EVALUATION OF COMPLEX ANAL FISTULA

– EUA, EAUS OR MRI?

Andrew Luck

Northern Adelaide Colorectal UnitLyell McEwin Hospital

ANAL FISTULA

• Fistula – “an abnormal track that connects two epithelialised surfaces”

• Anal fistula – perianal skin to anal canal– Secondary extensions– Associated abscess formation– Involvement of anal sphincters– Perianal Crohn’s disease.

Can imaging (pre-op or intra-op) help the surgeon?

CLASSIFICATION

A Subcutaneous

B Intersphincteric

C Trans-sphincteric

D Supra-sphincteric

E Extra-sphincteric

ANAL FISTULA

PRINCIPLES OF MANAGEMENT

• Control sepsis

• Eliminate fistula

• Preserve faecal continence

ANAL FISTULA

CONTROL SEPSIS

• Identify and drain abscesses– Horseshoe extensions

• Abscess either side of midline

• Drain high fistula – loose Seton

• Lay open low fistula

• Identify and control secondary tracts

ANAL FISTULA

CONTROL SEPSIS

• Need to know– Classification of fistula– Presence or absence of abscesses

• Number and location

– Presence or absence of secondary tracts• Number and location

• What can imaging offer?

ANAL FISTULA

ELIMINATE FISTULA

• Lay open (or cutting Seton)– Subcutaneous, inter-sphincteric, low trans-sphincteric

• Close fistula– Entire fistula

• Anal fistula plug• Fibrin glue

– Internal opening• Mucosal Advancement Flap

– Disconnect fistula• LIFT procedure

ANAL FISTULA

ELIMINATE FISTULA

• Need to know– Classification of fistula– Course of tract from external to internal opening– Location of internal opening

• What can imaging offer?

ANAL FISTULA

PRESERVE CONTINENCE

• Divide minimal sphincter– Internal – External

• Divide NO sphincter in certain situations– Anteriorly in female– Sphincter defect already present– Incontinence already present– Crohn’s disease

• Control sepsis

ANAL FISTULA

PRESERVE CONTINENCE

• Need to know

– Classification of fistula– Course of tract from external to internal opening– Location of internal opening– Presence or absence of abscesses

• Number and location

– Presence or absence of secondary tracts• Number and location

WHAT CAN IMAGING OFFER?

• Pre-operative imaging– Magnetic resonance imaging– Endo-anal ultrasound

• Intra-operative imaging– Endo-anal ultrasound

• With hydrogen peroxide

• Examples• Literature• What do I do?

EAUS – INTERSPHINCTERICPOSTERIOR ABSCESS

EAUS – TRANS-SPHINCTERIC FISTULA AT 7 O’CLOCK

EAUS – HORSESHOE ABSCESS

EAUS WITH PEROXIDE

EAUS WITH PEROXIDE

EAUS WITH PEROXIDE

EAUS WITH PEROXIDE

EAUS WITH PEROXIDE

EAUS WITH PEROXIDE

MRI – TRANS-SPHINCTERIC FISTULA WITH SETON

MRI – MULTIPLE TRACTS

MRI – MULTIPLE TRACTS

MRI – MULTIPLE TRACTS

MRI – SUPRALEVATOR COLLECTION

MRI – SUPRALEVATOR COLLECTION

MRI – SUPRALEVATOR COLLECTION

MRI – SUPRALEVATOR COLLECTION

LITERATURE

• Several studies compared preop imaging to preop clinical examination

• Sahni et al (Abdominal imaging 2008)– Sensitivity of preop assessment in

differentiating complex fistula from simple disease• Clinical examination 0.75 (0.65-0.86)• EAUS 0.92 (0.85-0.99)• MRI 0.97 (0.92-1.00)

BUCHANAN ET AL (RADIOLOGY 2004)

Clinical exam (%)

EAUS

(%)

MRI

(%)

P value

Primary tracts

61 81 90 <0.001

Abscesses 33 75 85 <0.001

Horseshoes 44 56 94 0.003

Internal opening

78 91 97 <0.001

BUCHANAN ET AL (RADIOLOGY 2004)

• Clinical exam did not include probes• EAUS did not include peroxide

• Gold standard – EUA!!– EUA modified by MRI findings if there was

disagreement • “our hospital ethical committee decreed that

there was overwhelming evidence that the MR images had to be available in the operating room and that non-disclosure was unethical”

DOES IT HELP THE SURGEON?

• Tinley et al (Colorectal disease 2006)– Intraoperative EAUS affected surgical

management in 9/17 (53%) of cases– Mainly assessment of amount of EAS above

fistula

• Buchanan et al (BJS 2003)– Pre op MRI altered management in 3/30 (10%) of

patients with primary fistulous disease– Identification of internal opening

DOES IT HELP THE SURGEON?

• Buchanan et al (Lancet 2002)– MRI in 71 patients with recurrent fistulas

• Surgery and MRI agreed in 40/71(56%)– 5/40 (13%) recurrence rate

• Surgery and MRI disagreed in 31/71 (44%)– 16/31 (52%) recurrence rate

– ALL 16 recurrences at site predicted by MRI

• Recurrence when surgeon followed MRI = 4/25 (16%)• Recurrence when surgeon ignored MRI = 8/14 ( 52%)

– p=0.008

DOES IT HELP THE SURGEON?

• Beets-Tan et al (Radiology 2001)– Preop MRI in 56 patients• ‘Important additional information’ in 12/56

(21%) patients– Primary fistula 2/24 (8%)– Recurrent fistula 4/17 (24%)– Crohn’s fistula 6/15 (40%)

–MRI interobserver agreement 0.65 (fistula classification) to 0.93 (abscess)

–MRI intraobserver agreement 0.75 (fistula classification) to 1.00 (horseshoe fistula)

WHAT DO I DO?

• Principles– Control sepsis– Eliminate fistula– Preserve continence– Do not cause undue pain

• Delay in definitive treatment• Unnecessary pre op investigations eg EAUS with

obvious abscess

– Perform EAUS personally– Know, trust and collaborate with MRI radiologist

WHAT DO I DO?

• History– Level of pain– Past history of anal fistula or abscess– Crohn’s disease– PH anal surgery

• Examination– Inspection

• Cellulitis, abscess, external opening, Crohn’s

– PR• Tenderness, masses, abscess, internal opening, tract

WHAT DO I DO?

• If severe pain and/or obvious abscess– EUA +/- EAUS as soon as possible

• Drain abscess• GENTLE probe for fistula

– Lay open if safe– Loose Seton if not sure

• If primary and most likely simple fistula– EUA +/- EAUS

• Low simple fistula – lay open• High fistula – loose Seton

– Post op MRI to plan next procedure

• Complex fistula – loose Seton(s) +/- Malecot catheter(s)– Post op MRI to plan next procedure

WHAT DO I DO?

• Recurrent fistula • Complex disease on initial examination • Crohn’s disease

• Pre op MRI– Discuss images with trusted radiologist

• Review options with patient• EUA +/- EAUS– Definitive surgical management