Hydrogen peroxide-enhanced transanal ultrasound in the assessment of fistula-in-ano

Fistula-in-ano: advances in treatment

BACKGROUND

Several techniques have been described for the management of fistula-in-ano, but all carry their own risks of recurrence and incontinence. Technology has evolved over the past 2 decades that may enable surgeons to deal with this troublesome issue with greater success. This review summarizes the history of fistula-in-ano management, the current techniques available, and describes new technologies.

METHODS

Medline searches were performed using the PubMed, Ovid, Embase, Cochrane, and Google Scholar databases to identify articles reporting on fistula-in-ano management using surgery alone, fibrin glues, and fistula plugs. Forty-one articles reporting on the history of fistula-in-ano management and the use of new technologies were included.

RESULTS

Conventional fistula surgery techniques have their place, but new technologies such as fibrin glues and the anal fistula plugs offer an alternative approach, with initial studies reporting good success rates.

CONCLUSIONS

New technologies provide promising alternatives to traditional methods of management. There is, however, a real need for high-quality randomized control trials.

Imaging of perianal Crohn's disease

Perianal fistulas and abscesses are common complications of Crohn's disease, affecting up to 50% of patients during their disease course. Accurate diagnosis and classification of perianal disease is crucial before and during treatment to plan an adequate approach for each patient and to avoid irreversible functional consequences. Although examination under anaesthesia has been considered the gold standard for diagnosis and classification of Crohn's disease perianal fistulas, taken alone it does not have perfect accuracy, stressing the need for concomitant or alternative, non-invasive, methods of evaluation. In this context, imaging modalities assessed for diagnosis, classification and monitoring of Crohn's disease perianal fistulas include pelvic magnetic resonance imaging, anorectal endoscopic ultrasonography, transcutaneous perianal ultrasound, fistulography and computed tomography. In particular, magnetic resonance imaging and endoscopic ultrasonography findings have shown the best accuracy, and the ability to influence therapeutic management of these patients. For transcutaneous perianal ultrasound too, good preliminary data have been reported. This paper reviews the available data on imaging methods for the management of perianal Crohn's disease.

Endorectal ultrasound (ERUS) in pelvic disorders

Endorectal ultrasound (ERUS) imaging is a complex process using electronic devices to control ultrasound waves and produce images of anatomic structures. It is a simple, cheep and well-tolerated procedure that provides excellent images of rectal and anal canal wall and pelvic floor muscles together with surrounding organs and tissues. The direct imaging of anal canal and pelvic floor muscles with surrounding tissues allows one to identify sphincter defects, anorectal abscesses and fistulas as well as great variety of benign and malignant pathology of the pelvis. Basically, techniques for ERUS are very similar, but there are some slight modifications regarding equipment, indications, and localization of pathologic process. We describe the technique, indications, results and pitfalls of ERUS with the Bruel and Kjaer type 1850 endosonic probe with 7 and 10 MHz transducers in benign pelvic disorders.

Simple clinical examination predicts complexity of perianal fistula

OBJECTIVE

To investigate the diagnostic value of the distance between external opening of perianal fistula and anal verge and to evaluate its relation to the type of fistula. Preoperative identification of complex fistulae is important for proper planning of treatment.

PATIENTS AND METHODS

One hundred and fifteen consecutive patients operated for perianal fistula were studied prospectively. The distance between the external opening and the anal verge was measured. Location of the external opening, demographic and medical history data were correlated with characteristics of the fistulae. Data analysis was performed using the SPSS statistical package. The association between categorical variables was examined using the chi(2)-test or Fisher's exact test for small sample. Comparison of continuous variables between two groups was analysed by t-test.

RESULTS

The mean distance between external opening and anal verge in simple fistulae was 2.8 cm (range 1.5-4.3, SD 0.689) and in complex fistulae it was 4.4 cm (range 3.5-6.0, SD 0.526). This difference was statistically significant -P < 0.0001. Age and previous operations (particularly attempted definitive operations) were also significantly related to the complexity of the fistula. Data concerning location and direction of the fistulous tracts confirm the validity of Goodsall's rule.

CONCLUSION

Simple preoperative clinical examination may reliably predict the complexity of a perianal fistula. Identification of these patients permits to select the cases that should have specific sophisticated preoperative work-up. The first definitive operation is most important to assure a successful outcome, thus such preoperative triage may also permit selective referral to a specialized colorectal team.

Controversies in the treatment of common anal problems

Treating common benign anal diseases has evolved towards more outpatient procedures with better outcome. However, minimizing post-procedure morbidities such as pain and the avoidance incontinence remain the most significant concerns. We introduce some controversies and highlight the developments in current surgical practice for the treatment of common anal problems.

