A systematic review of the accuracy of the digital rectal examination as a method of measuring prostate gland volume

Objective: There are many important clinical scenarios in which estimates of the volume of the prostate gland can have an influence on clinical decisions. The digital rectal examination is the simplest and most readily available method for measuring it. It is commonly performed numerous times every day by practising urologists and radiation oncologists. The prostate gland volume is the most studied parameter arising from it. Although reported in many heterogeneous studies, the accuracy of the digital rectal examination in measuring the volume has never been reviewed. Our aim was to conduct the world’s first systematic review. Methods: Articles from the literature were included if they compared the digital rectal examination with more accurate measures including fluid displacement after radical prostatectomy and transrectal ultrasound measurements. Results: Nineteen articles describing 7891 patients were reviewed and summarised. Wide variations were noted but most studies provided correlation coefficients that lay between 0.3 and 0.7. For those studies that did not involve special training in volume estimation or were not conducted by a urologist with a special interest in the correlation, the coefficients were below 0.6. For eight studies that analysed the estimated volume as a categorical variable, concordance was described using a variety of statistical tests but was generally high. Conclusions: The reported correlations were weak to moderate strength indicating that the digital rectal examination may not be accurate enough when quantitative measurements are required. However, enlargement of the prostate was detectable with high levels of concordance, indicating that the digital rectal examination is effective for that purpose. Level of evidence: Not applicable for this multicentre audit.