Pyloric stenosis overview

# Overview
Infantile pyloric stenosis 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 spasm and hypertrophy of the muscle surrounding this opening (the pylorus). 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. There is chloride loss due persistent vomiting that results in hypochloremia which impairs the kidney's ability to excrete bicarbonate. Infantile hypertrophic pyloric stenosis must be differentiated from other diseases that cause vomiting, poor feeding and dehydration, such as adrenal insufficiency, gastroenteritis, UTI, inborn errors of metabolism and acute renal failure. The hallmark of infantile pyloric stenosis is progressively worsening vomiting within the first few weeks to months of life. A positive history of bottle feeding and cesarean section delivery is suggestive of infantile pyloric stenosis. Palpation of the abdomen may reveal a mass in the epigastrium. This mass consists of the enlarged pylorus smooth muscle and it is called olive.Ultrasonography is the the modality of choice for the diagnosis of infantile pyloric stenosis. Infantile pyloric stenosis is typically managed with surgery. Ranstedt's extramuscular pyloromyotomy is the gold standard of treatment. After the surgery, once the stomach can empty into the duodenum, feeding can be started. There is occasionally recurrence in the immediate post-operative period, but the condition generally has no long-term impact on the child's future.

# Historical Perspective
In 1717, Dr. Patrick Blair reported autopsy findings of pyloric stenosis for first time. In 1911, Conrad Ramstedt witnessed complete recovery of a patient with pyloric stenosis after undergoing pyloroplasty.

# Classification
There is no established system for the classification of pyloric stenosis. It may be subclassified as infantile pyloric stenosis and adult-onset hypertrophic pyloric stenosis.

# Pathophysiology
The pathogenesis of infantile hypertrophic pyloric stenosis is not completely understood. However, infantile hypertrophic pyloric stenosis may result from abnormal innervation of the pyloric smooth muscle. The chloride loss due persistent vomiting results in hypochloremia which impairs the kidney's ability to excrete bicarbonate. This factor significantly prevents correction of the alkalosis. The secondary hyperaldosteronism develops due to the hypovolaemia. The body's compensatory response to the metabolic alkalosis is hypoventilation resulting in an elevated arterial pCO2.
In relatives of probands of infantile hypertrophic pyloric stenosis patients and monozygotic co-twins the recurrence pattern did not depict a single major inheritance. The incidence of infantile pyloric stenosis is approximately 400 per 100,000 individuals worldwide and it is four times more common in males. Most common laboratory findings consistent with the diagnosis of infantile pyloric stenosis and adult type pyloric stenosis include hypokalemia, hypochloremia, and metabolic alkalosis.

# Causes
The causes of infantile pyloric stenosis are unknown, but genetic and environmental factors might play a role in pathogenesis of infantile pyloric stenosis. common causes of adult-onset hypertrophic pyloric stenosis (HPS) include persisting duodenal hyperacidity, inheritance of a parietal cell mass (PCM) at the upper end of the normal range which causes persisting duodenal hyperacidity.

# Differentiating Pyloric stenosis overview from Other Diseases
Infantile hypertrophic pyloric stenosis must be differentiated from other diseases that cause vomiting, poor feeding and dehydration, such as adrenal insufficiency, gastroenteritis, UTI, inborn errors of metabolism and acute renal failure. Projectile vomiting and and palpation of an olive in abdominal physical examination are very helpful to distinguish infantile pyloric stenosis from other common causes of vomiting in infants.

# Epidemiology and Demographics
The incidence of infantile pyloric stenosis is approximately 400 per 100,000 individuals worldwide and it is four times more common in males. It  usually affects individuals of the Caucasian race. Asians individuals are less likely to develop Infantile pyloric stenosis. The prevalence of infantile pyloric stenosis in the course of 11 years (1989-1999) was approximately 7.3 per 100,000 individuals in one study. Studies showed the mortality rate of pyloric stenosis is very low and usually results from delays in diagnosis that causes sever dehydration and shock.

# Risk Factors
The most potent risk factors in the development of infantile pyloric stenosis are male gender, Caucasian race, bottle feeding, caesarean section delivery, first-born infant, preterm birth; and exposure to macrolides, nitrofurantoin, penicillins, and trimethoprim-sulphamethoxazole during pregnancy.

