Infantile hypertrophic pyloric stenosis

1. Infantile Hypertrophic Pyloric Stenosis Dr Muki MD 5 2013

2. INTRODUCTION Pyloric stenosis , or infantile hypertrophic pyloric stenosis (IHPS ) is a condition characterised by hypertrophy of the two muscle layers of the pylorus. The pyloric canal lengthens, the whole pylorus thickens , and the mucosa becomes oedematous causing functional obstruction of the gastric outlet.

3. Epidemiology The incidence of IHPS is approximately 2 to 5 per 1,000 births per year in most white populations. The male-to-female ratio is approximately 4:1 . Male and female children of affected fathers carry a risk of 5% and 2% respectively, of developing IHPS. The incidence is 2.4 per 1000 live births in whites, 1.8 in Hispanics, 0.7 in blacks, and 0.6 in Asians. It is also less common amongst children of mixed race parents.

4. Clinical Presentation Symptoms Vomiting is the first symptom in most children may occur after every feeding or only after some feedings Usually starts around 3 weeks of age, but may start any time between 1 week and 5 months of age Forceful (projectile vomiting) The infant is hungry after vomiting and wants to feed again

5. Other symptoms generally appear several weeks after birth and may include: Dehydration gets worse with the severity of the vomiting .Prolonged vomiting leads to the loss of large quantities of gastric secretions rich in H+ and Cl - . As a result of dehydration, the kidney attempts to conserve Na+ to maintain volume, by exchanging them for K+ and H+ .

6. Starvation can exacerbate diminished hepatic glucoronyl transferase activity, and indirect hyperbilirubinemia may be seen in 1-2% of affected infants . Failure to gain weight or weight loss . Wave-like motion of the abdomen shortly after feeding and just before vomiting occurs The peristaltic waves can be seen across abdomen passing from right to left and reverse immediately prior to vomiting

7. Etiology It has been found that,in IHPS specimens, the muscle layer is deficient in : – T he quantity of nerve terminals –Markers for nerve-supporting cells – Peptide-containing nerve fibers It is postulated that this abnormal innervation of the muscular layer leads to failure of relaxation of the pyloric muscle, increased synthesis of growth factors, and subsequent hypertrophy, hyperplasia, and obstruction.

8. There is an increased incidence of IHPS in infants receiving erythromycin. The reason is unclear, although a prokinetic effect on gastric muscle contraction is postulated.

9. Diagnosis Initially suggested by the typical clinical presentation. In physical examination : The mass is firm, mobile, approximately 2 cm, best palpated from the left, located in the midepigasrtrium beneath the liver edge. Palpation of the hard muscle mass or olive is diagnostic in conjunction with a typical history. Diagnosis by palpation of olive only successful 49% of cases in recent years vs. 78% 30 years ago. Palpation requires a calm infant with relaxed abdominal musculature, which is difficult in these hungry babies.

10. Ultrasonography is used to measure the thickness of the pyloric wall and the length of the pyloric canal . – normal wall thickness <2mm, IHPS >4 mm – normal length of the pyloric canal <10 mm, IHPS >14 mm Sensitivity and specificity as high as 100%

11. Differential Diagnosis Gastroesophageal reflux, with or without hiatal hernia. Differentiated by radiologic studies. Also amount of vomitus is smaller, and the infant does not usually lose weight. Adrenal insufficiency. Differentiated by absence of metabolic acidosis, hyperkalemia , and elevated urinary sodium. Viral gastroenteritis. Unusual in infants less than 6 weeks of age. Associated with significant diarrhea and sick contacts.

12. Treatment The preoperative treatment is directed toward correcting the fluid, acid-base, and electrolyte losses. Intravenous fluid therapy is begun with 0.45–0.9% saline, in 5–10% dextrose, with the addition of potassium chloride in concentrations of 30– 50mEq/L. Fluid therapy should be continued until the infant is rehydrated and the serum bicarbonate concentration is less than 30mEq/ dL , which implies that the alkalosis has been corrected. Most infants can be rehydrated within 24 hours

13. SURGICAL MANAGEMENT Once resuscitated the infant can undergo the Fredet-Ramstedt pylormyotomy , which is the procedure of choice . It consist of incision in to the sphincter muscle of pylorus. NG tube is passed and gastric content are aspirated just prior to surgery.

14. REFERENCES AND FURTHER READING Medscape Reference. Drugs, Diseases & Procedures. Paediatric Pyloric Stenosis [Online]. 2012 [ cited19th August 2012]. Available from: http://emedicine.medscape.com/article/803489-overview ( accessed25th November 2012). MacDonald NJ, Fitzpatrick GJ, Moore KP, Wren WS and Keenan M. Anaesthesia for congenital hypertrophic pyloric stenosis . A review of 350 patients. Br. J. Anaesth . 1987;59:672-677. Panteli C. New insights into the pathogenesis of infantile pyloric stenosis . Pediatr Surg Int. 2009:25(12 );1043-1052. Perger L, Fuchs JR, Komidar L, Mooney DP. Impact of surgical approach on outcome in 622 consecutive pyloromyotomies at a paediatric teaching institution. J Pediatr Surg. 2009;44:2119-25.

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