- Email: [email protected]
The use of computerized tomography to evaluate anorectal anomalies
The U s e of Computerized Tomography to Evaluate Anorectal Anomalies By Hiromichi Ikawa, Jotaro Yokoyama, Toru Sanbonmatsu, Kazuhiko Hagane, Masao Endo, Keizo Katsumata, and Eiichi Kohda
Tokyo. Japan 9 Computerized tomography {CT) was applied to various types of anorectal anomalies to directly image the anal sphincters. In n o r m a l cases and low type anomalies, CT demonstrated clear images of the puborectal muscle and external sphincters. Among high type anomalies, the distribution of sphincter muscle in patients with rectovesical fistula is totally different from that seen in patients w i t h r e c t o u r e t h r a l fistula. In t h e l a t t e r , the puborectal muscle is attached n o t only a r o u n d u r e t h r a , but also around the distal part of the blind r e c t u m ; e x t e r n a l sphincters are present as a mass beneath the perineum. In the rectovesical fistula, however, the puborectal muscle cannot be identified and the external sphincters exist only as a string-like structure. CT done postoperatively identified two different causes f o r i n c o n t i n e n c e . In one type, t h e p u l l - t h r o u g h colon missed the sphincteric musculature, and in the other, sphincters w e r e markedly hypoplastic. CT, therefore, provides adequate imaging to determine the type of operation needed to correct the abnormality. 9 1986 b y Grune & S t r a t t o n , Inc.
anal sphincters, patients with various types of anorectal malformations have been studied preoperative and or postoperatively with axial C T of the pelvic area. The clear images provided by CT give direct information regarding the localization and the development of the anal sphincters, and can hence more accurately direct therapy. MATERIALS AND METHODS
From 1982 to 1984, 16 patients with anorectal anomalies were scanned by CT on 26 occasions. Eleven patients (5 high type, 4 intermediate, and 2 low type) were examined by CT both preoperatively and postoperatively; 5 patients (3 high type, 2 low type) were examined only postoperatively. Five patients without anorectal disorders undergoing the abdominal CT for other reasons were studied as controls using the same methods applied to patients with anorectal anomalies. ACT / T GE 8800 scanner was used. Patients were placed supine and 1 cm axial sections parallel to pubococcygealline were obtained from the pubic bone to the perienum.
INDEX WORDS: Imperforate anus; CT scanning.
RESULTS
I N C E S T E P H E N S ~ emphasized the importance of the puborectal muscle for anal continence, most pediatric surgeons have accepted the principle that the operative management for anal anomalies must be based on preservation of the puborectal muscle. The distribution of the anal sphincters must be evaluated with accuracy preoperatively to preserve their integrity. Localization of sphincters has been estimated usually by the invertgram, 2 by study of the configuration of the rectum 3 produced during contraction of the puborectal muscle, or by electromyography 4 of subcutaneous external sphincter. These examinations, however, provide only indirect information regarding sphincter function or position. In order to provide more accurate accessment of the
S
From the Departments of Pediatric Surgery and Radiology, School of Medicine, Keio University, Tokyo. Presented before the 16th Annual Meeting of the American Pediatric Surgical Association, Kohala Coast, Hawaii, May 1-4, 1985. Address reprint requests to Hiromichi lkawa, MD, Department of Pediatric Surgery, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, Japan. 9 1985 by Grune & Stratton, Inc. 0022-3468/85/2006-0014503.00/0 640
In normal cases, the puborectal muscle was identified as a soft tissue mass that was anchored to the pubis anteriorly and attached posteriorly to the lateral and posterior walls of the rectum (Fig 1A). Anal sphincter was demonstrated as a oval shaped soft tissue mass composed of internal and external sphincter muscles that were impossible to differentiate (Fig 1B). In patients with anovestibular fistula, the localization and the development of puborectal muscle were essentially the same as seen in normal cases (Fig 2A). The anal sphincter was well developed but its center was displaced posterior to the orifice of the fistula (Fig 2B), In patients with the low rectovaginal anomaly, the blind rectum was surrounded by a well developed but anteriorly located puborectalis sling (Fig 3). The puborectal muscle and anal sphincters were present in the patients with rectourethral fistula. The puborectal muscle was attached around both the urethra and the distal blind pouch of rectum (Fig 4A). The anal sphincters were present, not as a fragmented structure but as a substantial mass beneath the perineum (Fig 4B). Reconstruction of the rectourethral fistula in the sagittal plane demonstrated that the superficial external sphincter extended to the coccyx posteriorly as the anococcygeal ligament and that the Journal of Pediatric Surgery, Vo120, No 6 (December), 1985: pp 640-644
CT SCANNING FOR ANORECTAL MALFORMATIONS
641
Fig 2. CT of the patient w i t h anovestibular fistula. (A) Cranial part of anal canal. Puborectal muscle is well developed. (B) Caudal part of anal canal, The center of well-developed external sphincter is displaced posteriorly to the orifice of the fistula. Fig 1. CT of normal infant showing (A) puborectalis muscle and (B) external sphincter muscle around anal canal.
