Postanal sinus: single or different etiologies?

Experience with five patients who presented with a postanal sinus (PAS), all of which appeared to have a similar etiology at first hand, is reviewed. All patients were female and presented with a perianal fistula located in the midline posterior to the anus between the internal and external sphincter. All patients had a similar history and age at presentation (the 1st decade of life), which increased our assumption of a similar etiology. Further examinations revealed no internal connection to hollow organs or other pelvic structures, proving that the fistula was a sinus in all cases. One patient had a scimitar sacrum. In four cases the sinus was excised transanally, in one through a posterior sagittal approach. All patients had normal anal function postoperatively. Histologic examination was performed in all cases and showed results ranging from various types of epithelium to dermoid and epidermoid cysts, dismissing the theory of a similar etiology. In our opinion, a PAS can be a presenting sign for a variety of retrorectal developmental pathologies and should be differentiated from fistula-in-ano.