Reliability of digital rectal examination (ore) measures to assess prostate size relative to transrectal ultrasonography (trus)

Thomas Rhodes, Scott M. Sech, Juan D. Montoya, Claus Roehrborn, Cynthia J. Girman

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Abstract

Digital rectal examination (DRE) is known to underestimate prostate volume measured by transrectal ultrasonography(TRUS), but the usefulness and reliability of scales to assess prostate size on DRE have not been evaluated. Each of 83 volunteers aged 43-82 (mean 60) yeas were examined using DRE and TRUS by three examiners with varying experience (PGY-2 surgery resident, PGY-4 urology resident, urology attending). Textual scales and visual aids (5-point enlargement scale, overlying prostate shapes of varying size) and 3-D prostate relief models (14 categories) were used to categorize prostate size. Intraclass correlation coefficients (ICC) and kappa statistics were used to quantify reliability. Sensitivity and specificity were calculated for classifying men with prostates larger than 30 and 40 ml. Mean±SD prostate volume by TRUS was 33.8±18.5 (range 9.3 -120.8) ml, and estimated as 32.1±13.0 ml by DRE. Correlations between DRE and TRUS were lower for less experienced examiners, ranging from r=0.61 to 0.73. Good reliability was found across examiners for DRE size estimates (ICC: 0.76), but reliability was even higher for the most experienced, examiner. Assessments aided by 3-D models correlated with TRUS volume (r=0.6 to 0.66). Visual and textual scales showed similar results (r=0.54 to 0.71). DRE consistently underestimated larger TRUS volumes. Higher sensitivity (SE), but lower specificity (SP) for identifying men with TRUS volumes >30 ml was found for the enlargement scale (SE=0.85 to 0.97; SP=0.4 to 0.53), 3-D model (SE=0.78 to 0.97,; SP=0.37 to 0.62), and overlying prostate shapes than for DRE estimated size (SE=0.61 to 0.72; SP=0.81 to 0.86), if underestimation was not accounted for. DRE underestimates TRUS volume. Enlargement scales may be useful in identifying men with TRUS prostate volumes larger than certain levels, and thus aid in therapeutic decision making when treatment success is volume dependent.

Original languageEnglish (US)
Number of pages1
JournalBritish Journal of Urology
Volume80
Issue numberSUPPL. 2
StatePublished - Dec 1 1997

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ASJC Scopus subject areas

  • Urology

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