Anorectal ultrasound for neoplastic and inflammatory lesions

Accurate staging of rectal and anal carcinoma is crucial for planning surgery and indicating adjuvant therapy. Although, computed tomography and magnetic resonance imaging are very sensitive in detecting metastatic disease, the local staging of rectal cancer with these techniques has been disappointing. Endorectal ultrasound (ERUS) and anal endosonography (AE) remain the most accurate methods for staging rectal and anal cancer. Anal endosonography is also of value in evaluating perianal sepsis: it can assist the surgeon in planning the surgical strategy by delineating the anatomy of fistula tracts, and can aid in puncturing abscesses in the operating room. Continued research and development has made the instrumentation for ERUS and AE more accurate and user-friendly. New techniques that have contributed significantly to the evolution of ERUS include three-dimensional ERUS, high-frequency miniprobes, transrectal ultrasound-guided biopsy techniques and hydrogen peroxide-enhanced endosonography. Further improvements can be expected from contrast enhancement with microbubbles and colour Doppler imaging. In this new millennium, new developments in ERUS and anal endosonography, such as tri-dimensional ERUS and anal endosonography and radial electronic probing, widen the role of ERUS in the staging of rectal and anal carcinoma, as well as for perianal inflammatory conditions.

Endosonographic imaging of anorectal diseases

OBJECTIVE

The normal sonographic anatomy of the anorectum, sonographic findings of anorectal diseases, and indications and limitations of endosonography compared with magnetic resonance imaging are reviewed. Methods. Endosonographic imaging was performed with a Siemens (Erlangen, Germany) FI 400 ultrasound scanner with an end-fire 7.5-MHz biplane endorectal probe and a B-K Medical (Sandhoften, Denmark) scanner with an 1850 axial-type side-fire 5.0- to 10.0-MHz rotating endoscopic probe.

RESULTS

Rectal carcinoma appears on endorectal sonography as a low-echogenicity lesion that abruptly interrupts the normal sequence of layers. The internal anal sphincter is seen very clearly on endoanal sonography, and it is easy to appreciate atrophy and small tears of this sphincter. Endoanal sonography cannot accurately show thinning of the external anal sphincter. Peroxide-enhanced endoanal sonography is especially useful for patients with recurrent perianal fistulas in whom scarring should be distinguished from recurrent fistulas and detection of the internal opening. However, sonography does not provide an adequate deep and global display of all adjacent pelvic and perineal spaces.

CONCLUSIONS

Endosonography can accurately stage primary rectal tumors and assess the internal anal sphincter. Peroxide-enhanced 3-dimensional imaging can increase the utility of endoanal sonography in detection and characterization of perianal fistulas and planning of optimal therapy. However, magnetic resonance imaging can be used a complementary modality to endosonography, especially for evaluation of external anal sphincter atrophy and deep pelvic inflammation.

Endosonography in anorectal disease: an overview

Anorectal endosonography (AE), which was introduced 20 years ago, derives from the study of urology. It was first used to evaluate rectal tumours and later also to investigate benign disorders of the anal sphincters and pelvic floor. The technique is easy to perform, it has a short learning curve and causes no more discomfort than a routine digital examination. A rotating probe with a 360 degrees radius and a frequency between 5 and 16 MHz is introduced to the rectum and then slowly withdrawn so that the pelvic floor and subsequently the sphincter complex are seen. Recently, it has become possible to reconstruct three-dimensional images. AE has been used for almost every possible disorder in the anal region and has increased our insight into anal pathology. The clinical indications for AE are: 1. Faecal incontinence in patients when surgery is an option. AE can show sphincter defects with excellent precision. There is a perfect correlation with surgical findings. Studies comparing AE with endoanal magnetic resonance imaging (MRI) have shown that both methods are equally good for demonstrating defects in the external anal sphincter; the internal anal sphincter is better visualized with AE. After sphincter repair, the effect is directly related to the decrease in the sphincter defect. 2. Perianal fistulae. AE has been shown to be accurate in staging perianal cryptoglandular fistulae and fistulae in Crohn's disease. When there is an external fistula opening, H2O2 can be introduced with a plastic infusion catheter. The tract then becomes visible as a hyperechoic lesion ("white"). It has been shown that this corresponds well with surgical findings. It is equally sensitive as endoanal MRI. Since recurrent cryptoglandular fistulae are complex in 50% and Crohn's fistula in 75%, it is mandatory to perform AE preoperatively in these patients to avoid missed tracts during surgery and subsequent recurrences. 3. Rectal tumors. In low tubulovillous adenomas or malignant polyps considered removable locally, confirming the local resectability (T0 or T1) is mandatory. Although larger rectal and more advanced tumours can be evaluated with AE, MRI is more sensitive in staging nodal involvement. 4. Anal carcinoma for staging. AE has been shown to stage better than the classical TNM classification for both local extension and prognosis. In conclusion, AE images the internal and external anal sphincter with high accuracy. It is easy to perform and is of particular value in the diagnosis of anal incontinence and perianal fistulae. It is excellent in staging anal carcinoma and can also be used in staging rectal carcinoma, especially very low large malignant polyps.

