Pyloric stenosis

Pyloric stenosis
Pyloric stenosis
Classification and external resources

Outline of stomach, showing its anatomical landmarks, including the pylorus.
ICD-10 K31.1, Q40.0
ICD-9 537.0, 750.5
DiseasesDB 11060 29488
MedlinePlus 000970
eMedicine emerg/397 radio/358
MeSH D046248

Pyloric stenosis (or infantile hypertrophic pyloric stenosis)[1] is a condition that causes severe vomiting in the first few months of life. There is narrowing (stenosis) of the opening from the stomach to the intestines, due to enlargement (hypertrophy) of the muscle surrounding this opening (the pylorus, meaning "gate"), which spasms when the stomach empties. It is uncertain whether there is a real congenital narrowing or whether there is a functional hypertrophy of the muscle which develops in the first few weeks of life.

Pyloric stenosis also occurs in adults where the cause is usually a narrowed pylorus due to scarring from chronic peptic ulceration. This is a different condition from the infantile form.


Signs and symptoms

Babies with this condition usually present any time in the first weeks to months of life with progressively worsening vomiting. The vomiting is often described as non-bile stained ("non bilious") and "projectile vomiting", because it is more forceful than the usual spittiness (gastroesophageal reflux) seen at this age. Some infants present with poor feeding and weight loss, but others demonstrate normal weight gain. Dehydration also can occur causing the baby to cry without having tears, and having less wet or dirty nappies such as going hours or a couple days without having anything.[2] Constant hunger, belching, and colic are other possible signs as the baby is not able to eat properly.


Diagnosis is via a careful history and physical examination, often supplemented by radiographic studies. There should be suspicion for pyloric stenosis in any young infant with severe vomiting. On exam, palpation of the abdomen may reveal a mass in the epigastrium. This mass, which consists of the enlarged pylorus, is referred to as the 'olive,' and is sometimes evident after the infant is given formula to drink. It is an elusive diagnostic skill requiring much patience and experience. There are often palpable (or even visible) peristaltic waves due to the stomach trying to force its contents past the narrowed pyloric outlet.

At this point, most cases of pyloric stenosis are diagnosed/confirmed with ultrasound, if available, showing the thickened pylorus. Although somewhat less useful, an upper GI series (x-rays taken after the baby drinks a special contrast agent) can be diagnostic by showing the narrowed pyloric outlet filled with a thin stream of contrast material; a "string sign" or the "railroad track sign". For either type of study, there are specific measurement criteria used to identify the abnormal results. Plain x-rays of the abdomen are not useful, except when needed to rule out other problems.

Blood tests will reveal hypokalemic, hypochloremic metabolic alkalosis due to loss of gastric acid (which contain hydrochloric acid and potassium) via persistent vomiting; these findings can be seen with severe vomiting from any cause. The potassium is decreased further by the body's release of aldosterone, in an attempt to compensate for the hypovolaemia due to the severe vomiting.


The gastric outlet obstruction due to the hypertrophic pylorus impairs emptying of gastric contents into the duodenum. As a consequence, all ingested food and gastric secretions can only exit via vomiting, which can be of a projectile nature. The vomited material does not contain bile because the pyloric obstruction prevents entry of duodenal contents (containing bile) into the stomach.

This results in loss of gastric acid (hydrochloric acid). The chloride loss results in hypochloremia which impairs the kidney's ability to excrete bicarbonate. This is the significant factor that prevents correction of the alkalosis.[3]

A secondary hyperaldosteronism develops due to the hypovolemia. The high aldosterone levels causes the kidneys to:

  • avidly retain Na+ (to correct the intravascular volume depletion)
  • excrete increased amounts of K+ into the urine (resulting in hypokalaemia).

The body's compensatory response to the metabolic alkalosis is hypoventilation resulting in an elevated arterial pCO2.=[pp\][[\=0808i[po9il;


Vertical Pyloromyotomy scar (large) 30 hrs post-op in a 1 month-old baby
Horizontal Pyloromyotomy scar 10 days post-op in a 1 month-old baby

Infantile pyloric stenosis is typically managed with surgery; very few cases are mild enough to be treated medically.

