3. INTRODUCTION
● Infantile hypertrophic pyloric stenosis (IHPS):
○ Affects young infants, in which the antropyloric portion of the stomach becomes
abnormally hypertrophy of the circular muscle of the pylorus and manifests as
obstruction to gastric emptying.
○ Can progress to near-complete obstruction of the gastric outlet, leading to forceful
vomiting.
○ HPS is a common cause of GI obstruction in the young infant and can be seen in about 0.2%
to 0.4% of children
○ Not present at birth, but mechanical obstruction typically develops in the first 2-8
weeks of life.
○ Most common condition requiring surgery in infants.
○ Treatment: Surgical pyloromyotomy.
○ Blair described a postmortem findings consistent with hypertrophic pyloric stenosis
in 1717.
○ First described by Hirschsprung in 1888.
4. EPIDEMIOLOGY
● Infantile hypertrophic pyloric stenosis (IHPS)
○ Occurs in approximately 2 to 3.5 per 1000 live births, although rates and trends vary markedly
from region to region.
○ It is more common in males than females (4:1 to 6:1).
○ Infants born preterm as compared with those born at term.
○ Approximately 30 to 40 percent of cases occur in first-born children (approximately 1.5-fold
increased risk).
■ less common in infants of older mothers.
■ Symptoms usually begin between 3 and 5 weeks of age, and very rarely occur after 12
weeks of age.
5. ANATOMY
The pylorus connects the stomach to the deudenum,
It has 2 parts which are the pyloric antrum opening part to the body of the stomach
Pyloric canal which is opening to the deudenum.(Has 2 muscles- inner circular and outer longitudinal)
Pyloric sphincter has 3 muscle layers middle circular with inner and outer longitudinal.
The pyloric sphincter is a thin circular band of visceral muscles surrounding the pyloric opening of the
inferior end of the stomach.
Role is act as valve to control the flow of partially digested food
Pyloric stenosis involves hypertrophy of circular muscle of the pylorus resulting in narrowing and
obstruction of the pyloric channel by compression of longitudinal folds of mucosa.
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10. PATHOPHYSIOLOGY
● Pyloric stenosis involves hypertrophy of circular muscle of the pylorus resulting in narrowing and
obstruction of the pyloric channel by compression of longitudinal folds of mucosa.
○ Grossly the pylorus becomes enlarged to resemble a tumor approximate the size and shape of an
olive (i.e. 2 cm long and 1 cm in diameter).
● Gastric fluid loss is associated with the loss of H+ and CL-. Fluid loss is different from that seen in
conditions with an open pylorus, which involves gastric, Pancreatic, biliary, and intestinal fluid.
○ Hyperchloremic hypokalemic biochemical disturbance observed in pyloric stenosis.
○ With protracted vomiting an extracellular volume deficit ensues, and urinary excretion of K+
AND H+ increases in an attempt to preserve Na+ and volume.
■ The initially alkalotic urine then becomes acidotic (Paradoxical aciduria).
■ With signs of protracted DeH2O should alert severity of the volume and total body K+
Deficit.
11. ETIOLOGY
The exact etiology of HPS is still unknown but probably multifactorial, involves genetic predisposition and
environmental factors.
Though now said to be acquired than congenital.
Other multiple factors such as neural and hormonal (Though not substantiated).
There is some evidence of higher incidence of HPS in babies of pregnant or breastfeeding women treated
with macrolide antibiotics; however, this evidence is less clear.
Other risk factors for HPS include prematurity, young maternal age, and maternal smoking
Association with B and O Blood groups and maternal stress during 3rd Trimester have been suggested.
Neonatal hypergastrinemia and gastric hyperacidity may play a role.
Prematurity (<37 weeks gestation) may be a risk factor; one study reported an incidence of 2.99/1000 in
preterm infants compared with 2.25/1000 in term infants.
Reduced neuronal NOS (Nitric oxide synthetase) – Mediates non-adrenergic noncholinergic smooth-
muscle relaxation throughout the gut.
12. GROWTH FACTORS AND GASTROINTESTINAL PEPTIDES.
● Many GIP or growth factors have a causal potential relationship to IHPS.
○ Substance P a neurotransmitter responsible for enteric muscle contraction has been implicated in
producing chronic pylorospasm leading to muscle hypertrophy
○ Present in higher concentration in the pyloric muscle of patients with HIS.