Valor actual de la ecografía endoanal en el diagnóstico de la enfermedad proctológica benigna

Endoanal ultrasound is undoubtedly one of the major advances that has taken place in the evaluation of anorectal disease and pelvic floor disorders in the last decade. The main indications for endoanal ultrasound are evaluation of the morphology of the sphincteric apparatus in patients with fecal incontinence, the localization of perianal abscesses and fistulas, the staging of anal cancer and follow-up of squamous cell carcinoma after conservative treatment, and the study and morphological confirmation of lateral internal sphincterotomy in patients with fissure-in-ano, amongst others. In this article we review the main indications and use of endoanal ultrasound in the diagnosis of benign proctological disease.

Anal abscesses and fistulas

Anal abscesses and fistulas are a common part of surgical practice. Most abscesses simply need to be drained and most fistulas can be safely laid open. Excessive probing should not be attempted when draining abscesses as this may lead to iatrogenic fistulas. A small percentage of fistulas are complex and very challenging to manage. Management involves an accurate diagnosis and a balance between eradication of the fistula and maintenance of continence. A decision should be made, based on clinical evaluation and anal ultrasound (if available), whether the fistula can be laid open. If it cannot be laid open, a loose seton is placed and the sepsis is allowed to settle. Once the sepsis is quiescent, a definitive repair can be attempted. There are various techniques available including rectal advancement flap, fibrin glue and cutaneous flaps all of which are discussed.

Endosonographic evaluation of perianal fistulas and abscesses: comparison of two instruments and assessment of the role of hydrogen peroxide injection

PURPOSE

The aims of this study were to compare the performance of a mechanical radial endosonoscope and an endorectal electronic probe and to evaluate the value of hydrogen peroxide (H(2)O(2)) injection in the diagnosis of perianal fistulas.

PATIENTS AND METHODS

Sixty-one patients underwent clinical and endosonographic studies for suspected perianal fistulas or abscesses. Endosonography was performed using two instruments: a mechanical radial endosonoscope (Olympus GF-UM20) and an electronic endorectal probe (Hitachi EUP-R53). The patients were re-examined during and following H(2)O(2) injection using both systems.

RESULTS

Thirty-seven fistulous tracts were visualized with the electronic endorectal probe versus only 9 with the mechanical radial endosonoscope. Four patients had anal stenosis, precluding the use of the larger electronic probe. Three fistulas were detected in these patients using the mechanical radial endosonoscope. H(2)O(2) injection was not feasible in 26 patients (43%). Visualization of 11 (31%) fistulas improved after administration of H(2)O(2). Six fistulous tracts not detected before H(2)O(2) administration were clearly visualized during injection and for several minutes thereafter.

CONCLUSIONS

Work-up of perianal fistula should be preferably performed using the endorectal electronic probe. However, the mechanical radial endoscope is preferred in patients with anal stricture. H(2)O(2) injection should become an integral part of every sonographic study of perianal fistulas.

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

PURPOSE

The 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.

METHODS

Three-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.

RESULTS

Patients 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.

CONCLUSIONS

In 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.

Venous oxygen embolism produced by injection of hydrogen peroxide into an enterocutaneous fistula

We report a venous oxygen embolism that occurred in a 66-yr-old man after 60 mL of 3% hydrogen peroxide was injected into a perianal fistula intraoperatively to locate its internal opening. The diagnosis was made after detecting hypoxemia, decreased end-tidal carbon dioxide tension, systemic hypotension, increased central venous pressure, and a new heart murmur. The patient recovered quickly and had no long-term sequelae. Oxygen embolism is a potentially fatal complication that can develop when hydrogen peroxide is used near venous spaces, and clinicians should be aware of the potential dangers when using this seemingly innocuous chemical.

Hydrogen peroxide-enhanced three-dimensional endoanal ultrasonography and endoanal magnetic resonance imaging in evaluating perianal fistulas: agreement and patient preference

OBJECTIVES

To determine agreement between hydrogen peroxide-enhanced three-dimensional endoanal ultrasonography (3D HPUS) and endoanal magnetic resonance imaging (MRI) in preoperative assessment of perianal fistulas, and to assess patient preference with regard to these techniques.

METHODS

Forty patients (31 males, aged 21-70 years) with symptoms of a perianal fistula and a visible external opening underwent preoperative 3D HPUS and endoanal MRI. The results were assessed separately by experienced observers. Fistulas were described according to the following characteristics: classification of the primary fistula tract according to Parks, location of the internal opening, presence of secondary tracts and fluid collections. Patients were asked to score the amount of discomfort experienced during both procedures and express their preference for either method.

