Pyloric Stenosis

• Gastric outlet obstruction due to hypertrophic pylorus muscle, edema and narrowing of the pyloric canal
• Antropyloric muscle spasm leads to vomiting and dehydration
• Acquired condition - children are not born with pyloric stenosis but appears to result from progressive thickening of the pylorus after birth
• 1:250-1000
• M 4-8x > F
• caucasion predilection
• Not congenital defect/abnormality
  
• Study by Wallgren - 1000 male infants had a barium swallow immediately after birth with no anatomic abnormalities of the pylorus identified
  
• five of these infants subsequently developed IHPS
  
• More recent study, 1400 consecutive newborn infants underwent ultrasound (US) measurements of the pylorus, with no abnormalities seen.
  
• nine of these infants subsequently developed IPHS
  
• Etiology - multifactorial threshold inheritance or effects of multiple interacting loci
  
• Other mechanisms possibly incplicated
• Abnormal muscle innervation - weak evidence
• GI peptides/growth factors
• elevated serum prostaglandins
• infant hypergastrinemia
• substance P
• epidermal growth factor (EGF)
• Transforming growth factor alpha (TGF-alpha)
• insulin-like growth factor-I
• somatostatin
• secretin
• enteroglucagon
• neurotensin
  
• Neurotrophin
• receptors to neurotrophins - tyrosine kinase A receptor c-Kit is not present in IHPS tissue
• The pylorus in IHPS is also deficient in glial-derived growth factors (suggesting immature development of enteric nervous system)
  
• Nitric Oxide
  
• reduced level of neuronal nitric oxide synthase
• altered expression of  neuronal nitric oxide synthase exon 1c  regulatory region
• NEJM article looked at NADPH (nicotinamide-adenine dinucleotide phosphate diaphorase - virtually identical to nitric oxide synthase) in biopsy specimens from IHPS patients. Hypertrophied circular muscle did not have any NAPDH diaphorase activity, but the longitudinal muscle was normal.
  
• Conclusion was that lack of NO synthase may cause pylorospasm leading to IHPS.
  
• Vanderwinden J.M., Mailleux P., Schiffmann S.N., et al: Nitric oxide synthase activity in infantile hypertrophic pyloric stenosis. N Engl J Med 1992; 327: pp. 511  PMID: 1378938
  

• Birth - 5 months (mean age = 3wks)
• regurgitation progesses to non-bilious vomiting (can lead to projectile vomiting)
• key to the vomiting is "progressive"
• wanting to feed immediately after postprandial emesis
• emesis with every feed...
  
• Classic physical exam finding of "olivelike" mass palpated in epigastric region found only in textbooks, board exams, and anesthetized patients in prone position with NG tube decompression

• Hypochloremic, hypokalemic, metabolic alkalosis (secondary to acid loss from vomiting)
• excess bilcarb can be excreted in urine with obligate sodium loss followed by Water
• secondary hyperaldo due to increased reninrelease causes distal proton secretion and paradoxic aciduria
• usually total body K+ depletion (can have low or normal K+)
• US preferred imaging study (dependent on ultrasonographer and institution, repeat if necessary)
• Pyloric thickness >4mm or length >16mm
  
• 89% sensitivity
• 100% specificity
• Upper GI series and pyloric US reveal elongated pyloric channel
• Upper GI also reveals semilunar indentations on antrum muscle thickness and double track pyloric channel

• Antral web
• Annular pancreas
• Duodenal stenosis
• Pyloric channel ulcer
• Gastritis
• Allergic Gastroenteropathy
• Pylorospasm
• GER

• Treatment is a MEDICAL, not a surgical emergency
• Need to reverse hypochloremic alkalosis, restore volume status
• No surgery until electrolyte abnormalities are normalized and stable (often can take several days post admission)
• Avoid NGT (suction may make alkalosis worse)
  
• Surgery is curative
• Weber-Ramstedt pyloromyotomy
• RUQ -Robertson incision, periumbilical, or laproscopic approach
• Incise long axis of serosa and muscle on avascular mid-anterior surface, from 2mm proximal to pyloric vein to 5mm onto the lower antrum
• watch for mucosa becoming thinner on the antral side
• Open cicular muscle bluntly with Benson retractor, spread to achieve pyloromyotomy
• If mucosa is violated, defect is closed in layers and pyloromyotomy repeated on the opposite side
• Leak test can be performed by insufflating air and looking for bubble
  
• Note: if using laproscopic approach - use umbilical camera port with two stab ports: one to grasp the stomach or duodenum and the other to perform the pyloromyotomy
• Successful surgery includes protrusion gastric mucosa + free movement muscle edges
• Laparoscopy vs Open approach
• Laparoscopic pyloromyotomy has become the standard in the U.S.
  
