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Pyloric Stenosis

Pyloric stenosis is a clinical condition characterized by the obstruction of the stomach’s pyloric lumen in infants usually due to muscular hypertrophy or hyperplasia of the luminal walls (Infantile hypertrophic pyloric stenosis (IHPS)). Pyloric stenosis may cause partial and complete obstruction of the gastric outlet preventing the active gastric emptying of food to the small intestines.


Patients suffering from IHPS presents with signs and symptoms within three to six weeks from birth. The following signs and symptoms are commonly seen among infants with IHPS:

  • Projectile vomitingBabies with IHPS will have forceful vomiting of ingested milk after 30 minutes of intake [5]. The severity of the infant’s vomiting increases with the pyloric narrowing of the lumen.
  • Persistent hunger: Infants with IHPS who frequently vomit will feel hungry more often.
  • Dehydration: The incessant vomiting may cause fluid and electrolyte imbalance that may lead to life-threatening dehydration.
  • Constipation: Patients diagnosed with IHPS may have obvious changes with their bowel movement due to the inadequate emptying gastric contents to the lower intestinal tract.
  • Weight changes: The pyloric stenosis in infant may prevent the infant from gaining weight and may also cause weight loss in advanced cases.
  • Abdominal contractions: Infants suffering from IHPS will show signs of wave-like contractions in the upper abdominal area due to the stomach propulsive force that pushes the food contents through a narrowed pyloric opening.
Weight Loss
  • She was referred for abdominal pain, fever, weight loss and eosinophilia. A sonographic examination revealed a concentric pyloric stenosis, with antral palsy and ascites.[ncbi.nlm.nih.gov]
  • Weight changes: The pyloric stenosis in infant may prevent the infant from gaining weight and may also cause weight loss in advanced cases.[symptoma.com]
  • Pyloric stenosis can keep a baby from gaining weight, and sometimes can cause weight loss.[mayoclinic.com]
  • Depending on the duration of symptoms, patients may suffer significant weight loss, even falling below birth weight.[mdedge.com]
  • Pyloric stenosis can lead to weight loss or poor weight gain from frequent vomiting, because the body cannot get the nutrients it needs from food.[rch.org.au]
Cyanotic Congenital Heart Disease
  • Prostaglandin E1 (PGE1) is widely used in neonates with cyanotic congenital heart disease who depend on the patency of the ductus arteriosus for oxygenation.[ncbi.nlm.nih.gov]
Death in Infancy
Paroxysmal Cough
  • Arch Dis Child 2007; 92 : 271-273 doi:10.1136/adc.2006.110007 Archimedes Nitin Maheshwai Specialist Registrar (Paediatrics), Oxford Deanery, UK; nitin023@rediffmail.com A 5-week-old infant is admitted to a high dependency unit with paroxysmal cough associated[web.archive.org]
  • Statistics from Altmetric.com A 5-week-old infant is admitted to a high dependency unit with paroxysmal cough associated with dusky episodes.[adc.bmj.com]
  • Only a single case series exists that suggests an association between azithromycin and IHPS. 10 The report describes how a set of triplets, who were born at 32 weeks’ gestation, were admitted at 7 weeks of life for paroxysmal cough and treated with azithromycin[pediatrics.aappublications.org]
Pleural Effusion
  • Chest radiography and computed tomography (CT) revealed a massive left pleural effusion and left tension pneumothorax. Abdominal CT revealed pyloric stenosis with a remarkably dilated stomach.[ncbi.nlm.nih.gov]
  • They include: Vomiting. The first symptom is usually vomiting.[kidshealth.org]