deep external sphincter was present at right angle to the urethra as a mass above the anal dimple (Fig 5). CT was unable to identify the puborectal muscle in a patient with rectocloacal fistula whose external sphincter was present only as a strand-like structure (Fig 6). CT was helpful in evaluating patients postopera-
Fig 3. CT of the patient with low rectovaginal fistula.
tively. Fig 7 is the image of an incontinent 9-year-old girl previously operated on by Rehbein's procedure for rectovesical fistula showing that the colon was pulled through to the left side of the sphincter muscle. CT of another incontient 9-year-old boy operated by Rehbein's procedure for rectourethral fistula, demonstrated that the colon was appropriately placed but that the puborectal muscle was too hypoplastic to allow fecal continence (Fig 8).
642
IKAWA ET AL
Fig 6. CT of rectocloacal fistula showing the sphincteric musculature as a strand-like structure.
By comparison, Fig 9 shows a CT of a 21/2-year-old boy with good continence who was operated on by our abdominoextended sacroperineal procedures for rectourethral fistula. This study demonstrates that the colon was pulled exactly through the center of both puborectal and the external sphincter muscle. DISCUSSION
Fig 4. CT of the patient with rectourethral fistuJa. (A) Note puborectalis muscle around distal part of blind rectum. (B) Note the mass of external sphincter,
The evaluation of the anal sphincter and the puborectal muscle and their relationship to the blind rectum is vitally important for the successful surgical correction of imperforate anus. CT can provide useful anatomic information, especially about high anomalies, and aid in the evaluation of postoperative incontinence. Stephens ~pointed out the importance of preserving the puborectalis sling surrounding the membraneous
Fig 5. Sagitta| reconstruction of rectourethral fistula showing t h e extention of superficial external sphincter (arrow 1 ) and a mass of deep external sphincter (arrow 2) above the anal dimple.
CT SCANNING FOR ANORECTAL MALFORMATIONS
Fig 7.
643
Postoperative CT of incontinent 9-year-old girl. Note
the pull-through colon is lateral to the sphincteric musculature.
urethra in the case of rectourethral fistula as the muscle responsible for postoperative continence, and that the external sphincters, although present, might be poorly developed and thought to contribute little to function. CT in patients with rectourethral fistula, however, demonstrated not only that the puborectal muscle was attached around the urethra and the blind pouch of rectum but that the external sphincters were also present as a substantial mass that we feel can be made to contribute to continence as suggested by the study of Yokoyama, 5 De Vries, 6 and Pena. 7 Our histopathologic study of horizontal sections of a case of rectourethral fistula, which demonstrates the existence of the sphincteric musculature, is consistent with the findings obtained by CT (Fig 10). Patients with rectovesical fistula or rectocloacal fistula, however, have
Fig 8.
Postoperative CT of incontinent 9-year-old boy. Note
that the sphincter complex is markedly hypoplastic.
Fig 9. Postoperative CT of continent 21/2-year-old boy, showing (A) the colon pulled through the center of puborectalis muscle and (B) the center of external sphincters,
deficient sphincteric musculature. Therefore, their management may have to be different from patients with rectourethral or rectovestibular fistulae. The puborectal muscle could not be identified by CT in patients with rectovesical fistula and the external sphincters were present only as a thin strand-like structure. These findings were confirmed by direct visualization of the hypoplastic sphincters during radical operation. This indicates that the rectourethral fistula should be handled differently from other high
Fig 10. Gross section of the patient with rectourethral fistula who died of severe associated anomalies, showing puborectalis muscle around blind rectum and the presence of the mass of external sphincters at the level of pubic bone.
