Radiology, Vol 187, 367-371, Copyright © 1993 by Radiological Society of North America
Colorectal adenomas: inflammatory changes that simulate malignancy after laser coagulation--evaluation with transrectal US
FJ Hulsmans, LM Mathus-Vliegen, S Bosman, A Bosma and GN Tytgat
Department of Radiology, Academic Medical Centre, Amsterdam, The Netherlands.
To evaluate the assumption that inflammatory changes in the rectal wall
after treatment of colorectal adenoma with photocoagulation may simulate
malignant infiltration, the findings were reviewed in 23 follow-up
examinations performed with transrectal ultrasound (TRUS) in 17 patients
with benign adenoma. Special attention was given to the appearance of the
wall layers underneath the adenoma. After partial coagulation, changes in
the colorectal wall were usually seen on TRUS scans obtained early in
follow-up; sometimes the thickened muscle layer had an irregular outer
margin. In three of the 13 early examinations, lesions mimicked malignancy.
To correlate these findings with histologic proof, an experimental study
was performed: Colorectal specimens from pigs were examined with ultrasound
(US) and microscopy. The abnormal sonographic appearance of specimens on US
scans was caused by an inflammatory reaction in the deep wall layers;
concomitant serositis appeared to be responsible for the
malignancy-mimicking irregular outer margin. In screening for malignancy in
colorectal adenoma, TRUS may cause overstaging during the first 6 weeks
after polypectomy or after a session of laser treatment and should be
avoided.
