What is pyloric stenosis?
Infantile pyloric stenosis is a relatively common condition that causes severe projectile non-bilious vomiting in the first few weeks of life. It results from hypertrophy of the muscles surrounding the pylorus leading to its narrowing and gastric outlet obstruction.
Pyloric stenosis epidemiology
Infantile pyloric stenosis occurs in the first 3–6 weeks of life.
- Infantile pyloric stenosis has also been reported in the first few days of life and in utero.
- Males are more commonly affected than females, with firstborn males affected about four times as often.
- It is commonly associated with people of Jewish ancestry.
- Pyloric stenosis is more common in Caucasians than Hispanics, Blacks, or Asians.
- The incidence of infantile hypertrophic pyloric stenosis is variable. It is:
− 2.4 per 1000 live births in Caucasians.
− 1.8 per 1000 live births in Hispanics.
− 0.7 per 1000 live births in Blacks.
− 0.6 per 1000 live births in Asians.
− Less common among children of mixed race parents.
− Caucasian babies with blood type B or O are more likely than other types to be affected.
What causes pyloric stenosis?
The exact cause is not known. It appears to be inherited in a multifactorial manner. Infantile hypertrophic pyloric stenosis has been reported in twins and several members of the same family suggesting genetic predisposition or familial component. There is a fivefold increase in the risk of developing infantile hypertrophic pyloric stenosis in firstdegree relatives if one member of the family is affected. Nitric oxide is an essential chemical transmitter responsible for relaxation of the pyloric sphincter muscles. Studies have shown deficiency in nitric oxide synthase in the myenteric plexus in patients with infantile hypertrophic pyloric stenosis.
Pathophysiology of pyloric stenosis
There is hypertrophy and hyperplasia of the two (circular and longitudinal) muscular layers of the pylorus.This leads to narrowing of the pyloric canal and gastric outlet obstruction. The pyloric canal becomes lengthened, and the whole pylorus becomes thickened. The mucosa is usually edematous and thickened. Infantile pyloric stenosis is characterized by persistent, non-bilious projectile vomiting due to gastric outlet obstruction. This results in loss of gastric acid with subsequent hypochloremia (chloride loss) and metabolic alkalosis (acid loss). Prolonged vomiting leads to loss of large quantities of gastric secretions rich in hydrogen and chloride. As a result of dehydration, the kidneys attempt to conserve Na+ to maintain volume by exchanging Na+ for K+ and hydrogen secreted as KHCO3 and H2CO3 (paradoxical aciduria). There is a metabolic alkalosis, but instead of having and alkalotic urine, it is acidic.
Signs and symptoms of pyloric stenosis
Following signs and symptoms are typical for pyloric stenosis:
- There is progressively projectile and non-bile-stained vomiting. The child remains hungry and
- takes food immediately after vomiting.
- Poor weight gain and malnutrition
- Ninety-five percent have a palpable pyloric mass (olive sign) which is felt in the right upper abdomen, especially after vomiting and during a test feed.
- May be dehydrated.
- Visible peristalsis in the epigastrium travelling from left to right.
- Indirect hyperbilirubinemia may be seen in 1–2 % of affected infants.
Pyloric stenosis diagnosis
Diagnosis is via a careful history and physical examination, often supplemented by radiographic studies. Abdominal radiographs are not necessary and may show a fluid-filled or air-distended stomach, suggesting the presence of gastric outlet obstruction. A markedly dilated stomach with exaggerated incisura (caterpillar sign) may be seen.Current imaging techniques, particularly ultrasonography, are noninvasive and accurate for identification of infantile hypertrophic pyloric stenosis. Ultrasonography is the method of choice for the diagnosis of hypertrophic pyloric stenosis, because it has a sensitivity and specificity of almost 100 %. Ultrasonography confirms hypertrophic pyloric stenosis when the pyloric muscle thickness is > 4 mm and the pyloric channel length is > 15 mm. An upper gastrointestinal (GI) series is also not necessary and should be done only in doubtful cases when other imaging tests are inconclusive or when the infant presents with atypical clinical features. It is diagnostic when showing the narrowed pyloric canal filled with a thin stream of contrast material, a “string sign” or the “railroad track sign”. Blood tests will reveal hypokalemic, hypochloremic metabolic alkalosis.
Pyloric stenosis treatment
The mortality and morbidity of infantile pyloric stenosis comes from the dehydration and electrolyte disturbance. Therefore, the infant must be initially stabilized by correcting the dehydration and hypochloremic alkalosis with IV fluids. This can usually be accomplished in about 24–48 h using ½ normal saline with K+ supplements. Infantile pyloric stenosis is typically managed with surgery.
Intravenous and oral atropine has been used to treat pyloric stenosis; however, it requires prolonged hospitalization, skilled nursing, and careful follow-up during treatment. It might be an alternative to surgery in children who have contraindications for anesthesia or surgery.The Ramstedt pyloromyotomy remains the standard procedure for pyloric stenosis. Pyloromyotomy can be done by open procedure or laparoscopically depending on the surgeon’s experience and preference. Care should be taken to avoid duodenal perforation during the procedure and, if this happens, the perforation should be closed and covered with an omental patch. Traditionally, the pyloromyotomy is performed through a right upper quadrant transverse incision. Recent studies have compared the operative time, cost, and hospital stay associated with the traditional right upper quadrant transverse incision, a circumbilical incision (believed to have better cosmesis), and a laparoscopic procedure. The laparoscopic pyloromyotomy has been found to be safe and effective, with shorter operative times and hospital stay.
Feeding can be initiated 4–8 h after recovery from anesthesia. Infants who are fed earlier than 4 h do vomit more frequently and more severely, leading to significant discomfort for the patient and anxiety for the parent.
As many as 80 % of patients continue to regurgitate after surgery; however, patients who continue to vomit 5 days after surgery may warrant further radiologic investigation. Patients should be observed for surgical complications:
- Incomplete pyloromyotomy
- Mucosal duodenal perforation
The prognosis of infantile pyloric stenosis is very good, with complete recovery.