644
IKAWA ET AL
type anomalies such as rectovesical and some types of rectocloacal fistula. Also, the operative procedure should be dictated by the findings of preoperative CT. If puborectal muscle and sphincters can be recognized in some degree, a procedure should be chosen in which all available sphincteric musculature is used to achieve maximal continence of a newly formed anal canal. If only a strand-like structure exists to represent the sphincter complex, other procedures should be considered to a u g u m e n t the pull-through operation since they m a y have little functional value. Kiesewetter s reported that the puborectal muscle was missed in pull-through operation with greater frequency than was generally appreciated, especially in the earlier group of cases that had been done by the classic blind abdominoperineal pull-through procedure. Missed puborectal muscle is usually diagnosed by a rectal examination that can detect any muscle component anterior to the rectum, or by a postrectoplasty defecogram, which demonstrates leakage of barium around a catheter or loss of anorectal angulation. Based on our experience, however, axial C T was superior for evaluating these patients with postoperative incontinence. This modality gives a diect image of
the muscle structures around anal canal and helps to clarify the anatomic correlations between anal sphincters, puborectal muscle, and the anal canal. C T defined two types of postoperative incontinence, one in which the new anorectum missed a portion or all of the puborectal muscle and external sphincters, and the other in which puborectal muscle and external sphincters were markedly hypoplastic. In the former, reposition of the rectum through the puborectalis sling and external sphincters should provide effective correction. In the latter, however, pull-through operation m a y not be sufficient because the sphincters m a y be too hypoplastic to maintain fecal continence. Additional maneuvers such as levatorplasty, 9 muscle transplantation, 1~ or as yet untried techniques m a y be r e q u i r e d to achieve success. Thus, C T d o c u m e n t a t i o n of the muscles of continence, plus direct visualization at the time of surgery, should increase our chances of making these children with difficult problems fully continent. ACKNOWLEDGMENT
We would like to thank Dr Patricia K. Donahoe (Massachusetts General Hospital) and Dr Mutsuhisa Fujioka (Saitama Children's Hospital) for their kind review of this paper. We also thank Tamami Hasuo for her editorial assistance.
REFERENCES
1. Stephens FD, Smith ED: Anorectal Malformations in Children. Chicago, Year Book Medical, 1971 2. Wangensteen OH, Rice CO: Imperforate anus. A method of determining the surgical approach. Ann Surg 92:77-81, 1930 3. Kelly JH: Cine radiography in anorectal malformations. J Pediatr Surg 4:538-546, 1969 4. Hayashi A, Yokoyama J, Katsumata K, et al: Electromyographic examination of external sphincter muscle in ano-rectal malformations. Jap J Pediatr Surg 18:283-287, 1982 5. Yokoyama J, Hayashi A, Ikawa H, et al: Abdomino-extended sacroperineal approach in high type anorectal malformation--and our new operative method. Zeitschrift ftir Kinderchirurgie. 1985 (in press) 6. De Vries PA, Pena A: Posterior sagittal anorectoplasty. J Pediatr Surg 17:638-643, 1982 7. Pena A, De Vries PA: Posterior sagittal anorectoplasty, impor-
tant technical consideration and new applications. J Pediatr Surg 17:796-811, 1982 8. Kiesewetter WB, Jefferies MR: Secondary anorectal surgery for the missed puborectal muscle. J Pediatr Surg 16:921-927, 1981 9. Kottmeier PK: A physiological approach to the problem of anal incontinence through use of the lavator ani as a sling. Surgery 60:1262-1266, 1966 10. Holschneider AM, Hecker WC: Reverse smooth muscle plasty: A new method of treating anorectal incontinence in infants with high anal and rectal atresia. J Pediatr Surg 16:917-920, 1981 11. Pickrell KL, Broadbent TR, Masters FW, et al: Construction of a rectal sphincter and restoration of anal continence by transplanting the gracilis muscle. Ann Surg 135:853-862, 1952 12. Hakelius L: Free autogenous muscle transplantation in two cases of total anal incontinence. Acta Chir Stand 141:69-75, 1975
