New aspects of 3D anal ultrasonography

3D US examination of the anal canal is a new method which makes it possible to determine the pathology of the external and internal anal sphyncter in minute detail. Combined with anoscopy and 2D anal endosonography it can be applied for establishing the exact extension and depth of the alteration. In case of anal incontinence the 3D reconstruction of the three levels of anal sphyncter adds extra value to the traditional anal sonography owing to the computer analysis of the whole wall structure.

Patients and Methods: 24 patients with complaints of incontinence were examined by 3D US. The normal anatomy of the anal sphyncter is accurately delineated.

Results: The hypoechoic internal anal spyhncter has an average thickness of 24mm; the external anal sphyncter appears sonographically as a mixed echogenic band outside the hypoechoic internal sphyncter with varying thickness. In obstrectic lesions the external sphyncter is always involved and the internal sphyncter may be damaged or show scar tissue. This method is very useful after sphyncteroplasty to show the size of the overlapping. In case of post-traumatic incontinence 3D US shows multifocal lesions which involve both the internal and the external sphyncter over their total length. Other somewhat rare causes of incontinence include: postsurgical trauma, congenital perineal diseases and anorectal infections. Diagnosing these conditions would benefit from the 3DUS exploration of the intersphyncteric space.

Conclusion: 3D US of anal canal is a new and reliable method in differenzial diagnostics, preoperative assessment and the follow up of lesions which ultimately lead to anal incontinence.