[Prostatic volume: suprapubic versus transrectal ultrasonography in the control of benign prostatic hyperplasia]

During the follow-up of benign prostatic hypertrophy, the urologist needs the repeated evaluation of the gland size to monitor the effectiveness of drug treatment. We investigated the comparative adequacy of transabdominal and transrectal US for prostatic measurements, to possibly replace the gold standard transrectal examination with cheaper, easier and less invasive transabdominal studies.

February, 1994, to May, 1996, we submitted 196 patients to prostate US, with a transabdominal convex probe and a transrectal biplanar probe. The three prostatic diameters were measured and prostatic volume and height calculated.

The transverse diameter was the same (+/- 5%) in 31.6% of cases, but transabdominal US overestimated it in 41.8% and underestimated it in 26.5% of cases. The AP diameter was the same in 33.1% of cases, but trans-abdominal US overestimated it in 15.3% and underestimated it in 51.5% of cases. The cranio-caudal diameter was the same in 25.5% of cases, but transabdominal US overestimated it in 59.1% and underestimated it in 15.3% of cases. Consequently, the volume calculated with transabdominal US was the same (+/- 15%) in 27.5% of cases, overestimated in 45.9% and under-estimated in 26.5% of cases; prostatic weight rates were about the same.

Prostatic volume and weight measured with transabdominal US are overestimated in about 50% of cases and are the same (+/- 15%) in about 27% of cases only. Therefore, transabdominal US appears less reliable than transrectal US for prostatic measurements and the latter technique remains the gold standard to monitor drug treatment effectiveness in benign prostatic hypertrophy follow-up.