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Urology/About the prostate size


QUESTION: A 50s patient’s prostate was diagnosed BPH with the size of 5.1 x 6.0 cm by the CT scan and the PSA 2.6.  How many percent larger is it than the normal prostate size and what size of the enlarged prostate may need the surgery? Thank you for your answer.

ANSWER: Randy:

We don't operate on prostates based on size so making any determination about surgery regarding size is pointless.  

The prostate is shaped like an ellipsoid and so to determine the size we need height, width and length.  These are multiplied together and then multiplied by 1.83 to get the overall volume.  Most normal prostates are around 30 cubic centimeters or cc's.  Above 50 is considered a bit big and over 100 is considered very big.  Your prostate is likely to be quite large based on the first two numbers you gave us.

Surgery is considered if the prostate is enlarged and causing symptoms not otherwise treatable with medications.  The size of the prostate may influence the choice of surgery but we never operate based solely on size.

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QUESTION: Thanks for the info. The CT scan only gives 2 numbers but not 3. According to the third number 1.83 rule you provided, the patient prostate volume should be about 56 cc (5.1 x 6 x 1.83) that is a bit big. Is it correct? If so, is there any way to slow or stop the prostate continuous growth or no way to stop it growth once it has becomed larger than the normal size?

ANSWER: Randy:

With only two measurements, you can't calculate the prostate volume accurately.  You must have all three: height, weight and length.  Then you multiply by 1.83.

We don't necessarily use any medication to slow the prostate from growing unless there are symptoms or some other good reason.  Finasteride and dutasteride can be used for this purpose.  You can discuss this with your urologist.

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QUESTION: I am confused by the medical examination method to determine the prostate size. You said, “You must have all three: height, width and length.  Then you multiply by 1.83.” Three numbers may only be obtained by the ultrasound, right? But, in reality we see doctors usually not order the ultrasound but CT or MRI to examine the prostate and therefore only obtain two numbers. So, what medical examination method do urologists rely on to determine the prostate volume and how large the prostate is? Can you explain it? Thank you.


It is not impossible to get the 3 numbers from the CT or MRI and this is often done.  The most reliable way is from transrectal ultrasound.

Usually, prostate size is estimated by a digital rectal exam by a urologist.  Since size alone is not usually a clinical issue for reasons described earlier, we don't concentrate on size unless we are considering surgery where the size can affect the choice of technique.


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Stephen W. Leslie, MD


Questions concerning erectile dysfunction, kidney stones and prostate disorders including prostate cancer. I have a special interest in kidney stone disease prevention.


Full time practicing urologist with 30 years experience. Associate Professor of Surgery and Chief of Urology at Creighton University Medical Center. Editor in Chief of eMedicine Urology internet textbook. Author of only NIH approved book written for patients by a urologist on the subject of kidney stones "The Kidney Stones Handbook". Inventor of the "Parachute" and "Escape" kidney stone baskets and the "Calculus" stone prevention analysis computer program.

American Urological Association, Ohio State Medical Association, Sexual Medicine Society

Men's Health, Journal of Urology, Urology, Healthwatch Magazine, Emergency Medicine Monthly, eMedicine, "The Kidney Stones Handbook", and numerous articles in various newspapers. He is also the editor of the Urology Board Review by McGraw-Hill used by urologists to study for their Board Certification Examinations.

Graduate of New York Medical College with residencies completed at Metropolitan Hospital New York, Albany Medical Center and University of Wisconsin-Madison.

Awards and Honors
Thirlby Award of the American Urological Association. Rated as one the country's Best Urologists by the Independent Consumer's Research Institute

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