Tokyo. Japan 9 Computerized tomography {CT) was applied to various types of anorectal anomalies to directly image the anal sphincters. In n o r m a l cases and low type anomalies, CT demonstrated clear images of the puborectal muscle and external sphincters. Among high type anomalies, the distribution of sphincter muscle in patients with rectovesical fistula is totally different from that seen in patients w i t h r e c t o u r e t h r a l fistula. In t h e l a t t e r , the puborectal muscle is attached n o t only a r o u n d u r e t h r a , but also around the distal part of the blind r e c t u m ; e x t e r n a l sphincters are present as a mass beneath the perineum. In the rectovesical fistula, however, the puborectal muscle cannot be identified and the external sphincters exist only as a string-like structure. CT done postoperatively identified two different causes f o r i n c o n t i n e n c e . In one type, t h e p u l l - t h r o u g h colon missed the sphincteric musculature, and in the other, sphincters w e r e markedly hypoplastic. CT, therefore, provides adequate imaging to determine the type of operation needed to correct the abnormality. 9 1986 b y Grune & S t r a t t o n , Inc.
anal sphincters, patients with various types of anorectal malformations have been studied preoperative and or postoperatively with axial C T of the pelvic area. The clear images provided by CT give direct information regarding the localization and the development of the anal sphincters, and can hence more accurately direct therapy. MATERIALS AND METHODS
From 1982 to 1984, 16 patients with anorectal anomalies were scanned by CT on 26 occasions. Eleven patients (5 high type, 4 intermediate, and 2 low type) were examined by CT both preoperatively and postoperatively; 5 patients (3 high type, 2 low type) were examined only postoperatively. Five patients without anorectal disorders undergoing the abdominal CT for other reasons were studied as controls using the same methods applied to patients with anorectal anomalies. ACT / T GE 8800 scanner was used. Patients were placed supine and 1 cm axial sections parallel to pubococcygealline were obtained from the pubic bone to the perienum.
INDEX WORDS: Imperforate anus; CT scanning.
RESULTS
I N C E S T E P H E N S ~ emphasized the importance of the puborectal muscle for anal continence, most pediatric surgeons have accepted the principle that the operative management for anal anomalies must be based on preservation of the puborectal muscle. The distribution of the anal sphincters must be evaluated with accuracy preoperatively to preserve their integrity. Localization of sphincters has been estimated usually by the invertgram, 2 by study of the configuration of the rectum 3 produced during contraction of the puborectal muscle, or by electromyography 4 of subcutaneous external sphincter. These examinations, however, provide only indirect information regarding sphincter function or position. In order to provide more accurate accessment of the
S
From the Departments of Pediatric Surgery and Radiology, School of Medicine, Keio University, Tokyo. Presented before the 16th Annual Meeting of the American Pediatric Surgical Association, Kohala Coast, Hawaii, May 1-4, 1985. Address reprint requests to Hiromichi lkawa, MD, Department of Pediatric Surgery, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, Japan. 9 1985 by Grune & Stratton, Inc. 0022-3468/85/2006-0014503.00/0 640
In normal cases, the puborectal muscle was identified as a soft tissue mass that was anchored to the pubis anteriorly and attached posteriorly to the lateral and posterior walls of the rectum (Fig 1A). Anal sphincter was demonstrated as a oval shaped soft tissue mass composed of internal and external sphincter muscles that were impossible to differentiate (Fig 1B). In patients with anovestibular fistula, the localization and the development of puborectal muscle were essentially the same as seen in normal cases (Fig 2A). The anal sphincter was well developed but its center was displaced posterior to the orifice of the fistula (Fig 2B), In patients with the low rectovaginal anomaly, the blind rectum was surrounded by a well developed but anteriorly located puborectalis sling (Fig 3). The puborectal muscle and anal sphincters were present in the patients with rectourethral fistula. The puborectal muscle was attached around both the urethra and the distal blind pouch of rectum (Fig 4A). The anal sphincters were present, not as a fragmented structure but as a substantial mass beneath the perineum (Fig 4B). Reconstruction of the rectourethral fistula in the sagittal plane demonstrated that the superficial external sphincter extended to the coccyx posteriorly as the anococcygeal ligament and that the Journal of Pediatric Surgery, Vo120, No 6 (December), 1985: pp 640-644
CT SCANNING FOR ANORECTAL MALFORMATIONS
641
Fig 2. CT of the patient w i t h anovestibular fistula. (A) Cranial part of anal canal. Puborectal muscle is well developed. (B) Caudal part of anal canal, The center of well-developed external sphincter is displaced posteriorly to the orifice of the fistula. Fig 1. CT of normal infant showing (A) puborectalis muscle and (B) external sphincter muscle around anal canal.