RESULTS

The median time interval between 3D HPUS and endoanal MRI was 14 days (range, 0-91 days). The methods agreed in 88% (35/40, kappa = 0.45) for the primary fistula tract, in 90% (36/40, kappa = 0.83) for the location of the internal opening, in 78% (31/40, kappa = 0.62) for secondary tracts, and in 88% (35/40, kappa = 0.63) for fluid collections. Both methods were associated with similar discomfort, and there was no patient preference for one procedure over the other.

CONCLUSIONS

3D HPUS and endoanal MRI are equally adequate for the evaluation of perianal fistulas. Both methods are associated with similar discomfort and patients have no preference for either procedure.

Clinical examination, endosonography, and MR imaging in preoperative assessment of fistula in ano: comparison with outcome-based reference standard

PURPOSE

To prospectively evaluate the relative accuracy of digital examination, anal endosonography, and magnetic resonance (MR) imaging for preoperative assessment of fistula in ano by comparison to an outcome-derived reference standard.

MATERIALS AND METHODS

Ethical committee approval and informed consent were obtained. A total of 104 patients who were suspected of having fistula in ano underwent preoperative digital examination, 10-MHz anal endosonography, and body-coil MR imaging. Fistula classification was determined with each modality, with reviewers blinded to findings of other assessments. For fistula classification, an outcome-derived reference standard was based on a combination of subsequent surgical and MR imaging findings and clinical outcome after surgery. The proportion of patients correctly classified and agreement between the preoperative assessment and reference standard were determined with trend tests and kappa statistics, respectively.

RESULTS

There was a significant linear trend (P < .001) in the proportion of fistula tracks (n = 108) correctly classified with each modality, as follows: clinical examination, 66 (61%) patients; endosonography, 87 (81%) patients; MR imaging, 97 (90%) patients. Similar trends were found for the correct anatomic classification of abscesses (P < .001), horseshoe extensions (P = .003), and internal openings (n = 99, P < .001); endosonography was used to correctly identify the internal opening in 90 (91%) patients versus 96 (97%) patients with MR imaging. Agreement between the outcome-derived reference standard and digital examination, endosonography, and MR imaging for classification of the primary track was fair (kappa = 0.38), good (kappa = 0.68), and very good (kappa = 0.84), respectively, and fair (kappa = 0.29), good (kappa = 0.64), and very good (kappa = 0.88), respectively, for classification of abscesses and horseshoe extensions combined.

CONCLUSION

Endosonography with a high-frequency transducer is superior to digital examination for the preoperative classification of fistula in ano. While MR imaging remains superior in all respects, endosonography is a viable alternative for identification of the internal opening.

Transcutaneous perianal sonography: A sensitive method for the detection of perianal inflammatory lesions in Crohn’s disease

AIM: Pelvic magnetic resonance imaging (MRI) and endoanal ultrasound which are established imaging methods for perianal inflammatory lesions in patients with Crohn’s disease require expensive specialized equipments and expertise. We investigated the feasibility and sensitivity of transcutaneous perianal ultrasound (PAUS) using regular ultrasound probes in the imaging of perianal inflammatory lesions. The sonographic findings were correlated to pelvic MRI-scans.

METHODS: We performed PAUS in 25 patients with Crohn’s disease and clinical signs of perianal inflammatory disease. Within a median of 10 d (range 0-75) these patients underwent MRI of the pelvis. Regular convex and linear high resolution probes were used for PAUS. The sonographic findings were correlated to the MRI findings by blinded investigators.

RESULTS: The sonographic investigations were well tolerated by all patients. Fistulae typically presented as hypoechoic tracks. Twenty-nine fistulae were detected in 22 patients. Abscesses were detected in 7 patients and presented as hypo- or anechoic formations. Twenty-six of 29 fistulae and 6 of 7 abscesses could be confirmed by MRI. Kappa statistics showed an excellent agreement (kappa > 0.83) between the two imaging methods.

CONCLUSION: PAUS is a simple, painless, feasible, real-time method that can be performed without specific patient preparation which is comparable in its sensitivity to pelvic MRI in the detection of perianal fistulae and/or abscesses. PAUS can especially be recommended as a screening tool in acute perianal disorders such as perianal abscess and for follow-up studies of perianal inflammatory disease.

