What is pyloric stenosis?

Pyloric stenosis is also known as infantile hypertrophic pyloric stenosis (IHPS).  This condition occurs when the pylorus becomes thickened and prevents food from the stomach to reach the intestines.  The pylorus is a muscular valve that regulates food transportation from the stomach to the first part of the intestines, also known as the duodenum.  Digested food in the stomach is known as chyme.  While food is being digested in the stomach, the pylorus will contract to prevent food from reaching the duodenum and when digestion is completed, it relaxes to allow chyme reach the duodenum.

In the United States, pyloric stenosis is the most common cause of intestinal obstruction in infancy.  It occurs in 2-4 per 1000 live births.  Whites are more commonly affected than Hispanics, Asians or blacks.  Males are 5 times more at risk of developing pyloric stenosis than females and is more common at about 2 to 6 weeks of age.

What are the risk factors for pyloric stenosis?

There are several factors which may increase the risk of developing pyloric stenosis and these include:

• Family history: Having a parent or a sibling affected by pyloric stenosis in the past may increase the risk of developing pyloric stenosis.
• Sex: Males are 5 times more at risk of developing pyloric stenosis than females.

• Ethnicity: Whites are more at risk of developing pyloric stenosis than blacks, Asians or Hispanics.
• Cigarette smoking during pregnancy: Smoking cigarettes during pregnancy may double the risk of your child having the condition.
• Premature birth: Premature babies are more at risk of developing pyloric stenosis than full-term babies.
• Bottle-feeding: Bottle-feeding is the most significant risk factor for developing pyloric stenosis.

What are the signs and symptoms of pyloric stenosis?

Pyloric stenosis usually occurs in babies aged between 2 to 6 weeks and the signs and symptoms include:

• Projectile vomiting: Projectile vomiting is when the baby vomit forcefully after having breast or formula milk.  The ingested milk may be ejected several feet away.  At first the vomiting is mild but gradually becomes more severe as the pylorus thickens.  Sometimes, there may be traces of blood in the vomit due to gastritis.
• Persistent hunger: Babies with pyloric stenosis often are hungry after having vomited.
• Dehydration: After several episodes of vomiting, the baby may become lethargic, have dry skin and decreased tearing which are signs of dehydration.
• Jaundice: The baby may develop jaundice (yellowing of the skin and the white of the eye) which resolves when the disease is corrected.
• Poor weight gain: This is because the baby is not digesting enough milk due to the vomiting.

• Constipation: Pyloric stenosis prevents food from entering the intestines and this results in constipation.
• Stomach contractions: This occurs as a result of the stomach trying to push food into the intestines before vomiting. They are usually seen over the baby’s upper abdomen. 

There are several other diseases which may resemble pyloric stenosis and these include:

• Renal failure
• Acute kidney injury
• Gastroenteritis
• Dehydration
• Urinary tract infection
• Sepsis
• Mid-gut volvulus

Making a diagnosis

To make a diagnosis, your doctor will ask you some questions to know more about the symptoms of the baby.  After the history taking, your doctor will perform a thorough physical examination to look for signs of pyloric stenosis.  Usually, your doctor may feel an olive-shaped lump and see wave-like contractions on the baby’s abdomen.  To confirm the diagnosis, your doctor may order some test and these include:

• Laboratory studies: Electrolytes, pH, blood urea nitrogen (BUN) and creatinine levels are ordered to measure the severity of the dehydration.  In addition, hypochloremic (decrease in chlorine levels), hypokalaemic (decrease in potassium levels) metabolic alkalosis (when the pH of the blood increases above 7.45) is the classic electrolyte and acid-base imbalance in pyloric stenosis.  The level of sodium may increase or decrease as a result of dehydration and renal failure.  Furthermore, the level of unconjugated bilirubin may be elevated.

• Imaging studies: Ultrasonography is the imaging of choice for the diagnosis of pyloric stenosis.  The scan often reveals a thickened pyloric muscle.  This test can even be done at bedside in the emergency department.  For the diagnosis of pyloric stenosis to be made, the pylorus length should be greater than 13 mm and the pyloric muscle wall thickness greater than 3 mm.  Signs of the disease identified on the scan are donut, antral nipple and shoulder signs.  If ultrasonography is not diagnostic, upper gastrointestinal imaging such as x-ray of the upper abdomen and gastroscopy can be done to confirm the diagnosis.  Gastroscopy is a procedure during which a tube containing a camera at its end is inserted into your mouth to reach your stomach.

What are the treatments for pyloric stenosis?

The main treatment options available to treat pyloric stenosis are medical and surgical care. 

Surgical care is the treatment of choice to treat pyloric stenosis.  The Ramstedt pyloromyotomy is a procedure during which the surgeon makes an incision on the right side of the upper abdomen to get access to the stomach (open pyloromyotomy).  Then, an incision is made in the muscles of the pylorus to reduce the compression exerted by the thickened pylorus upon the end of the stomach.  Nowadays, laparoscopic pyloromyotomy can be done.  This procedure is the same as open pyloromyotomy but the length of the incision made on the skin is significantly smaller, large enough to insert a tube through which the surgeon passes equipment.  This technique have fewer complications, reduced time to be able to eat normally and reduced hospital length of stay.

Medical care is reserved for those who cannot undergo surgery or general anaesthesia.  Atropine sulphate whether taken orally or intravenously can be used to stop the projectile vomiting.  Side effects of this medication include facial flushing, increased heart rate and a raised alanine transaminase (an enzyme or protein produced by the liver).

What are the complications of pyloric stenosis?

There are several complications associated with pyloric stenosis and these include:

• Dehydration
• Failure to grow
• Jaundice (yellowing of the skin and the white of the eye)

Prognosis

The Ramstedt pyloromyotomy procedure is curative and is associated with a very good prognosis.  Normal feeding patterns usually resumes after 24 hours.

J. Alastair, I. and Simon, M., 2016. Davidson's Essentials of Medicine. 2nd ed. London: ELSEVIER.

Parveen, K. and Michael, C., 2017. Kumar & Clarks Clinical Medicine. 9th ed. The Netherlands: ELSEVIER.

Subramaniam, S., 2020. Pediatric Pyloric Stenosis Treatment & Management.