Purpose or Case Report: Background: Infantile hypertrophic pyloric stenosis (IHPS) is a condition affecting young infants in which the circular muscle layer of pylorus becomes thickened, leading to narrowing and elongation of the pyloric channel. The pyloric mucosa becomes redundant and appears hypertrophic. On ultrasound, the thickened pylorus is often seen adjacent to the gallbladder and anteromedial to the right kidney. Infants with IHPS are asymptomatic at birth but, in the first few weeks of life, develop nonbilious forceful vomiting described as “projectile emesis” and present with partial gastric outlet obstruction. Surgical pyloromyotomy is curative.
Standard sonographic criteria include measurement of pyloric muscle >3 mm and elongation of pyloric canal >14 mm. Normal pyloric muscle thickness measures <2 mm. When pyloric muscle thickness measures between 2-3 mm, the exam is called as equivocal or borderline. Factors leading to equivocal exam may include incorrect technique that involves over measuring the pyloric muscle thickness, obliquely oriented section of pylorus and transient pylorospasm.
Purpose: The goals of this exhibit are-
1. To review the sonographic anatomy of normal and abnormal pylorus.
2. To illustrate our technical approach to diagnose IHPS with specific attention on how to accurately measure the muscle thickness and channel length.
3. To describe tips and tricks to minimize equivocal exams.
Methods & Materials: We retrospectively reviewed pylorus ultrasound exams performed at our institute to evaluate for IHPS and selected the most informative sonograms to illustrate sonographic anatomy of the pylorus and depict standard measurement techniques. Correlation was made with clinical and surgical outcomes.
Results: Typical sonographic imaging findings in normal and abnormal pylorus are illustrated. It is important to recognize zonal stratification in the pylorus with layers from inside out including innermost echogenic mucosa, thin hypoechoic muscularis mucosa, echogenic submucosa, hypoechoic muscularis externa and outermost serosa. While measuring pyloric muscle thickness, only the muscularis externa should be measured. In order to accomplish this, utilization of a high frequency linear transducer is key.
Conclusions: Through this exhibit, knowledge of sonographic anatomy of the normal and abnormal pylorus as well as systematic technical approach to measure the pylorus muscle thickness and canal length will be demonstrated to ensure correct diagnosis of IHPS and minimize equivocal exams.