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GASTROINTESTINAL CONDITIONS

Pyloric Stenosis

Hypertrophic pyloric stenosis occurs in 1.5 to 4 in 1000 live births, and more recent population-based studies suggest the incidence is decreasing over time. It remains a common cause of neonatal emesis and typically presents in the third to fifth week of life. The emesis is typically nonbilious and projectile, although some jaundiced infants may have emesis that has bilious appearance. Hypertrophic pyloric stenosis (HPS) occurs more frequently in male newborns, although providers should be aware that a patient whose mother had pyloric stenosis as an infant has a fourfold incidence of HPS. The precise etiology of the hypertrophied pylorus is unclear, but what was once thought to be an inherently congenital problem is now understood to be an acquired condition. The causes of pyloric stenosis are likely multifactorial, including both genetic and environmental causes. Caretakers often describe projectile nonbilious vomiting and infants present with dehydration and electrolyte imbalances. Physical exam may reveal a sunken fontanelle, lethargy, visible intestinal peristalsis, and in some infants a palpable “olive.” The “olive” is frequently appreciated by experienced examiners. A nasogastric tube is sometimes necessary to decompress the stomach while the hungry child is calmed by being allowed to drink glucose water, thereby allowing an exam which reveals the presence of an “olive.” The exam is best performed by standing to the right of the child, placing the left hand behind the lower back, and palpating just to the left of the midline with the right hand. The primary physiologic disturbance is hypokalemic hypochloremic metabolic alkalosis, which occurs due to the gastric losses from unremitting emesis. Evaluation should include a renal function panel and imaging. At centers where immediate ultrasound is not available and an “olive” is not palpated, an upper gastrointestinal (UGI) study may be obtained to delineate the obstruction and hypertrophied pylorus. Although exact size criteria vary by institution, it is commonly accepted that muscle wall thickness greater than 3 mm and length greater than 14 mm is abnormal in infants under 30 days old (Fig. 9-1). Infants who are diagnosed with pyloric stenosis must be adequately resuscitated before proceeding to the operating room for pyloromyotomy. The anesthetic risk is heightened when the patient’s bicarbonate level is 30 or greater, as the body attempts to compensate for the metabolic alkalosis with respiratory acidosis, which is accomplished with decreased respiratory drive or hypoventilation. Resuscitation goals should include correcting the metabolic alkalosis and additional electrolyte disturbances such as hypokalemia. Infants should be voiding adequately as a marker of resuscitation as well prior to the operating room. The surgical treatment of HPS is a pyloromyotomy performed laparoscopically or open. The pylorus is incised longitudinally so as to divide the hypertrophic fibers, but avoiding perforation of the mucosa. The hypertrophied wall is then spread until the entire length of the pylorus allows for bulging of the mucosa from the circular muscle fiber of the stomach to just proximal to ...

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