Age-related changes in innervation in hypertrophic pyloric stenosis

Risk factors for unsuccessful atropine therapy in hypertrophic pyloric stenosis

BACKGROUND

I.v. atropine (IA) for infantile hypertrophic pyloric stenosis (IHPS) is a good alternative to pyloromyotomy but has not been broadly accepted. The lower success rate is one of the greatest disadvantages of IA. We investigated the risk factors for unsuccessful results following IA for IHPS.

METHODS

Medical records of patients with IHPS who were admitted to Kimitsu Chuo Hospital between 2002 and 2016 and were initially given atropine sulfate were retrospectively reviewed. Atropine was given i.v. (0.1 mg/kg/day in eight divided doses). Oral feeding of milk was started with a small amount and increased in a stepwise fashion to full feed. IA therapy was defined as unsuccessful in the presence of projectile vomiting more than three times a day or intolerance to a predetermined amount of milk.

RESULTS

Of the 48 patients with IHPS, 33 patients were successfully treated with IA and 15 patients needed surgical intervention. On univariate analysis the risk factors for unsuccessful IA therapy were younger age, lower bodyweight, and shorter duration of symptoms before diagnosis. On multivariate analysis age at diagnosis < 30 days was the only significant risk factor for unsuccessful IA therapy (OR, 5.7 l P = 0.03).

CONCLUSIONS

Age at diagnosis < 30 days is a risk factor for unsuccessful IA therapy in IHPS. This might be considered when IA therapy is used for neonates with IHPS.

New insights into the pathogenesis of infantile pyloric stenosis

Infantile hypertrophic pyloric stenosis (IHPS) is the most common surgical cause of vomiting in infants. Despite numerous hypotheses, the aetiopathogenesis of IHPS is not fully understood. Genetic, extrinsic and hormonal factors have been implicated in the pathogenesis of the disease. Furthermore, abnormalities of various components of the pyloric muscle such as smooth muscle cells, growth factors, extracellular matrix elements, nerve and ganglion cells, synapses, nerve supporting cells, neurotransmitters and interstitial cells of Cajal have been reported. Recently, genetic studies have identified susceptibility loci for IHPS and molecular studies have concluded that smooth muscle cells are not properly innervated in IHPS.

A histological study of the hph-1 mouse mutant: an animal model of phenylketonuria and infantile hypertrophic pyloric stenosis

AIM

To quantify the chronological sequence of changes in the morphology and immunoreactivity for neurotransmitters in the pylorus of an animal model of infantile hypertrophic pyloric stenosis and phenylketonuria.

METHOD

Thirty specimens of pylorus from hph-1 mice and age/sex matched controls (age range: 10-180 days) were examined using conventional histology and immunohistochemistry for a variety of antigens: protein gene product 9.5, a pan neuronal marker; vasoactive intestinal polypeptide; nitric oxide synthase two antigens coalesced to the same inhibitory neurons in humans; substance P, a potent excitatory neurotransmitter; and calcitonin gene related peptide, a neurotransmitter implicated in the somatic afferent innervation of the stomach. The changes in the morphology of the muscle layers were quantified and statistically analysed for each age group (10, 20, 40, 90 and 180 days).

RESULTS

Between 10 and 90 days of age, all muscle layers of the hph-1 mice were hypertrophied, for example, 10 days, hph-1 longitudinal muscle mean diameter = 3.4, control = 1.8; hph-1 circular muscle width = 11.5, control = 4.7. The hph-1 mice were significantly smaller during this period (40 days, hph-1 weight = 10 g, control = 25 g). There was no change in the pattern of expression of the antigens examined within the hph-1 mice compared with the controls.

CONCLUSION

Hph-1 mice develop a transient smooth muscle hypertrophy of the pylorus attended by gastric distension and failure to gain weight. These changes resolve as the pyloric muscle hypertrophy resolves.

The association of erythromycin and infantile hypertrophic pyloric stenosis: causal or coincidental?

