title: Three-dimensional endoanal ultrasound is accurate and reproducible in determining type and height of anal fistulas.
abstract: OBJECTIVE
  Surgical treatment of high anal fistulas is associated with the potential risk of faecal incontinence and recurrence. The primary aim of this study was to determine the accuracy of three-dimensional endoanal ultrasound (3D-EAUS) in the assessment of height and type of anal fistulas, compared to the intra-operative findings (gold standard). The secondary aim was to evaluate the inter-observer reproducibility of 3D-EAUS.
  
  
  METHODS
  The study design was a prospective analysis of retrospective data. 299 patients (202 men), mean age 45.3 years, who underwent surgery for anal fistulas, were included. All patients were preoperatively assessed by 3D-EAUS. Two readers independently reviewed the volumes to determine the type and height of fistulas. Sensitivity, specificity, positive and negative predictive values, proportion of agreements and Cohen's kappa coefficient (κ) were calculated for both examiners. Ultrasound findings were compared with intra-operative data (reference standard), evaluated blindly by the surgeons.
  
  
  RESULTS
  At surgery, 201 (67%) were transsphincteric, 49 (16%) suprasphincteric, 47 (16%) intersphincteric and two (1%) extrasphincteric fistulas. Intra-operatively, 177 (59%) were low and 122 (41%) high fistulas. The overall accuracy of 3D-EAUS was 91% for fistula type (271/299 fistulas: 97% transsphincteric, 100% intersphincteric, 57% suprasphincteric, 0% extrasphincteric) and 92% for fistula height (275/299 fistulas: 80% high and 100% low). Both readers reported very good agreement with surgery in the assessment of fistula type (proportion of agreement 0.88, κ = 0.89) and height (proportion of agreement 0.90, κ = 0.91).
  
  
  CONCLUSIONS
  3D-EAUS is an accurate and reproducible modality for the assessment of type and height of anal fistulas.
authors.affiliation: Warsaw Proctology Centre, Saint Elisabeth Hospital, Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Kołodziejczak
authors.affiliation: Colorectal and Pelvic Floor Unit, Department of General Surgery, Regional Hospital, Treviso, Italy.
authors.forename: G A
authors.initials: GA
authors.lastname: Santoro
authors.affiliation: Department of General and Oncological Surgery with the Subunit of Vascular Surgery, Lord's Transfiguration Hospital, Warsaw, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Obcowska
authors.affiliation: Warsaw Proctology Centre, Saint Elisabeth Hospital, Warsaw, Poland.|Clinical Department of General and Colorectal Surgery and Multiple Trauma, St Barbara Regional Specialist Hospital No. 5, Sosnowiec, Poland.
authors.forename: Z
authors.initials: Z
authors.lastname: Lorenc
authors.affiliation: Department of Gerontology and Public Health, National Institute of Geriatrics, Rheumatology and Rehabilitation, Warsaw, Poland.
authors.forename: M
authors.initials: M
authors.lastname: Mańczak
authors.affiliation: Department of Radiology, National Institute of Geriatrics, Rheumatology and Rehabilitation, Department of Diagnostic Imaging, Second Faculty of Medicine, Medical University of Warsaw, Warsaw, Poland.
authors.forename: I
authors.initials: I
authors.lastname: Sudoł-Szopińska
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001003:Anal Canal / Q000000981:diagnostic imaging; D019160:Endosonography / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012003:Rectal Fistula / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D055815:Young Adult
keywords: Anal fistula; endoanal ultrasound; three-dimensional ultrasound