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
• It 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
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
• Frequently leads to a delay in diagnosis
11
12. DDX
• Pylorospasm
• Gastroesophageal reflux
• Food allergy
• Gastroenteritis
• Increased intracranial pressure
• Metabolic disorders
• Rare surgical causes
– Antral webs
– Pyloric atresia
– Dplication cyst of the antropyloric region
– Ectopic pancreatic tissue within the pyloric muscle
May be difficult to differentiate
from IHPS without further
imaging
12
13. Diagnosis
• Cardinal features of IHPS
– Nonbilious projectile vomiting
– Visible peristaltic waves in the left upper part of the
abdomen
– Hypochloremic, 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
• Pyloric 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
• Elongated pyloric channel
• Shoulder sign
– a bulge of the pyloric muscle into the antrum
• Double tract sign
– Parallel 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
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
• It invariably resolves postoperatively
22
23. Cont.
• Operative procedure
– It is important to emphasize that fluid and electrolyte
abnormalities must be corrected preoperatively
• Including 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
– Infants are 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
