Pyloric stenosis is a condition affecting infants where the muscle at the outlet of the stomach, known as the pylorus, thickens abnormally. This thickening creates a narrow opening, preventing breast milk or formula from passing from the stomach into the small intestine. A diagnostic ultrasound examination is the most common and reliable method used to confirm this condition in infants. This non-invasive imaging technique provides clear visualization of the pyloric muscle for accurate diagnosis.
Symptoms Prompting an Ultrasound Examination
Symptoms often lead medical professionals to suspect pyloric stenosis, prompting an ultrasound. A hallmark symptom is projectile vomiting, which is forceful and often travels several feet away from the infant. This vomiting is non-bilious and usually occurs shortly after feeding. The absence of bile indicates the obstruction is located before the bile duct enters the small intestine.
Infants with pyloric stenosis commonly display persistent hunger despite frequent feeding and vomiting. They may eagerly feed, only to vomit soon after, leading to a cycle of feeding and emesis. This inability to retain nutrients often results in poor weight gain or even weight loss. Dehydration can also develop, evidenced by fewer wet diapers, sunken soft spots on the head, or a lack of tears when crying. Occasionally, visible contractions or waves can be seen across the infant’s upper abdomen after feeding, as the stomach muscles attempt to push food through the narrowed pylorus.
What to Expect During the Ultrasound
Undergoing an ultrasound for pyloric stenosis is a straightforward, non-invasive procedure. Parents may be asked to give their baby a bottle of sugar water or formula just before or during the examination. This helps distend the stomach, allowing for better visualization of the pylorus.
The sonographer will apply a water-based gel to the baby’s upper abdomen. This gel helps the ultrasound waves travel effectively from the transducer to the body and back, creating clear images. A small, handheld device called a transducer is then gently pressed against the baby’s skin and moved across the abdomen. This device emits high-frequency sound waves that bounce off internal organs and return to the transducer, converting them into real-time images.
The entire examination usually lasts between 15 and 30 minutes. Parents are typically allowed to stay with their infant throughout the procedure. Ultrasound does not use ionizing radiation, making it a safe imaging modality for infants. The procedure is painless, though the baby might feel slight pressure from the transducer.
Diagnostic Criteria on Ultrasound
During the ultrasound, the sonographer examines the pylorus, focusing on specific measurements and visual characteristics. The pyloric muscle thickness (PMT) is the most important measurement. A measurement greater than 3 millimeters is considered indicative of pyloric stenosis. This thickening is a direct result of the muscle’s hypertrophy.
Another key measurement is the pyloric channel length (PCL). A channel length greater than 15 millimeters supports a diagnosis of pyloric stenosis. The overall pyloric diameter, which includes both muscle walls and the central lumen, is also assessed, with values exceeding 10-14 millimeters pointing towards the condition. These numerical criteria provide strong evidence for diagnosis.
Beyond measurements, sonographers look for specific visual signs. One common sign is the “target sign,” which appears as concentric rings on a transverse view of the pylorus. This appearance is created by the thickened muscle surrounding the central, fluid-filled lumen. Another visual cue is the “cervix sign” or “doughnut sign,” seen on a longitudinal view, where the elongated pyloric canal resembles a cervix due to the thickened and prominent muscle. These visual and numerical findings collectively help confirm the diagnosis.
Next Steps Following the Results
Following the ultrasound, the results determine the next course of action for the infant’s medical care. If the ultrasound is positive for pyloric stenosis, a definitive diagnosis is made. The standard treatment is a surgical procedure called a pyloromyotomy. This minimally invasive operation involves making a small incision in the thickened pyloric muscle, which allows the muscle to relax and open the passage between the stomach and the small intestine.
Conversely, if the ultrasound results are negative, it indicates pyloric stenosis is not the cause of the infant’s symptoms. Physicians will then explore other potential reasons for the vomiting and other clinical signs. Common alternative diagnoses include gastroesophageal reflux (GERD), where stomach contents flow back into the esophagus, or other feeding issues such as formula intolerance or overfeeding. Further investigation would then be pursued to identify the underlying problem and provide appropriate treatment.