The danger of pyloric stenosis comes from the dehydration and electrolyte disturbance rather than the underlying problem itself. Therefore, the baby must be initially stabilized by correcting the dehydration and hypochloremic alkalosis with IV fluids. This can usually be accomplished in about 24–48 hours.

Intravenous and oral atropine may be used to treat pyloric stenosis. It has a success rate of 85-89% compared to nearly 100% for pyloromyotomy, however it requires prolonged hospitalization, skilled nursing and careful follow up during treatment.[4] It might be an alternative to surgery in children who have contraindications for anesthesia or surgery.


The definitive treatment of pyloric stenosis is with surgical pyloromyotomy known as Ramstedt's procedure (dividing the muscle of the pylorus to open up the gastric outlet). This is a relatively straightforward surgery that can possibly be done through a single incision (usually 3–4 cm long) or laparoscopically (through several tiny incisions), depending on the surgeon's experience and preference.[5]

Today, the laparoscopic technique has largely supplanted the traditional open repairs which involved either a tiny circular incision around the navel or the Ramstedt procedure. Compared to the older open techniques, the complication rate is equivalent, except for a markedly lower risk of wound infection.[6] This is now considered the standard of care at the majority of Children Hospitals across the US, although some surgeons still perform the open technique. Following repair, the small 3mm incisions are hard to see.

The vertical incision, pictured and listed above, is no longer usually required. Though many incisions have been horizontal in the past years.

Once the stomach can empty into the duodenum, feeding can commence. Some vomiting may be expected during the first days after surgery as the gastro-intestinal tract settles. Very occasionally the myotomy was incomplete and projectile vomiting continues, requiring repeat surgery. But the condition generally has no long term side-effects or impact on the child's future.


Males are more commonly affected than females, with firstborn males affected about four times as often, and there is a genetic predisposition for the disease.[7] It is commonly associated with people of Jewish ancestry, and has multifactorial inheritance patterns.[8] Pyloric stenosis is more common in Caucasians than Hispanics, Blacks, or Asians. The incidence is 2.4 per 1000 live births in Caucasians , 1.8 in Hispanics, 0.7 in Blacks, and 0.6 in Asians. It is also less common amongst children of mixed race parents.[9] Caucasian babies with blood type B or O are more likely than other types to be affected.[7]


  1. ^ Hulka F, Campbell TJ, Campbell JR, Harrison MW (1997). "Evolution in the recognition of infantile hypertrophic pyloric stenosis". Pediatrics 100 (2): E9. doi:10.1542/peds.100.2.e9. PMID 9233980. 
  2. ^
  3. ^ Kerry Brandis, Acid-Base Physiology. Retrieved December 31, 2006.
  4. ^ Aspelund G, Langer JC (February 2007). "Current management of hypertrophic pyloric stenosis". Semin. Pediatr. Surg. 16 (1): 27–33. doi:10.1053/j.sempedsurg.2006.10.004. PMID 17210480. 
  5. ^
  6. ^ Sola JE, Neville HL (August 2009). "Laparoscopic vs open pyloromyotomy: a systematic review and meta-analysis". J. Pediatr. Surg. 44 (8): 1631–7. doi:10.1016/j.jpedsurg.2009.04.001. PMID 19635317. 
  7. ^ a b Dowshen, Steven (November 2007). "Pyloric Stenosis". The Nemours Foundation. Retrieved 2007-12-30. 
  8. ^ Fried K, Aviv S, Nisenbaum C (November 1981). "Probable autosomal dominant infantile pyloric stenosis in a large kindred". Clin. Genet. 20 (5): 328–30. doi:10.1111/j.1399-0004.1981.tb01043.x. PMID 7333028. 
  9. ^ Pediatrics, Pyloric Stenosis at eMedicine

External links

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