Pyloric stenosis: Clinical sciences

Pyloric stenosis occurs from hypertrophy of the circular and longitudinal muscle fibers of the pylorus, which acts as a muscular valve between the stomach and the duodenum. This most commonly presents between 2 and 6 weeks of age. Pyloric stenosis often leads to complete or near complete gastric outlet obstruction, which can present as forceful vomiting. Excessive vomiting can in turn cause further complications, such as dehydration and metabolic abnormalities like hypokalemic, hypochloremic metabolic alkalosis with paradoxical aciduria. Management of pyloric stenosis includes fluid resuscitation and correction of metabolic derangements, as well as surgical pyloromyotomy, which is considered curative.

Alright, if a patient presents with a chief concern suggesting pyloric stenosis, you should first perform an ABCDE assessment to determine whether your patient is unstable or stable. If the patient is unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access and initiate IV fluids for resuscitation. Most infants will show signs of severe dehydration and severe electrolyte abnormalities that need to be corrected during resuscitation. Finally, make sure to continuously monitor vital signs and keep the patient NPO.

Okay, once you’ve done acute management, your next step is to obtain a focused history and physical exam, along with labs like a CBC and CMP. The history is typically obtained from your patient’s caregivers, who may report episodes of immediate, post-prandial, nonbilious, projectile vomiting, as well as fewer wet diapers, which suggests dehydration.

Here’s a clinical pearl for you! “Projectile” vomiting refers to vomiting so forcefully that stomach contents are launched across a long distance. Be sure to ask caregivers for details when taking the history, because they might describe vomiting as “projectile” when their infant is simply spitting up!

Now, on physical exam, you might find signs of severe dehydration, such as hypotension, tachycardia, dry mucous membranes, a sunken fontanelle, or delayed capillary refill. Additionally, you might feel an olive-like mass that’s palpable in the right upper quadrant of the abdomen. On laboratory analysis, CBC is typically normal, while CMP shows electrolyte abnormalities consistent with a hypokalemic, hypochloremic metabolic alkalosis, as well as unconjugated hyperbilirubinemia in some cases. These findings together should make you suspect pyloric stenosis in the setting of severe hypovolemia. Your next step is to get an abdominal ultrasound to confirm your diagnosis.

Okay, findings on ultrasound that suggest a hypertrophic pylorus include pyloric wall thickening of 3 mm or greater, or a “target sign,” which indicates concentric hypertrophy. If these findings are found on ultrasound, you can diagnose pyloric stenosis.

Now that you have made the diagnosis, you will proceed with management. For patients that present in an unstable fashion, they will require continued fluid resuscitation and electrolyte management, as well as emergent consultation of your surgery team for pyloromyotomy.