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CHAPTER 59

Infantile Hypertrophic

Pyloric Stenosis

Lohfa B. Chirdan
Emmanuel A. Ameh
Amy Hughes-Thomas

Introduction paradoxical aciduria. Classically, this results in the occurrence of a
Infantile hypertrophic pyloric stenosis (IHPS) is a common surgical hypochloraemic hypokalaemic metabolic alkalosis. In severe cases with
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cause of vomiting in infancy in the Western world. Historically, it diagnostic delay, hypoglycaemia and hypoalbuminaemia can be observed.
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was described as a disease entity in 1888 by Harald Hirschsprung. It is known that the pyloric hypertrophy will eventually resolve, but
Gastrojejunostomy was used to treat this disease until 1912, when this takes a long period of time; the infant would usually succumb to the
extramucosal muscle-splitting pyloromyotomy was described by electrolyte derangement and dehydration before this happened.
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Ramstedt. This procedure has dramatically changed the outcome of Clinical Presentation
infants with IHPS.
Infants with pyloric stenosis usually present with a gradual onset of
Demographics worsening nonbilious vomiting, beginning between 3 to 6 weeks of age.
The reported incidence of IHPS in the Western world is 1–4 per 1,000 The pattern of vomiting can vary, but often it progresses to the character-
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live births. There is a male-to-female ratio of 4:1, with reported ratios istic “projectile” vomiting. Infants may present in the early stages of the
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ranging from 2.5:1 to 5.5:1. disease and be treated for reflux disease or undergone numerous formula
Pyloric stenosis appears to be more common in infants of caucasian changes before the diagnosis is made. Delay in diagnosis can result in
descent and is less common in India and among black and Asian significant electrolyte imbalance, weight loss, and failure to thrive.
populations, with a frequency that is one-third to one-fifth that in the The typical clinical features include the following:
white population. 7 • Nonbilious vomiting is usually forceful and postprandrial.
In about 6–33% of infants with IHPS, associated anomalies have
• The infant is hungry after vomiting and eager to feed, only to vomit
been described in the central nervous system (CNS), gastrointestinal
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tract (GIT), and urinary tract. again.
Aetiology • Weight loss occurs in severe cases.
Despite the frequency of pyloric stenosis, the aetiology remains unclear. • Signs of dehydration present in cases of repeated vomiting.
Genetic predisposition acting in conjunction with environmental factors • Scaphoid abdomen especially noted after recent vomiting.
is the most widely accepted explanation; however, debate still continues
as to whether it is a congenital or acquired disease. 9–11 Breast-feeding has • Visible peristalsis may be observed in the upper abdomen, usually
been suggested as offering some immunity to the disease. moving from the left hypochondrium towards the right side.
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First-born children have been noted to be more likely affected, and • A palpable mass is present in the right upper quadrant (90% in
a familial link is seen with a greater than fivefold increase in the risk experienced hands); this is best appreciated while the infant is being
in first-degree relatives. The genetics explaining this are likely to be fed with clear fluid.
polygenic, as no single locus has been identified. Male and female
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children of affected mothers carry a 20% and 7% risk, respectively, Differential Diagnosis
of developing the condition, whereas male and female children of The differential diagnosis of pyloric stenosis includes:
affected fathers carry a 5% and 2.5% risk, respectively. Furthermore, • gastro-oesophageal reflux;
an association is seen in twins, with concordance among monozygotic
twins of 0.25–0.44, and in dizygotic twins of 0.05–0.10. 13 • viral enteritis;
Pathophysiology • pylorospasm;
Pyloric stenosis is characterized by hypertrophy of the pyloric mus- • duodenal stenosis/duodenal web; and
culature, leading to a mechanical obstruction of the gastric outlet in • raised intracranial pressure.
the affected infant. Thus, hypertrophied pyloric antral muscle fibres
protrude distally into the duodenal lumen, producing a reflection of Evaluation
duodenal mucosa. Clinical Diagnosis
Infants with a diagnosis of pyloric stenosis will show characteristically Depending of the time to presentation, the clinical picture can vary enor-
low chloride and hydrogen ions as measured in the serum. The loss mously from a well-hydrated baby to an emaciated infant. Weight loss
of gastric secretions secondary to protracted vomiting will result in and dehydration coupled with an insatiable appetite lead to a character-
dehydration. As a result, through aldosterone-stimulated absorption, istic facies, with a furrowed brow, wrinkled appearance, and prominent
potassium is excreted in the urine in an attempt to conserve sodium. sucking pads. In some infants, the distended stomach may be identifiable
As potassium depletion worsens, sodium resorption across the renal in the hypochondrium, with active peristaltic activity visible through the
tubule is then achieved in exchange for a hydrogen ion, thereby creating