Endosonographic criteria for an internal opening of fistula-in-ano

Endosonography of anal canal diseases

Anal endosonography became a valuable imaging method for diagnosis of anal diseases because of its accessibility, relative simplicity of performance, and low cost. It is used most often to detect anal sphincter defects, to classify anal fistulas and perianal abscesses, and to stage anal tumors. This review presents a normal anatomy of the anal canal, examination technique, and normal endosonographic anatomy of anal sphincters. The endosonographic findings of anal sepsis, malignancy, trauma, abnormalities in Crohn disease, and ulcerative colitis, as well as the role for anal endosonography among other imaging modalities, are discussed.

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.