Diagnostic Tests for Benign Prostatic Hyperplasia
Laboratory Tests for BPH
Urinalysisexamination of a urine sample under a microscopeis performed in all patients who have lower urinary tract symptoms. Urinalysis is often the only laboratory test needed when symptoms are mild (International Prostate Symptom Score of 1 to 7) and the medical history and physical examination suggest no other abnormalities.
A urine culture (an attempt to grow and identify bacteria in a laboratory dish) is performed when a urinary tract infection is suspected. In the presence of severe or chronic symptoms of BPH, blood tests to detect abnormalities in creatinine, blood urea nitrogen, and hemoglobin are used to rule out the presence of kidney damage or anemia.
A prostate-specific antigen (PSA) test is generally recommended. PSA values alone are not helpful in determining whether symptoms are due to BPH or prostate cancer because both conditions can cause elevated levels. However, knowing a man's PSA level may help predict how rapidly his prostate will increase in size over time and whether problems such as urinary retention are likely to occur.
Special Diagnostic Tests for BPH
Men who experience moderate to severe symptoms (International Prostate Symptom Score of 8 or higher) may benefit from one or more of the following tests:
- pressure-flow urodynamic studies
- imaging studies
- filling cystometry
In this noninvasive test, a man urinates into an electronic device that measures the speed of his urine flow. A slow flow rate suggests an obstruction of the urethra. If the flow rate is high, urethral obstruction is unlikely, and therapy for BPH will not be effective in most instances. A normal urine flow rate is 15 mL per second or higher.
Pressure-flow urodynamic studies
These studies measure bladder pressure during urination by placing a recording device into the bladder and often into the rectum. The difference in pressure between the bladder and the rectum indicates the pressure generated when the bladder muscle contracts.
A high pressure accompanied by a low urine flow rate indicates urethral obstruction. A low pressure with a low urine flow rate signals an abnormality in the bladder itself, such as one related to a neurological disorder.
In general, imaging studies are done only in patients who have blood in their urine, a urinary tract infection, abnormal kidney function, previous urinary tract surgery, or a history of urinary tract stones.
Ultrasonography is the imaging study used most often in men with lower urinary tract symptoms. The test involves pressing a microphone-sized device (transducer) onto the skin of the lower abdomen. As the device is passed over the area, it emits sound waves that reflect off the internal organs. The pattern of the reflected sound waves is used to create an image of each organ.
Ultrasonography can be used to detect structural abnormalities in the kidneys or bladder, determine the amount of residual urine in the bladder, detect the presence of bladder stones, and estimate the size of the prostate.
Less frequently, an imaging study called intravenous pyelography may be performed. This procedure involves injecting a dye into a vein and taking x-rays of the urinary tract. The dye makes urine visible on the x-rays and shows any urinary tract obstructions or stones.
This test involves filling the bladder with fluid and measuring how much pressure builds up and how full the bladder is when the urge to urinate occurs. It is recommended for evaluating bladder function only in men who have a prior history of urological disease or neurological problems that could be affecting bladder function.
In this procedure, a cystoscope (a small lighted viewing device) is passed through the urethra into the bladder to directly view the two structures. Cystoscopy is usually performed just before prostate surgery to guide the surgeon in performing the procedure or to look for abnormalities of the urethra or bladder.