Comparison of contrast-enhanced with non-contrast endosonography in the diagnostics of anal fistulas

The objective of this paper is to compare the accuracy of standard, non-contrast endosonography (EAS) with contrast-enhanced endosonography (CE-EAS) in the diagnosis of anal fistulas. The group consisted of 126 patients (mean age: 43.1 years) with the clinical diagnosis of anal fistula. For anal endosonography, a Bruel & Kjaer unit with a 7.0-MHz transducer was used with a 3% solution of hydrogen peroxide as the contrast agent (1, 2, 3). In each case, EAS and CE-EAS diagnoses of the type and complexity of anal fistula, as well as the location of the internal opening, were determined. Results showed that CE-EAS was significantly more accurate in diagnosing the type of anal fistulas than NC-EAS (97 vs. 94%, respectively; P=02275), and in differentiating simple from complex tracks (92 vs. 75%, respectively; P<0.00001). CE-EAS was much more accurate in patients with recurrent fistulas (57 vs. 92%, respectively; P<0.00006), whereas in a subgroup of primary tracks, both methods were of comparable accuracy. Sensitivities of CE-EAS and EAS for internal opening were 89 and 65%, respectively. The conclusion of this paper is that CE-EAS significantly increases the accuracy of standard non-contrast EAS and is especially beneficial for the differentiation between simple and complex tracks.

Perianal fistulae following infliximab treatment: clinical and endosonographic outcome

BACKGROUND

Management of perianal and rectovaginal fistulae complicating Crohn's disease (CD) is unsatisfactory. Infliximab is effective in the treatment of fistulating CD. However, reopening of fistulae is frequent, suggesting the persistence of deep fistula tracts despite superficial healing. In this study, the clinical and endosonographic behavior of perianal fistulae were evaluated following infliximab infusions, as well as the role of anal endosonography (AE) in predicting their outcome.

METHODS

Thirty CD patients presenting with perianal and/or rectovaginal fistulae received an infusion of infliximab at a dose of 5 mg/kg at weeks 0 (entry into the study), 2, and 6. Laboratory and clinical assessments were repeated at same intervals and at week 10. AE was performed at entry and at week 10. Thereafter, the perianal region was re-examined every 6 months, and patients were investigated regarding draining of the fistula in the previous months.

RESULTS

Fifteen patients (53.6%) showed closure of the fistulae at week 10, but only 5 patients had the fistula tracts disappeared at AE. Clinical and AE closure of rectovaginal fistulae was less prevalent than that of perianal fistulae [14.3% versus 63.6% at week 6 (p = 0.035); 28.6% versus 59.1% at week 10 (p = 0.21); 14.3% versus 22.7% at AE (p = 1.00)]. The behavior of fistulae was not affected by their number and AE classification, presence of rectal disease, or setons. Twenty patients with perianal fistulae were followed for a median of 15.5 months. Patients with closed perianal fistulae at week 10 and disappearance of fistulae tract at AE showed a lower relapse rate than those with endosonographic persistence of fistula tract.

CONCLUSIONS

Infliximab can heal perianal and rectovaginal fistulae in approximately 60% and 30% of patients, respectively. Despite closure, most fistula tracts are still detectable at AE. Persistence of the internal tract is a condition at higher risk of fistula recurrence.

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.

Pre-operative assessment of anal fistulas using endoanal ultrasound

OBJECTIVE

To study the accuracy of endoanal ultrasound in pre-operative assessment of cryptoglandular anal fistulas, with respect to the site of the internal opening, type and depth of the fistula tract.

PATIENTS AND METHODS

A consecutive series of 151 patients with anal sepsis underwent pre-operative endoanal ultrasound assessment of a suspected anal fistula. Hydrogen peroxide was used to define the tract when there was doubt as to the course of the fistula. All patients subsequently had surgical exploration under anaesthesia, irrespective of findings at sonography. The site of the internal opening, depth and type of fistula were recorded at surgery, and concordance with the ultrasound was assessed.

RESULTS

One hundred and forty-five patients were subsequently shown to have a fistula at surgical exploration. Type of fistula: Two thirds were transsphincteric (63%) and one third were inter sphincteric (32%), with a few submucosal, and supra sphincteric fistulas. Ultrasound correctly predicted surgical findings in 82% of patients (124/151). Concordance was highest for transsphincteric fistulas (87%). Internal opening: Accuracy of predicting the site of the internal opening was 93% (140/151). The commonest site for the internal opening was the midline posteriorly (49%), followed by the midline anteriorly (25%), the rest lay laterally. Fistula depth: Ultrasound and surgical assessment of the depth of fistulas was concordant in 120 of 145 patients (83%).

CONCLUSIONS

Endoanal ultrasound has a high accuracy of predicting the site of internal opening of an anal fistula. Endoanal ultrasound is able to assess the type and depth of a fistula. This information is useful for pre-operative planning of fistula treatment.

Reliability of endosonography in evaluation of anal fistulae and abscesses

OBJECTIVE

To assess the reliability of anal endosonography (AES) in the diagnosis of anal fistulae and abscesses.

