Ano-rectal anomalies represent a diverse spectrum with different expression in the male and female [1]. A thorough understanding of both normal and pathological anatomy is a prerequisite for proper planning of reconstructive surgery [1]. Over successive years, a multitude of classification systems have been proposed based on embryological and radiological studies, as well as clinical and surgical observations [1]. In 2005, a new international classification system “Krickenbeck” was born trying to unify terminology so that pediatric surgeons all over the world would speak a common language [5]. The new classification was not only for the diagnosis, but also involved grouping of surgical procedures and postoperative results [5].
Since its introduction in 1982 [6], the PSARP procedure has gained widespread acceptance to become the standard technique for repair of ARA with rectourethral fistula in most pediatric surgical centers all over the world [10]. Through its perfect exposure, the trans-rectal approach to the fistula protects the urinary tract from possible iatrogenic injuries [10]. Protection of pelvic innervation is also feasible by sticking to the rectal wall during pelvic dissection. In this study, we present the surgical outcome of 62 consecutive cases belonging to two major clinical groups of ARA in the male (recto-urethral fistula, and imperforate anus without fistula) [5] who were treated by the same surgical procedure (PSARP) and same surgeon. Digital archiving included preoperative investigations and operative findings that were available for retrospective analysis.
Based on operative experience through this study group, the level of mid sacral vertebra (S3) was found to represent an important landmark indicating for the feasibility of perineal approach to mobilize the distal rectum. Below this level (when distal rectum was located opposite S4-S5), the PSARP procedure was a straight-forward approach to reach and mobilize the rectum; this was feasible in 51 consecutive cases. Meanwhile, a distal rectum located opposite the level of S3 (recto-prostatic fistula type 2) represents a ‘grey zone’ that can be approached from above (abdominal approach) or from below (perineal approach). Although the perineal approach (PSARP) was successful in 90% in this particular subgroup (nine out of ten consecutive cases), yet a higher level of surgical experience was needed to go with the dissection safely above urogenital structures that were frequently encountered in the surgical field. Here, the absent coccyx and last sacral piece may turn to be a favorable association that facilitates the access to the rectum from below when it becomes ‘relatively’ more superficial. Consequently, it is quite expected that a distal rectum located above S3 will be more accessible from above through abdominal/laparoscopic approach similar to recto-vesical fistula (only one case in this series with distal rectum opposite S2).
In this report, we emphasize on the well-known value of the distal colostogram in preoperative assessment for cases of anorectal anomalies. Not only for detection of presence and site of the fistula, but also other anatomical considerations should be looked for. The level of distal rectum in relation to the corresponding sacral vertebrae and the developmental status of the sacrum can alter the decision on how to approach the rectum. These anatomical considerations should be well studied and matched with the experience of the surgeon before attempting to dig the perineum in a blind manner from below searching for the rectum. This is especially important when dealing with cases lying in the grey zone (recto-prostatic fistula type 2). Although the perineal approach may be preferable (rapid recovery and avoids going through the abdomen), yet under certain circumstances (specific anatomy and surgeon’s experience), it might be safer to plan for an abdominal/laparoscopic approach from the start.
Fecal continence represents the primary functional outcome. Among several factors that affect continence, the degree of sacral dysplasia is of utmost importance [12]. Again, the middle sacral vertebra (S3) proved to play an important prognostic role in this respect; most authors would agree that the deficiency of more than two sacral pieces would be associated with poor prognosis for continence [12]. Pena innovated a sacral ratio that would be calculated on plain X-ray to judge on the degree of sacral dysplasia in a more objective way [12]. In this report, 17 cases were available for postoperative functional assessment using the Krickenbeck classification for postoperative results. Significant sacral dysplasia (three pieces deficient) was associated with lack of voluntary bowel control and severe soiling in two cases (recto-prostatic). The third case lacking voluntary bowel control had a good sacrum but delayed mental milestones (Down syndrome). Otherwise, all cases had voluntary bowel control (82%). On the other hand, the incidence of constipation was 47%, while significant fecal soiling (excluding mild occasional soiling) occurred in 59%. Except in the two cases with significant sacral dysplasia, soiling showed improvement with treatment of constipation. Although recto-prostatic fistula was associated with higher incidence and more severe degrees of sacral dysplasia, yet the number of cases available at follow-up in each group was too small to make sound comparison regarding the functional outcome.
Lastly, we came to a group of observations that we believe might be beneficial during surgical planning for these cases:
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Although classifying recto-urethral fistula into two subgroups (either recto-bulbar or recto-prostatic) is indicative for two different degrees of severity; however, this does not truly reflect all variants that can be seen in the spectrum. Moreover, there are no sharp boundaries existing between the two subgroups. A transitional overlap can often be observed (once has been described as recto-membranous).
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The level of distal rectum in the pelvis is usually but not always consistent with the site of the fistula [11]. The distal rectum may be located at a higher level while still communicating with the urethra at a lower level via a narrow fistulous tract (this is a relatively more common finding with recto-prostatic fistula).
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Practically speaking, the identification of the site of fistula needs to be complemented by identifying the level of distal rectum. Current surgical practice entails starting the dissection by the distal rectum to be followed by trans-rectal separation of the fistula. In this study, we could differentiate between two different degrees of severity among operated cases with recto-prostatic fistula depending on the level of distal rectum.
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The way of rectal termination (whether with or without fistula) does not appear to have a major impact on surgical decision. A common wall between rectal termination and the urinary tract anteriorly is almost always a constant finding in all cases even in absence of direct fistulous communication. Therefore, the same technique is applied for separation of the anterior rectal wall from the urinary tract in both groups.
Based on the above observations, we may need to revisit the anatomical classification of Stephens and Smith (1963) who used bony landmarks (the famous PC-line) to differentiate radiologically between a low and a high rectum. Using similar concept, we highlight a possible role for the sacrum in stratifying ARA [11]. Besides its well-known impact on the prognosis for continence, the sacral vertebrae can provide a scale for grading the level of distal rectum. Despite the obvious advantages of current classification of ARA into clinical groups [5], it appears that we are still in need for complementary anatomical stratification. Almost all clinical types share a common anatomical (embryological) feature which is the intimate relation (common wall) with the urogenital tract anteriorly. It remains always safer to start surgical dissection at the distal rectum posteriorly, and hence, the level of the distal rectum will remain the most decisive factor on surgical approach.
The limitation of the study may be related to its retrospective nature and the relatively small number of cases. However, the detailed digital archiving of preoperative investigations and operative findings greatly mitigated these drawbacks. Moreover, among the diversity of different types and procedures for ARA, included cases represented a relatively homogenous group who underwent the same procedure (same surgeon).