Ronald A. Furnival and Marissa A. Hendrickson
Hypertrophic pyloric stenosis is the most common surgical etiology of nonbilious vomiting in young infants presenting to the emergency department (ED) and the most common indication for abdominal surgery before 6 months of age (1). Pyloric stenosis occurs in 2 to 5 of every 1,000 infants, affecting four to five males for every female. The etiology of pyloric stenosis appears to be multifactorial, with a number of genetic, biochemical, and environmental associations (2). Erythromycin treatment during the first 2 weeks of life has been associated with a moderately increased risk for developing pyloric stenosis (2,3). Regardless of the underlying cause, pathologic gastric outlet obstruction results from hypertrophy of the pyloric muscle, leading to vomiting, dehydration, poor weight gain, and eventual hypochloremic metabolic alkalosis as the “classic” presentation.
CLINICAL PRESENTATION
The typical infant with pyloric stenosis has symptoms beginning on average at 3 weeks of age, with gradually worsening nonbilious vomiting. Pyloric stenosis is relatively rare among newborns younger than 1 week of age or infants older than 3 to 4 months of age; premature infants may present according to their corrected age (4). The progressive vomiting of pyloric stenosis is often characterized as “projectile” in nature, although it is not necessarily a key consideration in diagnosis and can be difficult to pinpoint historically (5). The infant with pyloric stenosis may also have a history of blood-streaked or “coffee-grounds” emesis from gastritis, weight loss or poor weight gain relative to the birth weight, and physiologic jaundice (1).
As infants with pyloric stenosis present at an earlier age, often without significant complications, their physical examination findings have become correspondingly more subtle. These infants often appear continuously hungry, even after vomiting an attempted feed. With more advanced cases, the infant may appear thin-limbed and cachectic, with reduced subcutaneous fat stores, weight loss, and evidence of dehydration in up to 30% of cases (6). Visible peristaltic waves may be noted in the epigastrium (5). There has been a decrease in the proportion of infants presenting with the classic findings of hypochloremic alkalosis, weight loss, and a palpable pyloric muscle mass or “olive” in the right epigastrium (7). The use of a sucrose-dipped pacifier, ventral decubitus positioning or flexed-hip positioning, nasogastric (NG) or orogastric tube placement for gastric emptying, and a very gradual approach may improve the likelihood of successful palpation of the olive (5). However, with the advent of modern imaging the frequency with which a palpable olive is documented has decreased from as high as 99% of cases in the 1970s to 13% currently (7).
DIFFERENTIAL DIAGNOSIS
The most common cause of nonbilious vomiting in the otherwise healthy infant is gastroesophageal reflux. The infant with reflux may have a history of overfeeding, positional variation in symptoms, or respiratory complications in the more advanced cases (8). Other common medical conditions presenting with nonbilious vomiting include viral gastroenteritis or an occult urinary tract infection, although both usually would have a history of shorter duration, with fever or other associated symptoms. Central nervous system disorders (hydrocephalus, intracranial hemorrhage, meningitis) may present with vomiting but seldom without associated neurologic findings in a healthy-appearing infant. Less common medical causes of nonbilious vomiting during infancy include congenital adrenal hyperplasia, inborn errors of metabolism, or renal insufficiency, which may present with characteristic electrolyte abnormalities (i.e., hyponatremia and hyperkalemia with the salt-wasting form of adrenal hyperplasia) or specific diagnostic laboratory findings (9).
Though pyloric stenosis is the most common surgical consideration associated with nonbilious vomiting in early infancy, other surgical conditions (intestinal malrotation with volvulus, intussusception, Hirschsprung disease, tracheoesophageal fistulas, esophageal or duodenal webs, duodenal atresia or stenosis, appendicitis, incarcerated hernia) must also be considered. Most infants with pyloric stenosis are initially well and gradually develop progressive vomiting over time. Congenital abnormalities of the upper gastrointestinal tract generally present early in the newborn period, without a progressive history of feeding difficulty. The infant with evidence of abdominal pain, abdominal distention, or bilious (either yellow- or green-stained) emesis must be considered to have an emergent surgical condition until proven otherwise. Immediate surgical consultation should be arranged, and imaging studies should be performed as necessary for diagnosis (10).
ED EVALUATION
If the infant’s history and physical examination raise the possibility of pyloric stenosis, carefully attempt to palpate the olive for diagnosis. If the olive can be felt, no further diagnostic work up is required, and the surgeon can be notified. An imaging evaluation is appropriate if the abdominal examination does not reveal the diagnosis.