  • They include: Vomiting - The first symptom of pyloric stenosis is usually vomiting.[web.archive.org]
  • Signs include: Vomiting after feeding. The baby may vomit forcefully, ejecting breast milk or formula up to several feet away (projectile vomiting). Vomiting might be mild at first and gradually become more severe as the pylorus opening narrows.[mayoclinic.com]
  • 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.[en.wikipedia.org]
Projectile Vomiting
  • Watch for these signs and symptoms: Projectile vomiting. Pyloric stenosis often causes projectile vomiting — the forceful ejection of milk or formula up to several feet away — within 30 minutes after your baby eats.[web.archive.org]
  • But these babies don't have projectile vomiting. gastroenteritis (inflammation in the digestive tract that can be caused by viral or bacterial infection) also can cause vomiting and dehydration.[kidshealth.org]
  • The classic presentation includes projectile vomiting and an infant who remains hungry after vomiting.[clinicaladvisor.com]
Abdominal Pain
  • She was referred for abdominal pain, fever, weight loss and eosinophilia. A sonographic examination revealed a concentric pyloric stenosis, with antral palsy and ascites.[ncbi.nlm.nih.gov]
  • Abdominal pain. Wave-like motion of the abdomen shortly after feeding and just before vomiting occurs. Cleveland Clinic News & More Cleveland Clinic News & More[my.clevelandclinic.org]
  • Common Symptoms of Pyloric Stenosis: Forceful vomiting of milk or baby formula, normally beginning at about 3 to 5 weeks old Constant hunger due to emptying of stomach Dehydration due to repeated loss of fluids Weight loss Small stools Abdominal pain[wakemed.org]
Failure to Thrive
  • Abstract We report a newborn with fetal alcohol syndrome with severe feeding intolerance and failure to thrive due to pyloric stenosis.[ncbi.nlm.nih.gov]
  • Failure to thrive/weight loss may progress to increasing volume depletion. An olive-shaped mass may be palpable in the right upper abdomen. Ultrasound shows pyloric channel length 17 mm and pyloric muscle thickness 4 mm.[bestpractice.bmj.com]
  • Everyone has an image of what the classic infant with Pyloric Stenosis looks like: Child has evidence of failure to thrive and appears wrinkled and dehydrated.[pedemmorsels.com]
  • Presentation A 25 days old male infant presented with complaints of non-bilious vomiting and failure to thrive. The baby was normal at birth with no other obvious abnormality.[sonoworld.com]
  • GER can lead to failure to thrive, chronic lung disease, esophagitis, and esophageal strictures. [45] Symptoms usually begin by 6 weeks of life but resolve by 2 years of age. [46] Barium swallow and radionuclide scan may show esophageal reflux, and endoscopy[online.epocrates.com]
Abdominal Mass
  • Olive-sized abdominal mass. A mass about the size of an olive may be felt in the upper abdomen. The mass should be hard, mobile, and non-tender. Pylorospasm. A spasm of the pyloric muscle may occur due to increased motility.[encyclopedia.com]
  • Among more common side effects are fever, rash, apnoea, diarrhoea, jitteriness, and flushing.[ncbi.nlm.nih.gov]
Cesarean Section
  • Infants delivered by cesarean section had a higher risk of pyloric stenosis. It is well established that delivery by elective cesarean section is less stressful for the fetus than normal vaginal delivery ( 28 ).[doi.org]
  • A meta-analysis that investigated perinatal factors associated with hypertrophic pyloric stenosis onset and reported that first-born (OR 1.19, 95% CI: 1.07-1.33), cesarean section delivery (OR 1.63, 95% CI: 1.53-1.73), preterm birth (OR 1.37, 95% CI:[emedicine.com]


