Pyloric Examination: Physical Findings and Diagnostic Approach
During a pyloric examination, the examiner typically feels for a firm, olive-shaped mass in the right upper quadrant of the abdomen, which represents the hypertrophied pyloric muscle characteristic of pyloric stenosis.
Physical Examination Technique
- Patient positioning: Examine infant in supine position, ideally during a calm state or after feeding
- Palpation method: Use gentle, deep palpation with fingertips in the right upper quadrant, just below the liver edge
- Target location: Between the right costal margin and umbilicus, slightly to the right of midline
- Timing: Optimal examination occurs immediately after the infant vomits when the abdomen is relaxed
Characteristic Findings in Pyloric Stenosis
- Pyloric "olive": A firm, mobile, non-tender mass approximately 1.5-2 cm in size 1
- Consistency: Smooth, firm mass that feels like an olive or small almond
- Mobility: The mass may move during palpation and can sometimes be more easily felt during feeding
- Visibility: In thin infants, peristaltic waves may be visible moving from left to right across the upper abdomen
Diagnostic Accuracy of Physical Examination
- Palpation of a pyloric mass has high specificity (97.5%) but moderate sensitivity (73.5%) 1
- The "olive" cannot be detected in 11-51% of confirmed cases of pyloric stenosis 2
- Positive likelihood ratio of 33 when a pyloric mass is palpated, making it highly diagnostic when present 1
Confirmatory Diagnostic Testing
- Ultrasound: Gold standard for diagnosis with 100% sensitivity and specificity when performed by experienced operators 3
- Measurements: Diagnostic criteria include:
- Pyloric muscle thickness >3 mm
- Pyloric channel length >15-18 mm
- Target sign (hypoechoic ring of hypertrophied muscle)
- Lack of gastric emptying 4
Common Pitfalls in Pyloric Examination
- Timing: Examining when the stomach is full or when the infant is crying reduces success
- Technique: Pressing too firmly can cause the infant to tense abdominal muscles, obscuring the mass
- Misinterpretation: Normal gastric antrum or other abdominal structures may be mistaken for pyloric "olive"
- Over-reliance on imaging: Despite high palpability rates (89%), diagnostic imaging is often overused 5
Clinical Context
For infants presenting with non-bilious projectile vomiting, a careful physical examination should be performed before proceeding to imaging. If the pyloric "olive" is palpated, this is highly diagnostic of pyloric stenosis and surgical consultation should be obtained. If not palpable but clinical suspicion remains high, ultrasound confirmation is warranted 5, 1.