MATERIAL AND METHODS

86 patients with different types of anal fistulae and abscesses were prospectively examined with a 7.0 MHz transducer. Type of anal fistulae, differentiation between simple and complex tracts, and location of their internal openings were defined. In 66 cases with permeable external opening, hydrogen peroxide solution was introduced into the fistula tract. Reliability of AES was defined after surgical treatment of all cases.

RESULTS

74 anal fistulae, including 43 transsphincteric, 11 intersphincteric, 6 suprasphincteric, 3 superficial, and 11 ano-vaginal were found on AES. 27 fistulae were complex, and 47 simple fistulae. In 10 patients a coexisting abscess was found; the remaining 12 abscesses were without any fistula. Surgery confirmed the type of anal fistula in 64 patients (86.5%), and location of internal openings in 60 cases (81.1%). All abscesses were confirmed.

CONCLUSION

AES showed high accuracy in diagnosing anal fistulae and abscesses.

Acquired gastrointestinal fistulas: classification, etiologies, and imaging evaluation

Fistulas are abnormal communications between two epithelial-lined surfaces. Gastrointestinal fistulas encompass all such connections that involve the alimentary tract, and they can be congenital or acquired in nature. This review focuses on acquired gastrointestinal fistulas. Development of an acquired gastrointestinal fistula can greatly affect patient outcome, yet the clinical manifestations are often protean in nature and the etiology, elusive. Imaging plays an important role in the detection and management of acquired gastrointestinal fistulas. The more routine use of cross-sectional imaging (especially computed tomography and magnetic resonance imaging) has altered the standard sequence of radiologic evaluation for possible fistulas, but fluoroscopic studies remain a valuable complement, especially for confirming and defining the anomalous communications. In this review, a classification scheme for gastrointestinal fistulas is provided, major causes are discussed, and individual fistula types are elaborated with an emphasis on contemporary imaging approaches.

Accuracy of hydrogen peroxide-enhanced ultrasound in the identification of internal openings of anal fistulas

OBJECTIVE: This prospective study was designed to assess the accuracy of hydrogen peroxide-enhanced ultrasound in the identification of internal openings of anal fistulas, with surgical findings as the golden standard. PATIENTS AND METHODS: A total of 143 consecutive patients (102 men; mean age, 45 years) with fistula-in-ano were assessed by hydrogen peroxide-enhanced ultrasound before surgery involving one radiologist. Ultrasound was performed using a B & K Diagnostic Ultrasound System trade mark with a 10-MHz rotating endoprobe. Hydrogen peroxide (3%) was infused into the fistula. All operations were perfomed by the same surgeon who was unaware of results of anal endosonography. RESULTS: In 128 (89.5%) patients, an internal opening was identified at surgery. Correct identification of an internal opening endosonographically was recorded in 80 (62.5%) patients. The internal opening was correctly identified by ultrasound in 32% (8/25) of patients with intersphincteric fistulas, in 77% (70/91) with transsphincteric fistulas, and in 17% (2/12) with suprasphincteric fistulas. CONCLUSION: The accuracy of hydrogen peroxide-enhanced anal endosonography for the identification of internal openings was still insufficient to justify pre-operative endosonography as a diagnostic method for routine use in patients with fistula-in-ano.

The role of anal ultrasound in the management of anal fistulas

OBJECTIVE: To assess the accuracy of anal ultrasound (AUS) for anal fistulas, and the impact of routine pre-operative AUS on their surgical management. METHODS: Pre-operative AUS was performed in 38 consecutive patients with an anal fistula using a 10-MHz Brüel & Kjaer probe. All patients underwent subsequent examination under anaesthetic (EUA) with documentation of the anatomy of the fistula before the surgeon was shown the AUS results. Agreement between AUS and EUA findings and any modification to the surgical treatment was recorded. RESULTS: There was 84% agreement between AUS and EUA findings regarding presence and site of fistulas. One fistula not seen at AUS was found at EUA, and 5 fistulas seen on AUS were not demonstrated at EUA. AUS influenced the surgery undertaken in 9/24 (38%) patients; demonstrating occult sphincter defects (2 patients), reclassifying fistulas from low to higher fistulas (3 patients), deciding a surgical treatment open to doubt (2 patients) and helping identify an obscure fistula not initially found at EUA (2 patients). CONCLUSIONS: Accuracy of AUS in the assessment of anal fistulas is confirmed. Operative management is influenced in 38% of cases, usually towards more conservative treatment. We recommend the use of pre-operative AUS in the assessment of anal fistulas.

Contrast-enhanced endosonography for the diagnosis of anal and anovaginal fistulas

PURPOSE

We assessed whether contrast-enhanced anal endosonography (AES) with hydrogen peroxide improves the identification of anal fistulas and their internal openings compared with non-contrast AES.

