Learning curve of transrectal ultrasound

Transrectal ultrasound is the most accurate means of assessing the degree of invasion for rectal neoplasms. A learning curve for performing and interpreting these studies exists, but it is unknown how long or steep it is. We reviewed our initial results with transrectal ultrasound to determine our accuracy and to define the learning curve.

All patients undergoing transrectal ultrasound during our initial 30 months of experience were included. Each patient was staged with transrectal ultrasound and, after resection, the histopathologic stage was compared with transrectal ultrasound staging. The accuracy of transrectal ultrasound was calculated at intervals as experience was gained.

A total of 42 examinations were performed on 41 neoplasms in 41 patients. Comparison between transrectal ultrasound and the pathologic stage could be made in 36 studies. Overall accuracy of degree of wall invasion was 78 percent. Overstaging occurred with eight neoplasms, and one lesion was understaged. Accuracy of transrectal ultrasound staging improved with time: 58 percent of the initial 12 studies were staged correctly compared with 87.5 percent accuracy in the remaining 24 examinations (P = 0.048).

A definite learning curve was apparent. We conclude that transrectal ultrasound is a relatively simple procedure to learn and, once a moderate degree of experience is gained, should be routinely incorporated into the evaluation of rectal neoplasms.