Diagnosis of Benign Prostatic Hyperplasia (BPH), Enlarged Prostate

A physical examination, patient history, evaluation of symptoms, laboratory tests, and other tests provide the basis for a diagnosis of benign prostatic hyperplasia (BPH). The physical examination includes a digital rectal examination (DRE), and symptom evaluation is obtained from the results of the AUA Symptom Index.

Digital Rectal Examination (DRE)

DRE typically takes less than a minute to perform. In this procedure, the physician inserts a lubricated, gloved finger into the patient's rectum to feel the surface of the prostate gland through the rectal wall to assess the size, shape, and consistency of the gland. Healthy prostate tissue is soft, like the fleshy tissue of the hand where the thumb joins the palm. Malignant tissue is firm, hard, and often asymmetrical or stony, like the bridge of the nose. If the examination reveals the presence of unhealthy tissue, additional tests are performed to determine the nature of the abnormality.

AUA Symptom Index

The AUA (American Urological Association) Prostate Symptom Index is a questionnaire designed to evaluate urinary problems in men and to help diagnose BPH. In this questionnaire, the patient answers seven questions related to common symptoms of benign prostatic hyperplasia. The frequency of each symptom is then rated on a scale of 1 to 5. These numbers added together provide a score that is used to evaluate the condition. An AUA score of 0 to 7 indicates a mild condition; 8 to 19 indicates a moderate condition; and 20 to 35 indicates a severe urinary problem.

PSA and PAP Tests

Blood tests may be used to check the levels of prostate specific antigen (PSA) and prostatic acid phosphatase (PAP) in a patient who may have benign prostatic hyperplasia. These tests can help the physician rule out prostate cancer.

Prostate-specific antigen (PSA) is a specific antigen produced by the cells of the prostate capsule (membrane covering the prostate) and periurethral glands. Patients with benign prostatic hyperplasia (BPH) or prostatitis produce larger amounts of PSA. The PSA level also is determined in part by the size and weight of the prostate.

The test measures the amount of PSA in the blood in nanograms per milliliter (ng/mL). A PSA of 4 ng/mL or lower is normal; 4–10 ng/mL is slightly elevated; 10–20 is moderately elevated; and 20–35 is highly elevated. Most men with slightly elevated PSA levels do not have prostate cancer, and many men with prostate cancer have normal PSA levels. A highly elevated level may indicate the presence of cancer.

However, the PSA test can produce false results. A false positive result occurs when the PSA level is elevated and there is no cancer. A false negative result occurs when the PSA level is normal and prostate cancer is present. Because of this, a biopsy usually is performed to confirm or rule out cancer when the PSA level is high.

PSA in the blood may be bound molecularly to one of several proteins or may exist in a free, or unbound, state. Total PSA (also known as PSA II) is the sum of the levels of both forms and free PSA measures the level of unbound PSA only. Studies suggest that malignant prostate cells produce more bound PSA; therefore, a low level of free PSA in relation to total PSA might indicate prostate cancer, and a high level of free PSA compared to total PSA might indicate a normal prostate, BPH, or prostatitis.

Evidence suggests that PSA levels increase with age (called age-specific PSA). A PSA of up to 2.5 ng/mL for men age 40–49 is considered normal, as is 3.5 ng/mL for men age 50–59, 4.5 ng/mL for men age 60–69, and 6.5 ng/mL for men 70 and older. The use of age-specific PSA levels is not endorsed by all medical professionals.

Urodynamic Testing

Urodynamic tests are used to measure the volume and pressure of urine in the bladder and to evaluate the flow of urine. These tests, which usually are performed in a physician's office, are particularly useful for diagnosing intrinsic sphincter deficiency and uncertain cases of mixed, overflow, urgency, or total incontinence. Additional tests may be conducted if symptoms indicate that blockage is caused by a condition other than BPH.

Uroflowmetry is a simple test performed to record urine flow, to determine how quickly and completely the bladder can be emptied, and to evaluate obstruction. With a full bladder, the patient urinates into a device that measures the amount of urine, the time it takes for urination, and the rate of urine flow. Patients with stress or urge incontinence usually have a normal or increased urinary flow rate, unless there is an obstruction in the urinary tract. A reduced flow rate may indicate BPH.

A pressure flow study measures pressure in the bladder during urination and is designed to detect a blockage of flow. It is the most accurate way to evaluate urinary blockage. This test requires the insertion of a catheter through the urethra in the penis and into the bladder. The procedure is uncomfortable and rarely may cause urinary tract infection UTI).

Post-void residual (PVR) test measures the amount of urine that remains in the bladder after urination. The patient is asked to urinate immediately prior to the test and the residual urine is determined by ultrasound or catheterization. PRV less than 50 mL generally indicates adequate bladder emptying and measurements of 100 to 200 mL or higher often indicate blockage. Nervousness and other types of stress may affect the result; therefore, the test is often repeated.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 09 Jun 1998

Last Modified: 31 Aug 2015