Which tests for the workup of benign prostatic hyperplasia (BPH) are optional according to the AUA guidelines?

Updated: Feb 19, 2021
  • Author: Levi A Deters, MD; Chief Editor: Edward David Kim, MD, FACS  more...
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Urine flow rate measurement is useful in the initial assessment and to help determine the response to treatment. It may be performed prior to embarking on any active treatments, including medical treatment.

A maximal flow rate (Qmax) is the single best measurement, but a low Qmax does not help differentiate between obstruction and poor bladder contractility. For more detailed analysis, a pressure-flow study (urodynamic testing) is required. A Qmax value of greater than 15 mL/s is considered by many to be normal. A value of less than 7 mL/s is widely accepted as low.

The results of flow rate measurements are somewhat effort- and volume-dependent. Therefore, the best plan to make a reasonable determination of significance is to obtain at least 2 tracings with at least 150 mL of voided volume each time.

Obtain post-void residual (PVR) urine volume in order to gauge the severity of bladder decompensation. PVR can be determined invasively with a catheter or noninvasively with a transabdominal ultrasonic scanner. A high PVR (ie, 350 mL) may indicate bladder dysfunction and/or bladder outlet obstruction and may predict a poor response to treatment.

Although pressure-flow studies are somewhat invasive, requiring catheterization of the urethra and placement of a transrectal pressure transducer, the findings may prove useful for evaluating for bladder outlet obstruction (BOO).

Urodynamic studies are the only way to help distinguish poor bladder contraction ability (detrusor underactivity) from outlet obstruction. BOO is characterized by high intravesical voiding pressures (>60 cm water) accompanied by low urine flow rates (Qmax < 15 mL/s).

Cytologic examination of the urine may be considered in patients with predominantly irritative voiding symptoms. Risk factors for bladder cancer (smoking, previous bladder cancer) should alert the physician to consider this noninvasive test.

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