Endosonography in benign anorectal disease: an overview

Background: Endosonography may be used for diagnosing various anorectal disorders. This review addresses its technique and clinical use in benign anorectal disease. Methods: The English literature available on anal endosonography was reviewed. The different modalities, the endosonography technique itself and its value in benign anorectal disease were described. Results: Anal endosonography is easy to perform, has a short learning curve and causes less discomfort than routine digital examination. Anal sphincters can be clearly visualized and distinction is possible between the internal (hypoechoic) and external (hyperechoic) anal sphincters. Other pelvic floor structures, like the puborectalis muscle, can also be visualized. Endosonography is mostly used in the assessment of faecal incontinence; it has brought new insight into the pathophysiological mechanisms of this disorder and can select patients with traumatic incontinence for sphincter repair. It has replaced electromyographical sphincter mapping, which is a painful and time-consuming procedure. In perianal sepsis, endosonography assists in defining fistula tract anatomy. The use of contrast agents has significantly increased the accuracy of endosonography in the assessment of perianal fistulae. In addition, endosonography is an excellent alternative to expensive MRI. Besides its use in incontinence and perianal sepsis, with anal endosonography surgical possibilities can be evaluated in individual patients, for example, to decide whether a sphincter repair or a lateral sphincterectomy is preferable. Finally, endosonography may occasionally identify internal sphincter myopathy in patients with intractable constipation or proctalgia. Conclusion: Anal endosonography images the internal and external sphincters with high accuracy. It is easy to perform and is especially valuable in the diagnosis of anal incontinence and perianal sepsis.