Diagnostic ultrasound ( PDFDrive )

302 PART II Abdominal and Pelvic Sonography
A
B
C
D
FIG. 8.54 Rectal Tumors Seen at Transrectal Sonography. (A) Rectal carcinoma: T1. Hypoechoic mass between 6 o’clock and 8 o’clock
is noted. The submucosa (the echogenic line) and the muscularis propria (the external hypoechoic line) are intact. (B) Rectal carcinoma: T2. Tumor
is seen anteriorly. The muscularis propria (arrows) is the hypoechoic line that is thickened and nodular, consistent with tumor involvement.
(C) Rectal carcinoma: T3. A large tumor involves the entire right lateral wall of the rectum. Invasion of the perirectal fat (arrows) is noted in several
locations. A large node is seen at the 6 o’clock position; smaller nodes are seen at 5 o’clock and 8 o’clock. (D) Metastatic prostate carcinoma
to rectal wall. Hypoechoic mass is seen between 10 o’clock and 1 o’clock. It involves the deep layers of the rectal wall and not the rectal mucosa.
There is a small lymph node (arrow). (With permission from Berton F, Gola G, Wilson S. Perspective on the role of transrectal and transvaginal
sonography of tumors of the rectum and anal canal. AJR Am J Roentgenol. 2008;190[6]:1495-1504. 106 )
Recurrent rectal cancer ater local resection is usually
extraluminal, involving the resection margin secondarily. Serial
transrectal sonography may be used in conjunction with serum
carcinoembryonic antigen levels to detect these recurrences. A
pericolic hypoechoic mass or local thickening of the rectal wall,
in either deep or supericial layers, is taken as evidence of recurrence.
Previous radiation treatment may produce a difuse
thickening of the entire rectal wall, usually of moderate or high
echogenicity, with an appearance that is usually easily diferentiated
from the focal hypoechoic appearance of recurrent cancer.
Sonographic-guided biopsy of a detected abnormality facilitates
histologic diferentiation of recurrence from postoperative,
inlammatory, or postradiation change.
Prostatic carcinoma may invade the rectum directly, or more
remote tumors may involve the rectum, usually as a result of
seeding to the posterior peritoneal pouch. Because these tumors
initially involve the deeper layers of the rectal wall, with mucosal
involvement occurring as the disease progresses, their sonographic
appearance is distinct from that of primary rectal carcinoma
(see Fig. 8.54D).
Benign mesenchymal tumors, especially of smooth muscle
origin, are uncommon in the rectum. When seen, their sonographic
features are the same as elsewhere (Fig. 8.56). Mucous
retention cysts, resulting from obstruction of mucous glands,
produce cystic masses of varying size that are located deep in
the rectal wall.
Anal Canal
Cancer of the anal canal is a very rare tumor that is well shown
on anal sonography (Fig. 8.57).