Current Management of Fistula-in-ano Dr. Leung Tak Lun Canice Department of Surgery North District Hospital

Case Presentation M/47 Hx of perianal abscess On and off perianal discharge P/E FIA with external opening at 4 oc position, 3cm from anal verge Internal opening at 4 oc, above dentate line

EUA and Rigid sigmoidoscopy Transpincteric FIA with ext. opening at 4 oc Internal opening at 4 oc, above dentate line External tract at left ischorectal fossa excised Seton inserted Plan for tightening of seton in 4/52

At 2nd operation Seton already broken and lost Basically healed fistula Curettage of granulation tissue done

Recurrence!! 4 months later c/o persistent discharge MRI offered

MRI finding -> transphincteric type of FIA with bifurcation tract near the anus and ending at 5 and 7 o’clock position

Reoperation Intra-op finding Transphincteric FIA with external opening at 4 oc Internal opening at 4cm from anal verge just below level of levator ani but at the top of internal sphinter Curettage of the track done and seton inserted again

Follow up Well and no discharge

Etiology Pre-existing abscess Anal gland theory Anal glands 8 or more in number Form small abscess at interspincteric plane when infected Other causes include congenital, pelvic sepsis, trauma, hidradenitis suppurativa, haemorrhoid, iatrogenic, inflammatory bowel disease, TB, maligancy

Parks Classification

Clinical presentation Anal discharge preceded by episode of pain and perianal swelling Repeated episode of perianal sepsis

Clinical assessment History Physical examination Palpation of the perineum Digital examination

Clinical assessment EUA Light GA Palpation Methylene blue, hydrogen peroxide injection probing

Imaging modality Fistulogram Endoanal ultrasound MRI

Fistulography Disappointing Accuracy 16% only Difficult to relate the track to the sphincter and levator ani The acute track are just column of inflamed granulation tissue without a lumen

Endoanal ultrasound High accuracy (93%) of predicting the site of internal opening of an anal fistula Overall concordance for type of fistula is 82% Colorectal Disease, 4, 436-440

Hydrogen peroxide improve the concordance with type of fistula from 80% to 89% Colorectal Disease, 4, 436-440

Endoanal ultrasound

MRI Advantage of MRI Multiplanar imaging High soft tissue differentiation to show the track system in relation to the underlying anatomy in a projection relevant to surgical exploration

MRI Concordance rate with surgical exploration of 86% to 88% in initial reports Currently Up to 100% sensitivity for primary tract 96% for abscess 100% for horse extension 96% for internal opening

Axial / Coronal view

T1 axial T2 axial

T1 coronal T2 coronal

Gadolinium enhancement with fat suppression – axial view

Gadolinium enhancement with fat suppression – coronal view

Role of Imaging FIA has significant recurrence rate up to 25% Due to part of the track system not being recognised at surgery Inadequate drainage of sepsis False communication found by injudicious probing

Radiology can demonstrate clinically undetected sepsis, can guide initial surgery and reveal the site of residual sepsis

In one prospective study of MRI in primary fistula (BJS 2002) 30 patients MRI led to further exploration in 2 cases 1 patient require further surgery at a median FU of 12 months

Other prospective study (Lancet 2002; 360: 1661-2) 71 patients Agreement between MRI and surgery in 25 cases -> 12% recurrence MRI led to further surgery in 15 cases -> 13.3% recurrence Disagreement in 31 cases but no further surgery undertaken -> 51.6% recurrence

Recurrence rate for individual surgeons who always, sometimes or never acted on the discrepant MRI finding were 16%, 30%, 57% respectively

Treatment outcome Low FIA

Low FIA

Fibrin glue injection

The End