LETTER TO THE EDITOR
|Year : 2015 | Volume
| Issue : 4 | Page : 200-201
Posterior ectopic anus: Myth or reality?
Anand Pandey, Shailendra Pal Singh, Vipin Gupta, Rajesh Verma
Department of Surgery, Uttar Pradesh Rural Institute of Medical Sciences and Research, Saifai, Etawah, Uttar Pradesh, India
|Date of Web Publication||2-Sep-2015|
Dr. Rajesh Verma
Department of Surgery, Uttar Pradesh Rural Institute of Medical Sciences and Research, Saifai, Etawah - 206 301, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Pandey A, Singh SP, Gupta V, Verma R. Posterior ectopic anus: Myth or reality?. J Indian Assoc Pediatr Surg 2015;20:200-1
Ectopic anus (EA) denotes an anus which is not situated at its normal position in the perineum. If the anal orifice is located in the perineum in a more posterior location than normal, it will be a posterior ectopic anus (PEA). We came across two such patients.
A 3-month-old male child was referred for complain of constipation since birth. On perineal examination, the posterior displacement of the anus was seen, suggesting it to be PEA [Figure 1]a. The anal position index (API) was 0.6. The parents were informed about the need of magnetic resonance imaging (MRI) and possible surgery to correct the problem. They did not turn up after consultation. Another patient, a 14-day-old male child was referred for intestinal obstruction. On examination, there was Bells stage II necrotising enterocolitis (NEC). On perineal examination, there was severe perianal redness. The anus was displaced posteriorly, and the anal dimple was visible anteriorly [Figure 1]b. The API was 0.64. He was planned for urgent laparotomy; however, before any operative intervention, the patient succumbed to severe septicemia.
|Figure 1: (a) Patient 1 who presented with constipation. Anus is close to the sacrum. (b) Patient 2 who presented with necrotising enterocolitis (NEC). There is severe perianal redness. The posterior anus and anal pit are evident|
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These two patients represent an extremely uncommon variant of a broad spectrum of anorectal malformation (ARM). It has been suggested that the usual anal position is midway between the fourchette (scrotum) and the coccyx. 
Usually PEA is after posterosagittal anorectoplasty (PSARP). We are unable to explain the embryology of this condition. Kluth,  in his animal model studies, noticed that the normal embryology of the hindgut clearly demonstrates that the area of the future anal orifice is formed in an early phase of development, and forms a fixed point in cloacal and hindgut development. He also noted that in all abnormal mouse embryos, the dorsal cloacal membrane and the dorsal cloaca were missing. These structures are considered essential for the normal establishment of the anal orifice and the lower rectum. In case of a defective cloacal anlage, a missing or misplaced anal orifice may result. 
To detect EA, use of anal position index (API),  computerized eight-channel manometry,  and MRI  have been described. The normal value of API in males is 0.54 ± 0.07.  This was about 0.6 in both patients of this report.
There are certain limitations to this report. MRI was not performed and we had not used any muscle stimulator; hence, whether the displaced anus was outside the sphincter muscle is not documented. Hence, despite constipation or NEC, it cannot be directly attributed to PEA. API measurements taken may be wrong; however, we feel that our measurements were correct.
If there is clinico-radiological evidence of PEA, it may be treated by PSARP. However, given the limitations above, the cause effect relationship between the anal position and symptomatology or the potential therapeutic benefit from surgery are not clearly established. Having said this, given the rarity of the entity, this relationship will be difficult to prove.
To conclude, there is a real possibility of getting a patient like these. Proper assessment and adequate treatment may be rewarding.
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