The definition of perineal fistula is undisputed and it is one of the most common anorectal malformations in pediatric surgery. However, the special type of perineal fistula (SPF) with a highly dilated colon is very rare and the number of cases reported in the literature is limited to date. In our patients with SPF, the dilated proximal colon was located in front of the iliac crest, which undoubtedly contributed to the complexity of the operation.
In this study, incidence of the special type of perineal fistula with high dilated colon was 8.97% (7/78). This incidence may reflect that surgeons often ignore to raise the importance of SPF. About 42.8% of all patients with SPF had spine syndrome of tethered cord which is far higher than NPF.
The diagnosis of perineal fistula is well recognized, and almost all neonates can be diagnosed at birth. A true perineal fistula is a narrow perineal foramen with no visible anal canal, and is located in the center of the anal sphincter but is not completely surrounded by the sphincter mechanism [9–11]. In boys, the fistula is often found in the normal anal area and root of the scrotum. The fistula in girls is mostly located between the normal anal area and posterior labia. The clinical presentation of SPF is similar to that of a perineal fistula, but the position of the dilated colon is unlikely to be the same as in a normal perineal fistula. However, some surgeons do not perform a preoperative examination to get a correct understanding of the anatomical structure of these anorectal malformations, including the related fistula communication between the rectum and genitourinary tract. In our neonatal unit, all newborns with the anorectal malformation of a perineal fistula were screened by a distal colostogram to confirm the position of the distal rectum. We found that there was a special type of perineal fistula associated with a highly dilated colon. This special type of perineal fistula, if unrecognized preoperatively, may complicate surgical operations to repair anorectal deformities. Therefore, it is imperative that a thorough evaluation (e.g., ddistal colostogram) be performed to identify an SPF so that it can be correctly treated. There is a lack of consensus in the literature on the best imaging method for accurate anatomical diagnosis at birth. Some authors believe that perineal ultrasound is the best option, while others prefer MRI [12, 13]. We believe that no matter which investigation is used to assess the anatomy of the anorectal malformation, preoperative evaluation is essential in children diagnosed with a perineal fistula to identify the possibility of a highly dilated colon. Therefore, we suggest a ddistal colostogram in the newborn period as well as a pelvic MRI to thoroughly evaluate the anatomy of the anorectal malformation.
Another important decision before surgery is to determine whether to transfer the patient to a center with extensive experience in pediatric surgery. Although there is no consensus on this point, there is strong evidence from adult studies that the surgeon’s technique is independently associated with better outcomes [14–16]. In some local hospitals, surgeons may lack awareness of anorectal malformations. Therefore, we recommend that if there is no pediatric surgeon available at a local hospital, patients should be transferred to a center with extensive pediatric surgery experience.
In most patients born with a SPF, management includes a diverting colostomy. Colostomy is valuable because it can avoid the complications of secondary colon dilation and pseudo-incontinence . In our case series, all patients were managed with a diverting colostomy before the definitive repair.
Although it is the most straightforward anorectal malformation to repair [18, 19], perineal fistula remains a constant point of confusion. With regard to radical surgery, it is essential to select an appropriate surgical approach that ensures optimal defecation function, as blind surgery can seriously affect the long-term defecation function. In this study, we introduced the procedure of correcting this abnormality using a posterior sagittal approach and laparoscopic approach, which can accurately expose the position of the distal rectum. These two approaches can avoid potential complications of a fistula, urethral injury, or intrasphincter anal dislocation.
Our routine is to calibrate the anus 3 weeks after surgery and continue to expand it for several months every day. With regard to the postoperative outcome of anorectal malformation treatment, particularly regarding continence, it has been reported that 100% of the patients have bowel control in recto-perineal fistulas and the postoperative pain was also minimal . In our study, 86% of the followed-up NPF patients were continent after the correction surgery at the end of the follow-up period. However, 57.1% of the SPF patients had abnormal bowel function, including constipation and fecal incontinence. Inadequate surgery, coupled with a natural propensity for constipation, can lead to severe fecal impaction that can cause substantial rectal dilation. This dilation can hamper rectal mobility and ultimately affect fecal control. In particular, when surgeons do not perform an adequate preoperative evaluation to accurately understand the anatomy of the anorectal malformation, including an associated fistulous communication between the rectum and the urogenital tract, it may affect the optimal surgical management. Due to this, patients may have to undergo multiple operations and may develop a defecation dysfunction. In our study, children who underwent more than two repair operations had lower BFS than those who had only one operation. In addition, the BFS in SPF patients was lower than that in NPF patients, although the difference was not statistically significant. Therefore, repeated operations and a highly dilated colon may be risk factors for abnormal defecation function in these patients. Although the majority of these patients can be managed with drugs, careful follow-up is vital (as with all patients who have anorectal malformations), so that the patients who need early management of their bowel function can be identified .