Gordon N. Buchanan

Effect of MRI on clinical outcome of recurrent fistula-in-ano

Recurrent fistula-in-ano is usually due to sepsis missed at surgery, which can be identified by MRI. We aimed to establish the therapeutic effect of MRI in patients with fistula-in-ano. We did MRI in 71 patients with recurrent fistula, with further surgery done at the discretion of the surgeon. Surgery and MRI agreed in 40 patients, five (13%) of whom had further recurrence, compared with 16 (52%) of 31 in whom surgery and MRI disagreed (p=0.0005). Further recurrence in all 16 was at the site predicted by MRI. For surgeons who always acted on MRI, further recurrences arose in four of 25 (16%) operations versus eight of 14 (57%) operations for those who ignored imaging (p=0.008). Surgery guided by MRI reduces further recurrence of fistula-in-ano by 75% and should be done in all patients with recurrent fistula.

Efficacy of Fibrin Sealant in the Management of Complex Anal Fistula

AbstractPURPOSE: A prospective trial was conducted to establish long-term healing of complex idiopathic anorectal fistula, without extension, after fibrin glue treatment, with clinical assessment and magnetic resonance imaging to determine tract healing. METHODS: Twenty-two patients undergoing glue instillation after fistula curettage and irrigation were followed up for a median of 14 months. Clinical assessment, short tau inversion recovery sequence magnetic resonance imaging, and combined short tau inversion recovery and dynamic contrast-enhanced magnetic resonance imaging were performed at a median of three months postoperatively, and their ability to predict outcome in the presence of early skin healing was determined. RESULTS: Of 22 patients, 19 (86.5 percent) had transsphincteric fistulas, 1 (4.5 percent) had a suprasphincteric fistula, 1 (4.5 percent) had an extrasphincteric fistula, and 1 (4.5 percent) had a rectovaginal fistula. None had clinical or radiologic evidence of secondary extension. Despite skin healing in 17 (77 percent) of 22 patients at a median of 14 days after treatment, only 3 (14 percent) remained healed at 16 months. Magnetic resonance imaging with short tau inversion recovery sequences in combination with dynamic contrast-enhanced magnetic resonance imaging predicted outcome in all 10 assessments (100 percent), compared with short tau inversion recovery sequence alone in 16 (94 percent) of 17 assessments or clinical examination in 12 (71 percent) of 17 (P = 0.02). CONCLUSIONS: The success rate of fibrin glue application for complex anorectal fistulas without extension is 14 percent. Magnetic resonance imaging predicts outcome at an earlier stage than clinical examination.

Value of hydrogen peroxide enhancement of three-dimensional endoanal ultrasound in fistula-in-ano.

PURPOSEThe aim of this prospective study was to compare the accuracy of three-dimensional endoanal ultrasound with that of hydrogen peroxide enhanced three-dimensional endoanal ultrasound in diagnosing recurrent or complex fistula-in-ano.METHODSThree-dimensional endoanal ultrasound reconstructions were performed before and after hydrogen peroxide enhancement in 19 patients with suspected recurrent or complex fistula-in-ano. Two experienced observers derived a consensus fistula classification after a blinded random review of the data sets. The accuracy of three-dimensional endoanal ultrasound and that of hydrogen peroxide–enhanced three-dimensional endoanal ultrasound were compared with a reference standard derived from surgical findings and magnetic resonance imaging and modified by outcome over a median follow-up of 13 months.RESULTSPatients had previously undergone a median of three fistula operations. Four had Crohn’s disease. There were 21 internal openings and primary tracks in 19 patients: 1 superficial, 1 intersphincteric, 18 transsphincteric, and 1 extrasphincteric. Fourteen patients had 19 secondary tracks. Both techniques detected fistula tracks in 19 of 21 (90 percent) patients. There was no significant difference between three-dimensional endoanal ultrasound and hydrogen peroxide–enhanced three-dimensional endoanal ultrasound in classifying internal openings (19/21 (90 percent) vs. 18/21 (86 percent)), primary tracks (17/21 (81 percent) vs. 15/21 (71 percent)), or secondary tracks (13/19 (68 percent) vs. 12/19 (63 percent)). Where three-dimensional endoanal ultrasound correctly detected an internal opening, gas from hydrogen peroxide enhancement was present in 8 of 18 (44 percent) studies. Similarly, gas made primary tracks more conspicuous in 6 of 19 (32 percent) and secondary tracks in 6 of 13 (46 percent) of those detected.CONCLUSIONSIn recurrent or complex fistula-in-ano, endoanal ultrasound proved more accurate for detecting primary tracks and internal openings than for detecting extensions. Hydrogen peroxide improved conspicuity of some tracks and internal openings and so may be helpful in difficult cases, although no overall diagnostic benefit was demonstrated.