deep external sphincter was present at right angle to the urethra as a mass above the anal dimple (Fig 5). CT was unable to identify the puborectal muscle in a patient with rectocloacal fistula whose external sphincter was present only as a strand-like structure (Fig 6). CT was helpful in evaluating patients postopera-
Fig 3. CT of the patient with low rectovaginal fistula.
tively. Fig 7 is the image of an incontinent 9-year-old girl previously operated on by Rehbein's procedure for rectovesical fistula showing that the colon was pulled through to the left side of the sphincter muscle. CT of another incontient 9-year-old boy operated by Rehbein's procedure for rectourethral fistula, demonstrated that the colon was appropriately placed but that the puborectal muscle was too hypoplastic to allow fecal continence (Fig 8).
642
IKAWA ET AL
Fig 6. CT of rectocloacal fistula showing the sphincteric musculature as a strand-like structure.
By comparison, Fig 9 shows a CT of a 21/2-year-old boy with good continence who was operated on by our abdominoextended sacroperineal procedures for rectourethral fistula. This study demonstrates that the colon was pulled exactly through the center of both puborectal and the external sphincter muscle. DISCUSSION
Fig 4. CT of the patient with rectourethral fistuJa. (A) Note puborectalis muscle around distal part of blind rectum. (B) Note the mass of external sphincter,
The evaluation of the anal sphincter and the puborectal muscle and their relationship to the blind rectum is vitally important for the successful surgical correction of imperforate anus. CT can provide useful anatomic information, especially about high anomalies, and aid in the evaluation of postoperative incontinence. Stephens ~pointed out the importance of preserving the puborectalis sling surrounding the membraneous
Fig 5. Sagitta| reconstruction of rectourethral fistula showing t h e extention of superficial external sphincter (arrow 1 ) and a mass of deep external sphincter (arrow 2) above the anal dimple.
CT SCANNING FOR ANORECTAL MALFORMATIONS
Fig 7.
643
Postoperative CT of incontinent 9-year-old girl. Note
the pull-through colon is lateral to the sphincteric musculature.
urethra in the case of rectourethral fistula as the muscle responsible for postoperative continence, and that the external sphincters, although present, might be poorly developed and thought to contribute little to function. CT in patients with rectourethral fistula, however, demonstrated not only that the puborectal muscle was attached around the urethra and the blind pouch of rectum but that the external sphincters were also present as a substantial mass that we feel can be made to contribute to continence as suggested by the study of Yokoyama, 5 De Vries, 6 and Pena. 7 Our histopathologic study of horizontal sections of a case of rectourethral fistula, which demonstrates the existence of the sphincteric musculature, is consistent with the findings obtained by CT (Fig 10). Patients with rectovesical fistula or rectocloacal fistula, however, have
Fig 8.
Postoperative CT of incontinent 9-year-old boy. Note
that the sphincter complex is markedly hypoplastic.
Fig 9. Postoperative CT of continent 21/2-year-old boy, showing (A) the colon pulled through the center of puborectalis muscle and (B) the center of external sphincters,
deficient sphincteric musculature. Therefore, their management may have to be different from patients with rectourethral or rectovestibular fistulae. The puborectal muscle could not be identified by CT in patients with rectovesical fistula and the external sphincters were present only as a thin strand-like structure. These findings were confirmed by direct visualization of the hypoplastic sphincters during radical operation. This indicates that the rectourethral fistula should be handled differently from other high
Fig 10. Gross section of the patient with rectourethral fistula who died of severe associated anomalies, showing puborectalis muscle around blind rectum and the presence of the mass of external sphincters at the level of pubic bone.