The safety profile of erythromycin is notable for the frequent occurrence of intolerable gastrointestinal effects. One of the more serious of these is infantile hypertrophic pyloric stenosis (IHPS). A recent cluster of IHPS cases prompted an epidemiological investigation which identified oral erythromycin chemoprophylaxis of pertussis as the major risk factor. Evidence suggests an association between early postnatal erythromycin exposure and IHPS. There is no substantive evidence of a risk associated with prenatal exposure, with the single published case-control study to date producing negative findings. The epidemiological investigations of the association with early postnatal exposure have reported significantly elevated odds ratios but have a variety of methodological limitations that prevent definitive conclusions being made. Nevertheless, the concordance of findings across studies increases the strength of evidence favouring an association. The prominent gastrokinetic properties of erythromycin have been postulated as the mechanism behind this phenomenon. A comprehensive assessment of this potential adverse effect should consider its biological plausibility in light of known gastrointestinal physiology, its modulation by erythromycin, and the known pathophysiology of IHPS. Gastrointestinal motor activity in the fasted mammal consists of three phases, phase III being large amplitude contractions called migrating motor complexes (MMC) that can be initiated by motilin and erythromycin. The gastrokinetic effects of erythromycin are variable and complex and include effects on the timing, duration, amplitude and distribution of MMCs. It has been speculated that the motilinomimetic effects of erythromycin on antral smooth muscle function, such as the MMC, may mediate the effect via work hypertrophy. Although intuitively plausible and consistent with hypertrophic obstructive changes similar to IHPS observed in hyperplastic rat ileum after artificially induced mechanical obstruction, there is no direct evidence of this phenomenon. Further complicating the association is the limitations of our knowledge about the pathophysiology of IHPS, including numerous genetic abnormalities, increased parietal cell mass, and gastric hyperacidity. The implications of the reported findings with erythromycin on the benefit-risk profiles of newer macrolides and azalides must be considered. The available data on the comparative gastrokinetic properties of macrolides are significant for the potent gastrokinetic properties and its acid degradation products, the marked variation in gastrokinetic properties associated with macrolide ring size, and the requirement for specific glycosidic linkages at the C-3 and C-5 carbons of the macrolide ring. The variation in gastrokinetic properties associated with variations in molecular structure suggests that if the association between erythromycin and IHPS is causal it may not be a class effect.

Gastrin, somatostatin and infantile hypertrophic pyloric stenosis

Despite multiple and often contradictory research, no firm conclusions regarding the role of hypergastrinaemia in infantile hypertrophic pyloric stenosis (IHPS) have been established. Evaluation of somatostatin, the main physiological antagonist of gastrin, has not been assessed in previous studies. Long-term evaluation following pyloromyotomy suggests persistent abnormalities in gastrin and somatostatin in IHPS. The objective of this case-controlled study was to compare fasting serum gastrin and somatostatin levels in IHPS. Serum sample were collected from 39 children with IHPS at the time of pyloromyotomy and 20 age-matched controls with no evidence of gastrointestinal disease. Standard radioimmunoassay techniques were used to detect circulating levels of the hormones. A two-tailed t-test was used for statistical analysis. The levels of the two hormones (mean +/- SEM) revealed that there was no evidence of hypergastrinaemia in IHPS compared with controls (75.6 +/- 16.1 and 68.1 +/- 7.8 ng l(-1), respectively), but that the level of somatostatin was significantly elevated (38.9 +/- 6.4 and 30.5 +/- 5.8 ng l(-1), p = 0.016). An inverse trend in the gastrin/somatostatin levels could not be identified in IHPS.

CONCLUSION

Somatostatin but not gastrin is raised in IHPS. Somatostatin is known to inhibit the actions of inhibitory neurotransmitters in the pylorus and may explain the development of pylorospasm, which is believed to be important in the development of pyloric tumours. These results do not agree with a previous long-term follow-up study, but reflect the hormonal imbalance at the time of pyloric hypertrophy.