Evaluation of perianal sepsis: comparison of anal endosonography and magnetic resonance imaging.

The purpose of this study was to compare prospectively the diagnostic yield of anal endosonography (AES) and magnetic resonance imaging (MRI) in the assessment of perianal fistulae and abscesses. There were 39 patients (14 men, 25 women; mean age, 40 years) who underwent AES, performed with a 10-MHz rotating endoanal probe and MRI at 1.0 T (axial and coronal T2-weighted turbo spin-echo (TSE) and turbo-STIR sequences). Fistulae were classified as subcutaneous, intersphincteric, transsphincteric, high (i.e., high extrasphincteric or suprasphincteric), rectovaginal, and horseshoe and were compared with the surgical findings in all patients. Overall, 58 fistulae (subcutaneous, N = 7; intersphincteric, N = 9; transsphincteric, N = 16; high, N = 17; rectovaginal, N = 5; and horseshoe, N = 4) were detected at surgery. MRI showed a sensitivity of 84% and AES of 60% (P <.05). False-positive diagnoses were made in 6 patients (15%) with MRI and in 15 patients (26%) with AES, for a specificity of 68% and 21%, respectively (P <.05). Our findings show that MRI is superior to AES in the assessment of fistula-in-ano before major surgery. AES should be used only for orientation before minor procedures, such as incision or drainage of subcutaneous fistulae.

Transrectal sonography of anal sphincter infiltration in lower rectal carcinoma.

OBJECTIVE: The purpose of the study was to assess the accuracy of transrectal sonography in determining invasion by lower rectal cancer into the anal canal. SUBJECTS AND METHODS: Thirty-eight patients (14 women, 24 men; mean age, 65 years) with lower rectal cancer underwent transrectal sonography before surgery. Both depth of infiltration and tumor invasion into the anal canal were assessed, and results were compared with histopathology of the resected specimens. RESULTS: Infiltration into the anal canal was found histopathologically in 12 (32%) of 38 patients. Transrectal sonography revealed a true-positive diagnosis in 11 of these 12 patients. A false-positive diagnosis of anal canal infiltration was made in two patients for a sensitivity of 91%, a specificity of 85%, and an accuracy of 92%. In the 11 patients diagnosed correctly on transrectal sonography, the depth of tumor infiltration into the anal canal corresponded with histopathology. CONCLUSION: This study shows that transrectal sonography is an accurate method for assessment of anal canal infiltration in lower rectal cancer.

Peritumoral tissue reaction at transrectal US as a possible cause of overstaging in rectal cancer: histopathologic correlation.

PURPOSE: To assess if peritumoral tissue reaction (PTR) can be differentiated from tumor with transrectal ultrasound (TRUS) to avert overstaging. MATERIALS AND METHODS: Preoperative TRUS results in 40 consecutive patients with biopsy-proved rectal cancer were compared with histopathologic reports on the specimens (study 1). To test the hypothesis that areas more anechoic than the tumor were deemed responsible for incorrect staging in study 1, a prospective study was undertaken in another 40 consecutive patients (study 2). The thickest part of PTR was measured, and results were compared with the histopathologic findings. RESULTS: In study 1, 28 (70%) of 40 rectal cancers were staged correctly with TRUS. PTR was responsible for the misinterpretation in six of seven overstaged cases. In study 2, 38 (95%) of 40 cancers were staged correctly, and the presence or absence of PTR was described in 39 cases (98%). A statistically significant positive correlation was noted between histopathologic classification of PTR and its thickness measured with TRUS (P = .0001). CONCLUSION: Because of its more anechoic appearance, PTR may be differentiated from the tumor by means of TRUS. This may lead to a statistically significantly higher accuracy of TRUS in the staging of rectal cancer due to the avoidance of overstaging.