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Centre for Evidence-
Based Medicine

Pyloric stenosis - Ultrasound is diagnostic

Clinical Bottom Line

In young infants with projective vomiting but no palpable pyloric tumour, ultrasound is useful to rule in and rule out pyloric stenosis.


Neilson D, Hollman AS. The ultrasonic diagnosis of infantile hypertrophic pyloric stenosis: technique and accuracy. Clinical Radiology 1994;49:246-247.

Clinical Question

In young infants with projectile vomiting and no palpable pyloric tumour, what is the probability of hypertrophic pyloric stenosis with a negative or a positive ultrasound of the pylorus?

Search Terms

'pyloric-stenosis' and 'infant' and 'ultrasound' and ('diagnosis' or 'sensitivity-and-specificity')

The Study

  1. Reference-standard - review of final diagnosis (time after test not stated) and operative findings applied to all.
  2. Test - Ultrasound scan (USS) of the pylorus: considered positive if pyloric canal length ≥ 16 mm, diameter of pylorus ≥ 11 mm, muscle thickness ≥ 2.5 mm and/or dynamic appearance of pylorus.
  3. Study setting - retrospective audit of infants less than 5 months old who had projectile vomiting, no clearly palpable pyloric tumour and who were referred for ultrasound.

The Evidence

Reference standard - pyloric stenosis at follow-up
+ -
Test + 66 1 67
USS - 2 78 80
68 79 147
95% CI
LR+ 77 11 to 538
LR- 0.03 0.01 to 0.12
Pre-test probability 46% 38% to 54%
Post-test probability Test + 99% 87% to 100%
Test - 2.5% 0% to 12%


  1. Surgeons deciding diagnosis were not blind to the ultrasound result.
  2. Unclear whether positive test result based on one or all of above criteria.
  3. Test was always performed by consultant paediatric radiologists.

Appraised By

O. Duperrex, R Gilbert; 24 Mar. 00

Expiry Date

March 2000