. The transverse diameter is not a useful discriminator for HPS. The use of current values will delay the diagnosis and timely treatment of this condition.

Keywords: children; hypertrophic pyloric stenosis; ultrasound.

Figure 1

Longitudinal scan (long) of the normal pylorus (transverse section of the abdomen) with the patient in a right lateral decubitus position for exact measurement of the length of the canal. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 2

Transverse scan of the normal pylorus (sagittal section of the abdomen) with the patient lying right side down for measurement of the pyloric diameter (7.1 mm) and muscle thickness (1.2 mm). [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 3

(a) Longitudinal scan of hypertrophic pyloric stenosis (HPS) (transverse section of the abdomen) with the patient lying supine for measurement of the length of the elongated pyloric canal (16.0 mm). (b) Transverse scan of HPS (sagittal section of the abdomen) with the patient supine for measurement of the pyloric diameter (9.2 mm). (c) Transverse axis view of HPS (sagittal section of the abdomen), with the patient supine, showing anisotropy obscuring anterior and posterior muscle margins and side‐to‐side measurement of muscle thickness (2.6 mm). [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 4

(a) Image of a collapsed distal antrum, taken during the passage of a peristaltic wave simulating an elongated canal, suggestive of hypertrophic pyloric stenosis (HPS). (b) Same patient as in (a). After passage of the wave, the antrum opens and the pylorus is clearly seen to be normal. Image (b) acquired 20 sec after image (a). [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 5

Histogram of the pyloric lengths of the normal and hypertrophic pyloric stenosis groups. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 6

Histogram of muscle thickness of the normal and hypertrophic pyloric stenosis groups. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 7

Muscle thickness of the normal and hypertrophic pyloric stenosis groups showing false negatives and false positives. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 8

Histogram of the pylorus diameter of the normal and hypertrophic pyloric stenosis groups. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 9

(a) Longitudinal scan of hypertrophic pyloric stenosis (HPS) (transverse section of the abdomen) with the patient supine demonstrating a sausage‐shaped mass representing foveolar cell hyperplasia (FCH) (f) in the pylorus eccentrically narrowing the lumen (l). Note hypertrophied muscle (m). (b) Transverse scan of HPS (sagittal section of the abdomen) with the patient supine. From internal to external, note FCH (f), the eccentric crescentic lumen (l), the submucosa (sm) and the hypertrophied muscle (m). [Colour figure can be viewed at wileyonlinelibrary.com]