Diagnostic ultrasound ( PDFDrive )

CHAPTER 8 The Gastrointestinal Tract 305
Fecal Incontinence
Anal endosonography, performed with the addition of a hard
cone attachment to a radial 7.5-MHz probe, allows accurate
assessment of the anal canal, including the internal and external
sphincters. 109 Performed primarily for assessment of fecal
incontinence, this test shows the integrity of the sphincters with
documentation of the degree and size of muscle defects. We do
not use this technique any longer, preferring instead assessment
of the sphincter and perianal sot tissues with a combination of
transvaginal and transperineal scan. 37,110-113
Young women, following traumatic obstetric delivery, are most
oten alicted with fecal incontinence. he internal anal sphincter,
in continuity with the muscularis propria of the rectum above,
is seen as a thick circular hypoechoic or hypoechoic ring just
deep to the convoluted mucosal echoes (Fig. 8.58). he external
anal sphincter, in contrast, is less well deined and more echogenic,
appearing gray on the ultrasound examination, and in continuity
with ibers from the puborectalis sling. Traumatic disruption of
the muscle layers will show as defects in the continuity of the
normal muscle texture, most oten anterior (Fig. 8.59). Posttraumatic
scarring may be associated with a change of shape of
the anal canal from round to oval.
Perianal Inlammatory Disease
Perianal inlammatory disease is seen in two distinct patient
populations: (1) those with Crohn disease who develop perianal
inlammation as part of their disease and (2) those who develop
a perianal abscess or perianal istula as a spontaneous
event. he irst group is described earlier in the section on Crohn
disease. In other patients, perianal infection arises in small,
A
B
C
FIG. 8.58 Normal Rectum and Anal Canal. (A) Transvaginal
approach. Cross-sectional image of rectum taken
with vaginal probe showing the normal, convoluted rectal
mucosa; prominent submucosa (white); and the muscularis
propria as a thin, hypoechoic rim (arrows). The rectum is
usually oval, as shown here. (B) Transperineal approach.
Anal canal shows the thick, well-deined internal anal sphincter
(arrows) as a continuous hypoechoic ring continuous
with the muscularis propria of the rectal wall above. The
external anal sphincter is less well deined and echogenic.
(C) Transperineal approach. Rotation of the probe by 90
degrees from image B shows the anal canal in long axis (arrows,
internal anal sphincter).