Physical Examination
The infant may appear underweight and dehydrated, with visible peristaltic waves across the upper abdomen prior to emesis. Severe illness may be indicated in an underweight infant with the classic scaphoid abdomen.18
Palpation of an olive-shaped mass in the upper left quadrant of the epigastric region is pathognomonic for IHPS; the mass may be found more easily after emesis has occurred.19 To facilitate palpation, the hips can first be flexed to relax the abdominal wall. Next, the examiner should palpate gently for the “olive” in the space midway between the umbilicus and the xiphoid, between the two rectus muscles.3 All other findings in the physical exam should be within normal limits.
Imaging and Laboratory
Studies
An experienced provider can make a diagnosis of IHPS based on clinical examination alone in 60% to 80% of cases.20 However, most surgeons require the diagnosis to be confirmed with one of the following imaging studies before surgery.19
The diagnosis of IHPS can be confirmed by an upper GI series, but this is not commonly ordered as the primary diagnostic study. Ultrasound has become the modality of choice9; it can be used to quantify the size of an elongated, thickened pyloric muscle. The hypertrophied pylorus ranges in length from 14 to 16 mm, with thickness measuring more than 3.0 to 3.5 mm.1,19,21
An upper GI contrast study is rarely used for diagnosis of IHPS, but when this test is ordered to detect other gastrointestinal disease processes (eg, malrotation), IHPS may be identified incidentally.19 During an upper GI study, contrast material is propelled through the pyloric mucosa, and the string sign or the double-track sign may be visualized, revealing the mucosal filling defect.2
Abdominal x-ray may reveal a dilated stomach or a blockage, with a possible finding of gas in the gastric bubble but extending no further into the intestine.19
A study by Hernanz-Schulman2 was conducted to quantify the sensitivities and specificities associated with different diagnostic tools and the clinician’s experience and proficiency in using them. According to this study, palpation by a surgeon has a sensitivity of 31% to 99% and a specificity of 85% to 99% for detection of the pathognomonic olive-shaped mass. Ultrasound performed by an experienced technician has 97% to 100% sensitivity and 99% to 100% specificity for detecting IHPS. An upper GI series has 90% to 100% sensitivity and 99.5% specificity.
Venous blood gas and electrolyte levels are both helpful in making a diagnosis of IHPS.19,22 In a study by Oakley and Barnett,22 the following lab values were found useful in confirming the presence of pyloric stenosis: pH > 7.45; chloride 3 mEq/L. Sodium and potassium deficits may also be present.2,22
Before treatment is considered, the degree of dehydration must be determined by clinical examination and urinary output, as well as serum bicarbonate and chloride levels.3 Other laboratory tests to be ordered include urinalysis and a complete blood count (including platelets).
TREATMENT/MANAGEMENT
Initial management of vomiting in children should begin with fluid replacement if the patient appears dehydrated or if lab findings suggest an electrolyte imbalance. If surgery is later deemed necessary, this will reduce the risk for postoperative apnea.1,23
If IHPS is suspected, a pediatric surgery consult should be obtained. Before anesthesia is considered, serum bicarbonate should be measured with results no higher than 28 mEq/L, and the serum chloride level should be at least 100 mEq/L.3 Imaging, such as ultrasound or the upper GI series, may be ordered to confirm the diagnosis.
Surgical correction by a pyloromyotomy is curative. Presurgical gastric decompression via nasogastric tube placement will reduce the risk for postoperative vomiting and gastritis.20
Surgery
Although a variety of nonsurgical interventions, including oral and IV atropine and balloon dilation, have been described in the literature,3,24-26 the preferred treatment for IHPS is surgical intervention. Surgical correction has been so consistently successful (that is, provided the procedure is performed by a pediatric surgeon or other surgeon with appropriate experience3) that the treatment of choice for IHPS is the Ramstedt pyloromyotomy, which was first performed in 1912.6,27,28
Although the approach may differ based on the individual surgeon’s preference, the pyloric muscle is pulled through an incision in the abdominal wall. A longitudinal incision is made through the muscle with blunt dissection to the submucosa on the anterior surface of the pylorus. The pylorus is then returned to the abdominal cavity, and the abdominal incision is sutured.3,20
The laparoscopic approach, first described in the literature in the mid-1990s,29 is gaining popularity among surgeons, although recent studies have demonstrated that open and laparoscopic procedures are comparably safe and effective for the management of IHPS.30-33 Results from a recent study by Jia et al30 indicate that the laparoscopic approach results in reduced postoperative emesis, shorter length of hospital stay, and shorter recovery times; Hall et al31 emphasize the advantages of laparoscopic pyloromyotomy and recommend it over open surgery in facilities with experienced surgeons.