Importance of high-frequency and low-frequency three-dimensional endoanal ultrasound scan in diagnosing perianal fistula and abscess


  • Someswara Rao Meegada Department of Colorectal Surgery, Apollo Hospitals, Hyderabad, Telangana, India
  • Kishore V. Alapati Department of Colorectal Surgery, Apollo Hospitals, Hyderabad, Telangana, India
  • Mathai Varughese Department of Colorectal Surgery, Apollo Hospitals, Hyderabad, Telangana, India



Endoanal ultrasound, Perianal fistula, LF, HF


Background: Three-dimensional endoanal ultrasound scanning (3D-EAUS) is the first line of investigation in the management of perianal fistula and abscess. High frequency (HF) and low frequency (LF) are 2 frequency modes in 3D-EAUS which have different resolutions and penetration depth. Our study aims to compare the 3D images of HF with LF modes.

Methods: This is a retrospective study of the 3D-EAUS images of patients with perianal fistula and abscess (perianal sepsis) who underwent 3D-EAUS from January 2019 to December 2020 in our hospital. The scans with both high and LF setting images were included in our study

Results: The 53 3D-EAUS images were randomly selected, out of them images with both HF and LF modes were included. The dimensions of both HF and LF 3D cuboid images were measured. The volume of tissue measured in HF and LF modes were 155 ml and 380 ml respectively. The LF images scored 22/24 points and the HF images scored 16/24 points.

Conclusions: LF and HF modes complement each other. LF mode can better delineate tracts and abscesses in extra-sphincteric space than HF mode. HF mode can better delineate tracts and abscesses in inter-sphincteric space as well as internal openings. We recommend routine use of both frequency modes while performing 3D-EAUS. Operating surgeons should gain expertise in performing the scan and reading the 3D image.


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. 2008;29(6):454-71.

Garcés-Albir M, García-Botello SA, Espi A, Pla-Martí V, Martin-Arevalo J, Moro-Valdezate D, et al. Three-dimensional endoanal ultrasound for diagnosis of perianal fistulas: reliable and objective technique. World J Gastrointestinal Surg. 2016;8(7):513.

West RL, Dwarkasing S, Felt-Bersma RJ, Schouten WR, Hop WC, Hussain SM, et al. Hydrogen peroxide-enhanced three-dimensional endoanal ultrasonography and endoanal magnetic resonance imaging in evaluating perianal fistulas: agreement and patient preference. Eur J Gastroenterol Hepatol. 2004;16(12):1319-24.

Nagendranath C, Saravanan MN, Sridhar C, Varughese M. Peroxide-enhanced endoanal ultrasound in preoperative assessment of complex fistula-in-ano. Tech Coloproctol. 2014;18(5):433-8.

Kim Y, Park YJ. Three-dimensional endoanal ultrasonographic assessment of an anal fistula with and without H2O2 enhancement. World J Gastroenterol. 2009;15(38):4810-5

Brillantino A, Iacobellis F, Reginelli A, Monaco L, Sodano B, Tufano G, et al. Preoperative assessment of simple and complex anorectal fistulas: Tridimensional endoanal ultrasound? Magnetic resonance? Both? Radiol Med. 2019;124(5):339-49.

Buchanan GN, Bartram CI, Williams AB, Halligan S, Cohen CR. Value of hydrogen peroxide enhancement of three-dimensional endoanal ultrasound in fistula-in-ano. Dis Colon Rectum. 2005;48:141-7.

Lengyel AJ, Hurst NG, Williams JG. Pre-operative assessment of anal fistulas using endoanal ultrasound. Colorectal Dis. 2002;4(6):436-40.

Li J, Chen SN, Lin YY, Zhu ZM, Ye DL, Chen F, et al. Diagnostic Accuracy of Three-Dimensional Endoanal Ultrasound for Anal Fistula: A Systematic Review and Meta-analysis. Turk J Gastroenterol. 2021;32(11):913.

Ratto C, Grillo E, Parello A, Costamagna G, Doglietto GB. Endoanal ultrasound-guided surgery for anal fistula. Endoscopy. 2005;37(08):722-8.

Emile SH, Magdy A, Youssef M, Thabet W, Abdelnaby M, Omar W, et al. Utility of endoanal ultrasonography in assessment of primary and recurrent anal fistulas and for detection of associated anal sphincter defects. J Gastrointestinal Surg. 2017;21:1879-87.

Almeida IS, Jayarajah U, Wickramasinghe DP, Samarasekera DN. Value of three-dimensional endoanal ultrasound scan (3D-EAUS) in preoperative assessment of fistula-in-ano. BMC Res Notes. 2019;12(1):1-5.

Lucas VS, Burk RS, Creehan S, Grap MJ. Utility of high-frequency ultrasound: moving beyond the surface to detect changes in skin integrity. Plast Surg Nurs. 2014;34(1):34-8.

Cho DY. Endosonographic criteria for an internal opening of fistula-in-ano. Dis Colon Rectum. 1999;42:515-8.

Sudoł-Szopińska I, Kołodziejczak M, Szopiński TR. The accuracy of a postprocessing technique--volume render mode--in three-dimensional endoanal ultrasonography of anal abscesses and fistulas. Dis Colon Rectum. 2011;54(2):238-44.

O'Rourke K, Kibbee N, Stubbs A. Ultrasound for the Evaluation of Skin and Soft Tissue Infections. Mo Med. 2015;112(3):202-5.

Santoro GA, Di Falco G. Benign anorectal diseases. Diagnosis with endoanal and endorectal ultrasound and new treatment options. Italy: Springer-Verlag. 2006;355-64.

Deen KI, Williams JG, Hutchinson R. Fistulas in ano: endoanal ultrasonographic assessment assists decision making for surgery. Gut. 1994;35:391-4.

Navarro A, Rius J, Collera P. Anal fistulas: results of ultrasonographic studies. Dis Colon Rectum. 1998;41:A57

Harkin J, Perring S. Assessing the performance of 360∘ ultrasound probes designed for endoanal ultrasound. IPEM-Translation. 2022;2:100007.






Original Research Articles