[Sonography of hypertrophic pyloric stenosis. Statistical analysis of the values and the diagnostic criteria].

On the basis of 149 patients with the clinical suspicion of hypertrophic pyloric stenosis, sonographic diagnostic criteria were defined retrospectively. The normal ranges for the various criteria were calculated on the basis of 90 patients in whom hypertrophic pyloric stenosis had been excluded. No correlation could be found between these normal ranges and chronological age. Cut-off values between normal (n = 90) and abnormal (n = 59) were calculated by means of ROC analysis. The cut-off value of 14 mm resulted in a sensitivity of 76.9% and a specificity of 97.8% for the diameter, while the cut-off value of 18 mm gave a sensitivity of 80.3% and a specificity of 100% for the canal length. The muscle wall thickness had a sensitivity of 84.4% and a specificity of 95.5% when 4 mm was taken as the cut-off value. Combination of several parameters did not improve the results. The influence of the prevalence on the positive and negative predictive values is calculated by applying the above-mentioned cut-off values and the corresponding sensitivities and specificities. A diagnostic procedure is recommended; this is shown in the form of a flow chart for various possible prevalences.