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Anterior Ectopic Anus: A Simplified Approach

Ahmed H. Al-Salem

Department of Pediatric Surgery, Maternity and Children Hospital, Dammam, Saudi Arabia


Abstract

Background: Anterior ectopic anus is a common condition that is easily missed and several operative procedures are described to treat it. This report presents our experience with anterior ectopic anus pathology and describes a modified surgical technique.

Patients and Methods: The records of all children treated for anterior ectopic anus between January 2009 and December 2013 were reviewed for age at diagnosis, sex, clinical features, operative treatment and outcome. The operative technique is also described.

Results: Seventeen infants and children (16 females and 1 male) were treated for anterior ectopic anus. Their mean age at diagnosis was 6.3 months (1 month-19 months). Postoperatively, all had good functional and cosmetic results but four of them continued to have constipation which responded to laxatives. One had superficial infection and wound dehiscence. She underwent reoperation with good results.

Conclusions: Anterior ectopic anus is one of the causes of constipation in infants and children. Physicians caring for these patients should be aware of this and early diagnosis is important for surgical correction. Although, there are several surgical techniques to treat anterior ectopic anus, a modified Anal Shift operation is a simple and safe procedure with good functional and cosmetic results.

Keywords: anterior ectopic anus, constipation, anal shift operation


Correspondence

Ahmed H. Al-Salem
P. O. Box 61015
Qatif 31911
Saudi Arabia
Fax: 9668630010
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.


Introduction

Anorectal malformations include a wide spectrum of defects and the majority of newborns with imperforated anus are usually diagnosed immediately after birth. Anterior ectopic anus is a common congenital abnormality that is commonly missed; underreported and very little is written about. It has been estimated that more than one third of children examined for chronic constipation have an anterior ectopic anus [1, 2, 3, 4]. In the past, the diagnosis of anterior ectopic anus was based on clinical evaluation. Reisner et al. proposed a quantitative measurement using the anal position index: the ratio of anal-fourchette distance to coccyx-forurchette distance for females and the ratio of anal-scrotum distance to coccyx-scrotum distance for males for proper diagnosis of anterior ectopic anus [4]. Anterior ectopic anus is diagnosed if the anal position index is less than 0.46 in boys and less than 0.34 in girls [1, 4, 5].

Anterior ectopic anus is more common in females and it has been reported that female gender, later birth order and higher maternal age are risk factors for anterior ectopic anus [6]. The usual presentation of anterior ectopic anus is with early onset constipation since birth or at the time of weaning from breast feeding [1, 2, 3, 4]. Although the overall incidences of constipation are comparable among children with or without anterior ectopic anus, children with anterior ectopic anus tend to have constipation with increasing age [1]. Add to this the fact that an anterior ectopic anus may have long term effects in females following pregnancy and delivery to the close proximity of the anus to the vagina.

There are several operative procedures to treat anterior ectopic anus and some of these procedures are extensive and may necessitates a preliminary colostomy [2, 7, 8, 9]. This report presents our experience with anterior ectopic anus and describes a modified surgical technique.

Patients and Methods

A total of 17 children with anterior ectopic anus were operated on over a 5-year period (January 2009 - December 2013). Their records were reviewed for age at presentation, sex, clinical features, diagnosis, management and outcome. In all the diagnosis of anterior ectopic anus was made clinically based on the anal position index as described by Genc et al. [10]. The anal position index was calculated as the ratio of anus-fourchette distance to coccyx-fourchette distance for females and anus-scrotum distance to coccyx-scrotum distance for males (Fig. 1A, 1B, and 1C).

Figure 1: Clinical photographs showing anterior ectopic anus.

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All were operated on by a modification of Ashok Shah’s Anal Shift technique [9]. All patients undergo a good preoperative bowel preparation and are given antibiotics. A Foley’s catheter is inserted and kept for 5 days post-operatively. The patient is placed in a lithotomy position. The sites of incision are marked as in Fig 2.

Figure 2: A clinical photograph showing the two incisions used to treat anterior ectopic anus. Note the inverted U incision posteriorly.

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An inverted U incision is made at the proper anal opening site with an extension upwards to the site of the existing anal opening. The incision is made as an inverted U rather than the inverted V. This gives a broader edge for the raised flap to be sutured to the posterior edge of the anteriorly placed anus. The incision is deepened to include the skin and subcutaneous tissues and a flap is raised. The raised flap is sutured to the posterior edge of the anal opening. The other incision is a transverse incision made mid-way between the anal opening and the fourchette. The length of this incision is equal to the distance between the posterior edges of the anterior ectopic anus and the proper position of the anal opening. This incision is deepened and care must be taken not to injure the underlying rectum. The incision is closed longitudinally in two layers using absorbable sutures (Fig 3).

Figure 3: A clinical photograph showing the end result of operating on anterior ectopic anus. Note the good perineal body and the distance created between the vaginal fourchette and anal opening.