○ Increase in the gene expression of EGF, TGF- a and Insulin like growth factor-1 and an increase
in immunostaining activity in IHPS
○ Somatostatin, secretin, entero-glucagon, and neurotensin have also been implicated but their role
has not been substantiated, and no clear etiologic-relationship has been identified.
13. ● NEUROTROPHINS, NEURAL DEVELOPMENT AND NERVE FUNCTION
○ Neurotrophins, noted to be decreased in IHPS
○ The pylorus in IHPS is deficient in glial derived growth factors
○ Reduced density of nerve supporting cells in the circular and longitudinal muscle layers in
infants with IHPS.
○ Decreased numbers of interstitial cells of cajal,
○ Lack of Heme oxygenese-2
14. ETIOLOGY
• Environmental factors;
• Maternal smoking during pregnancy increases the risk for IHPS by 1.5 to 2.0-fold.
• Several studies have suggested that bottle feeding rather than breastfeeding increases the
risk for IHPS.
• Genetic factors;
• Identified a susceptibility locus that contains the apolipoprotein A1 (APOA1) gene
cluster.
• for observed associations between low plasma cholesterol at birth and risk of IHPS. The
study also confirmed previous findings of two other susceptibility loci (near MBNL1 and
NKX2-5), which are small contributors to overall risk.
15. ● Antibiotics;
○ Macrolides:
■ Both erythromycin and azithromycin are associated with increased risk of IHPS,
particularly when administered to infants younger than two weeks of age. The
risk of IHPS with clarithromycin is not known.
● Several studies have reported an association between the use of macrolide
antibiotics by women during late pregnancy or while breastfeeding and the
development of IHPS in their offspring.
16. CLINICAL FEATURES
● Non-bilious projectile vomiting at 2-8 weeks of life.
○ The vomiting occurs immediately after feeding and varies in intensity, depending upon the degree of
stenosis present.
○ The vomiting increases in severity to become projectile and will typically involve the entire volume
of the feed.
○ Infants remain hungry after the vomiting and looks well in between.
○ Might be with blood or coffee ground as a result of gastritis.
● Delay in presentation or diagnosis and may present with dehydration
● Jaundice An indirect hyperbilirubinemia can be seen in HPS in a small percentage of infants due to
decreased levels of glucuronyl transferase when the liver is deprived of substrate from poor caloric intake.
● Preterm usually diagnosed 2 weeks later than terms.
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18. DIAGNOSIS
● HISTORY
○ Forceful vomiting, non bilious occurs after feeds.
○ Ask for appetite (Strong appetite), Urine output (DeH20), Stool (If blood suggest infectious colitis), Diet (Exposure to cow
film or soy proteins through formula milk: trigger for dietary protein intolerance.), Medication (Macrolide antibiotics to
mother and child). Family history of stenosis
● PHYSICAL EXAM
○ poor weight gain or even weight loss
○ Jaundice is observed in approximately 5% of infants.
○ Palpating the hypertrophied pylorus, also referred to as the palpable "olive“
■ This "olive" is described as a firm, mobile, olive shaped mass that is found to the right of the umbilicus beneath the
liver edge.
○ Another finding is the gastric peristaltic wave that can be seen after feeding.
■ A wave traversing the abdomen from left to right, representing intense contractions against an obstruction.
○ Abdominal distention may be a late finding, as is usually the case with proximal GI obstructions.
● BLOOD INVESTIGATIONS (FBC, U&E, Blood gases)
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21. ● Ultrasound (Gold- standard): Approximately 95% sensitivity
○ Diagnosis include an elongated pyloric channel (longer than 15 to 19 mm), an enlarged pyloric diameter (greater
than 10 to 14 mm), and a thickened muscle wall (greater than 3 to 4 mm
○ Pyloric mass
● Point-of-care ultrasound (POCUS) in the emergency room setting has also shown to accurately diagnose HPS
● Upper GI contrast Study.
○ Signs:
■ bulge of the pyloric muscle into the antrum, known as the "shoulder sign"
■ streaks of barium flowing through the stenosed channel, producing either a single "string sign "or a "double
track sign" (if there are parallel streaks)
■ Mushroom like sign
■ Bird beak at pylorus
■ A "caterpillar sign" has also been described on plain films or upper GI of patient’s with HPS where the
stomach appears dilated and air filled with undulating borders secondary to vigorous peristaltic gastric
waves. This gives the appearance of a caterpillar.