Abdominal imaging is performed in 70% to 90% of infants with pyloric stenosis, including those with a palpable olive. Though an increased use of imaging is credited with the earlier diagnosis and improved clinical condition of today’s infants with pyloric stenosis, imaging is not necessary for those with a clear diagnostic examination. Upper gastrointestinal contrast imaging has been used, but ultrasound has increasingly become the modality of choice (11). With growing experience in ultrasonography among surgeons and emergency physicians, bedside ultrasound is emerging as a possibility (12–14). In patients with pyloric stenosis, ultrasound shows a thickened and elongated pylorus, with a thickness of 3 mm or greater, and pyloric length of 15 mm or longer, having 100% sensitivity and 97% to 99% specificity for the diagnosis (15).
KEY TESTING
• Infants suspected of having pyloric stenosis should be evaluated with focused abdominal ultrasound to establish diagnosis.
• Assess serum glucose and electrolytes for hypoglycemia, metabolic alkalosis, hyperchloremia, and hypokalemia.
ED MANAGEMENT
Once the diagnosis of pyloric stenosis is clear, intravenous (IV) access should be obtained, and the infant should remain NPO. NG tube placement for gastric decompression is controversial as it may increase complications, so it is generally not recommended (16). Blood should be obtained for the measurement of serum glucose and electrolytes. With earlier recognition of the condition electrolyte abnormalities, ranging from metabolic acidosis early on, to the classic hypochloremic metabolic alkalosis with more advanced illness, are uncommon (<15% of cases) (7). Infants presenting with elevated serum bicarbonate (>25 mEq/L) and severe hypochloremia (<99 mEq/L) generally have had a longer duration of vomiting, with more severe dehydration and greater weight loss, and as a result may have longer hospital stays (5,7).
The primary goals of preoperative care are IV fluid resuscitation and correction of any electrolyte and acid–base imbalances. Preoperative fluid resuscitation should consist of one or two initial 20 mL/kg IV boluses of normal saline, followed by 5% dextrose and one-half normal saline at 1.5 times the infant’s maintenance rate. If the serum potassium is not elevated, 20 mEq/L of KCl should be added to the IV infusion. Complete fluid resuscitation with correction of alkalosis prior to surgery decreases the risk of postoperative apnea (5).
CRITICAL INTERVENTIONS
• The dehydrated infant with suspected pyloric stenosis should receive 20 mL/kg IV normal saline boluses and have a serum glucose and electrolyte panel sent to the lab while awaiting surgical consultation or imaging studies.
• Adjust the IV fluid infusion to 5% dextrose and one-half normal saline at 1.5 × the maintenance rate after the initial boluses. Include 20 mEq/L KCl if the serum potassium is not elevated.
• Keep the infant NPO.
DISPOSITION
The infant with diagnosed pyloric stenosis must be hospitalized for fluid resuscitation and surgical intervention. The Ramstedt extramucosal pyloromyotomy remains the standard approach, with excellent cosmetic and functional outcomes, minimal morbidity, and very low mortality (<0.5%) (17–22). Though the open procedure has had a record of remarkable success and longevity, laparoscopic pyloromyotomy is gaining favor. A number of recent studies have shown small improvements in some outcomes with the laparoscopic approach, including shorter stays, improved cosmesis, and better cost-effectiveness (19,22–26). Excellent outcomes for either procedure appear to be volume dependent for both the surgeon and the institution, with fewer complications noted for those with larger numbers of procedures (17,20,21) and in children’s hospitals compared to general hospitals (27). Early postoperative feeding protocols have reduced the total hospital length of stay for the average infant with pyloric stenosis to 48 hours, with few complications. Post-pyloromyotomy vomiting is common, with coexisting gastroesophageal reflux present in 10% to 15% of affected infants. This vomiting usually resolves within 1 to 2 weeks after surgery; persistent vomiting may represent the very rare failed pyloromyotomy. Nonsurgical medical therapy for pyloric stenosis with IV atropine has been studied primarily in Europe and Japan, but it requires a significantly longer hospital stay than pylorotomy, has an unacceptably high failure rate, and is rarely used in North America (28).
Common Pitfalls
• Assuming that bilious vomiting in the infant <2 months of age is pyloric stenosis. Bilious emesis mandates an immediate UGI for possible malrotation and volvulus, as well as prompt surgical consultation.
• Inadequate IV fluid resuscitation in the infant with hypochloremic metabolic alkalosis.
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