# Screening
Screening for pyloric stenosis is not recommended.

# Natural History, Complications, and Prognosis
The symptoms of pyloric stenosis usually develop in the first days of life, and start with projectile vomiting. If left untreated, infants with mild infantile pyloric stenosis can develop severe electrolyte imbalances include hypokalemia , hypochloremia, and metabolic alkalosis. In rare cases of untreated pyloric stenosis, patients may develop significant problems on the cognition, receptive language, fine motor, and gross motor skills compared to the normal infants due to long term malnutrition. Complications of infantile pyloric stenosis before surgery include vomiting and failure to gain weight in newborn period. Prognosis is generally excellent and surgery usually provides complete relief of symptoms. Infants usually tolerate small, frequent feedings several hours after surgery

# Diagnosis
Ultrasonography is the the modality of choice for the diagnosis of infantile pyloric stenosis. The thickened prepyloric antrum bridging the duodenal bulb and distended stomach and crowded intervening mucosa that protrudes into the distended portion of the antrum (nipple sign) may be seen in Ultrasonography of patients with infantyle pyloric stenosis.

## History and Symptoms
The hallmark of infantile pyloric stenosis is progressively worsening vomiting within the first few weeks to months of life. A positive history of bottle feeding and cesarean section delivery is suggestive of infantile pyloric stenosis. The most common symptoms of infantile pyloric stenosis include vomiting, belching, persistent hunger. Less common symptoms of infantile pyloric stenosis include failure to gain weight or weight loss, jaundice, lethargy and decreased urine output. The hallmark of adult type pyloric stenosis is progressively worsening projectile vomiting. A positive history of chronic peptic ulcers and fibrosis near the gastric outlet is suggestive of adult type pyloric stenosis. The most common symptoms of adult type pyloric stenosis include vomiting with occasional relief after vomiting, belching, epigastric pain. Less common symptoms of adult type pyloric stenosis include failure to gain weight or weight loss and symptoms of dehydration like increased thirst, dry mouth and decreased urine output.

## Physical Examination
Palpation of the abdomen may reveal a mass in the epigastrium. This mass consists of the enlarged pylorus smooth muscle and it is called olive. Palpation of a hypertrophied pylorus is very useful in diagnosis of hypertrophic pyloric stenosis.Peristaltic waves may be palpated or may be seen in abdominal exam of patients with infantile pyloric stenosis. Hypothermia and tachycardia with regular pulse and tachypnea may be present. In skin examination cyanosis, poor skin turgur, jaundice and pallor may be present.

## Laboratory Findings
Most common laboratory findings consistent with the diagnosis of infantile pyloric stenosis and adult type pyloric stenosis include hypokalemia, hypochloremia, and metabolic alkalosis.

## Electrocardiogram
There are no ECG findings associated with pyloric stenosis.

## Xray
There are no significant abdominal x-ray findings associated with infantile pyloric stenosis.

## CT scan
There are no CT scan findings associated with infantile pyloric stenosis.

## MRI
There are no MRI findings associated with infantile pyloric stenosis.

## Ultrasound
Ultrasonography is the modality of choice for the diagnosis of infantile pyloric stenosis. The thickened pre-pyloric antrum bridging the duodenal bulb and distended stomach could be seen in the ultrasound of patients with infantile pyloric stenosis. Demonstration of the pylorus is achieved by identifying the duodenal cap, distended stomach, and intervening pyloric channel. In patients with pyloric stenosis, the variable hypertrophy of the smooth muscle and crowded intervening mucosa which is thickened to a variable degree, and protrudes into the distended portion of the antrum (nipple sign)  may be observed on ultrasonography.

## Other Imaging Findings
Upper gastrointestinal series (barium meal) may be helpful in the diagnosis of infantile pyloric stenosis. Findings on an upper gastrointestinal series suggestive of infantile pyloric stenosis include delayed gastric emptying, elongated pylorus with a narrow lumen (string sign), and the pylorus indents the contrast-filled antrum (shoulder sign).

## Other Diagnostic Studies
There are no other diagnostic studies associated with pyloric stenosis.

# Treatment

## Medical Therapy
Decompression of stomach by suction via nasogastric tube and Initial correction of fluid and electrolyte imbalance, oral administration of atropine sulfate, and oral feeding with 10 ml of 10% glucose are important in treatment of pyloric stenosis.

## Surgery
Infantile pyloric stenosis is typically managed with surgery. Ranstedt's extramuscular pyloromyotomy is the gold standard of treatment. After the surgery, once the stomach can empty into the duodenum, feeding can be started. There is occasionally recurrence in the immediate post-operative period, but the condition generally has no long-term impact on the child's future.

## Primary Prevention
There are no established measures for the primary prevention of pyloric stenosis.

## Secondary Prevention
There are no established measures for the secondary prevention of pyloric stenosis.