Three-Dimensional Endoanal Ultrasound in Proctological Practice

Conventional axial endoanal ultrasonography is somewhat limited in its utility to adequately appreciate the longitudinal extent of normal anal structures and that of perianal pathology (1). The linear extent of disease is of considerable importance in perirectal sepsis where it may adequately define the relationship of some complex fistulous tracks to the main sphincter muscle mass. In fecal incontinence, there is some evidence that less than satisfactory functional results following overlapping external anal sphincteroplasty can result from an incomplete repair of the full extent of the external anal sphincter (EAS) muscle defect itself (2,3). Here, there is a fine balance between excessive mobilization of the EAS for adequate repair and devascularization/denervation of the muscle that results in a less-thanoptimal outcome, providing some potential advantages in a preoperative imaging modality that accurately defines the rostral extent of the EAS defect. This view would be reinforced by the available results of techniques that provide high-resolution coronal images of the anal canal [most notably, endoanal magnetic resonance imaging (MRI)] and that appear to correlate anatomically with conventional endoanal ultrasonographic images and with operative findings at sphincteroplasty (4–10). Three-dimensional (3D) endoanal ultrasound represents a novel method of reconstruction from close-stepped axial endosonographic images of the anal canal using computerized software with data interpolation to create 3D images of the anal canal (11). Although not widely available and still somewhat experimental, the potential advantages of this modality will be to define constitutive gender and age differences in the normal anal canal and to validate this technique for clinical preoperative use in decision making of complex and recurrent high transand suprasphincteric fistulain-ano where there tends to be poor coupling of conventional endoanal probes against the puborectalis, and consequently a relative inability with traditional technology in adequate definition of the translevator extent of disease. In theory, 3D endoanal reconstructed images also may assist in