Pyloric stenosis is a disorder that occurs when the pyloric sphincter muscle, which is found at the outlet of the stomach, thickens and becomes enlarged causing the cavity (lumen) of the pylorus to narrow and lengthen. This blocks the passage of food from the stomach to the small intestine (the portion of bowel that continues digestion after food leaves the stomach).
Pyloric stenosis occurs due to enlargement of the walls of the pyloric sphincter. The pyloric sphincter is a circular smooth muscle at the outlet of the stomach that controls the flow of food from the stomach to the small intestine. The muscle cells become enlarged (hypertrophied) causing a narrowing (stenosis) of the pyloric lumen. This causes food to be pushed back into the stomach. Symptoms of pyloric stenosis typically appear two to six weeks after birth. In rare cases it occurs in older adults, not of genetic cause but due to an ulcer (inflammatory lesion of the mucous-like tissue in the stomach) or hardening of the tissue (fibrosis) at the outlet of the stomach. Alternate names associated with the disorder are Hypertrophic pyloric stenosis and Infantile hyper-trophic pyloric stenosis.
The exact cause of pyloric stenosis is unknown. It generally occurs in one in 300 births. The incidence of pyloric stenosis may be higher if a parent or sibling had the condition. It is also more common in the first-born child. Family correlation studies have shown that there is higher expression (concordance) of pyloric stenosis in identical twins (monozygotic) than in fraternal twins (dizygotic). The risk for first-degree relatives (brothers, sisters) of females is higher than those of males. This is also true of second-degree relatives (cousins).
It has been suggested that motilin receptors, which are responsible for motility, might have an involvement in pyloric stenosis. The development of functional motilin receptors occurs around the age of onset for most cases of pyloric stenosis. Studies have found that the use of an antibiotic, called erythromycin for pertussis (a contagious respiratory disease also known as whooping cough) prophylaxis may increase the risk for pyloric stenosis. Erythromycin is a motilin agonist (acts on something to produce a predictable response) and high doses can cause an increase in non-propagated contractions and motility. The lack of neuronal nitric oxide synthase in pyloric tissue may cause a spasm (a twitching or involuntary contraction) in the pyloric muscle in individuals with pyloric stenosis. Neuronal nitric oxide synthase is needed for the synthesis of nitric oxide, which opposes the contraction force in active muscle.
Pyloric stenosis affects males three to four times more than females and appears to have an increased incidence in caucasians.
Signs and symptoms
- Regurgitation and non-bilious vomiting. Infants may bring food back up during or after feeding. Vomiting may become projectile (expelled with force) and vomit may have a "coffee ground" color. Vomit should not contain stomach bile, which is acidic and a brownish-green color. This would be contraindicative of pyloric stenosis.
- Olive-sized abdominal mass. A mass about the size of an olive may be felt in the upper abdomen. The mass should be hard, mobile, and non-tender.
- Pylorospasm. A spasm of the pyloric muscle may occur due to increased motility.
- Additional abnormalities. These include hunger, irritability, lethargy (prolonged sleepiness or sluggishness), weight loss, decreased urine output, constipation, and gastric (stomach) peristalsis (rhythmic contraction of smooth muscle) from the left to right.
An individual's medical history and physical assessment by a doctor are necessary for a diagnosis of pyloric stenosis. A palpable mass, the size of an olive, in the upper abdominal area usually confirms a diagnosis of pyloric stenosis. When physical findings are inconclusive, an abdominal ultrasound or barium study may be performed to confirm diagnosis. An ultrasound, the preferred method of confirmation, is a non-invasive study that uses high frequency sound waves to distinguish the image of internal structures of the body. A barium study involves the ingestion of a radiographic dye. The movement of the dye through the gastrointestinal (GI) tract can be followed by fluoroscopy or x ray studies. It has been suggested that the Lipper GI series may be an effective step in confirming pyloric stenosis. This test consists of aspirating (withdrawal of fluid) and measuring gastric contents. The amount of aspirated contents is indicative of pyloric stenosis and studies have demonstrated this method to be a reliable diagnostic tool.
In adults with symptoms of pyloric stenosis, a barium swallow study is used to diagnose the disorder. X rays are taken of the abdominal structures after the ingestion of the barium radioisotope (a radioactive form of a chemical element).
Treatment and management
As of 2000, the only treatment for pyloric stenosis is surgical pyloromyotomy. Making an incision into the pyloric muscle and spreading the walls of the muscle apart completes the surgery. This allows gastric mucosa to push up through the incision and relieve the blockage.
Blood analysis should be performed before surgery and intravenous (going into the vein) fluids should be given to correct electrolyte (sodium, potassium, calcium etc.) imbalances and rehydrate infants. Following surgery the infant should start on an oral electrolyte (elements necessary for cell functioning) solution (pedialyte). Feedings will be gradually increased until the infant is tolerating 2-3 ounces of breast-milk or formula without complications. The stomach needs time to heal; therefore vomiting due to increased feedings is common. Infants are usually discharged 24–48 hours following surgery. It has been suggested that rapid advancement of the strength and volume of feedings is effective and may allow for quicker discharge from the hospital.
Adults being treated for pyloric stenosis usually have a stomach tube inserted into the muscle that remains in place after sugery.
Recurrence of pyloric stenosis after surgery is rare. As of 2000, there has been no occurrence of conditions later in life related to the occurrence of pyloric stenosis during infancy.
The prognosis of pyloric stenosis is very good for those that are diagnosed early and treated with surgery. Life expectancy of infants diagnosed with pyloric stenosis is the same as that of the average individual. Parents should contact a doctor if pyloric stenosis is suspected.
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Yale University Department of Surgery. <http://www.yalesurgery.med.yale.edu>.
Laith Farid Gulli, MD and Tanya Bivins, BS