Emergency Radiology

, Volume 22, Issue 3, pp 329–335 | Cite as

CT of acute perianal abscesses and infected fistulae: a pictorial essay

  • Nadia J. Khati
  • Nicole Sondel Lewis
  • Aletta Ann Frazier
  • Vincent Obias
  • Robert K. Zeman
  • Michael C. Hill
Pictorial Essay


Computed tomography (CT) is an effective, readily available diagnostic imaging tool for evaluation of the emergency room (ER) patients with the clinical suspicion of perianal abscess and/or infected fistulous tract (anorectal sepsis). These patients usually present with perineal pain, fever, and leukocytosis. The diagnosis can be easy if the fistulous tract or abscess is visible on inspection of the perianal skin. If the tract or abscess is deep, then the clinical diagnosis can be difficult. Also, the presence of complex tracts or supralevator extension of the infection cannot be judged by external examination alone. Magnetic resonance imaging (MRI) is the best imaging test to accurately detect fistulous tracts, especially when they are complex (Omally et al. in AJR 199:W43–W53, 2012). However, in the acute setting in the ER, this imaging modality is not always immediately available. Endorectal ultrasound has also been used to identify perianal abscesses, but this modality requires hands-on expertise and can have difficulty localizing the offending fistulous tract. It may also require the use of a rectal probe, which the patient may not be able to tolerate. Contrast-enhanced CT is a very useful tool to diagnose anorectal sepsis; however, this has not received much attention in the recent literature (Yousem et al. in Radiology 167(2):331–334, 1988) aside from a paper describing CT imaging following fistulography (Liang et al. in Clin Imaging 37(6):1069–1076, 2013). An infected fistula is indicated by a fluid-/air-filled soft tissue tract surrounded by inflammation. A well-defined round to oval-shaped fluid/air collection is indicative of an abscess. The purpose of this article is to demonstrate the usefulness of contrast-enhanced CT in the diagnosis of acute anorectal sepsis in the ER setting. We will discuss the CT appearance of infected fistulous tracts and abscesses and how CT imaging can guide the ER physician in the clinical management of these patients.


Anorectal Sepsis CT imaging Fistula Abscess 


Conflict of interest

The authors declare that they have no conflict of interest.


  1. 1.
    Omally RB, Al-Hawary MM, Wasnik AP, Liu PS, Hussian HK (2012) Rectal imaging: part 2, perianal fistula evaluation on pelvic MRI—what the radiologist needs to know. AJR 199:W43–W53CrossRefGoogle Scholar
  2. 2.
    Yousem DM, Fishman EK, Jones B (1988) Crohn disease: perirectal and perianal findings at CT. Radiology 167(2):331–334CrossRefPubMedGoogle Scholar
  3. 3.
    Liang C, Jiang W, Zhao B, Zhang Y, Du Y, Lu Y (2013) CT imaging with fistulography for perianal fistula: does it really help the surgeon? Clin Imaging 37(6):1069–1076CrossRefPubMedGoogle Scholar
  4. 4.
    Hyman N (1999) Anorectal abscess and fistula. Prim Care 26(1):69–80CrossRefPubMedGoogle Scholar
  5. 5.
    Gage KL, Deshmukh S, Macura KJ, Kamel IR, Zaheer A (2013) MRI of perianal fitulas: bridging the radiological–surgical divide. Abdom Imaging 38:1033–1042CrossRefPubMedCentralPubMedGoogle Scholar
  6. 6.
    Seow-Choen F, Hay AJ, Heard S, Phillips RK (1992) Bacteriology of anal fistulae. Br J Surg 79(1):27–28CrossRefPubMedGoogle Scholar
  7. 7.
    Barleben A, Mills S (2010) Anorectal anatomy and physiology. Surg Clin N Am 90:1–15CrossRefPubMedGoogle Scholar
  8. 8.
    Gunn ML, Kohr JR (2010) State of the art: technologies for computed tomography dose reduction. Emerg Radiol 17(3):209–218CrossRefPubMedGoogle Scholar
  9. 9.
    Kalra MK, Rizzo SM, Novelline RA (2005) Reducing radiation dose in emergency computed tomography with automatic exposure control techniques. Emerg Radiol 11(5):267–274CrossRefPubMedGoogle Scholar
  10. 10.
    Rickard MJFX (2005) Anal abscesses and fistulas. ANZ J Surg 75:64–72CrossRefPubMedGoogle Scholar
  11. 11.
    Rizzo JA, Naig AL, Johnson EK (2010) Anorectal abcess and fistula-in-ano: evidence-based management. Surg Clin N Am 90:45–68CrossRefPubMedGoogle Scholar
  12. 12.
    Whiteford MH (2007) Perianal abscess/fistula disease. Clin Colon Rectal Surg 20:102–109CrossRefPubMedCentralPubMedGoogle Scholar
  13. 13.
    Ziech M, Felt-Bersma R, Stoker J (2009) Clinical imaging. Clin Gastroenterol Hepatol 7:1037–1045CrossRefPubMedGoogle Scholar
  14. 14.
    Nimikos IN (1997) Anorectal abscesses: need for accurate anatomical localization of the disease. Clin Anat 10:239–244CrossRefGoogle Scholar
  15. 15.
    Parks AG, Gordon PH, Hardcastle JD (1976) A classification of fistula-in-ano. Br J Surg 63(1):1–12CrossRefPubMedGoogle Scholar
  16. 16.
    de Miguel CJ, del Salto LG, Rivas PF, del Hoyo LF, Velasco LG, de las Vacas MI, Marco Sanz AG, Paradela MM, Moreno EF (2012) MR imaging evaluation of perianal fistulas: spectrum of imaging features. RadioGraphics 32:175–194CrossRefGoogle Scholar

Copyright information

© American Society of Emergency Radiology 2014

Authors and Affiliations

  • Nadia J. Khati
    • 1
  • Nicole Sondel Lewis
    • 2
  • Aletta Ann Frazier
    • 3
    • 4
  • Vincent Obias
    • 5
  • Robert K. Zeman
    • 6
  • Michael C. Hill
    • 1
  1. 1.Department of Radiology, Body Imaging SectionThe George Washington University HospitalWashingtonUSA
  2. 2.Department of RadiologyMedstar Georgetown University HospitalWashingtonUSA
  3. 3.Department of Diagnostic Radiology and Nuclear MedicineUniversity of Maryland Medical CenterBaltimoreUSA
  4. 4.American Institute for Radiologic PathologySilver SpringUSA
  5. 5.Division of Colon and Rectal Surgery, Department of Colon and Rectal SurgeryThe George Washington University HospitalWashingtonUSA
  6. 6.Department of Radiology and Radiation Oncology Department of RadiologyThe George Washington University HospitalWashingtonUSA

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