Final Pr. ID: Poster #: EDU-033
IHPS has a history that is intimately related to the evolution of Ultrasound(US). US was first used to diagnose IHPS as far back as 1977 (Teele and Smith), and as US technology advanced, the diagnosis of IHPS became more refined. We can make precise measurements for the pyloric muscle wall thickness (MWT), pyloric canal length (CL), and transverse pyloric diameter (TPD), and we have highly sensitive and specific signs (i.e. target, shoulder, double-track signs, etc) to aid us in the diagnosis of IHPS (Hernanz-Schulman 1998).
Why: IHPS is the most common cause of gastric outlet obstruction and one of the most common conditions requiring surgery in infants. The exact pathogenesis of IHPS is unknown, but it is an acquired, gradual and progressive disorder.
Who: The classic picture is 5 to 8-week old Caucasian male (4:1 M:F) who presents with non-bloody, non-bilious projectile vomiting. Classic physical exam findings including visible peristalsis and palpable pyloric olive are present in less than 50% cases. Delay in diagnosis can cause serious consequences.
When: We can typically do US at any age at the time of the next feed and as the baby is being bottle fed (ideally).
How: We use a linear 12-5 or curved 8-5 transducer, with 2D and cine imaging. The baby is placed in supine position, and we begin scanning at the epigastric region. We find the gastroesophageal junction and trace the lesser curvature of the stomach medially to find the pylorus.
What: Once we find it; we measure the MWT, CL, and TDP, and look for all the signs. One way to remember the normal limits is our “Rule of 4s”. In IHPS, MWT is more than 4mm, CL is 4x4 = 16mm, and TDP is 4+4+4 = 12+mm. The signs include target sign (hypertrophied hypoechoic muscle surrounding echogenic mucosa), shoulder/nipple sign (bulging of hypertrophied pyloric muscle into the lumen of the antrum), and double-track sign (elongated pylorus with hypoechoic lumen, sandwiched between echogenic mucosa). If the measurements do not meet our “rule of 4s” and there are none of the signs, we can confidently rule out IHPS, or we may consider another differential diagnosis, like pylorospasm and mucosal hypertrophy due to other causes like prostaglandins. We’ve come a long way with refining and defining US diagnosis of IHPS until finally ultrasound is now the gold standard diagnostic modality for IHPS. Read More