Diagnosis of Pyloric Stenosis

When an infant is evaluated for pyloric stenosis, the physician reviews the baby's medical history for vomiting patterns and other symptoms. Diagnosis involves a physical examination and diagnostic tests (e.g., blood tests, imaging tests).

When conducting the physical exam, the doctor checks the abdomen for an olive-sized lump—the thickened pyloric muscle. Blood tests can be used to detect low levels of electrolytes, such as calcium, sodium, magnesium, and potassium, and other fluids. Low blood levels can result from dehydration and persistent vomiting.

Imaging tests, such as ultrasound, contrast (barium) x-rays, also may be performed. Ultrasound is a noninvasive test that uses high-frequency sound waves to produce images of abdominal organs. This test can be used to detect abnormalities, including pyloric stenosis.

In contrast x-rays, the infant drinks an oral contrast solution (barium) and a series of x-rays is taken. The contrast solution lines the esophagus, stomach, and small intestine and makes it easier for the physician to detect problems with the pylorus and/or stomach upon x-ray. X-rays also may show if the barium can pass through the pylorus from the stomach to the small intestine.

Pyloric Stenosis Differential Diagnosis

A number of medical conditions can cause symptoms that are similar to those caused by pyloric stenosis. Physicians consider these conditions when reviewing symptoms, and rule them out when appropriate:
  • Adrenal gland problems (e.g., congenital adrenal hyperplasia [CAH]; caused by abnormal production of adrenal hormones and may cause significant salt/electrolyte loss)
  • Allergies
  • Gastroenteritis (inflammation of the stomach and intestinal lining)
  • Gastroesophageal reflux disease (GERD)
  • Hiatal hernia (condition in which the stomach protrudes through the diaphragm into the chest; may be congenital [present at birth])
  • Improper feeding
  • Kidney failure or inflammation of the kidneys
  • Malrotation of the intestine (twist or obstruction of the intestine that may develop before birth)
  • Metabolic disorders
  • Pyloric atresia (condition in which the pylorus is not present or is abnormally closed), pyloric antral web (malformation of the pylorus, resulting in a web-like structure), or pyloric diaphragm (condition in which the area near the pylorus is malformed affecting function of the valve)
  • Pylorospasm (spasm of the pyloric valve)
  • Urinary tract infection (UTI)

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 27 Aug 2008

Last Modified: 01 Oct 2015