The back story of pyloric stenosis is fascinating. It is a relatively minor surgical condition today, but the disease had a mortality of 100 percent before 1904, when only five operative cases were known to have been performed in the United States. The dying process was slow and painful, and parents watched their infants slowly starve to death.
The pyloromyotomy procedure currently used to treat pyloric stenosis was introduced by Conrad Ramstedt, MD, in 1911 at the Children's Hospital of Munster, and is still called the Ramstedt procedure. Before surgical management was introduced for this gastric outlet obstruction, multiple unsuccessful medical therapies had been attempted, including treating infants with bromides, antipyrine, cocaine, novocain, belladonna, and atropine.
Attempts at emergency fluid resuscitation involved administration subcutaneously or as nutrient enemas, the rectal administration of nutrient-containing solutions. Only atropine has shown evidence of success. In fact, a 2005 article by Kawahara, et al., described 45 of 52 patients (86.5%) whose projectile-vomiting was stopped using intravenous atropine. (J Pediatr Surg. 2005;40:1848.) Treatment with intravenous atropine (median of 7 days) was followed by oral atropine (median of 44 days). The median hospital stay was 13 days (6-36 days). The relevance of a medical therapy to us in emergency medicine is the patient who is clinically unstable or has contraindications for immediate surgery. Atropine is also relevant to physicians working in austere environments.
Pyloric stenosis occurs in two to four per 1000 live births. Pathologic hypertrophy and hyperplasia of the circular and longitudinal muscular layers of the pylorus occur, resulting in marked narrowing of the gastric antrum. These changes result in gastric outlet obstruction. It is more common in male infants, and the reported male-to-female ratio is 4:1 to 6:1. It is also more common in preterm infants, and most commonly occurs in firstborn children (30-40%).
Symptoms typically begin between 3 and 5 weeks of age and are rare after 12 weeks. Infants will eventually demonstrate nonbilious, forceful vomiting after every feeding and then be ready to eat again almost immediately. (See the video of an infant with a classic presentation of pyloric stenosis.) The patient will have metabolic abnormalities if the vomiting is prolonged and the presentation late. Hypochloremic and hypokalemic metabolic alkalosis is now less common, but these abnormalities historically contributed to the death of infants. Hyperperistalsis may be observed traveling left to right across the abdomen just before emesis.
Watch a video of an infant with pyloric stenosis experiencing hyperperistalsis.
An olive may also be palpated in the right upper quadrant. An association between early postnatal macrolide use and pyloric stenosis is well documented. (Ital J Pediatr. 2019;45:20; http://bit.ly/2zQvocH; Eur J Pediatr. 2019;178:301.) Ultrasound is highly sensitive and specific for pyloric stenosis. A target should be seen on the transverse view, and measurement criteria are as follows:
- Pyloric muscle thickness (PMT): 3-4 mm
- Pyloric muscle length (PML): 15-19 mm
- Pyloric diameter (PD): 10-14 mm
An important caveat is that normal values do vary with the size and gestational maturity of the infant. (Pediatr Surg Int. 2009;25:1053; http://bit.ly/2PTwG1A.) Consequently, the small or young infant will typically not meet these measurement standards. Ultrasound is highly sensitive and specific in making the diagnosis, but a barium swallow may sometimes be required. Specific signs seen during barium examination include the shoulder sign, antral nipple sign, cervix sign, and target sign. Because the basics of pyloric stenosis are well known to most emergency physicians, this blog will focus on a few things you may not know or have not seen.
Early-Onset Pyloric Stenosis
Most cases of PS occur after 3 weeks of age, but approximately five percent of infants present much earlier. Early presentation of pyloric stenosis appears to be associated with a positive family history. Strongly consider the diagnosis if a vomiting infant outside the typical age range presents with a family history of PS.
Watch a video of an infant with a family history of pyloric stenosis who was diagnosed at 13 days of age.
Again, the clinical takeaway is that sonographic diagnostic measurements specific to this age exist and can prevent delays in diagnosis and treatment.
Watch a video of an infant with weight loss from pyloric stenosis.
Finding the Olive
The olive is the hypertrophied pylorus that is potentially palpable at the lateral edge of the rectus abdominis muscle in the right upper quadrant. This may be a relatively subjective examination, and requires a calm infant who is not crying. Most clinicians rely on ultrasound to make the diagnosis, and a search for the olive is less commonly done, but some pearls are helpful for finding it.
- Be sure the infant is calm. A sucrose-soaked pacifier may help relax the infant.
- The olive is best palpated immediately after an episode of emesis because a distended antrum can obscure the examination. Gastric contents may need to be removed by a nasogastric tube.
- Palpate for the olive in the right upper quadrant lateral to the abdominis rectus muscle.
Hypochloremic and Hypokalemic Metabolic Alkalosis
Severe prolonged vomiting results in the loss of hydrochloric acid from the stomach and in the kidneys retaining hydrogen ions in favor of potassium. The alkalosis is perpetuated by urinary losses of Na+ and HCO3 as part of the compensation for chloride losses. This derangement also occurs in vomiting adults with pyloric stenosis or gastric outlet obstruction.
Unconjugated hyperbilirubinemia is another lesser known laboratory abnormality seen in infants. The association has even been labeled as icteropyloric syndrome. The elevated bilirubin resolves after surgery. The clinical diagnosis of pyloric stenosis can be summarized as the three Ps: projectile vomiting, peristalsis, and a palpable olive.