A 4-week-old boy is brought to your OPD by his mother because he has had increasing amounts of vomiting over the past week. Initially it staed as "spitting up" after a few meals a day, but now the baby is having projectile vomiting after every meal. She says the vomitus is non-bloody and non- bilious and the baby appears hungry after he vomits. This is her first child and she is not sure if this is normal. Physical examination is unremarkable. Laboratory studies show: Sodium: 140 mEq/L Potassium: 3.0 mEq/L Chloride: 87 mEq/L Bicarbonate: 30 mEq/L At this time the most appropriate next step is to
This baby has presented with the typical picture of pyloric stenosis. Projectile nonbilious vomiting is seen in viually all patients. Patients also often develop a hypokalemic, hypochloremic metabolic alkalosis from the persistent vomiting. On exam, the upper abdomen may be distended after feeding and prominent peristaltic waves from left to right may be seen. The classic physical exam finding of an "olive-shaped" mass in the epigastric area is not always felt. An ultrasound is the least invasive, safest diagnostic test. The typical appearance on ultrasound is a hypoechoic ring with a hyperdense center. The pyloric muscle thickness measures greater than 4mm. Since this patient has the symptoms of pyloric stenosis, it is inappropriate to do nothing (choice A). A plain film of the abdomen (choice B) will most likely appear normal unless there is a complete obstruction of the pyloric outlet. Again, this study would expose the baby to unnecessary radiation. And, in this case, it would not help you to establish the diagnosis. A barium enema (choice D) will not help to make the diagnosis in this patient. The fact that the vomitus is nonbilious puts the point of obstruction prior to the entrance of the sphincter of Oddi. A study performed from below will not help to see what is happening so high in the intestinal tract. If you suspected intussusception (paroxysmal abdominal pain, vomiting, diarrhea, heme-positive stool, and sausage-shaped mass in upper mid abdomen on palpation), then a barium enema (or air enema) would be both diagnostic and therapeutic.
do nothing
obtain an abdominal radiograph
obtain an abdominal ultrasound
order a barium enema