Clinical, manometric and sonographic assessment of the anal sphincters. A comparative prospective study

One hundred patients with various anorectal disorders but intact anal sphincters were evaluated prospectively by three independent observers to determine the specificity, sensibility and accuracy of digital exploration and anal ultrasound compared to anal manometry, in assessing internal and sphincter hypertonicity (IH) and the relaxation of sphincters on straining (SR). Accuracy of the digital examination in evaluating IH was 80 vs 74%, while the SR was detected by the three observers in 82, 71 and 65% of cases. The thickness of internal sphincter increased with age (r = 0.37, P = 0.01), whereas the resting tone decreased with age (r = 0.27, P = 0.06). There was an inverse correlation between the sonographic thickness of the internal sphincter and the manometric resting tone (r = 0.29, P = 0.004). The internal sphincter thickness was 1.97 +/- 0.41 mm in constipated patients, 2.06 +/- 0.39 in the others (P = 0.03). In conclusion, IH and SR may be assessed by digital exploration with a good accuracy and the thickness of internal sphincter at ultrasound may change according to its functional state.