How important is the role of the internal anal sphincter in fecal continence? An experimental study in dogs

Effects of extensive mobilization and tension anastomosis in anorectal reconstruction (experimental study)

PURPOSE

Anorectoplasty and pull-through procedure can be performed with extensive mobilization or tension anastomosis, which can compromise bowel blood perfusion. We aimed to analyze the hypoxia biomarker values and histopathological findings in both conditions to correlate the occurrence of anal stenosis and defecation disorders in experimental models.

METHODS

We created anorectal reconstruction models with impaired vascularization of the anorectum (group I) and tension anastomosis (group II) in rats. A third group of animals underwent sham operation (group III) and another as controls (group IV). Hypoxia biomarker values were assessed in all groups. The histopathological changes on the postoperative days 3 and 35, anal stenosis and defecation disorders on day 35 were compared.

RESULTS

Hypoxia biomarker values confirmed postoperative ischemia in groups I-III compared to control. Group I and II rats had a similarly pronounced ischemia with histopathologic changes in the anorectum on the postoperative day 3 and accompanied by severe fibrosis on day 35. Compared to the sham operation, both groups showed defecation disorders with significant anal stenoses.

CONCLUSION

Extensive rectal mobilization to about the same extent as tension anastomosis has a major impact on postoperative rectal ischemia, resulting in severe fibrotic changes in the anorectum and defecation disorders in the long term.

Post-operative strictures in anorectal malformation: trends over 15 years

AIM

For decades, paediatric surgeons have employed the standard posterior sagittal anorectoplasty (PSARP) approach to deal with patients with anorectal malformations (ARM). In recent years, we noted an apparent increase in the incidence of anal stricture after surgical repair of ARM following the introduction of laparoscopic pull-through and techniques aiming to preserve the internal sphincter-the internal sphincter sparing approach (ISSA). We decided to analyse our data to find out if these new trends had added to the problem of post-operative strictures.

METHODS

All patients with ARM at our institution from January 2000 to December 2015 were identified. A retrospective case note review was carried out. Data collected included patient demographics, type of ARM, operative details, and post-operative outcomes.

RESULTS

114 patients were identified. Ten patients were excluded. Of the remaining 104 children, 48 (46%) were female. Median age was 8.3 (range 1.2-16.8) years. Types of ARM were as follows: perineal fistula (15 patients), anterior stenotic anus (12), imperforate anus without fistula (10), vestibular fistula (32), rectourethral (bulbar) fistula (11), rectourethral (prostatic) fistula (14), rectovesical fistula (7), and cloaca (3). Twenty-seven patients with a perineal fistula or anterior stenotic anus underwent perineal procedures that were variably described by the different operating surgeons. The majority (15 patients) had an anoplasty, 5 had anal transposition, 5 had limited PSARP, and 2 patients had ISSA. Two patients with a cloacal anomaly underwent open cloacal reconstruction. Of the remaining 75 patients, 45 had a PSARP approach, 6 had a laparoscopic-assisted pull-through, and 18 had ISSA. Four girls with vestibular fistula had anal transposition and two boys with imperforate anus without fistula had anoplasty. 15 (14%) children developed anal stricture. Stricture incidence differed according to operation type. PSARP was the most commonly performed procedure, with only 6% developing a stricture. In contrast, 30% of ISSA patients and 50% of children who had laparoscopic pull-through developed a stricture. Strictures also occurred in 11 and 12% of children having anal transposition and anoplasty, respectively.

CONCLUSION

The laparoscopic-assisted pull-through involves tunnelling the sphincter muscle complex. We found that often the tunnels were not wide enough, resulting in narrowing not just at the ano-cutaneous junction but also at the deeper level. 50% developed strictures. We have modified our technique by ensuring that the tunnels are generous enough to allow the rectum to be pulled through without any resistance. ISSA unfortunately resulted in 30% of our patients developing strictures. This approach, started in 2004, was, therefore, abandoned in 2013. The standard Pena's PSARP, with or without a laparotomy, has stood the test of time. Any modification of this approach must be carefully thought through and audited meticulously. Strictures can cause significant morbidity, which may need several revisions, and the resulting redo anoplasties run the risk of sphincter damage, ironically which the newer modifications of ISSA were trying to conserve.

Immunohistochemical confirmation of the presence of smooth muscle in the normal neonatal anorectum and in neonates with anorectal malformations

AIM

To evaluate the presence of smooth muscle in relation to the anorectum in neonates that are normal and in neonates with anorectal malformations using immunohistochemical staining of antibodies specific to smooth muscle actin (SMA).

METHODS

Research ethics committee approval was obtained to study historical neonatal tissue sections. 7-15-μ thickness, sagittal sections of both normal anorectums (NA) and neonates with anorectal malformations (ARM) were available to study. The fragile tissue predates the development of charged glass microscope slides that are inherent to contemporary immunohistochemistry (IHC). Normal appendix sections on non-charged slides were used to establish and optimise a novel, steam generated heat, antigen retrieval protocol. This technique of "gentle" antigen retrieval allows preservation of tissue architecture whilst maintaining adequate staining of tissue on non-charged glass microscope slides. NA and ARM tissue was stained and compared to control NA and ARM sections.

