Three-dimensional anal endosonography may improve staging of anal cancer compared with two-dimensional endosonography.
OBJECTIVE
Three-dimensional (3-D) endosonography is a new method of staging anal carcinoma that has not yet been validated in comparison with two-dimensional (2-D) endosonography, the latter using only a single scan plane. The aim of this study was to investigate the differences between the two endosonographic techniques.


METHODS
Thirty patients with an endosonographically detectable anal tumor were examined with a 10 MHz rotating endoprobe. Cross-sectional images of the anal sphincters were stored on a 3-D system during retraction of the endoprobe through the anal canal. Afterwards, any projection could be reconstructed. Cross-sectional images (2-D) were compared with reconstructed projections (3-D) according to five parameters concerning tumor spread and presence of regional lymph nodes. In this study, a scale of 0 to 5 points on critical issues was used; ideally, the results should be identical in 2-D and 3-D endosonography.


RESULTS
The 3-D method detected a median of 5 diagnostic findings, compared with a median of 4 findings with the 2-D method ( P = 0.001). In eight patients the lateral tumor margin was visualized only by 3-D endosonography. The median number of lymph nodes visualized in 3-D was 1 (range, 0-13), in 2-D the median number was 0 (range, 0-6), P = 0.002.


CONCLUSIONS
Use of 3-D endosonography in patients with anal carcinoma improves detection of perirectal lymph nodes and may improve that of tumor invasion, compared with 2-D endosonography. This may affect local tumor staging and thus planning of treatment. A study with histopathologic correlation is needed to verify this endosonographic study.
Department of Radiology, Section of Ultrasound X4123, Rigshospitalet, Copenhagen, Denmark. rh11801@rh.dk
Anders F
AF
Christensen
Michael B
MB
Nielsen
Svend A
SA
Engelholm
Henrik
H
Roed
Lars B
LB
Svendsen
Hanne
H
Christensen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000000981:diagnostic imaging; D001005:Anus Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D002277:Carcinoma / Q000000981:diagnostic imaging* / Q000473:pathology*; D019160:Endosonography / Q000379:methods*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods; D017063:Outcome Assessment, Health Care