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Late Clinical Outcome and the InternalAnal Sphincter of the Patients with High Type Anorectal Malformation

T. Kuroda, M. Saeki,
Tokyo, Japan

 

Abstract 

Background: The purpose of this study is to investigate the age-related improvement of defecation function in high type anorectal malformation in relation to the assessment of the internal anal sphincter.

Material and Methods: The function of defecation was studied every 5 years up to 25 years postoperatively according to the scoring system by Japanese Study Group of Anorectal Anomalies in forty-three patients operated for recto-urethral fistula; 13 operated with sacro-perineal procedure and 30 operated with endorectal pull-through (ERPT) procedures. The internal anal sphincter was assessed by anorectal manometry and histology, and the results were analyzed with the clinical outcome.

Results: The defecation scores of the sacro-perineal cases exceeded those of ERPT cases at all age groups; the averaged total score was 6.0 in the sacro-perineal cases vs. 2.1 for Rehbein’s and 3.6 in Kiesewetter-Rehbein’s cases at 5 years old, 6.5 vs. 4.1 and 4.2 at 10 years old, and 7.0 vs. 5.5 and 5.7 at 15 years old. The anorectal reflex was seen in 6 of 9 sacro-perineal cases examined, whereas seen in none of 7 Rehbein’s cases examined. Histologically, the well-developed and thickened internal circular muscle at the rectal end was found only in 28.8% of the cases, whereas discontinuation and hypoplasty of the muscle were seen in most of the cases examined.

Conclusions: The present results indicate that the internal sphincter muscle at the rectal end may be histologically maldeveloped in high type anorectal malformations; however, they can potentially develop after transplanted and contribute to the improvement of passive continence in the late post-operative period.

Key words: High type anorectal malformation, internal anal sphincter, sacroperineal anoplasty

 

Correspondence: 

Tatsuo Kuroda, M.D.; Department of Surgery National Center for Child Health and Development;

2-10-1 Okura, Setagaya-ku, Tokyo 157-8535, Japan

TEL:+81-3-3416-0181 / FAX:+81-3-3416-2222

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

The clinical impact of the utilization of the intrinsic circular muscle located at the rectal end as internal anal sphincter is widely accepted in the surgical repair of the high type anorectal malformations [1, 2, 3]. However, the practical significance of this muscle has remained yet controversial in high type anomalies [4, 5]. The present study aimed to describe the histology of the internal anal sphincter muscle in high type anomaly, and to review the late clinical outcomes in relation to the histological and manometrical findings and the surgical utilization of internal anal sphincter.

Materials and methods

1) Materials

Forty-three male patients with recto-urethral fistula, the most common high type anorectal malformation in male, were involved in the current study. The patients had the definitive surgery in our department form 1976 to 1997, and the age at the latest assessment ranged from 6 years through 36 years with the median age of 27 years old. Of 43 cases, thirty patients were operated with endo-rectal pull-through (ERPT) procedures (25 with Rehbein’s procedure and 5 with Kiesewetter-Rehbien’s procedure), whereas 13 patients were operated with sacroperineal procedure [6, 7, 8].

2) Clinical assessment

The post-operative function of defecation was scored in 43 patients at the age of 5, 10, 15, 20, and 25 years according to the clinical scoring system proposed by the Japanese Study Group of Anorectal Anomalies (JSGA) (Table 1) [9,10] by two full-trained pediatric surgeons. Defecation problems were also studied in each patient by retrospective review or interview.

3) Manometrical study

The ano-rectal manometry was studied post-operatively at the averaged age of 4 years and 8 months in 16 patients (9 operated with the sacro-perineal procedure and 7 with Rehbein’s procedure). The pressure profile of the reconstructed anal canal was measured by the open-dip method, and anorectal reflex was examined using K-Y microballoon system (Yufu Inc. Tokyo, Japan) in each patient.

4) Histological assessment of the rectal end

In seven patients operated with the sacro-perineal procedure, a 5mm x 50 mm strip-tissue of the rectal end containing whole thickness was harvested from the posterior wall at the time of the definitive surgery. The tissues were sectioned in the sagittal direction, and the hematoxylin and eosin histology was examined.

Table 1. Clinical Scoring for Defecation Function (Japanese Study Group of Anorectal Anomalies)

A. Sensation Score 2 always sensible
1 sometimes lost
0 always insensible
B. Constipation Score 4 no constipation
3 infrequent use of laxatives and enemas
2 daily use of laxatives or enemas
1 constipation requiring finger evacuation of stools
C. Soiling Score 4 no soiling
3 soiling only at diarrhea
2 infrequent(less than once a week) soiling
1 frequent(twice a week or more) soiling
0 daily soiling
D.Staining Score 2 no staining
1 infrequent(less than daily) staining
0 daily staining

Results

1) Clinical assessment (Table 2)

