Pyloric stenosis

Infantile hypertrophic pyloric stenosis is a process that causes severe projectile non-bilious vomiting in the first few months of life.

It is due to narrowing of the opening of the first part of the small intestine, the duodenum, due to hypertrophy of the muscle surrounding this opening, which spasms when the stomach empties.

This hypertrophy is noted clinically as an olive-shaped mass in the middle upper part or right upper quadrant of the infant’s abdomen.

Pyloric stenosis is the leading cause of the obstruction in the first months of life, with incidence of 1-3 per 1000 live births.

Affects 4-5 times as many boys as girls.

Typically presents two to eight weeks after birth, with projectile vomiting, weight-loss, and dehydration.

More common in Caucasians than Hispanics, Blacks, or Asians.

Thre incidence is 2.4 per 1000 in Caucasians, 1.8 in Hispanics, 0.7 in Blacks, and 0.6 in Asians.

It is also less common among children of mixed race parents.

Caucasian babies with blood type B or O are more likely to be affected.

Genetic predisposition is well established with aggregation in families and estimated heritability of more than 80%.

Marked changes in the incidence of hypertrophic pyloric stenosis has occurred in several countries over the last decades indicating the presence of modifiable environmental factors.

Infantile hypertrophic pyloric stenosis can be a part of the Smith-Lemli-Opitz syndrome which is an disorder of autosomal recessive congenital disorder caused by mutations in the 7-dehydrocholesterol reductase gene.

In the above disorder 15% present with hypertrophic pyloric stenosis.

Environmental factors such as erythromycin exposure, especiallybat 2weeks of life, and feeding practice may have some relationship.

Can occur in adults where the cause is usually a narrowed pylorus due to scarring from chronic peptic ulceration.

Babies present any time in the first weeks to months of life with progressively worsening vomiting.

The vomiting is non-bile stained and projectile.

Some infants present with poor feeding, weight loss, hunger, belching and colic.

Dehydration may result

Diagnosis is made by history and physical examination, often supported by radiographic studies.

There mass in the epigastrium may be difficult to appreciate, but may be evident after feeding.

Visible and palpable peristaltic waves due to the stomach trying to force its contents through the narrowed pyloric outlet may be present.

Most cases are diagnosed or confirmed by ultrasound showing the thickened pylorus.

An upper GI series can be diagnostic by showing the narrowed pyloric outlet filled with a thin stream of contrast material, known as the “string sign”.

Plain radiographs of the abdomen are generally not useful.

Infants may present with hypokalemia, and hypochloremic metabolic alkalosis due to loss of gastric acid.

The hypertrophic pylorus impairs emptying of gastric contents into the duodenum resulting in vomiting, which can be of a projectile nature.

Cause of the hypertrophy is unknown.

It is commonly associated with people of Jewish ancestry, and has multifactorial inheritance patterns.

The vomitus does not contain bile because the pyloric obstruction prevents entry of duodenal contents containing bile into the stomach.

Vomiting can result in loss of gastric acid causing hypochloremia which impairs the kidney’s ability to excrete bicarbonate.

Secondary hyperaldosteronism can develop due to the hypovolemia and causes the kidneys to retain Na+, and excrete increased amounts of K+ into the urine resulting in hypokalemia.

Typically managed with surgery.

Danger relates to the dehydration and electrolyte disturbances that may develop.

Requires initial stabilization by correcting the dehydration and hypochloremic alkalosis with IV fluids.

Intravenous and oral atropine may be used to treat pyloric stenosis, with a success rate of 85-89%, but requires prolonged hospitalization.

The definitive treatment is surgical pyloromyotomy known as Ramstedt’s procedure where the dividing the muscle of the pylorus to open up the gastric outlet.

This type of surgery be done through a single conventional incision or laparoscopically

The laparoscopic technique has largely supplanted the traditional open repair, and is now considered the standard of care at the majority of children’s hospitals.

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