Background: Endosonography may be used for diagnosing various anorectal dis
orders. This review addresses its technique and clinical use in benign anor
ectal disease. Methods: The English literature available on anal endosonogr
aphy was reviewed. The different modalities, the endosonography technique i
tself and its value in benign anorectal disease were described. Results: An
al endosonography is easy to perform, has a short learning curve and causes
less discomfort than routine digital examination. Anal sphincters can be c
learly visualized and distinction is possible between the internal (hypoech
oic) and external (hyperechoic) anal sphincters. Other pelvic floor structu
res, like the puborectalis muscle, can also be visualized. Endosonography i
s mostly used in the assessment of faecal incontinence; it has brought new
insight into the pathophysiological mechanisms of this disorder and can sel
ect patients with traumatic incontinence for sphincter repair. It has repla
ced electromyographical sphincter mapping, which is a painful and time-cons
uming procedure. In perianal sepsis, endosonography assists in defining fis
tula tract anatomy. The use of contrast agents has significantly increased
the accuracy of endosonography in the assessment of perianal fistulae. In a
ddition, endosonography is an excellent alternative to expensive MRI. Besid
es its use in incontinence and perianal sepsis, with anal endosonography su
rgical possibilities can be evaluated in individual patients, for example,
to decide whether a sphincter repair or a lateral sphincterectomy is prefer
able. Finally, endosonography may occasionally identify internal sphincter
myopathy in patients with intractable constipation or proctalgia. Conclusio
n: Anal endosonography images the internal and external sphincters with hig
h accuracy. It is easy to perform and is especially valuable in the diagnos
is of anal incontinence and perianal sepsis.