From the Guidelines
The normal adult prostate gland measures approximately 3 cm in length, 4 cm in width, and 2 cm in depth, with an average volume of 20-30 cubic centimeters or grams, as indicated by recent guidelines 1. The prostate typically weighs about 20-25 grams in young adult men. These dimensions can vary based on age, with the prostate gradually enlarging throughout a man's life due to benign prostatic hyperplasia (BPH). By age 60, many men have prostates exceeding 30 grams, with some reaching 50-100 grams or more. This enlargement occurs primarily in the transition zone of the prostate, which surrounds the urethra, explaining why BPH commonly causes urinary symptoms. Some key points to consider when evaluating prostate dimensions include:
- The prostate's size is clinically important for diagnosing conditions like BPH and prostate cancer, with volume measurements typically obtained through transrectal ultrasound, MRI, or estimated during digital rectal examination 1.
- Understanding normal prostate dimensions helps clinicians evaluate prostate health and determine appropriate treatment approaches for prostate-related conditions.
- Recent studies have emphasized the importance of accurate prostate volume measurements, with a threshold of >30cc on imaging being a key factor in determining treatment options for patients with LUTS associated with BPH 1.
From the FDA Drug Label
In A Long-Term Efficacy and Safety Study, prostate volume was assessed yearly by magnetic resonance imaging (MRI) in a subset of patients. In patients treated with finasteride tablets who remained on therapy, prostate volume was reduced compared with both baseline and placebo throughout the 4-year study. Finasteride tablets decreased prostate volume by 17.9% (from 55.9 cc at baseline to 45.8 cc at 4 years) compared with an increase of 14.1% (from 51.3 cc to 58.5 cc) in the placebo group (p<0.001). Mean prostate volume at baseline ranged between 40 to 50 cc. The mean prostate volume as measured by transrectal ultrasound was 36.3 mL (±20.1 mL). Prostate volume was ≤20 mL in 16% of patients, ≥50 mL in 18% of patients and between 21 and 49 mL in 66% of patients
The prostate dimensions are as follows:
- Mean baseline prostate volume: 40-50 cc, with a mean of 55.9 cc in one study and 36.3 mL in another
- Range of prostate volume: ≤20 mL in 16% of patients, ≥50 mL in 18% of patients, and between 21 and 49 mL in 66% of patients 2
From the Research
Prostate Dimensions
- The size of the prostate can be estimated through digital rectal examination (DRE) or transrectal ultrasound (TRUS) [(3,4)].
- Studies have shown that DRE tends to underestimate prostate volume, particularly for larger prostates [(3,4)].
- For example, one study found that DRE-estimated volumes for prostates categorized as small, medium, or large were underestimated in 59%, 58%, and 53% of patients, respectively 3.
- However, DRE has been shown to have a positive predictive value of 94% in identifying prostates above 30 cc 3.
- Prostate volumes can range from small to large, with volumes above 30 cc considered clinically significant [(3,4)].
- The average underestimation of prostate volume by DRE compared to TRUS measurement has been reported to be between 9% and 12% for prostate volumes 30 to 39 mL and between 17% and 27% for prostate volumes 40 to 49 mL 4.