Endosonographic elastography of the anal sphincter in patients with fecal incontinence

Objective. In fecal incontinence the role of elastography has not yet been evaluated. We performed a trial to further characterize the internal and external anal sphincter in patients with fecal incontinence and compared a visual assessment scale with a computerized program for quantifying elastic properties of the anal sphincter. Material and methods. Fifty consecutive patients with fecal incontinence were studied (n = 31 following lower anterior resection, n = 8 with Crohn's disease, n = 9 following colon surgery, n = 2 others). Elastogram color distribution within the sphincter representing elastic properties was quantified using a visual analog scale and an off-line computerized area calculation program. Results. The main finding was that the inner anal sphincter (IAS) differed significantly from the external anal sphincter (EAS) with regard to elastogram color distribution. There were no significant correlations with clinical and functional parameters. There was, however, a non-significant increase in the percentage of blue (hard) areas in the IAS in patients neoadjuvantly irradiated for rectal or cervical cancer compared to non-irradiated patients, which was accompanied by a significant decrease in the resting sphincter pressure (p < 0.009). Conclusions. The IAS, a smooth muscle, and the EAS, a striated muscle, have different elastogram color distributions, probably reflecting their different elastic properties. The absence of significant correlations with the major clinical and functional parameters suggests that in routine clinical practice ultrasound real-time elastography may not yield additional information in patients with fecal incontinence. There may be exceptions, particularly in irradiated patients.