METHODS

The study group comprised 12 patients who had various types of anal fistulas with visible external openings. AES was performed before and about 15 seconds after injection of 1 ml of 3% hydrogen peroxide into the fistula tract through the external opening.

RESULTS

Both contrast and non-contrast AES revealed 7 transsphincteric, 2 intersphincteric, 1 suprasphincteric, and 2 anovaginal fistulas. Simple tracts were found in 8 cases and complex tracts in 4 cases on non-contrast AES. Contrast-enhanced AES revealed 9 simple and 3 complex fistulas. One fistula that appeared complex on the non-contrast study appeared simple after contrast agent administration. Contrast-enhanced AES demonstrated more internal openings than non-contrast AES did. Surgery confirmed 11 of the fistulas; an internal opening could not be located surgically for the other tract.

CONCLUSIONS

Contrast-enhanced AES appears to be superior to non-contrast AES in the preoperative assessment of anal and anovaginal fistulas and in demonstrating and locating their internal openings.

Assessment and classification of never operated and recurrent cryptoglandular fistulas-in-ano using hydrogen peroxide enhanced transanal ultrasound

OBJECTIVE

Classification and visualization of fistula-in ano is used to determine surgical treatment according to the type of fistula, predict the recurrence rate and incontinence risk and compare the results of treatment published in literature. Hydrogen peroxide enhanced transanal ultrasound (HPUS) with the peroxide introduced through the external opening of the fistula gives a clear and accurate visualization of the track in relation to the sphincters. The aim of this study was to review never operated and recurrent cryptoglandular fistulas-in-ano visualized with the aid of HPUS in order to establish the anatomical differences.

PATIENTS AND METHODS

Eighty-one patients with never operated (48) or recurrent (33) cryptoglandular fistulas-in-ano were assessed by clinical examination and HPUS.

RESULTS

Never operated fistulas were single track, trans- or inter-sphincteric fistulas in 80%. In 15%, the tracks were sinus with no connection to the pectinate line. Two patients (5%) had a transsphincteric fistula with a ramification. No supra- or extra-sphincteric fistulas were found in the never operated fistula group. In the recurrent fistula patients, 57% had a single trans or intersphincteric track, 15% of the patients had a single track supra or extrasphincteric fistula and 27% had a ramified fistula.

CONCLUSIONS

All never operated cryptoglandulair fistulas-in-ano were inter- or trans-sphincteric. An extra track was found in 5%. Recurrent fistulas-in-ano were supra or extrasphincteric in 15% and ramified in 27%. Therefore, never operated fistula-in-ano does not require any special investigation before surgical treatment. However, before treating recurrent fistulas, visualization by HPUS is recommended to detect supra or extrasphincteric fistulas or ramification.

Peroxide-enhanced anal endosonography: technique, image interpretation, and clinical applications

Because current techniques for examination and imaging of perianal fistulas tend to underestimate the extent, location, and course of perianal fistulas--information essential for decisions about surgical management--the use of hydrogen peroxide was investigated as an image-enhancing contrast agent for confirmation of the presence of and improvement in the depiction of fistulas during endoanal ultrasonography (US). After conventional endoanal US was performed with a side-fire 7.5- or 10.0-MHz rotating endoprobe, external perianal openings were cannulated and approximately 1 mL of peroxide was administered. After reinsertion of the endoprobe, the entire course of the echogenic fistula, including its relation to the internal and external sphincters and the levator ani muscle, was depicted in real time in three dimensions. This depiction of fistulas permits accurate classification, which facilitates surgical planning. In experience with more than 60 patients, peroxide-enhanced endoanal US was found to be a useful technique for documentation of the presence, number, and internal course of perianal fistulas and for characterization of abnormalities seen at endosonography performed without use of contrast enhancement. In addition, the technique permitted surgeons to stratify patients into treatment groups and has been especially useful for planning surgical treatments.

Comparison of hydrogen peroxide instillation with Goodsall's rule for fistula-in-ano

BACKGROUND

Identification of the internal opening is an essential step in the management of fistula-in-ano. The predictive accuracy of Goodsall's rule is compared with instillation of hydrogen peroxide for fistulas-in-ano.

METHODS

Thirty-five patients (32 male, three female; median age 42 years; range: 6 months-70 years) were studied. Hydrogen peroxide solution was injected into the external opening of the fistula track and effervescence was observed at the internal opening within the anal canal. A fistula track was either excised or incised. Setons were placed within high fistulas.

