Comparison of transanal and external perineal ultrasonography

Anal endosonography with rotating endoprobes provides state-of-the-art imag ing of sphincter integrity: however, the technique is not widely available and requires expensive equipment. Since pelvic anatomy permits the use of s tandard external ultrasound probes, we tested the feasibility, tolerance an d reproducibility of uniplanar perineal sonography. with respect to visuali sation of the anal sphincter, using both convex and linear 3.5- to 7.5MHz a nd 360 degrees rotating 7-MHz probes. Twenty healthy nulliparus female volu nteers were investigated. Two operators performed endosonography and perine al sonography in duplicate, each blinded to the findings of the other. We t hen used this technique to examine 20 postpartum primiparus patients. The e xamination was well tolerated by all subjects. The internal anal sphincter appeared in perineal sonography as a hypoechogenic ring surrounded by an ec hogenic ring representing the external anal sphincter. Endosonography revea led six sphincter tears, four external and internal sphincter tears, one is olated external tear and one isolated internal tear. Perineal sonography re cognised in all cases external sphincter tears. In one case the internal sp hincter defect was missed. Perineal sonography appears to be a feasible alt ernative to anal endosonography in female patients and provides good inform ation on external sphincter defects suggesting that this procedure might be particularly useful in incontinence screening. Perineal sonography gives a good image of internal sphincter. The lack of an isolated internal defect cannot be considered as relevant to our study.