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The end result is creation of a proper perineal body which also leads to an increase in the distance between the vagina and the new anal opening (Fig 4A and 4B). The anal opening is dilated and packed with gauze soaked in povidone iodine which is removed 24 hours later (Fig 5A and 5B). Post-operatively, the patient is kept nil by mouth for 4 days to avoid contamination of the wound. The patient is discharged home on the 6th-7th post-operative day to be followed up in the clinic.

Figure 4: Clinical photographs showing preoperative and post-operative anterior ectopic anus.

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Figure 5: A,B - Post-operative clinical photographs of anterior ectopic anus being dilated. Note the proper anal position and good perineal body.

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Results

Seventeen children with anterior ectopic anus were operated on. Sixteen females and one male who were born with anterior ectopic anus were treated by modified Anal Shift technique. Their mean age at diagnosis was 6.3 months (1 month-19 months). All were suffering from variable degrees of constipation. Two of them had a pre-operative contrast enema which showed a prominent posterior shelf of the rectum with dilatation of the colon proximally (Fig 6). An interesting finding was the familial occurrence of anterior ectopic anus in two families of our patients. In each family there were three affected sisters. Post-operatively, all had a normal anal function. Four of them continued to have constipation that responded to simple laxatives. Cosmetically, the anal opening appeared normal without stenosis and a satisfactory vulvo-anal distance. One patient had superficial wound infection with dehiscence; she underwent reoperation with good results.

Figure 6: A lower contrast enema showing prominent posterior shelf of the rectum with dilatation of the colon proximally characteristic of anterior ectopic anus.

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Discussion

Commonly newborns are discharged home once they pass normal meconium and are otherwise well. Newborns with anorectal malformations are commonly diagnosed immediately after birth either because of absence of a normally located anus or when they pass small amounts of meconium through an abnormally placed opening. Newborns with anterior ectopic anus on the other hand usually have a normal looking anal opening and so escape identification during the newborn period and many of these patients present subsequently with constipation [1, 2, 3, 4]. This was the case for the majority of our patients who presented beyond the newborn period with variable degrees of constipation. The occurrence of anterior ectopic anus in two families of our patients, three sisters in each family suggests a familial occurrence and possible genetic predisposition of anterior ectopic anus.

Anterior ectopic anus is a normal looking anus but anteriorly displaced and the external anal sphincter is distributed all around the circumference of the anal canal, including the ventral aspect of the anal canal as was evaluated by preoperative magnetic resonance imaging [11]. Anterior ectopic anus is characterized by a short perineal body and it is believed to result from developmental malformation of the mid-portion of the external anal sphincter which leads to weakness of corresponding segment of the anal canal [12]. Anterior ectopic anus is underdiagnosed but increasingly being recognized as a cause of constipation in infants and children.

The normal anal position is midway between the vaginal fourchette and coccyx in females and the scrotum and coccyx in males. The anal position index is a simple method used to evaluate the anal position. Initially this was first described by Bar-Maor and Eitan and called it the anogenital index which was modified subsequently by Reisner et al. who called it the anal position index [5, 13]. The anal position index was defined as the ratio of the scrotal-anal distance to the scrotal-coccygeal distance in boys, and as the ratio of the fourchette-anal distance to the fourchette-coccygeal distance in girls [5, 10, 13, 14, 15]. An anal position index of less than 0.34 in girls and less than 0.46 in boys is diagnostic of an anterior ectopic anus. Anterior ectopic anus is believed to be more common than was previously thought and it is much more common in girls than boys. In a previous study on 357 children (191 boys and 166 girls), the incidence of anterior ectopic anus was 43.4% in girls and 24.6% in boys (P < 0.01) [1].

There are several surgical techniques to treat anterior ectopic anus. These include cutback, posterior anal transposition, posterior sagittal ano-rectoplasty (PSARP), posterior anoplasty with sphincterotomy and anterior sagittal anorectoplasty (ASAPR) [2, 7, 8, 9, 15]. Some of these procedures are extensive, may not be cosmetically acceptable and may necessitate a preliminary diverting colostomy. Anal Shift procedure on the other hand is a simple and safe surgical procedure with good functional and cosmetic results [9]. It does not necessitate a preliminary diverting colostomy and the minimal dissection eliminates the chances of stricture and anal stenosis. The inverted U incision posteriorly allows a flap of sufficient length and width to be raised and sutured without the fear of the sutures to cut through as in the inverted V incision.

In conclusion, anterior ectopic anus is one of the causes of constipation in infants and children. Physicians caring for these patients should be aware of this and early diagnosis is important for surgical correction. Surgical correction is important in these patients not only to treat constipation and have a good cosmetic appearance but also avoid long term effects in females following pregnancy and delivery to the close proximity of the anus to the vagina.

Although, there are several surgical techniques to treat anterior ectopic anus, Anal Shift operation is a simple and safe procedure with good functional and cosmetic results.

 


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