eMedicine Specialties > General Surgery > Colorectal

Fistula-in-Ano: Workup

Author: Dennis F Zagrodnik II, MD, FACS, Consulting Staff, Premier Surgical of Wisconsin, SC
Contributor Information and Disclosures

Updated: Jul 16, 2009

Workup

Laboratory Studies

  • No specific laboratory studies are required; the normal preoperative studies are performed based on age and comorbidities.

Imaging Studies

  • Radiologic studies: These are not performed for routine fistula evaluation. They can be helpful when the primary opening is difficult to identify or in the case of recurrent or multiple fistulae to identify secondary tracts or missed primary openings.9
  • Fistulography10
    • This involves injection of contrast via the internal opening, which is followed by anteroposterior, lateral, and oblique x-ray images to outline the course of the fistula tract.
    • The accuracy rate is 16-48%.
    • The procedure is well tolerated but requires the ability to visualize the internal opening.
    • Except in the case of recurrent disease, fistulography may be slightly more useful than a careful examination under anesthesia.
  • Endoanal/endorectal ultrasound
    • These studies involve passage of a 7- or 10-MHz transducer into anal canal to help define muscular anatomy differentiating intersphincteric from transsphincteric lesions.
    • A standard water-filled balloon transducer can help evaluate the rectal wall for any suprasphincteric extension.
    • Studies show that the addition of hydrogen peroxide via the external opening can help outline the fistula tract course. This may be useful to help delineate missed internal openings.
    • These studies are reported to be 50% better than physical examination alone to help find an internal opening that is difficult to localize.
    • This modality has not been used widely for routine clinical fistula evaluation.
  • MRI: Findings show 80-90% concordance with operative findings when observing a primary tract course and secondary extensions. MRI is becoming the study of choice when evaluating complex fistulae and recurrent fistulae. It has been shown to improve recurrence rates by providing information on otherwise unknown extensions.11,12
  • CT scan
    • A CT scan is more helpful in the setting of perirectal inflammatory disease than in the setting of small fistulae because it is better for delineating fluid pockets that require drainage than for small fistulae.
    • CT scan requires administration of oral and rectal contrast.
    • Muscular anatomy is not delineated well.
  • A barium enema/small bowel series: This is useful for patients with multiple fistulae or recurrent disease to help rule out inflammatory bowel disease.

Other Tests

  • Anal manometry
    • Pressure evaluation of the sphincter mechanism is helpful in certain patients.
      • Decreased tone observed during preoperative evaluation
      • History of previous fistulotomy
      • History of obstetrical trauma
      • High transsphincteric or suprasphincteric fistula (if known)
      • Very elderly patients
    • If decreased, surgical division of any portion of the sphincter mechanism should be avoided.

Diagnostic Procedures

  • Examination under anesthesia
    • An examination of the perineum, digital rectal examination, and anoscopy are performed after the anesthesia of choice is administered.
    • This examination is necessary before surgical intervention, especially if outpatient evaluation causes discomfort or has not helped delineate the course of the fistulous process.
    • Several techniques have been described to help locate the course of the fistula and, more importantly, identify the internal opening.
      • Inject hydrogen peroxide, milk, or dilute methylene blue into the external opening and watch for egress at the dentate line. In the authors' experience, methylene blue often obscures the field more than it helps identify the opening.
      • Traction (pulling or pushing) on the external opening may also cause a dimpling or protrusion of the involved crypt.
      • Insertion of a blunt-tipped crypt probe via the external opening may help outline the direction of the tract. If it approaches the dentate line within a few millimeters, a direct extension likely existed. Care should be taken to not use excessive force and create false passages.
  • Proctosigmoidoscopy/colonoscopy
    • Rigid sigmoidoscopy can be performed at the initial evaluation to help rule out any associated disease process in the rectum.
    • Further colonic evaluation is performed only as indicated.

More on Fistula-in-Ano

Overview: Fistula-in-Ano
Workup: Fistula-in-Ano
Treatment: Fistula-in-Ano
Follow-up: Fistula-in-Ano
Multimedia: Fistula-in-Ano
References
Further Reading
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References

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  2. Cosman BC. All's Well That Ends Well: Shakespeare's treatment of anal fistula. Dis Colon Rectum. Jul 1998;41(7):914-24. [Medline].

  3. Sainio P. Fistula-in-ano in a defined population. Incidence and epidemiological aspects. Ann Chir Gynaecol. 1984;73(4):219-24. [Medline].

  4. Hancock BD. ABC of colorectal diseases. Anal fissures and fistulas. BMJ. Apr 4 1992;304(6831):904-7. [Medline].

  5. Hamalainen KP, Sainio AP. Incidence of fistulas after drainage of acute anorectal abscesses. Dis Colon Rectum. Nov 1998;41(11):1357-61; discussion 1361-2. [Medline].

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  9. Sun MR, Smith MP, Kane RA. Current techniques in imaging of fistula in ano: three-dimensional endoanal ultrasound and magnetic resonance imaging. Semin Ultrasound CT MR. Dec 2008;29(6):454-71. [Medline].

