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The pathology of infantile hypertrophic pyloric stenosis after healing
J M Vanderwinden1, H Liu, R Menu
1Laboratoire de Neuropathologie et de Recherche sur les Neuropeptides, Faculté de Médecine, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles, Belgium.
Insights
Infantile hypertrophic pyloric stenosis (IHPS) pathology resolves after surgery. Pyloric tissue examined post-pyloromyotomy showed normal musculature and nerve markers, suggesting milder enteric nervous system involvement than previously thought.
Area of Science:
- Gastroenterology
- Pediatric Surgery
- Developmental Biology
Background:
- Infantile hypertrophic pyloric stenosis (IHPS) is a common congenital condition causing gastric outlet obstruction.
- The underlying pathophysiology of IHPS remains largely unknown, despite its frequent occurrence.
- While surgical pyloromyotomy (PM) resolves IHPS symptoms, the long-term histological changes in the pylorus are not well understood.
Observation:
- The study analyzed pyloric biopsy specimens from two infants at 4 months and 2 years post-pyloromyotomy (PM) for IHPS.
- Histological and immunohistochemical analyses compared post-healed IHPS tissue with initial IHPS specimens and normal controls.
- Markers for the enteric nervous system (S-100, nerve growth factor receptor) and interstitial cells of Cajal (c-kit) were assessed, along with nitric oxide synthase.
Findings:
- Post-PM pyloric tissue in IHPS cases showed normalized circular muscle thickness, resolving the characteristic hypertrophy.
- Immunohistochemical staining for enteric nervous system markers and interstitial cells of Cajal returned to patterns similar to normal pyloric tissue.
- In contrast, specimens from the time of PM exhibited significant reductions in these markers within the hypertrophic muscle.
Implications:
- The pathological features of IHPS appear to be reversible within months following pyloromyotomy.
- These findings suggest that the enteric nervous system's involvement in IHPS may be less severe or more adaptable than previously assumed.
- Understanding these post-healing changes offers new insights into IHPS pathophysiology and aligns with the generally excellent long-term clinical outcomes.
Introduction:
Infantile hypertrophic pyloric stenosis (IHPS) is a common surgical affection of unknown etiology. The muscular hypertrophy is known to resolve within a few months after pyloromyotomy (PM). The pathology of IHPS has been studied extensively at the time of PM, but the fate of the pylorus after healing remains unknown.
Materials And Methods:
We had the rare opportunity to study two pyloric biopsy specimens obtained 4 months and 2 years (respectively) after an uncomplicated PM for IHPS. They were compared with the initial specimen in one case, with 26 other specimens of IHPS, and with five normal controls. Immunohistochemistry using the avidin-biotin complex (ABC) system was performed for S-100 and nerve growth factor receptor, as markers for the enteric nervous system, and for the tyrosine kinase receptor c-kit, as a marker for the interstitial cells of Cajal (pacemaker cells). NADPH-diaphorase histochemistry was performed as a marker for the neuronal enzyme nitric oxide synthase, which produces the inhibitory neurotransmitter nitric oxide.
Results:
In both cases of IHPS, after healing, the circular musculature was not hypertrophic. For all markers studied, the distribution appeared similar to that in the normal pylorus. In contrast, all specimens obtained at the time of PM displayed a severe reduction of the different markers in the hypertrophic musculature.
Discussion:
The pathological features observed in the circular layer in IHPS appear to resolve within a few months after PM. This suggests that the involvement of the enteric nervous system in IHPS might be milder than generally assumed. The etiology remains obscure, but our occasional observations may provide new insight into the pathophysiology of IHPS, and are in agreement with the excellent longterm clinical outcome for IHPS.