A detailed clinical history of the infant may give away the diagnosis of IHPS. Physical examination of the abdomen will reveal a wave-like motion of the stomach area during ingestion of milk. An olive size lump will be palpable at the area of the gastric outlet reflecting the hypertrophic muscle of the disease. Blood tests are ordered to determine the presence of electrolyte imbalance and uncover early signs of dehydration. Imaging studies like abdominal ultrasound, computed tomography (CT scan), and magnetic resonance imaging (MRI) confirm the diagnosis pyloric stenosis [6].

Left Pleural Effusion
  • Chest radiography and computed tomography (CT) revealed a massive left pleural effusion and left tension pneumothorax. Abdominal CT revealed pyloric stenosis with a remarkably dilated stomach.[ncbi.nlm.nih.gov]
Helicobacter Pylori
  • The acquired pyloric stenosis was treated medically with a proton pump inhibitor and Helicobacter pylori eradication therapy with excellent recovery.[ncbi.nlm.nih.gov]
Intranuclear Inclusion Bodies
  • Biopsies revealed large cells with intranuclear inclusion bodies, which stained positive for the anti-CMV antibody. Local TA injections are useful, however, CMV ulcer might occur as adverse events.[ncbi.nlm.nih.gov]
Pleural Effusion
  • Chest radiography and computed tomography (CT) revealed a massive left pleural effusion and left tension pneumothorax. Abdominal CT revealed pyloric stenosis with a remarkably dilated stomach.[ncbi.nlm.nih.gov]


Infantile hypertrophic pyloric stenosis should always be treated as a medical emergency in the emergency room setting. It is imperative that the acid-base balance and the electrolyte deficiency should be corrected promptly to avoid grave complications [7]. Signs of shock due to dehydration are immediately treated with an intravenous bullous of crystalloid fluids at 20 mL/Kg. Infants presenting with milder symptoms are given intravenous fluids at 1.5 to 2 times the normal maintenance rate with 5% dextrose in 0.33% or 0.25% sodium chloride admixed with 2-4 mEq of Potassium Chloride per 100 ml solution.

Urine output and acid base balance are continually monitored while in the patient is admitted in the hospital. The definitive treatment for pyloric stenosis is the surgical correction of the obstruction by pyloromyotomy. This procedure may be performed through laparoscopic surgery for shorter hospital stay and for cosmetic reasons [8]. A cohort study in the United Kingdom, demonstrated that laparoscopic pyloromyotomy shortens time until full feedings, lessens incidence of emesis, and lowers the requirement of analgesia among IHPS patients [9]. Post-operative infants are regularly monitored for the recurrence of persistent vomiting which is a sign of an inadequate pyloromyotomy procedure [10].


Patients suffering from infantile hypertrophic pyloric stenosis carry an excellent prognosis after surgical intervention. In fact, infants may be given small portion of feedings in increasing frequency a few hours post operatively. Patients subjected to laparoscopic pyloromyotomy will have faster recovery, better cosmesis, and lesser post-operative emesis compared to those exposed to the traditional surgical approach [4]. Untreated patients may develop dehydration and serious malnutrition problems in the future.


The definitive etiology of pyloric stenosis is still unknown, although studies have been focusing on the active role of genes and environment on its occurrence and prevalence. Parents with pyloric stenosis are most like to give birth to children with IHPS. Pyloric stenosis in adults and may be idiopathic or secondary to ulcers, tumors or inflammatory diseases. 


In the United States, the current incidence of infantile hypertrophic pyloric stenosis is 2 to 4 cases per 1000 live births. Mortality rate is usually very low and unexpected. Deaths usually occurs with the late diagnosis of the pyloric stenosis due to dehydration and hypovolemic shock. IHPS has predilection with the white race compared to the black, Hispanic and Asian races. They appear less common among siblings with mixed racial lineages.

Males are predisposed to IHPS more than females with 4 is to 1 ratio, with 30% of cases occurring among first born males. Pyloric stenosis begins to manifest within the first 3 weeks of life where it is usually diagnosed at that age group. 

Sex distribution
Age distribution


The pathogenesis of pyloric stenosis is primarily due to the marked hypertrophy and hyperplasia or the circular and longitudinal muscle layer of the pylorus. These cellular changes leads to the lengthening of the pyloric canal and the pyloric sphincter becomes thickened. The soft tissue mucosa becomes grossly edematous and thick leading to the mechanical obstruction of the gastric outlet to the small intestine. Advanced cases of pyloric stenosis may lead to stomach dilatation due to long standing partial obstruction.

The etiology of IHPS is described to be multifactorial involving hereditary factors and extrinsic factors [1]. Other etiologic factors like infantile hypergastrinemia, exposure to macrolide antibiotics [2], abnormal myenteric plexus innervation, and neuron devoid of nitric oxide synthase. Children who bottle fed are at risk in developing IHPS during infancy [3].


