• Most common cause of gastric outlet obstruction

• Hypertrophy and hyperplasia of the muscular layers of the pylorus

• Usually nonbilious vomiting at 4-8 weeks of age

• Dehydration, poor weight gain, malnutrition, metabolic alterations, and lethargy

• Ultrasonography - barium upper GI study – endoscopy

Surgical treatment

Hypertrophic pyloric stenosis (HPS)

In typical cases, HPS can be easily diagnosed by clinical symptoms, physical examination, and the presence of metabolic alkalosis. Palpation of a pyloric mass is conclusive and does not require further investigation.

If a pyloric mass is not detected or palpation is equivocal, an ultrasonic scan (US) is the proce- dure of choice. Despite the high accuracy of US, false negative results have been described (espe- cially during early stages of the disease). In this situation, an upper gastrointestinal endoscopy may be a good alternative to an upper gastrointes- tinal series. The advantages of EGD consist of direct assessment of the pylorus and coexistent conditions such as esophagitis, hiatal hernia, or gastritis that may interfere with the postoperative recovery. The obvious disadvantages are invasive- ness and a high cost compared with sonography or upper GI series. However, the very low rate of serious complications, elimination of radiation exposure, as well as an earlier diagnosis and shorter hospitalization, may compensate for any initial expenses and risk of the procedure.

The most reliable endoscopic sign of HPS is a bulging of the tight pylorus into the pre-pyloric antrum with the mucosal folds converted toward the depressed center of the pyloric channel. In the early stage of the disease, when a muscle hypertrophy is not as “stiff” and allows some relaxation, a diameter of pyloric ring less than 5mm, an elongation and irregularity of the pyloric channel are diagnostically significant.

Inability to advance the endoscope beyond the pylorus should be interpreted in favor of HPS only in conjunction with the other endoscopic signs of pyloric stenosis. Concomitant findings of esophag- itis or gastritis may help to predict and prevent such complications as recurrent vomiting or bleeding in the early postoperative period.