Prostatic volume determination by transabdominal ultrasonography: Does accuracy vary significantly with urinary bladder volumes between 50 to 400 mL?

Introduction: In Ghana, trans-abdominal ultrasonography is the main sonographic method of prostatic volume evaluation. The examinations are done when the patient's bladder is full. However, the delay and the discomforting experiences associated with a full bladder have been well documented. In an attempt to investigate other less discomforting options, this study was undertaken to determine if sonographic transabdominal prostatic evaluations performed at urinary bladder volumes of 50-99 mL differ significantly to evaluations done at volumes of 100-199, 200-299 and 300-399 mL.

Methods: A prostatic study of adult patients was undertaken in Accra, from 2014 to 2015. Using an ultrasound machine, 79 sets of prostatic measurements were recorded at a urinary bladder volume of 50-99 mL (V1 as our reference volume), and at least one of three other urinary bladder volumes (V2 = 100-199 mL, V3 = 200-299 mL and V4 = 300-399 mL), in 66 males. Twelve of the participants had multiple sets of prostate volume measurements. SPSS was used to analyse the data. T-test, Bland-Altman plots and linear regression were used to compare and test for the existence of proportional biases in measurements.

Results: There was a statistically significant difference in prostatic volumes recorded at V1 and V2 (P = 0.017). However, the prostatic volume differences recorded for V1/V3, and V1/V4 groups of data were all not statistically significant (P > 0.05). The limits of agreement for the set of measurements spread from approximately -29 to +18 mL for V1/V2, -48 to +36 mL for V1/V3 and -12 to +12 mL for V1/V4 variables. There was no proportional bias in the V1/V2 (P = 0.55) and V1/V4 (P = 0.463) measurements.

Conclusion: Urinary bladder volume of 50-99 mL produces prostatic volume measurements comparable to volumes measured in patients with a full (300-399 mL), or nearly full urinary bladder (200-299 mL). A urinary bladder volume of 50-99 mL may therefore be adequate for scanning the prostate gland, and is likely to be tolerated much better by patients.