644
IKAWA ET AL
type anomalies such as rectovesical and some types of rectocloacal fistula. Also, the operative procedure should be dictated by the findings of preoperative CT. If puborectal muscle and sphincters can be recognized in some degree, a procedure should be chosen in which all available sphincteric musculature is used to achieve maximal continence of a newly formed anal canal. If only a strand-like structure exists to represent the sphincter complex, other procedures should be considered to a u g u m e n t the pull-through operation since they m a y have little functional value. Kiesewetter s reported that the puborectal muscle was missed in pull-through operation with greater frequency than was generally appreciated, especially in the earlier group of cases that had been done by the classic blind abdominoperineal pull-through procedure. Missed puborectal muscle is usually diagnosed by a rectal examination that can detect any muscle component anterior to the rectum, or by a postrectoplasty defecogram, which demonstrates leakage of barium around a catheter or loss of anorectal angulation. Based on our experience, however, axial C T was superior for evaluating these patients with postoperative incontinence. This modality gives a diect image of
the muscle structures around anal canal and helps to clarify the anatomic correlations between anal sphincters, puborectal muscle, and the anal canal. C T defined two types of postoperative incontinence, one in which the new anorectum missed a portion or all of the puborectal muscle and external sphincters, and the other in which puborectal muscle and external sphincters were markedly hypoplastic. In the former, reposition of the rectum through the puborectalis sling and external sphincters should provide effective correction. In the latter, however, pull-through operation m a y not be sufficient because the sphincters m a y be too hypoplastic to maintain fecal continence. Additional maneuvers such as levatorplasty, 9 muscle transplantation, 1~ or as yet untried techniques m a y be r e q u i r e d to achieve success. Thus, C T d o c u m e n t a t i o n of the muscles of continence, plus direct visualization at the time of surgery, should increase our chances of making these children with difficult problems fully continent. ACKNOWLEDGMENT
We would like to thank Dr Patricia K. Donahoe (Massachusetts General Hospital) and Dr Mutsuhisa Fujioka (Saitama Children's Hospital) for their kind review of this paper. We also thank Tamami Hasuo for her editorial assistance.
REFERENCES
1. Stephens FD, Smith ED: Anorectal Malformations in Children. Chicago, Year Book Medical, 1971 2. Wangensteen OH, Rice CO: Imperforate anus. A method of determining the surgical approach. Ann Surg 92:77-81, 1930 3. Kelly JH: Cine radiography in anorectal malformations. J Pediatr Surg 4:538-546, 1969 4. Hayashi A, Yokoyama J, Katsumata K, et al: Electromyographic examination of external sphincter muscle in ano-rectal malformations. Jap J Pediatr Surg 18:283-287, 1982 5. Yokoyama J, Hayashi A, Ikawa H, et al: Abdomino-extended sacroperineal approach in high type anorectal malformation--and our new operative method. Zeitschrift ftir Kinderchirurgie. 1985 (in press) 6. De Vries PA, Pena A: Posterior sagittal anorectoplasty. J Pediatr Surg 17:638-643, 1982 7. Pena A, De Vries PA: Posterior sagittal anorectoplasty, impor-
tant technical consideration and new applications. J Pediatr Surg 17:796-811, 1982 8. Kiesewetter WB, Jefferies MR: Secondary anorectal surgery for the missed puborectal muscle. J Pediatr Surg 16:921-927, 1981 9. Kottmeier PK: A physiological approach to the problem of anal incontinence through use of the lavator ani as a sling. Surgery 60:1262-1266, 1966 10. Holschneider AM, Hecker WC: Reverse smooth muscle plasty: A new method of treating anorectal incontinence in infants with high anal and rectal atresia. J Pediatr Surg 16:917-920, 1981 11. Pickrell KL, Broadbent TR, Masters FW, et al: Construction of a rectal sphincter and restoration of anal continence by transplanting the gracilis muscle. Ann Surg 135:853-862, 1952 12. Hakelius L: Free autogenous muscle transplantation in two cases of total anal incontinence. Acta Chir Stand 141:69-75, 1975