• Ongoing debate as to which approach is superior
• As experience with laparoscopy  increases, outcome numbers noted below may improve
  
• Average length of stay - similar
• Average time to feeding - slightly shorter in Laparoscopic
  
• Range = 19-35hrs vs 20-61hrs in open approach
  
• Wound infection rates - simlar
• Average operative time - similar
• Range = 24-41min vs 19-33min in open approach
• Perforation rate - similar
  
• 4 studies cited higher perforation rate in laparoscopy but not statistically significant
• IL-6 levels (surrogate for stress) - lower in laparoscopy
• Fujimoro et al reported significantly lower levels 24hrs post-op
  
• Cost - higher for laparoscopy
• Aethetics - less noticeable scar in laparoscopy

• Post-operative vomiting occurs in 50% of cases due to local edema, delayed gastric emptying, and GER
• Frequent vomiting persisting beyond 3-4 days may suggest incomplete myotomy or unsuspected perforation
• Post-op contrast study may demonstrate leak but unable to assess completeness of myotomy
• Radiographic appearance of the pylorus will not improve for several weeks post-op
• Vomiting that is frequent and persistent 1week post-op should prompt re-exploration
  
• Normal pyloric thickness is seen by 6wks postop, but some gastric outlet abnormalities may persist on barium studies
• Long term complications/sequelae are minimal. Studies of adults 17-27yrs post-op reveal no GI differences (measureable) between post-op group and controls
  

• Feeding can be started 4hrs post-op for most infants
• Hemetemesis from gastritis may benefit from additional 6-12hrs delayed feeding
• Early aggresive feeding has higher incidence of  early post-op emesis, but this approach is usually successful and allows for earlier discharge
  
• Sample Feeding Schedule (note 3hr increments)
  
• 4hrs post-op - Pedialyte, 30mL
  
• 7hrs post-op - Formula (or breastmilk), 30mL
• 10hrs post-op - Formula (or breastmilk), 45mL
• 13hrs post-op - Formula (or breastmilk), 45mL
• 16hrs post-op - Formula (or breastmilk), 60mL
• 19hrs post-op - Formula (or breastmilk), 75mL
• 22hrs post-op - Formula (or breastmilk), as desired - back to normal feeds / prn
• For very small infants starting volume may be reduced to 15mL and increased in 15mL increments, as shown above. Normal feeding for smaller infants/premature infants may be less then shown above.
  

• Infantile hypertrophic pyloric stenosis was first reported / first references in the early 1700s.
  
• 1717 - Blair 1 described an infant with postmortem findings consistent with hypertrophic pyloric stenosis
  
• 1888 - Hirschsprung2 provided the first complete description of hypertrophic pyloric stenosis
• He believed that this entity was congenital and represented failure of involution of the fetal pylorus
  
• He named it angeborener pylorusstenose (congenital pyloric stenosis)
• 1908 - Dufour and Fredet3 in a landmark paper, suggested that surgical correction could be accomplished by splitting the hypertrophied pyloric muscle to the submucosa and closing the muscle transversely.
  1912 - Ramstedt 4 suggested that closure of the muscle was not necessary, and the current standard operation was established.
  
• of note - non-operative management had been tried mostly in Europe with frequent small feedings. Aspiration and malnutrition combined with higher mortality and prolonged duration of morbidity make this an unacceptable option in the U.S.
   
  

• eosinophilic gastroenteritis
• apert syndrome
• zellweger
• trisomy 18
  
• smith-lemli-opitz syndrome
• cornelia de lange syndrome
• erythromycin in neonates when given within first 2wks of life
  
• female infants of mothers treated with macrolide abx during pregnancy and while breastfeeding
• Icteropyloric syndrome (most common clinical association with IHPS)
  
• hyperbilirubinemia that resolves with surgical correction of pyloric stenosis
• may be associated with decreased glucuronyl transferase (5% of affected infants)
  
• posible mutation in bilirubin uridine diphosphate glucuronyl tranferase gene UGT1A1
• Direct hyperbili not typical and requires further investigation
• hiatal hernia
• peptic ulcer
• congenital nephrotic syndrome
• congenital heart disease
• congenital hypothyroidism