Pyloric stenosis (or
infantile hypertrophic pyloric stenosis) is a condition that causes severe vomiting in the first few months of life. There is narrowing (
stenosisA stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a "stricture" ....
) of the opening from the stomach to the intestines, due to enlargement (
hypertrophyHypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...
) of the muscle surrounding this opening (the
pylorusThe pylorus is the region of the stomach that connects to the duodenum. It is divided in two parts:* the pyloric antrum, which connects to the body of the stomach.* the pyloric canal, which connects to the duodenum....
, 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.
Males are more commonly affected than females, with firstborn males affected about four times as often, and there is a
genetic predispositionA genetic predisposition is a genetic effect which influences the phenotype of an organism but which can be modified by the environmental conditions. Genetic testing is able to identify individuals who are genetically predisposed to certain health problems....
for the disease. It is commonly associated with people of Jewish ancestry. Pyloric stenosis is more common in whites than Hispanics, African Americans, or Asians. The incidence is 2.4 per 1000 live births in whites, 1.8 in Hispanics, 0.7 in African Americans, and 0.6 in Asians. It is also less common amongst children of mixed race parents. Caucasian babies with
blood typeA blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells...
B or O are more likely than other types to be affected.
Pyloric stenosis also occurs in adults where the cause is usually a narrowed pylorus due to scarring from chronic peptic ulceration. This is a completely different condition from the infantile form.
Symptoms
Babies with this condition usually present any time in the first weeks to months of life with progressively worsening
vomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Undesired vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure...
. 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 diapers such as going hours or a couple days without having anything.. Constant hunger, belching, and colic are other possible signs as the baby is not able to eat properly.
Diagnosis
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,
palpationPalpation is used as part of a physical examination in which an object is felt to determine its size, shape, firmness, or location...
of the abdomen may reveal a mass in the
epigastriumThe epigastrium is the upper central region of the abdomen. It is located between the costal margins and the subcostal plane....
. 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)
peristalticPeristalsis is a radially symmetrical contraction of muscles which propagates in a wave down the muscular tube. In humans, peristalsis is found in the contraction of smooth muscles to propel contents through the digestive tract. Earthworms use a similar mechanism to drive their locomotion...
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
ultrasoundDiagnostic sonography is an ultrasound-based diagnostic imaging technique used to visualize subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions. Obstetric sonography is commonly used during pregnancy and is widely...
, if available, showing the thickened pylorus. Although somewhat less useful, an
upper GI seriesUpper GI series, also upper gastrointestinal tract radiography, is a radiologic examination of the upper gastrointestinal tract. It consists of a series of X-ray images of the esophagus, stomach and duodenum...
(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 signString sign, or gastrointestinal string sign, is a medical term for a radiographic finding on an Upper GI series, in which the patient is given a radio-opaque material, such as barium, to drink...
" 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
hypokalemicHypokalemia Hypokalaemia refers to the condition in which the concentration of potassium in the blood is low. The prefix hypo- means low...
,
hypochloremicHypochloremia is an electrolyte disturbance whereby there is an abnormally depleted level of the chloride ion in the blood.It rarely occurs in the absence of other abnormalities.It can be associated with hypoventilation....
metabolic alkalosisMetabolic alkalosis is a metabolic condition in which the pH of the blood is elevated beyond the normal range . This is usually the result of decreased hydrogen ion concentration, leading to increased bicarbonate, or alternatively a direct result of increased bicarbonate...
due to loss of
gastric acidGastric acid is a secretion produced in the stomach. It is one of the main ditotonic solutions secreted, together with several enzymes and intrinsic factors...
(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.
Pathophysiology
The gastric outlet obstruction due to the hypertrophic pylorus impairs emptying of gastric contents into the
duodenumThe duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of 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
bileBile or gall is a bitter yellowish, blue and green fluid secreted by hepatocytes from the liver of most vertebrates. In many species, bile is stored in the gallbladder between meals and upon eating is discharged into the duodenum where the bile aids the process of digestion of lipids by...
because the pyloric obstruction prevents entry of duodenal contents (containing bile) into the stomach.
This results in loss of gastric acid (
hydrochloric acidHydrochloric acid is the solution of hydrogen chloride in water. It is a highly corrosive, strong mineral acid and has major industrial uses. It is found naturally in gastric acid....
). The
chlorideThe chloride ion is formed when the element chlorine picks up one electron to form an anion Cl
−...
loss results in
hypochloremiaHypochloremia is an electrolyte disturbance whereby there is an abnormally depleted level of the chloride ion in the blood.It rarely occurs in the absence of other abnormalities.It can be associated with hypoventilation....
which impairs the kidney's ability to excrete bicarbonate. This is the significant factor that prevents correction of the alkalosis.
A secondary
hyperaldosteronismHyperaldosteronism, also aldosteronism, is a medical condition where too much aldosterone is produced by the adrenal glands, which can lead to lowered levels of potassium in the blood.-Types:...
develops due to the
hypovolemiaIn physiology and medicine, hypovolemia is a state of decreased blood volume; more specifically, decrease in volume of blood plasma...
. The high
aldosteroneAldosterone is a hormone that increases the reabsorption of sodium and water and the release of potassium in the kidneys. This increases blood volume and, therefore, increases blood pressure. Many drugs, such as spironolactone, lower blood pressure by blocking the aldosterone receptor...
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 pCO
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Treatment
Infantile pyloric stenosis is typically managed with surgery. It is important to understand that 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.
Very few cases are mild enough to be treated medically. The definitive treatment of pyloric stenosis is with surgical
pyloromyotomyPyloromyotomy is a surgical procedure in which an incision is made in the longitudinal and circular muscles of the pylorus. It is used to treat hypertrophic pyloric stenosis....
known as Ramstedt's procedure (dividing the
muscleMuscle is the contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
of the
pylorusThe pylorus is the region of the stomach that connects to the duodenum. It is divided in two parts:* the pyloric antrum, which connects to the body of the stomach.* the pyloric canal, which connects to the duodenum....
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
laparoscopicallyLaparoscopic surgery, also called minimally invasive surgery , bandaid surgery, keyhole surgery is a modern surgical technique in which operations in the abdomen are performed through small incisions as compared to larger incisions needed in traditional surgical procedures.Practicioners of "open"...
(through several tiny incisions), depending on the surgeon's experience and preference.
Today a tiny circular incision around the navel is most commonly performed. This will leave minimal scar tissue. 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
duodenumThe duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of 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 (muscle division) 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.
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