RESULTS

There were 24 simple fistulas, compared to 11 complex fistulas (horseshoe, n = 4; abscess, n = 4). Eighteen external openings were anterior and 17 were posterior. Thirty-four of 35 (97%) internal openings were identified. Only 20 internal openings were in accordance with Goodsall's rule (positive predictive value: 59%). Predictive accuracy was greater for anterior external openings (13 of 18 (72%)) versus posterior external openings (six of 17 (41%); P = 0.016). For recurrent fistulas, seven of 17 fistula tracks had an internal opening in accordance with Goodsall's rule, resulting in a positive predictive value of 41%. (Positive predictive value: anterior 67% vs posterior 12.5%; P = 0.0009.)

CONCLUSION

The overall predictive accuracy of Goodsall's rule was poor chiefly because of poor predictive accuracy in posterior and recurrent fistulas. The use of Goodsall's rule alone in decision-making before surgical intervention is not recommended.

Endoanal ultrasound or magnetic resonance imaging for preoperative assessment of anal fistula: a comparative study

OBJECTIVE

To compare endoanal ultrasound (EUS) with a 10-MHz probe vs. bodycoil magnetic resonance imaging (MRI) in the preoperative evaluation of anal fistula.

SUBJECTS AND METHODS

23 patients with fistula in the anal region underwent preoperative 0.5 T bodycoil MRI and 10 MHz EUS which included probing in 6 patients. The results of the EUS and MRI were compared against the surgical findings as a reference method.

RESULTS

In classification of the primary tract there was agreement between EUS and surgical findings in 14 (61%) and between MRI and surgery in 11 (48%). Concerning the presence of an internal opening the corresponding figures were 17 (74%) and 10 (43%) and in judging the presence of an extension or an abscess 15 (65%) vs. 11 (48%), respectively. In three out of eight patients with nonhealing or recurrence after surgery preoperative imaging had shown an extension and/or an abscess that was not identified by the surgeon.

CONCLUSION

EUS, sometimes complemented with probing, is well comparable to bodycoil MRI in classifying and describing the topography of an anal fistula.

How can the assessment of fistula-inano be improved?

PURPOSE

Fistula-in-ano anatomy and its relationship with anal sphincters are important factors influencing the results of surgical management. Preoperative definition of fistulous track(s) and the internal opening play a primary role in minimizing iatrogenic damage to the sphincters and recurrence of the fistula.

METHODS

Physical examination and endoanal ultrasound (performed with a 10 MHz endoprobe), either conventionally or with an injection of hydrogen peroxide, were performed in 26 consecutive patients. Results were matched with surgical features to establish their accuracy in preoperative fistula-in-ano assessment.

RESULTS

Accuracy rates of clinical examination endoanal ultrasound, and hydrogen peroxide-enhanced ultrasound were 65.4, 50, and 76.9 percent for primary tracks, 73.1, 65.4, and 88.5 percent for secondary tracks, and 80.8, 80.8, and 92.3 percent for horseshoe extensions, respectively. Compared with physical examination and endoanal ultrasound, accuracy of hydrogen peroxide-enhanced ultrasound was higher for transsphincteric and intersphincteric primary tracks and horseshoe extensions. Both endoanal ultrasound and hydrogen peroxide-enhanced ultrasound displayed a significantly higher accuracy in detecting the internal openings (53.8 and 53.8 percent, respectively) compared with clinical evaluation (23.1 percent; P = 0.027).

CONCLUSIONS

Our data suggest that hydrogen peroxide-enhanced ultrasound can be very reliable and useful in the definition of fistula anatomy, its relationship with anal sphincters, and, hence, surgical strategy. It also improves identification of secondary extensions, particularly horseshoe tracks. This method, besides being safe, economic and reputable, both preoperatively and postoperatively, could be helpful in checking operative results and recurrence.

Imaging of anorectal disease

BACKGROUND

Over the past two decades developments in imaging have changed the assessment of patients with anorectal disease.

METHODS

The literature on imaging techniques for anorectal diseases was reviewed over the period 1980-1999.

RESULTS

For the staging of primary rectal tumours, phased array magnetic resonance imaging (MRI) may be regarded as the most appropriate single technique. The combination of endosonography or endoluminal MRI with ultrasonography or spiral computed tomography yields similar results. All techniques have limitations both for local staging and in the assessment of distant metastases. MRI or positron emission tomography is preferable for tumour recurrence. For perianal fistula, high-resolution MRI (phased array or endoluminal) is the technique of choice. For constipation, defaecography is the preferred technique, nowadays with emphasis on functional information. The role of magnetic resonance defaecography is currently being evaluated. For faecal incontinence, endosonography and endoluminal MRI give similar results in detecting sphincter defects; endoluminal MRI has the advantage of detecting external sphincter atrophy.

CONCLUSION

High-resolution MRI, endosonography and defaecography are currently the optimal imaging techniques for anorectal disease.