  10. Weisman RI, Orsay CP, Pearl RK, Abcarian H. The role of fistulography in fistula-in-ano. Report of five cases. Dis Colon Rectum. Feb 1991;34(2):181-4. [Medline].

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  13. American Society of Colon and Rectal Surgeons. Practice parameters for treatment of fistula-in-ano--supporting documentation. The Standards Practice Task Force. Dis Colon Rectum. Dec 1996;39(12):1363-72. [Medline].

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  18. Abbas MA, Lemus-Rangel R, Hamadani A. Long-term outcome of endorectal advancement flap for complex anorectal fistulae. Am Surg. Oct 2008;74(10):921-4. [Medline].

  19. Chung W, Kazemi P, Ko D, Sun C, Brown CJ, Raval M, et al. Anal fistula plug and fibrin glue versus conventional treatment in repair of complex anal fistulas. Am J Surg. May 2009;197(5):604-8. [Medline].

  20. Johnson EK, Gaw JU, Armstrong DN. Efficacy of anal fistula plug vs. fibrin glue in closure of anorectal fistulas. Dis Colon Rectum. Mar 2006;49(3):371-6. [Medline].

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  22. Loungnarath R, Dietz DW, Mutch MG, Birnbaum EH, Kodner IJ, Fleshman JW. Fibrin glue treatment of complex anal fistulas has low success rate. Dis Colon Rectum. Apr 2004;47(4):432-6. [Medline].

  23. Champagne BJ, O'Connor LM, Ferguson M, Orangio GR, Schertzer ME, Armstrong DN. Efficacy of anal fistula plug in closure of cryptoglandular fistulas: long-term follow-up. Dis Colon Rectum. Dec 2006;49(12):1817-21. [Medline].

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  26. Present DH, Rutgeerts P, Targan S, Hanauer SB, Mayer L, van Hogezand RA, et al. Infliximab for the treatment of fistulas in patients with Crohn's disease. N Engl J Med. May 6 1999;340(18):1398-405. [Medline].

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  28. Topstad DR, Panaccione R, Heine JA, Johnson DR, MacLean AR, Buie WD. Combined seton placement, infliximab infusion, and maintenance immunosuppressives improve healing rate in fistulizing anorectal Crohn's disease: a single center experience. Dis Colon Rectum. May 2003;46(5):577-83. [Medline].

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Keywords

fistula-in-ano, fistula, anus, anorectal fistula, hemorrhoidectomy, sphincterotomy, perianal fistula, anorectal abscess, Crohn disease, Crohn's disease, anal fissures, actinomycoses, anorectal sepsis, intersphincteric fistula, transsphincteric fistula, trans-sphincteric fistula, suprasphincteric fistula, supra-sphincteric fistula, extrasphincteric fistula, extra-sphincteric fistula, Goodsall rule, Parks classification

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Contributor Information and Disclosures

Author

Dennis F Zagrodnik II, MD, FACS, Consulting Staff, Premier Surgical of Wisconsin, SC
Dennis F Zagrodnik II, MD, FACS is a member of the following medical societies: American College of Chest Physicians, American College of Surgeons, American Medical Association, Phi Beta Kappa, Society of American Gastrointestinal and Endoscopic Surgeons, Southeastern Surgical Congress, and Wisconsin Medical Society
Disclosure: Nothing to disclose.

Medical Editor

Oscar Joe Hines, MD, Assistant Professor, Department of Surgery, University of California at Los Angeles School of Medicine
Oscar Joe Hines, MD is a member of the following medical societies: Alpha Omega Alpha, American Association of Endocrine Surgeons, American College of Surgeons, Association for Academic Surgery, Society for Surgery of the Alimentary Tract, and Society of American Gastrointestinal and Endoscopic Surgeons
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

David L Morris, MD, PhD, Professor, Department of Surgery, St George Hospital, University of New South Wales, Australia
Disclosure: RFA Medical None Director; MRC Biotec None Director

CME Editor

Paolo Zamboni, MD, Professor of Surgery, Chief of Day Surgery Unit, Chair of Vascular Diseases Center, University of Ferrara, Italy
Paolo Zamboni, MD is a member of the following medical societies: American Venous Forum and New York Academy of Sciences
Disclosure: Nothing to disclose.

Chief Editor

John Geibel, MD, DSc, MA, Vice Chairman, Professor, Department of Surgery, Section of Gastrointestinal Medicine and Department of Cellular and Molecular Physiology, Yale University School of Medicine; Director of Surgical Research, Department of Surgery, Yale-New Haven Hospital
John Geibel, MD, DSc, MA is a member of the following medical societies: American Gastroenterological Association, American Physiological Society, American Society of Nephrology, Association for Academic Surgery, International Society of Nephrology, New York Academy of Sciences, and Society for Surgery of the Alimentary Tract
Disclosure: AMGEN Royalty Other

 
 
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