Reappraisal of endorectal pull-through procedure. I. Anorectal malformations

Embryonic development of the internal anal sphincter in rats with anorectal malformations

BACKGROUND/PURPOSE

The embryogenesis of the internal anal sphincter (IAS) in anorectal malformations (ARMs) remains unclear. This study aimed to investigate the development of the smooth muscle in the terminus of the digestive tract in normal and abnormal rats.

METHODS

Rat embryos with ARMs were generated by administration of ethylenethiourea to pregnant rats. The normal rat embryos and embryos with ARMs from E13.5 to E21 were serially sectioned in the sagittal plane and stained immunohistochemically using specific antibody to α-smooth muscle actin (SMA). Temporospatial study was carried out on circular muscle of the distal portion of the hindgut.

RESULTS

α-Smooth muscle actin immunolabeling cells could not be observed in the hindgut on E13.5, E14, and E14.5. On E15, there were α-SMA immunolabeling circular muscle cells in the hindgut; and the distal portion of the circular muscle was not thickened in the normal and ARMs rats. From E16 onward, the smooth muscle with slight dilated terminus, which was characterized by the features of IAS, could be noted in the primitive anorectum. In the normal group, the circular muscle in the distal portion of the hindgut thickened slightly and became the musculature with shutter-like bundles. In the ARMs group, the α-SMA immunolabeling myogenic precursors of the smooth muscle could be observed in the primitive anorectum as well. The musculature was similar to that in the normal group. On E15 and E16, there was no significant difference in the development of the circular muscle in the 2 groups. Moreover, the terminus of the circular muscle in the hindgut did not reach the orificium fistulae in ARMs rats. From E17 onward, in ARMs rats, the funnel-shaped distal hindgut communicated the genitourinary tract with a narrow fistula; the dilated musculature at this portion thinned gradually and formed an acute angled extremity in the ARMs group rather than formed blunt extremity in the normal group; the terminus circular muscle in the dorsal hindgut reached the orificium fistulae. During the following gestational days, the circular muscle of the hindgut in both normal and ARMs rats continued its own tendency.

CONCLUSION

The IAS primordium started to appear at the terminus of the hindgut on E15 in the 2 groups. The IAS in the ARMs group failed to develop as well as that in the normal group. The IAS dysplasia occurred in the late embryonic development (E17-E21).

Evaluation of outcome of anorectal anomaly in childhood: the role of anorectal manometry and endosonography

The aim of this study was to evaluate role of anorectal manometry (ARM) and anal endosonography (ES) in assessment of the internal anal sphincter (IAS) quality on continence outcome following repair of anorectal anomalies (ARA). We devised a scoring system to evaluate the quality of the IAS based on ARM and ES and correlated the scores with clinical outcome, using a modified Wingfield score (MWS) for faecal continence. We also assessed the implication of megarectum and neuropathy on faecal continence. Of 54 children studied, 34 had high ARA and 20 had low ARA. Children with high ARA had poor sphincters on ES and ARM, and also poor faecal continence compared to those with low ARA. The presence of megarectum and neuropathy was associated with uniformly poor outcome irrespective of the IAS quality. The correlations between MWS on one hand, and ES and ARM scores for IAS on the other hand were weak in the whole study group, ES r = 0.27, P < 0.04, and ARM r = 0.39, P < 0.004. However, the correlations were strong in those who had isolated ARA without megarectum or neuropathy, ES r = 0.51, P < 0.02 and ARM r = 0.55, P < 0.01, respectively. In conclusion, the ARM and ES are valuable in evaluation of continence outcome in children after surgery for ARA and those with good quality IAS had better faecal continence. The IAS is a vital component in functional outcome in absence of neuropathy and megarectum.

Studies on the rectoanal reflex in children and in experimental animals: an evaluation of neuronal control of the rectoanal reflex

A single-chamber pressure probe for rectal electromanometry was developed which seems to be superior to the complicated multichamber systems not only for clinical but also for experimental purposes. Measurements of rectoanal reflex were carried out in 268 cases with abnormal bowel function, in 103 cases following operation for Hirschsprung's disease, and in 61 cases of imperforate anus to assess postoperative continence. Experimental studies were performed in 36 dogs, 27 of which were used for short-term and 9 for long-term studies. The results of clinical and experimental studies are described and discussed, with accompanying literature. From clinical and experimental studies, the neuronal pathways of the rectoanal reflex are schematized. The normal rectoanal reflex is mediated by both the sacral cord and the myenteric neurons. It is concluded that measurements of the anal resting pressure and the rectoanal reflex constitute a valuable method to distinguish between normal and pathological sacral and myenteric innervation.

Continence and reflex pressure profile after surgery to correct the imperforate anus

To clarify the cause of constipation which follows surgery for the supralevator type of disorder associated with the imperforate anus, rectal compliance, percentage maximum static anorectal pressure, and reflex profile were measured by anorectal manometry in 108 normal controls and 42 patients. Patients with constipation had a low percentage anorectal pressure (50%), high rectal compliance, associated with megarectum, and defecation of the staining type with constipation due to a reaction in anorectal motility.

The internal sphincter in anorectal malformations: morphologic investigations in neonatal pigs

The knowledge of sphincter anatomy in anorectal malformations is still inadequate and contradictory. Therefore, morphologic investigations were carried out in 33 neonatal piglets with congenital anal atresias. Of the 24 male animals 12 had high anomalies with a rectourethral fistula. The remaining 12 piglets had low anomalies; in nine cases we were able to demonstrate an anocutaneous fistula. Of the nine female animals, six had high anomalies with a rectovaginal fistula. The three female piglets with low anomalies had an anovestibular or an anocutaneous fistula. In all animals we could demonstrate a normal internal sphincter, which surrounded the proximal part of the fistulae. The position of the internal sphincter therefore depended on the localization of the fistula orifice into the rectal pouch. This differed greatly. The form of the internal sphincter also differed greatly. Sometimes the muscle had the form of a tube or an acute-angled funnel as in healthy piglets. However, mostly the internal sphincter was spread out wide and had the form of a disc or a flat dish. The proximal region of the fistulae in anal atresias has most features of a normal anal opening: (1) it is surrounded by an internal sphincter, (2) the rectal pouch in the region of the internal sphincter as well as the fistulae are hypoganglionotic, (3) the proximal fistula region is lined by transitional epithelium, and (4) it contains anal glands. We, therefore, consider that the fistula should be designated as an ectopic anal canal. The most important result was the demonstration of a normal internal sphincter even in high and intermediate anomalies of anal atresias.(ABSTRACT TRUNCATED AT 250 WORDS)