1. Volume 121, Issue 5, Pages 1064-1072 (November 2001)
A comparison of endoscopic ultrasound, magnetic resonance imaging, and exam under anesthesia for evaluation of Crohn's perianal fistulas 
David A. Schwartz, Maurits J. Wiersema, Kika M. Dudiak, J.G. Fletcher, Jonathan E. Clain, William J. Tremaine, Alan R. Zinsmeister, Ian D. Norton, Lisa A. Boardman, Richard M. Devine, Bruce G. Wolff, Tonia M. Young-Fadok, Nancy N. Diehl, John H. Pemberton, William J. Sandborn 
Gastroenterology 
Volume 121, Issue 5, Pages (November 2001)
DOI: /gast
Copyright © 2001 American Gastroenterological Association Terms and Conditions

2. Fig. 1
Fistula Anatomy Recording Form. Modified with permission from Choen S, Burnett S, Bartram CI, Nicholls RJ. Comparison between anal endosonography and digital examination in the evaluation of anal fistulae. Br J Surg 1991;78:
Gastroenterology  , DOI: ( /gast )
Copyright © 2001 American Gastroenterological Association Terms and Conditions

3. Fig. 2
The Parks' classification. (A) A superificial fistula tracks below both the internal anal sphincter and EAS complexes. (B) An inter-sphincteric fistula tracks between the internal anal sphincter and the EAS in the inter-sphincteric space. (C) A trans-sphincteric fistula tracks from the inter-sphincteric space through the EAS. (D) A supra-sphincteric fistula leaves the inter-sphincteric space over the top of the puborectalis and penetrates the levator muscle before tracking down to the skin. (E) An extra-sphincteric fistula tracks outside of the internal and external anal sphincters and penetrates the levator muscle into the rectum. Modified with permission from Parks AG, Gordon PH, Hardcastle JD. A classification of fistula-in-ano. Br J Surg 1976;63:
Gastroenterology  , DOI: ( /gast )
Copyright © 2001 American Gastroenterological Association Terms and Conditions

4. Fig. 3
A graphic representation of patient movement throughout the course of the study.
Gastroenterology  , DOI: ( /gast )
Copyright © 2001 American Gastroenterological Association Terms and Conditions

5. Fig. 4
Example of a study patient illustrating the use of all 3 diagnostic modalities. The patient presented with recurrent perianal pain and drainage. (A) The radial EUS image shows a trans-sphincteric fistula with horseshoeing. (B) The linear ultrasound image shows a long fistula tract with air within it. (C) The MRI image illustrates a complex horseshoe fistula. (D) The patient then had an EUA that confirmed a horseshoe fistula.
Gastroenterology  , DOI: ( /gast )
Copyright © 2001 American Gastroenterological Association Terms and Conditions