Hypertrophic Pyloric Stenosis in a Four-Week-Old Infant: Radiological Diagnosis and Pitfalls.

Infantile hypertrophic pyloric stenosis (IHPS) is a common acquired condition of infancy, characterized by pyloric muscle hypertrophy leading to complete or near-complete gastric outlet obstruction. A typical presentation includes projectile, non-bilious vomiting. While the palpable "olive" and visible peristaltic waves are classic signs, ultrasonography is the diagnostic modality of choice due to its high accuracy. Diagnosis relies on established sonographic thresholds for pyloric muscle thickness and canal length. Differential diagnoses include transient pylorospasm, which resolves on its own, and prostaglandin-induced mucosal hypertrophy, where only the muscular wall should be measured. Herein, we present the case of a four-week-old male infant with projectile non-bilious vomiting and failure to thrive. Ultrasonography confirmed the diagnosis, demonstrating the classic radiological signs. The patient was successfully managed with fluid resuscitation and a Ramstedt pyloromyotomy. This case highlights the pivotal role of ultrasonography in diagnosing IHPS, discusses relevant differential diagnoses, and underscores the importance of recognizing potential imaging pitfalls, such as a posteriorly displaced pylorus due to an overdistended stomach.