5.Hypertrophic Pyloric Stenosis prp.pptx

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1. Hypertrophic Pyloric Stenosis Yonas Ademe July, 2017 1

2. Epidemiology IHPS is the most common cause of GOO in infants The prevalence ranges from 1.5 to 4.0 per 1000 live births in Caucasian infants but is less prevalent in African-American and Asian children Reports have suggested that the incidence is increasing I t is more common in boys than girls, with a ratio of approximately 2:1 to 5:1 2

3. Anatomy and Histology The gross appearance of the pylorus in IHPS is that of an enlarged, pale muscle mass usually measuring 2 to 2.5 cm in length and 1 to 1.5 cm in diameter Histologically , there is marked muscle hypertrophy and hyperplasia primarily involving the circular layer and hypertrophy of the underlying mucosa 3

4. Etiology No definitive causative factors have been identified for IHPS IHPS is now thought to be caused by a mechanism other than a developmental defect and it is generally agreed that IHPS is not a congenital abnormality Both genetic and environmental factors seem to play a role in the pathophysiology Alterations in relaxation of the pyloric muscle secondary to neuronal and local neurotransmitter abnormalities are also impicated Reduced nitric oxide may contribute to the pathogenesis 4

5. Cont. Evidence for a genetic predisposition includes: Variability among races A clear male preponderance An increased risk to first-born infants with a positive family history The risk for IHPS in the offspring of mothers who had pyloric stenosis as infants is greater than if the father had IHPS Certain ABO blood types Incidence is increased in infants with type B and O blood groups 5

6. Cont. Environmental factors associated with IHPS include: The method of feeding (breast-feeding versus formula feeding) Transpyloric feeding of premature infants Erythromycin exposure Administered for pertussis postexposure prophylaxis Seasonal variability 6

7. Associations Tracheoesophageal fistula H ypoplasia or agenesis of the inferior labial frenulum 7

8. Clinical features The typical clinical finding in an infant with IHPS is the onset of nonbilious vomiting at 2 to 8 weeks of age with a peak occurrence at 3 to 5 weeks Initially, the emesis may not be frequent or forceful, but over a period of several days it progresses to nearly every feeding and becomes forceful ( projectile) On occasion, there may be blood in the emesis that gives it a coffee-ground appearance as a result of gastritis or esophagitis 8

9. Cont. Infants with IHPS remain hungry after emesis and are otherwise not ill appearing or febrile A significant delay in diagnosis leading to severe dehydration, however, results in a lethargic infant Some infants have diarrhea (starvation stools) and are thought to have gastroenteritis 9

10. Cont. 2% to 5% of infants have jaundice from indirect hyperbilirubinemia , which can reach levels as high as 15 to 20 mg/ dL This is believed to be secondary to glucuronyl transferase deficiency 10

11. Cont. In premature infants IHPS is generally diagnosed 2 weeks later than in term infants The emesis may not be projectile and evolves more slowly F requently leads to a delay in diagnosis 11

12. DDX Pylorospasm G astroesophageal reflux Food allergy Gastroenteritis I ncreased intracranial pressure M etabolic disorders Rare surgical causes Antral webs P yloric atresia D plication cyst of the antropyloric region E ctopic pancreatic tissue within the pyloric muscle May be difficult to differentiate from IHPS without further imaging 12

13. Diagnosis C ardinal features of IHPS Nonbilious projectile vomiting V isible peristaltic waves in the left upper part of the abdomen H ypochloremic , hypokalemic metabolic alkalosis 13

14. Cont. A definitive diagnosis can be made in 75% of infants with IHPS by careful physical examination of the upper part of the abdomen To be successful in palpating an enlarged pylorus (“the olive”), the infant must be calm, warm, and cooperative with preferably an empty stomach Procedure (may take 5 to 15 minutes) Supine position and legs bent to relax the abdominal muscles The examining hand should be placed on the epigastrium After the edge of the liver has been identified with the fingertips, gentle pressure deep to the liver and progressing caudally in the midline a third of the distance between the umbilicus and xiphoid should reveal a palpable pylorus Finding ≈2 cm in length, movable, olive shaped, and hard 14

15. Cont. U/S It is the standard imaging modality for diagnosing IHPS Sensitivity of ≈95% Criteria for a positive US study P yloric muscle thickness of 3.5 (in premature infants) to 4 mm or more and a pyloric channel length of 16 mm or greater Some centers also determine pyloric diameter and consider more than 14 mm to be abnormal 15

16. Cont. UGI contrast examination If US is not available or diagnostic Findings E longated pyloric channel S houlder sign a bulge of the pyloric muscle into the antrum D ouble tract sign P arallel streaks of barium seen in the narrowed channel If barium does not leave the stomach, it is not possible to confirm the diagnosis of IHPS because pylorospasm can also produce transient complete GOO Barium is generally preferred compared with water-soluble contrast to avoid the chemical pneumonitis should aspiration occur 16

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18. Treatment Pre-operative preparation The length of preparation depends on the severity of the fluid, acid-base and electrolyte abnormalities Most infants with IHPS should be able to be resuscitated within a 24-hour period With severe metabolic and fluid abnormalities, however , aggressive resuscitation should be avoided because it can produce rapid fluid and electrolyte shifts, possibly leading to seizures and other complications Oral feedings should be discontinued A NG tube should not be placed routinely Because it removes additional fluid and hydrochloric acid from the stomach, which perpetuates the electrolyte and acid-base imbalance 18

19. Cont. Cont. IV administration of 5% dextrose in 0.45 normal saline containing 20 mEq /L of KCl is the optimal resuscitation regimen for fluid and electrolyte replacement Under circumstances of extreme hypokalemia , the concentration of KCl can be increased to 30 mEq /L Withholding KCl in the IV fluid while awaiting urine output only delays appropriate replacement The exception (rare) is knowledge of preexisting renal impairment or evidence of acute renal compromise 19

20. Cont. Cont. IV fluid therapy should be correlated with the level of dehydration An initial rate for fluid resuscitation is 1.25 to 2 times the normal maintenance rate until adequate fluid resuscitation and urine output are achieved 20

21. Cont. Cont. Hyponatremia is rarely a problem Nonetheless , it is common to see normal saline given as an initial bolus However , there is little rationale for the use of normal saline because it enhances the hypokalemia by dilution and provides an excess amount of sodium 21

22. Cont. Cont. It is necessary to monitor urine output and serum electrolytes It is not usually necessary to evaluate the indirect hyperbilirubinemia , which occurs in a small percentage of infants with IHPS, further I t invariably resolves postoperatively 22

23. Cont. Operative procedure I t is important to emphasize that fluid and electrolyte abnormalities must be corrected preoperatively I ncluding having a serum bicarbonate below 30 mEq /L to avoid respiratory depression and prolonged postoperative intubation Before the induction of anesthesia, it is important to aspirate the stomach The operative procedure of choice remains the Ramstedt pyloromyotomy Laparoscopic technique is equally successful 23

24. Cont. Non-operative treatment It was practiced in the past in some European countries I nfants a re managed with frequent small feedings with or without atropin It may take months for the hypertrophied muscle to resolve The practice necessitates either a prolonged hospital stay or an attentive caregiver at home and may lead to aspiration and malnutrition The occasional mortality and the prolonged interval from diagnosis to resolution led to abandonment of this type of management 24

25. Cont. Endoscopic balloon dilation This has been successfully used in infants with persistent vomiting secondary to incomplete pyloromyotomy 25

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