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23. ● METABOLIC ABNORMALITIES:
○ Vomiting leads to loss of HCL
○ Hypochloremia will impaire the ability of kidney to excrete the bicarbonate
○ Hyperaldosteronism will develop because of hypovolemia
○ High aldosterone will cause Na+ retention (To correct the fluid vol.) and increase excretion of K to the
urine.
○ At certain limit when the K depleted, the Na reabsorb in exchange with hydrogen ion.
○ Despite that the baby is in metabolic alkalosis the baby will develop paradoxical alkalosis
○ The rapid compensatory mechanism for metabolic alkalosis is hypoventilation which will lead to respiratory
acidosis due to elevated level of arterial pCO2.
26. TREATMENT
● NON OPERATIVE
● OPERATIVE
● NON OPERATIVE
○ Oral Atropine
■ Atropine sulfate, which induces smooth muscle relaxation has potential to relax the hypertrophied pylorus.
■ shown to be successful in up to 80% in some studies and can be considered when surgical expertise is not
available or for patients who are not good surgical candidates.
■ Atropine might suppress gastrointestinal peristalsis, which potentially reduces pyloric muscular hypertrophy.
○ Balloon dilatation:
■ Endoscopically guided balloon dilation for IHPS has been described.
■ However, because balloon dilatation does not reliably disrupt the seromuscular ring, attempts at this technique
are best reserved for patients in whom general anesthesia would pose a significant risk or in whom a surgical
approach to the pylorus is not possible.
27. RESCUSCITATE PATIENT
○ Not a surgical emergency.
○ Access the level of severity of fluid and electrolyte abnormalities.
○ NPO.
○ NGT (+/-) can cause more loss of fluids.
○ Fluid (D5 0.45 NS) + 20mEq/L KCL.
○ Monitor the Urine output and serum electrolyte.
○ ***** End point of resus*****
■ Adequate Urine output of greater than 1.5mls/kg/hr.
■ Chloride level greater than 100 mEq/l
■ Bicarbonate level to less than 30 mEq/L (high Bicarb leads to Alkalosis induced apnea)
28. ● OPERATIVE TREATMENT.
○ Pyloromyotomy
■ Definitive management of infantile hypertrophic pyloric stenosis (IHPS) is surgery.
■ The timing of surgery depends upon the clinical status of the infant.
● If the child is well-hydrated with normal electrolytes, and if surgeons with expertise in the
procedure are available, surgery may take place on the day of diagnosis.
● Surgery should be delayed in the setting of dehydration and/or electrolyte derangements.
■ The classical operation for IHPS is Ramstedt pyloromyotomy,
● which involves a longitudinal incision of the hypertrophic pylorus with blunt dissection to the
level of the submucosa.
● it relieves the constriction and allows normal passage of stomach contents into the duodenum.
● Procedure of choice regardless the abdominal access (open or closed).
30. REFERENCES
• Rich BS, Dolgin SE. Hypertrophic Pyloric Stenosis. Pediatr Rev. 2021;42(10):539-545.
• Kilegman RM, St Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM. Chapter 355. Pyloric Stenosis and
Other Congenital Abnormalities of the Stomach. In: Behrman RE, St Geme JW, et al (eds). Nelson Textbook of
Pediatrics, 21st edition. 2020, Elsevier, Philadelphia pp. 1946-1950.e1.
• Galea R, Said E. Infantile Hypertrophic Pyloric Stenosis: An Epidemiological Review. Neonatal Netw.
2018;37(4):197-204. doi: 10.1891/0730-0832.37.4.197.
• Abdellatif M, Ghozy S, Kamel MG, Elawady SS, Ghorab MME, Attia AW, Le Huyen TT, Duy DTV, Hirayama
K, Huy NT. Association Between Exposure to Macrolides and the Development of Infantile Hypertrophic Pyloric
Stenosis: A Systematic Review and Meta-analysis. Eur J Pediatr. 2019;178(3):301-314. doi: 10.1007/s00431-
018-3287-7.
• Park JS, Byun YH, Choi SJ, Lee JS, Ryu JM, Lee JY. Feasibility of Point-of-Care Ultrasound for Diagnosing
Hypertrophic Pyloric Stenosis in the Emergency Department. Pediatr Emerg Care 2021;37(11):550-554.
• Chen F, Cernigliaro J, Bhatt S. The Caterpillar Sign. Abdom Radiol. 2021;46:394–395. doi.org/10.1007/s00261-
020-02611-6.
• Jobson M, Hall NJ. Contemporary management of pyloric stenosis. Sem Pediatr Surg. 2016;25:219-224.
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