Imaging of Perianal Fistulas Manon Ziech, Richelle Felt–Bersma, Jaap Stoker  Clinical Gastroenterology and Hepatology  Volume 7, Issue 10, Pages 1037-1045 (October 2009) DOI: 10.1016/j.cgh.2009.06.030 Copyright © 2009 AGA Institute Terms and Conditions

Figure 1 Diagram of perianal fistulas. ss, suprasphincteric fistula; sf, superficial fistula (or submucosal fistula); is, intersphincteric fistula; ts, trans-sphincteric fistula; es, extrasphincteric fistula. Clinical Gastroenterology and Hepatology 2009 7, 1037-1045DOI: (10.1016/j.cgh.2009.06.030) Copyright © 2009 AGA Institute Terms and Conditions

Figure 2 Anal ultrasound in a 35-year-old man with CD. (A) The probe (p) is in the rectum. A large hypoechogenic (h) area is visible at and just above the level of the puborectal muscle. (B) Hydrogen peroxide is injected into the external fistula opening. The tract to the internal opening (i.o.) is visible. The fistula (f) branches are visible at the level of the external anal sphincter. (C) The hypoechogenic area now is partly hyperechogenic and a horseshoe configuration of the fistula (f) becomes clear. (D) Longitudinal image. The extent of the fistula clearly is visible. Clinical Gastroenterology and Hepatology 2009 7, 1037-1045DOI: (10.1016/j.cgh.2009.06.030) Copyright © 2009 AGA Institute Terms and Conditions

Figure 3 A 40-year-old man with CD and a perianal fistula. (A) Coronal T2-weighted fast spin echo image shows a trans-sphincteric fistula (curved arrows) at the right side with a seton in situ (arrow). The rectal wall is thickened, and some small lymph nodes and some adjacent fat infiltration indicating disease activity at the rectum are visible. l, levator ani muscle; e, external sphincter muscle. (B) Diagram of panel A, the fistula is indicated in dotted lines. (C) Axial T2-weighted fast spin echo image shows the trans-sphincteric course of the tract and the internal opening with a seton (s). The tract is wide and hyperintense (curved arrow), indicating either granulation tissue or fluid. g, gluteal muscle. (D) Axial T1-weighted, fat-saturated fast spin echo image after intravenous contrast agent shows enhancement of the almost complete tract, indicating that it is granulation tissue (curved arrow). e, external anal sphincter; io, internal obturator muscle; g, gluteus muscle. (E) Diagram of panels C and D, the fistula and granulation tissue are indicated in dotted lines. Clinical Gastroenterology and Hepatology 2009 7, 1037-1045DOI: (10.1016/j.cgh.2009.06.030) Copyright © 2009 AGA Institute Terms and Conditions

Figure 4 A 46-year-old man with extensive CD who underwent proctocolectomy with ileostomy. g, gluteus muscle; p, prostate. (A) Axial T2-weighted fast spin echo image shows a hyperintense collection with extensive surrounding hypointense scar tissue. (B) An axial fat-saturated, T2-weighted fast spin echo image showing that the collection is also hyperintense (arrow), indicating this either could be filled with fluid (ie, an abscess) or could be granulation tissue. (C) Axial fat-saturated, T1-weighted fast spin echo image obtained after administration of intravenous contrast medium shows strong enhancement of the rim whereas the core does not enhance, indicating an abscess with a rim of inflammatory tissue (arrow). (D) Diagram of panels A, B, and C. The abscess is indicated in dotted lines. Clinical Gastroenterology and Hepatology 2009 7, 1037-1045DOI: (10.1016/j.cgh.2009.06.030) Copyright © 2009 AGA Institute Terms and Conditions

Figure 5 A 42-year-old man with a cryptoglandular fistula. (A) Coronal T2-weighted fast spin echo image with endoanal coil shows a subtle trans-sphincteric fistula (curved arrow). i, internal anal sphincter; e, external anal sphincter; p, puborectal muscle; c, coil. (B) Diagram of panel A. The fistula is indicated in dotted lines. Clinical Gastroenterology and Hepatology 2009 7, 1037-1045DOI: (10.1016/j.cgh.2009.06.030) Copyright © 2009 AGA Institute Terms and Conditions

Figure 6 A 33-year-old man with CD and a perianal fistula. (A) Coronal T2-weighted fast spin echo image shows a trans-sphincteric fistula (curved arrow) with the internal opening (arrow). r, rectum; e, external sphincter; p, puborectal muscle. (B) Diagram of panel A. The fistula is indicated in dotted lines. (C) Axial T2-weighted fast spin echo image shows a subtle internal opening (arrow) of the trans-sphincteric tract (curved arrow). (D) Diagram of panel C. The fistula is indicated in dotted lines. Clinical Gastroenterology and Hepatology 2009 7, 1037-1045DOI: (10.1016/j.cgh.2009.06.030) Copyright © 2009 AGA Institute Terms and Conditions