Table 2 summarizes the JSGA defecation scores of each clinical item in three different operative procedures at each age. The scores were generally improved with aging. The patients operated with sacro-perineal procedure revealed definitely higher scores compared to those operated with ERPT procedures at all age groups; averaged total score was 6.0 in the sacro-perineal cases vs. 2.1 in Rehbein’s cases and 3.6 in Kiesewetter-Rehbein’s cases at 5 years old, 6.5 vs. 4.1 and 4.2 at 10 years old, and 7.0 vs. 5.5 and 5.7 at 10 years old. In sacro-perineal cases, the sensation was scored full in all patients even at the early age of 5 years, while the staining score was not fully improved in the older ages. The constipation score was fully improved by the age of 10 years, whereas the soiling score remained slightly lower. In contrast, in the patients operated with ERPT procedures, the constipation score was not fully improved until older ages, and the soiling score was further lower than the constipation scores at all ages. 

late clinical outcome 1

Fig. 1 A. Internal circular and outer longitudinal smooth muscles at the rectal end in patient #1 (X 13.2) Internal circular and outer longitudinal smooth muscles were widely separated by the interstitial fibrous tissue. Internal circular muscle bundles are loose and hypoplastic, whereas outer longitudinal bundles are dense and well developed.
Abbreviations: IC: internal circular smooth muscle of the rectal end L : longitudinal smooth muscle

Table 2. Scoring of the post-operative function of defecation

Total Score

Age
Rehbein
Kiesewetter-Rehbein
Sacro-perineal

 

5 yr
2.1±1.49
3.6±1.14
6.0±0.95

 

10yr
4.1±1.89
4.2±1.30
6.5±0.53

 

15yr
5.5±1.20
5.7±0.58
7.0±0.70

 

20yr
5.4±2.07

 

25yr
3.7±2.89

Soiling Score

Age
Rehbein
Kiesewetter-Rehbein
Sacro-perineal

 

5 yr
0.8±0.90
2.0±1.41
3.4±0.67

 

10yr
2.0±1.38
2.4±0.89
3.4±0.52

 

15yr
2.9±0.95
3.3±0.58
3.6±0.55

 

20yr
3.0±1.41

 

25yr
1.7±2.08

 Constipation Score

Age
Rehbein
Kiesewetter-Rehbein
Sacro-perineal

 

 

5 yr
3.8±0.60
3.2±1.10
3.4±0.79 

 

10yr
3.5±0.81
2.6±0.89
4.0 

 

15yr
3.4±0.87
3.3±1.15
4.0 

 

20yr
3.4±0.79 

 

25yr
4.0 

 Sensation Score

Age
Rehbein
Kiesewetter-Rehbein
Sacro-perineal

 

 

5 yr
1.2±0.72
1.8±0.45
2.0 

 

10yr
1.7±0.46
2.0
2.0 

 

15yr
2.0
1.7±0.58
2.0 

 

20yr
1.9±0.38 

 

25yr
1.7±0.58

 Staining Score

Age
Rehbein
Kiesewetter-Rehbein
Sacro-perineal

 

 

5 yr
0.2±0.39
0.2±0.45
1.0±0.43

 

10yr
0.6±0.60
0.6±0.55
1.1±0.41 

 

15yr
1.1±0.86
1.3±0.58
1.4±0.58 

 

20yr
1.1±0.90 

 

25yr
0.3±0.58

Defecation habit was established at the averaged age of 4.0 years (ranging 2 to 7 years) in sacro-perineal cases, whereas established at 8.7 years (ranging 6 to 10 years) in the Kiesewetter-Rehbein cases according to the retrospective review. In Rehbein’s cases, toilet habit was not fully established in older ages.

The toilet troubles during school hours were complained complained frequently regardless of the operative procedures, such as shortage of time for toiletting and discrimination among friends. Among the recently interviewed patients, however, three out of 12 patients (25.0%) operated with sacroperineal procedure complained mild staining during exercises, with no episode of soiling. In contrast in the patients operated with ERPT procedures, eleven out of 18 patients (61.1%) were suffering from soiling (8 patients) and severe staining (3 patients) during exercises.

2) Manometric study (Table 3)

Six out of nine patients operated with sacro-perineal procedure showed positive anorectal reflex postoperatively, whereas none of 7 cases operated with Rehbein’s procedure showed the significant reflex. The averaged resting anal pressure was 33.0 cmH2O in the sacro-perineal cases, whereas 24.0 cmH2O in Rehbein’s cases.

3) Histology of the rectal end (Table 4, Fig. 1)

Table 4 summarizes the histology of the rectal end in 7 patients. Well-defined thickening of the intrinsic circular muscle at the rectal end was seen in 2 cases (28.6%), while the muscle bundles were loose, hypoplastic, and surrounded by fibrous tissues in other 5 patients. Among these 5 patients, vacuolar degeneration of muscle fibers was seen in 2 patients. Four patients showed the discontinuation or partial thinning of the internal circular muscle at the rectal end. The outer longitudinal and internal circular muscle layers were widely separated at the rectal end with interstitial fibrous tissue in all of 7 patients. Relationship was not evident between the histology of the internal circular smooth muscle at the rectal end and the JSGA total clinical score at 5 years old. In contrast to the internal circular bundles, outer longitudinal muscle was well developed in all patients.