Imaging anal fistula

The management of fistula-in-ano has been based on digital examination and operative findings. MR imaging has shown significant limitations to this approach, particularly in the management of recurrent fistula. The most cost-effective approach may be using a combination of endosonography and MR imaging. Preoperative confirmation of fistula complexity facilitates surgery planning of sphincter saving techniques and prevents sepsis being missed, which has been shown to reduce recurrence. Imaging has a significant role to play in this condition to improve patient outcome.

Magnetic resonance imaging for primary fistula in ano

This was a prospective study designed to determine the therapeutic impact of magnetic resonance imaging (MRI) in primary fistula in ano, and to assess its effect on outcome.

MR imaging of fistula-in-ano

Accurate preoperative assessment of fistula-in-ano is mandatory if the fistula is not to recur. In recent years, MRI has become pre-eminent for fistula assessment and recent studies have shown that not only is MRI more accurate than surgical assessment, but that surgery based on MRI can reduce further disease recurrence by approximately 75%. The main role of MRI is to alert the surgeon to fistula tracks and extensions that would otherwise have gone undetected and, thus, untreated at the time of surgical assessment under general anaesthetic.

Potential clinical implications of direction of a trans-sphincteric anal fistula track

The longitudinal direction of a trans‐sphincteric anal fistula track through the anal sphincter complex may have implications regarding fistulotomy.

Pilot study: fibrin sealant in anal fistula model.

PURPOSEThe aim of this study was to investigate the failure of fibrin sealant treatment for fistula-in-ano in an experimental porcine model and to determine histologic changes associated with the sealant and setons.METHODSThree surgically created fistulas were treated by seton drainage in each of eight male pigs. After 26 days, magnetic resonance imaging was performed and setons were removed. Two pigs were killed as controls for stereologic histologic fistula track assessment. In six, fistulas were curetted, and in four the fistulas were treated with fibrin sealant. In these four sealant and two seton pigs, magnetic resonance imaging was repeated a median of 47.5 days after fistula formation. The pigs were killed and stereologic histologic fistula track examination was performed to determine granulation tissue and fistula lumen volumes. These values were compared among control, seton, and sealant groups over time, and related to fistula volumes derived from magnetic resonance imaging.RESULTSSealant was not visible microscopically within tracks, although some sections revealed a foreign body–type reaction. On stereologic assessment, granulation tissue volumes were smaller in sealant and seton groups than in controls (median, 88 vs. 187 vs. 453 mm3, respectively; P = 0.002) and decreased over time (median, 408 and 152 mm3 (Day 42) vs. 88 and 75 (Day 53), respectively; P = 0.002). Fistula lumen (P < 0.001), and granulation tissue combined with fistula lumen volumes (P = 0.002) were similarly smaller. Magnetic resonance imaging of fistula intensity was less in the sealant group than in the seton group and controls (mean, 777 vs. 978 vs. 1214 units/mm2, P = 0.003). Magnetic resonance imaging fistula volumes were least in sealant and seton groups vs. controls (P = 0.024), decreasing significantly in the sealant group over time (P = 0.018). No direct relationship was found between imaging and histologic volumes.CONCLUSIONSIn an experimental porcine model of anal fistula, granulation tissue was still present, albeit diminished, following track curettage combined with seton or sealant therapy, and was minimal in the sealant group, confirming some benefit from this procedure. Eradication of all longstanding granulation tissue may ensure complete success of fibrin sealant therapy.

Experimental model of fistula-in-ano.

PURPOSEThis study was designed to create and evaluate an experimental porcine model of fistula-in-ano.METHODSInitial cadaveric dissection enabled refinement of the technique for fistula formation and histoanatomical study of the porcine anal canal. Subsequently, three surgically created fistulas were treated by seton drainage in each of eight male pigs (weight, 38–41 kg). After 26 days, magnetic resonance imaging at 1.5 Tesla was performed and setons removed under general anesthesia, enabling clinical and microbiologic track assessment. Two pigs were killed for histologic fistula track assessment.RESULTSHistoanatomical assessment noted a rudimentary internal anal sphincter, together with structures resembling anal glands. Artificial fistulas persisted during seton drainage and were more often associated with fecal than skin-derived organisms compared with both perineal and anal canal swabs (P = 0.002). All six fistulas assessed histologically had a lumen, and abundant surrounding granulation tissue similar to that seen in human fistula-in-ano. Epithelialization was not evident in any track. Fistulas were visualized as high signal tracks using magnetic resonance imaging.CONCLUSIONSPorcine anal anatomy resembles that of humans, and an experimental model proved suitable when assessed by magnetic resonance imaging, microbiology, and histologically, which demonstrated abundant granulation tissue. This model could be further used to investigate fistula treatments.

Randomized clinical trial of the costs of open and laparoscopic surgery for colonic cancer (Br J Surg 2004; 91: 409–417)

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