IHPS is a congenital defect of the pylorus that presents within the third to sixth weeks of life; thus, no modifiable activities or lifestyle modifications can be afforded to prevent its occurrence. It genetic nature, may prompt attending pediatricians to carefully examine the abdomen and note for early signs of pyloric stenosis among siblings of parents with IHPS. There are no guidelines for the prevention of aquired pyloric stenosis.


Pyloric stenosis is an uncommon medical condition that results from the muscular thickening of the gastric pylorus. Pyloric stenosis is commonly seen among infant patients presenting with forceful vomiting, dehydration, and weight loss. Infantile pyloric stenosis is the most common cause of intestinal obstruction among infants. Pyloric stenosis rarely occurs in adults and may be caused by ulcers, tumors or inflammatory diseases.

Patient Information


Pyloric stenosis is a clinical condition characterized by the partial or complete obstruction of the pyloric lumen usually due to muscular hypertrophy or hyperplasia of the luminal walls.


Genetic transmission is implicated for most of the cases. Environmental factors like maternal macrolide therapy, infant bottle feeding, and infantile gastrinemia play a role. Rarely pyloric stenosis may be aquired. 


Infants will frequently present with post prandial projectile vomiting 30 minutes after feeding. They will appear to be hungry a few minutes after vomiting. Patients will have signs of dehydration and weight loss. A wave-like movement of the stomach will be physically observable among infants.


A detailed clinical examination and history will clinch the diagnosis. Blood tests for acid-base balance and electrolytes are monitored. Imaging studies can definitively establish its diagnosis.

Treatment and follow-up

The condition is a medical emergency that will require immediate fluid resuscitation, and correction of the acid-base and electrolyte imbalance. The definitive treatment is surgical pyloromyotomy.



  1. Panteli C. New insights into the pathogenesis of infantile pyloric stenosis. Pediatr Surg Int. Sep 16 2009.
  2. Lund M, Pasternak B, Davidsen RB, Feenstra B, Krogh C, Diaz LJ, et al. Use of macrolides in mother and child and risk of infantile hypertrophic pyloric stenosis: nationwide cohort study. BMJ. Mar 11 2014; 348:g1908.
  3. McAteer JP, Ledbetter DJ, Goldin AB. Role of bottle feeding in the etiology of hypertrophic pyloric stenosis.JAMA Pediatr. Dec 2013; 167(12):1143-9.
  4. Taqi E, Boutros J, Emil S, Dube S, Puligandla P, Flageole H. Evaluation of surgical approaches to pyloromyotomy: a single-center experience. J Pediatr Surg. May 2007; 42(5):865-8.
  5. Cincinnati Children's Hospital Medical Center. Evidence based clinical practice guideline for hypertrophic pyloric stenosis. Cincinnati (OH): Cincinnati Children's Hospital Medical Center; 2007 Nov 14.
  6. Maheshwari P, Abograra A, Shamam O. Sonographic evaluation of gastrointestinal obstruction in infants: a pictorial essay. J Pediatr Surg. Oct 2009; 44(10):2037-42.
  7. Pandya S, Heiss K. Pyloric stenosis in pediatric surgery: an evidence-based review. Surg Clin North Am. Jun 2012; 92(3):527-39, vii-viii.
  8. Saha N, Saha DK, Rahman MA, Aziz MA, Islam MK. Laparoscopic versus Open Pyloromyotomy for Infantile Hypertropic Pyloric Stenosis: An Early Experience. Mymensingh Med J. Jul 2012; 21(3):430-4.
  9. Aldridge RD, MacKinlay GA, Aldridge RB. Choice of incision: the experience and evolution of surgical management of infantile hypertrophic pyloric stenosis. J Laparoendosc Adv Surg Tech A. Feb 2007; 17(1):131-6.
  10. Leclair MD, Plattner V, Mirallie E, Lejus C, Nguyen JM, Podevin G. Laparoscopic pyloromyotomy for hypertrophic pyloric stenosis: a prospective, randomized controlled trial. J Pediatr Surg. Apr 2007; 42(4):692-8.

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Last updated: 2019-07-11 21:46