Discussions

Postoperative function of defecation in anorectal malformations may be affected by many factors such as type of anomaly, aging, function of the internal anal sphincter muscle, and the surgical procedures. Among these factors, the functional potential and the appropriate surgical utilization of the internal anal sphincter identified at the rectal end seemed most important for the late clinical outcome. To study the clinical significance of the internal anal sphincter in the high type anomaly, age-related alteration of the defecation score was analyzed together with the manometric and histological assessment of the internal anal sphincter muscle in the current study. The study was designed to review the cases with a single high type anomaly in male who were operated on in a single institution to eliminate the bias factors such as surgical skill and the type of anomaly. The patients operated with posterior sagittal anorectoplasty (PSARP) [11], the most widely spread surgical procedure at present, were eliminated in the present study in order to compare the clinical results among the procedures without dissecting pelvic muscles.

late clinical outcome 2

Fig. 2 B. Internal circular muscle at the rectal end in patient #2 (X 25) Hypoplastic and loose muscle bundles were surrounded by fibrous interstitial tissue, and the internal circular layer was discontinued partly in the sagittal section (arrowhead). 

Clinical assessment according to the JSGA scoring system showed age-related improvement of the scores,especially in continence, in each surgical procedure. The scores were generally improved until 15 post-operative years, and no longer altered thereafter. The higher scores, however, may be provided not only by the improved physical function of defecation but also by the innovations of their toilette habit. The patients seem to acquire the appropriate life style to adopt the incontinence for their social lives as they grow older by using enema or laxatives to empty their bowel. Therefore, the clinical assessment by the scoring at higher ages may not fully reflect the postoperative function of the internal anal sphincter.

Table 3. Anorectal Manometry

Resting anal pressure Ano-rectal reflex
Sacro-perineal cases 33.0±11.7 cmH2O 66.7% ( 6/9 )
Rehbein's cases 24.0±15.0 cmH2O 0% ( 0/7 )

The current assessment yet showed definitely higher scores in sacro-perineal patients compared to ERPT patients at all age groups, though not statistically significant. In the sacroperineal procedure, the rectal end including the most caudal internal circular smooth muscle is transplanted downward to the anus, whereas in ERPT procedures, the muscle remained is higher at the fistula site. These clinical outcomes may indicate that the transplanted internal circular muscle works post-operatively as internal anal sphincter to preserve passive continence after the sacroperineal procedure. This hypothesis is supported by another observation that anorectal reflex was seen postoperatively in 77.8% of the patients operated with sacroperineal procedure, whereas seen in none of the patients operated with ERPT procedures.

Table 4. Histology of the most caudal internal circular muscles

Case muscle bundles degeneration sagittal continuity thickening total score
at 5 yrs.old
#1 Y.T. loose mild uncertain unclear 5

#2 U.R.

loose (+) discontinued unclear 5
#3 O.R. loose (+) uncertain unclear 7
#4 I.T. loose (-) partial thinning unclear 5
#5 F.S. loose mild partial thinning unclear 7
#6 M.T. dense (-) normal relatively 6
#7 K.S. dense (-) normal clear 6

The clinical importance of the thickened internal circular smooth muscle has been emphasized in the surgical repair, since this muscle was first identified at the rectal end in high type anorectal malformations [1, 2, 3, 11, 12]. And some articles insisted that this muscle functioned post-operatively like internal anal sphincter to preserve passive continence [1,13]. Nevertheless, the internal circular smooth muscle located at the rectal end showed a wide spectrum of histology, and the well-developed and thickened muscle similar to the internal anal sphincter in normal children is rarely seen in the present series. Meier-Ruge et al also reported that the intrinsic muscle layers and/or internal anal sphincter were characteristically abnormal and hypoplastic in high type anomalies [14].

The present results may suggest that the most caudal internal circular muscles have the potential to develop as the internal anal sphincter, even though they are histologically loose and undeveloped at the definitive surgery. Husberg et al reported irregularity and varied thickness of internal anal sphincter in the post-operative Magnetic Resonance Imaging (MRI), which did not correlate with the function [15]. The present histological findings and clinical outcomes seemed compatible with those reported by Husberg et al. In contrast, the lower clinical scores and negative anorectal reflex in ERPT cases indicate that the internal circular muscles preserved at the higher site rarely acquire the function as internal anal sphincter.

The present results encourage the transplant of rectal end with minimal trimming in the surgical repair of high type anomalies. However, the disturbance of rectal innervation may occur during the surgical mobilization of the rectal end in the sacroperineal procedure, which may cause severe constipation [16, 17]. Holschneider et al recently pointed out that the innervation of the rectal end might be disturbed primarily in anorectal malformations from his histological investigation, suggesting that this may be the cause of the high incidence of constipation after the transplant procedures [5]. Further studies should be required to improve the function of defecation in the high type anorectal malformations.

 

 

 

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