Normal Prostate Volume and Central Calcifications
Normal Prostate Volume
The normal prostate volume is approximately 20-30 mL (or cc), with volumes >30 mL generally considered enlarged and indicative of benign prostatic hyperplasia (BPH). 1
Volume Thresholds for Clinical Decision-Making
Prostates <30 mL: Considered normal to small; transurethral incision of the prostate (TUIP) is preferred over TURP for obstructive symptoms in this size range 1
Prostates 30-80 mL: Moderate enlargement; most surgical interventions (TURP, laser vaporization, laser enucleation) are appropriate for this range 1
Prostates >80 mL: Significantly enlarged; open prostatectomy, bipolar enucleation, or laser enucleation are preferred approaches 1
Prostates >50-60 cm³: Represent a relative contraindication for brachytherapy due to technical limitations 1
Clinical Context
The prostate volume directly influences treatment selection for BPH, with 5-alpha reductase inhibitors (5-ARIs) requiring a minimum prostate volume of >30 cc or PSA >1.5 ng/mL for reliable therapeutic response 1
Digital rectal examination (DRE) consistently underestimates prostate volume by 9-12% for volumes 30-39 mL and by 17-27% for volumes 40-49 mL, making transrectal ultrasound (TRUS) the preferred method for accurate volume assessment 2
PSA density (PSAD), calculated as PSA value divided by prostate volume, helps distinguish BPH from prostate cancer, with a cutoff of 0.15 ng/mL/cc commonly used 1
Central Calcifications: Clinical Significance
Central (or intraprostatic) calcifications are extremely common benign findings, occurring in approximately 88.6% of prostate specimens, and are predominantly associated with benign prostatic hyperplasia rather than malignancy. 3
Distribution and Characteristics
Location: Calcifications occur most commonly in the transition zone (central prostate), followed by peripheral zone, with 65% versus 35% distribution respectively 4
Density: Mean radiodensity is 227 Hounsfield Units (HU) on CT imaging, with a range of 133-1,966 HU 4
Prevalence: Found in 54% of prostate cancer patients undergoing imaging, though this represents an incidental finding rather than causation 4
Association with Pathology
Benign association: Calcifications occur mostly in benign glands and/or stroma of all prostatic zones, strongly associated with BPH 3
Rare malignant association: Only 4 out of 298 cases (1.3%) showed calcifications directly within prostatic adenocarcinoma tissue—3 cases in tumor glands and 1 case in tumor stroma 3
Ejaculatory system involvement: Calcifications also occur in seminal vesicles (58.1%) and ejaculatory ducts (17.1%), representing a benign degenerative process 3
Clinical Implications for Treatment
Ultrasound therapy limitation: Calcifications create significant barriers to transurethral ultrasound therapy due to acoustic impedance mismatch (1.63 vs 3.20 MRayl) and high attenuation coefficient (0.78 vs 2.64 dB/MHz^1.1/cm), leaving untreated tissue regions behind calcifications 5
Pressure and temperature effects: Calcifications increase peak ultrasound pressure by 100% on average while maximum temperature rises only 9%, with elevated temperatures occurring between the transducer and calcifications 5
Treatment adaptation: Longer sonication durations (20-60 seconds) with selective transducer element positioning can potentially treat tissue behind calcifications, though caution is required when calcifications are near the urethra, bladder neck, or rectal wall 5
Brachytherapy considerations: In 12 patients with calcifications within MRI-visible tumors and 24 patients with calcifications within 9 mm of tumor borders, seed placement and dosimetry may be affected 4
Key Clinical Pitfall
Do not interpret central prostatic calcifications as indicators of malignancy—they are overwhelmingly benign findings related to chronic inflammation, prostatic secretion stasis, or BPH, and should not trigger unnecessary biopsies or aggressive workup in the absence of other concerning features such as elevated PSA, abnormal DRE, or suspicious MRI findings 3, 4