Post-void Residual Urine Volume Test - Indications, Preparation, Procedure, and Findings

What Is Post-void Residual Urine Volume?

Patients with problems in the urinary bladder or the organs of the other urinary tract are more vulnerable to suffering from urinary retention. It is a condition wherein the urine remains in the bladder or the kidneys for prolonged periods and increases the risk of urinary tract infections. The amount of urine that remains in the bladder after urinating is known as post-void residual urine volume. Usually, urine should not be in the bladder after the patient urinates. However, the problem arises when the urine remains in the bladder. As a result, the doctor recommends a post-void residual urine test to understand the exact cause of urinary retention.

Why Does the Doctor Recommend the Patient Undergo a Post-void Residual Urine Volume Test?

The doctor usually recommends the patient undergo the post-void residual (PVR) urine test to evaluate the symptoms of acute and chronic urinary retention symptoms. Urinary retention might occur due to numerous problems, including:

• Urinary tract obstruction.

• Enlargement of the prostate gland.

• Side effects of certain medications.

• Narrowing of the tube that carries urine outside the body (urethra).

• Neurogenic urinary bladder.

The patients usually experience the following problems if they are unable to empty their urinary bladder:

• Urinary frequency.

• Urinary incontinence or urine leakage.

• Urinary tract infections.

• Stones in the urinary bladder.

• Kidney problems.

How Should the Patient Prepare for the Test?

The patient need not make any specific preparations before the procedure. It is a simple test accomplished through a bladder scan, ultrasound, or measuring the urine drained through the urinary catheter. The patient might be asked to urinate and empty the bladder as much as possible before the procedure. The doctor will conduct the test immediately after the patient urinates to obtain accurate results. Though PVR tests can be done through several methods, ultrasound, and bladder catheterization are the most commonly used.

What Happens in the Ultrasound PVR Test?

The ultrasound PVR test is non-invasive and is not performed under anesthesia. Instead, the patient is asked to lie on the table to conduct the test. For example, the doctor might perform one of the following tests listed below:

• Bladder Scan - An ultrasound technician mainly carries out this procedure. First, the technician applies a gel over the patient's abdomen. Next, the technician moves a probe-like device known as the transducer over the area. A monitor is attached to the ultrasound scan, and the images of the bladder and other urologic organs are obtained on the screen. The doctor can look over these images and calculate the amount of urine in the bladder.

• Vaginal Ultrasound - This procedure is similar to the one mentioned above, the only difference being the gel is applied to the probe. Next, the probe is inserted into the female's vagina. Finally, the images are obtained on the computer screen, and the doctor assesses the amount of urine in the vagina or bladder.

How Does the Bladder Catheterization Procedure Help Measure the Post-void Residual Urine Volume?

Bladder catheterization or urethral catheterization is the gold standard for determining the post-void residual urine volume. Sometimes the test results might vary depending on the size, shape, and type of catheter used. As the anatomy of the male and female genital tract is different, the catheter insertion technique is also different. However, the overall procedure and the technique are similar:

• The patient is laid in an appropriate position.

• The doctor applies a numbing gel or a local anesthetic over the catheter's site.

• The doctor inserts the catheter through the urethra into the urinary bladder.

• The doctor inflates the balloon with sterile water, and saline drains the urine out of the bladder.

• The doctor calculates the amount of urine present.

What Happens After the PVR Test?

PVR is an outpatient procedure, so the patient does not have to stay in the hospital. If the patient has undergone the bladder catheterization procedure, the doctor slowly removes the catheter from the urethra, and can go home. The patient might feel uncomfortable after the procedure because it takes time for the effect of anesthesia to wear off. In such situations, the patient must drink sufficient water daily and urinate frequently. The doctor might recommend antibiotics to prevent urinary tract infections. Patients with the symptoms of urinary retention or high residual volume must consult their doctor and discuss the methods to overcome them. The treatment options mainly include medications, surgery, or catheter use.

What Are Some of the Risks of the PVR Test?

Patients who have undergone ultrasound PVR tests are at the lowest risk because it is a non-invasive procedure. However, the ones who have undergone bladder catheterization might develop urinary tract infections or show the presence of blood in their urine or stools. The doctor might prescribe antibiotics to eliminate the risk of infections. Studies report that patients undergoing bladder catheterization are vulnerable to developing bacterial infections. This is because the average growth rate of bacteria is between 3 to 10 percent per day of catheterization.

What Are the Normal Findings of the PVR Test?

Nothing has been known clearly about the exact PVR values for males and females, but the research suggests that the values mentioned below can be considered normal:

• For Adults:

  • Less Than 50 mL - Adequate bladder emptying.

  • More Than 200 mL - Inadequate bladder emptying.

• For Children:

  • Over 20 mL - Abnormal PVR.

• For Elderly Patients:

  • 50 to 100 mL - Normal PVR.

What Are Some of the Causes of Elevated Post-void Residual Urine Volume?

Some of the underlying causes of elevated post-void residual urine volume are listed below:

• Spinal disorders.

• Traumatic brain injury.

• Neurogenic bladder.

• Vitamin B12 deficiency.

• Alcoholism.

• Multiple sclerosis.

• Parkinson's disease.

• Heavy metal poisoning.

• Prostate cancer.

• Bladder stones.

• Cystocele.

• Paraphimosis.

• Enlargement of the prostate gland.

• Tumors.

• Vesicoureteral reflux.

• UTI (urinary tract infections) in children.

It can also be elevated due to the side effects of the following medications:

• Anticholinergics.

• Antihistamines.

• Tricyclic antidepressants.

• Diazepam.

• NSAIDs (non-steroidal anti-inflammatory drugs).

• Opioids.

• Amphetamines.

Conclusion:

Post void residual urine test is commonly used to measure the residual urine volume. In addition to measuring the volume, it helps the doctor detect the causes of urinary retention and other conditions that might interfere with the urine flow. There are no specific limitations or contraindications of the test, but the patient must understand the procedure carefully before undergoing it. Also, the patient need not worry as the PVR test can be done in a non-invasive manner too, so the risk of trauma or discomfort after the procedure is the least.