RESULTS

SMA staining was observed in sagittal sections of both normal neonatal anorectums and neonates with anorectal malformations, confirming the presence of smooth muscle.

CONCLUSION

This preliminary work confirms the presence of smooth muscle in the anorectum of neonates that are normal and in neonates with anorectal malformations. It is likely that the smooth muscle complex demonstrated represents the internal anal sphincter in the normal anorectum. It is postulated that the smooth muscle complex seen in anorectal malformations may represent a similar internal anal sphincter complex which maybe of functional significance. Further IHC of tissue sections will allow reconstruction of the exact three-dimensional smooth muscle structure of the anorectum in neonates that are normal and neonates with 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).

Posterior sagittal approach with perirectal dissection for reconstructive surgery of severe urogenital anomalies

There are many approaches for surgery of complicated congenital and acquired urogenital anomalies in children with intact rectum. Pena advocates the mid-sagittal division of the sphincter mechanism posterior and anterior to the rectum, along with opening of the posterior and anterior rectal walls. The aim of this study is to determine whether the posterior sagittal approach with perirectal dissection (PSAPD) and elevation of the mobilized rectum would impair fecal continence when used for correction of complicated urogenital anomalies in children with normal rectum. Between 1988 and 1994 the authors performed PSAPD in eight infants and children with an intact anorectum. Indications for PSAPD were high vaginal atresia, Mullerian duct remnants, prostatic rhabdomyosarcoma, and traumatic vesicovaginal fistula. After a mean 10-year follow-up the bowel habits were assessed. Anorectal and uromanometric studies and a detailed questionnaire (modified Holschneider's scoring) sent to children or parents were evaluated. Three patients who preoperatively were clinically fecal continent had soiling only at the time of diarrhea. Early postoperative low anorectal pressure profile normalized during the follow-up. Seven patients had a fecal continence score above 23, two of them with maximum points of 26. Only one girl had a low score of 15. The authors conclude the PSAPD which offers a few advantages over the sagittal division of the rectum provides an alternative approach for selected lesions of the genitourinary tract in children with a normal rectum. Our results suggest that fecal continence is either preserved or partially affected.

Feasibility of perineal sagittal approaches in patients without anorectal malformations

Perineal sagittal approaches (posterior sagittal anorectoplasty and anterior and posterior sagittal transanorectal approaches) allow complete anatomic exposure of the perineum and lower pelvis. Moreover, they reduce the risk of damaging important structures because the incision is led in the midline. Therefore, many surgeons have used these approaches to treat diseases other than anorectal malformations (ARM), including intestinal dysganglionosis, trauma, pseudohermaphroditism, presacral mass, and rectal duplication. The aim of this study was to describe a small series of patients operated on via these approaches at Gaslini Children's Hospital over a 5-year period. We retrospectively evaluated 10 patients consecutively operated on via a perineal sagittal approach, with or without sphincteric structure involvement, between January 1997 and December 2001. All of these patients were without ARM. Indications included retrorectal abscesses (two), iatrogenic anal canal stenosis (one), postinflammatory anal canal stenosis (one), internal anal sphincter neurogenic achalasia (one), female pseudohermaphroditism (one), benign sacrococcygeal teratomas (two), malignant sacrococcygeal teratoma (one), and perineal rhabdomyosarcoma (one). Protective colostomy was used in four patients. The parameters that we analysed included technical details, possible complications, perineal cosmetic appearance, and outcome. No complications were experienced. The postoperative cosmetic perineal appearance was excellent in all patients, and continence, when assessed, was always considered satisfactory. All tumours underwent complete gross resection. However, one patient with malignant sacrococcygeal teratoma died as a result of the malignant process 2 years after surgery. Although our study was carried out on a small series of patients, it confirmed that perineal sagittal approaches can be used not only for ARM but also for other conditions involving perirectal pouches, presacral space, and urogenital structures, as these approaches are safe and provide excellent cosmetic results as well as satisfactory functional outcome. Although tumours can be treated via these approaches, outcome remains related to the nature and malignancy of the disease itself.

Does the posterior sagittal approach with perirectal dissection impair fecal continence in a normal rectum?

The aim of this study was to determine, using human material and animal experiments, whether the posterior sagittal approach with perirectal dissection (PSAPD) in patients with an intact anorectum is a suitable means of exposure for the correction of complicated anomalies of the genitourinary tract without impairment of fecal continence. Over the last 6 years, the authors have performed PSAPD in seven children with an intact anorectum. At the time of operation, their ages ranged from 8 months to 14 years. All patients showed normal fecal continence at the end of follow-up (averaging 32 months). Only after completion of the study did the authors read that Peña et al had found that PSAPD provoked severe changes in bowel control in dogs. This contradiction prompted the authors to repeat the animal experiments, and they could not reproduce the favorable results obtained in children. This might be explained by the following factors: the surgical dissection used in the dogs was more extensive, anatomic differences between man and dog, the relatively much younger age of the animals (versus the patients), and the shorter follow-up and lack of educability of the dogs. The authors conclude that PSAPD is a suitable approach for selected lesions of the genitourinary tract in children who have a normal rectum and it does not impair fecal continence.