Abstract:

In 1976, Parks, Gordon and Hardcastle published their article entitled ‘A classification of Fistula- in ano.’ Their classification was based on the identification of four types of fistula: inter sphincteric, trans sphincteric, supra sphincteric and extra sphincteric. An intersphincteric fistula runs downwards between the internal and external sphincters. The trans sphincteric fistula runs from the intersphincteric space, through the external anal sphincter into the ischiorectal space. The supra sphincteric fistula runs upward between the internal sphincter and external sphincter and then bends around the pubo rectalis muscle and penetrates the pelvic floor, to traverse downwards through the ischiorectal fossa.

An extra sphincteric fistula passes through the external anal sphincter and then branches out into two tracks- one extending cephalad penetrating the pelvic floor and finally ending in rectum and the other extending caudally ending in the external opening. Although this classification does not take into account the circumferential extend of the disease it is widely used because of its simplicity. Another reason is that this classification relates the anatomical relation of the fistulous track to the anal sphincters which is relevant for the choice of treatment.  

References:

[1.] Beets-Tan, R., G., Beets, G., L., van der Hoop, A., G., et al (2001). Preoperative MR imaging of anal fistulae: does it really help the surgeon? Radiology, 218, 75–84.

[2.] Buchanan, G., Halligan, S., Williams, A., et al (2002). Effect of MRI on clinical outcome of recurrent fistula-in-ano. Lancet, 360, 1661–1662.

[3.] Domkundwar, S., V., Shingare, A., B. Role of transcutaneous perianal ultrasonography in evaluation of fistula in ano. J.Ultrasound in medicine, 26, 29-36.

[4.] Fishman-Javitt, M., C., Lovecchio, J., L., Javors, B., Naidich, J., B, McKinley, M., Stein, H., L. (1987). The value of MRI in evaluating perirectal and pelvic disease. Magn Reson Imaging, 5, 371–380.

[5.] Frudinger, A., Bartrum, C., I., Halligan, S. ,Kamm, M., A. (1998). Examination techniques for anal endosonography. Abdominal imaging, 23, 301-303.

[6.] Goodsall, D., H., Miles, W., E. Diseases of the anus and rectum. London, England:Longmans,Green.

[7.] Halligan, S., Stoker, J. (2006), Imaging of Fistula in ano. Radiolog, 239, 18-33.

[8.] Kuijpers, H., C., Sculpen, T. (1985). Fistulography for fistula in ano; is it useful? Dis Colon Rectum, 28, 103-104.

[9.] Koelbel, G., Schmiedl, U., Majer, M., C., et al (1989). Diagnosis of fistulae and sinus tracts in patients with Crohn disease: value of MR imaging. AJR Am J Roentgenol, 152, 999–1003.

[10.]   Law, P., J., Bartram, C., I. (1989). Anal endosonography: technique and normal anatomy. Gastrointestinal Radiology, 14, 349-535.

[11.]   Lunniss, P., J., Armstrong, P., Barker, P., G., et al (1992). Magnetic resonance imaging of anal fistulae. Lancet, 340, 394–396.

[12.]   Madsen, S., M., Myschetzky, P., S., Heldmann, U., Rasmussen, O., O, Thomsen, H., S. (1999). Fistula in ano: evaluation with low-field magnetic resonance imaging (0.1 T). Scand J Gastroenterology, 34, 1253–1256.

[13.]   Mallouhi, A., Bonatti, H., Peer, S., Lugger, P., Conrad, F., Bodner, G. (2004). Detection and characterization of perianal inflammatory disease: accuracy of transperineal combined gray scale and color Doppler sonography. J Ultrasound Med, 23, 19–27.

[14.]   Milligan, E., T., Morgan, C., N. (1934). Surgical anatomy of the anal canal with special reference to anorectal fistulae. Lancet, 2, 1213-1217.

[15.]   Parks, A., G., Gordon, P., H., Hardcastle, J., D. (1976). A Classification of fistula in ano. British Journal of surgery, 63, 1-12.

[16.]   Platell, C., Mackay, J., Collopy, B., Fink, R., Ryan, P., Woods, R. (1996). Anal pathology in patients with Crohn's disease. Aust N Z J Surg, 66, 5–9.

[17.]   Scratter-Sehn, A., U., Lochs, H., Vogelsang, H., Scurawitzki, H., Herold, C., Scratter, M. (1993). Endoscopic ultrasonography versus computed tomography in the differential diagnosis of perianorectal complications in Crohn’s disease. Endoscopy, 25, 582-586.

[18.]   Spencer, J., A., Chapple, K., Wilson, D., Ward, J., Windsor, A., C., Ambrose, N. (1998). Outcome after surgery for perianal fistula: predictive value of MR imaging. AJR Am J Roentgenol, 171, 403–406.

[19.]   Stewart, L., K., McGee, J., Wilson, S., R. (2001). Transperineal and transvaginal sonography of perianal inflammatory disease. AJR Am J Roentgenol, 177, 627–632.

[20.]   Sultan, A., H., Kamm, M., A., Hudson, C., N., Thomas, J, Bartram, C., I. (1993). Anal sphincter disruption during vaginal delivery. New England Journal of Medicine, 329, 1905-1911.

[21.]   Schwartz, D., A., Wiersema, M., J., Dudiack, K., M, etal (2001). A comparison of endoscopic ultrasound,magnetic resonance imaging and examination under anaesthesia for evaluation of Crohn’s perianal fistulae. Gastroenterology, 121, 1064-1072.

[22.]   Taylor, S., A., Halligan, S., Bartram. C., I. (2003). Pilonidal sinus disease: MR imaging distinction from fistula in ano. Radiology, 226, 662–667.

[23.]   Weisman, R., I., Orsay, C., P., Pearl, R., Ketal (1991). The role of fistulography in fistula in ano:report of five cases. Dis Colon Rectum, 34, 181-184.

[24.]   Winter, A., M, Hanauer, S., B. (1998). Medical management of perianal Crohn's disease. Semin Gastrointest Dis, 9, 10–14