Voiding Mechanics

•Bladder   •Spinal Cord   •Brain

Before we can appreciate the dysfunction of OAB, let’s review the steps of normal micturition.

First, the bladder receives urine from the ureters.

Then, the bladder fills slowly at low pressures.

Next, once the bladder’s detrusor muscle reaches a threshold of distention (normally between 300-400 ml) sensory nerve endings in the bladder send the fullness sensation and the need to urinate to the spinal cord via the pelvic nerve.

Then, this same fullness message is sent via other nerves to the brain, where the brain sends messages back down spinal cord and out the peripheral nerves to start voiding--at an appropriate time and place.

These steps are referred to as the micturition reflex where the external sphincter relaxes, the pressure in the detrusor rises while the pressure in the urethra  falls, the bladder neck opens and urine flows.

 

•History   •Physical   •Labs and Post Void Residual (PVR)   •Voiding Diary

During the past 4 weeks, how bothered were you by: Not at all A little bit Some-what Quite a bit A great deal A very great deal 1. Frequent urination during daytime hours? 0 1 2 3 4 5 2. An uncomfortable urge to urinate? 0 1 2 3 4 5 3. A sudden urge to urinate with little or no warning? 0 1 2 3 4 5 4. Accidental loss of small amounts of urine? 0 1 2 3 4 5 5. Night-time urination? 0 1 2 3 4 5 6. Waking up at night because you had to urinate? 0 1 2 3 4 5 7. An uncontrollable urge to urinate? 0 1 2 3 4 5 8. Urine loss associated with a strong desire to urinate? 0 1 2 3 4 5 Are you a male? If male, add 2 points to your score

To help people with this underreported problem, clinicians need to know when their clients have this problem. As clinicians we should start by asking our patients about their experience with the symptoms of OAB and/or incontinence. One way to do this is by having them complete the OAB-V8 Overactive Bladder-Validated 8-Question Awareness Tool developed by Coyne. A score of 8 or greater may indicate OAB. A review of past and current medical/surgical conditions and medications is required to identify if these contribute to the symptoms experienced. Physical exam should include an assessment of the belly, which may reveal bladder distention; a pelvic and rectal exam for women to identify weak sphincter or pelvic floor muscles, assess the condition of the vaginal tissues and to check for fecal impaction. Men should have a rectal exam to identify an enlarged prostate and fecal impaction. They should also have a neurological exam to test reflexes, tests for muscle strength and sensation should also be performed to rule out other neurological causes of the OAB symptoms. A urine sample should be obtained and analyzed for red and white blood cells, for protein and glucose. Blood work should include glucose and calcium. Elevated levels can contribute to polyuria which may cause symptoms of OAB--which can be reversed with treatment strategies for these lab results. A post void residual (PVR) test may be performed, either by ultrasound or catheterization to see if the bladder is emptying completely. A normal post void residual is 50-60ml. Two hundred milliliters of urine in the bladder after voiding on at least two separate occasions indicates a problem and these clients should be referred to an urologist. People with OAB usually do NOT have high PVR’s. A bladder diary is an important part of the assessment process and engages the patient in problem identification and possible solutions. The diary should be kept for a minimum of three days. The days do not need to be consecutive, and should be sure to include at least one day that falls on a weekend and on a “typical” working day as appropriate. Fluid intake (amount and type), voiding (times and amounts, symptoms preceding), and any leakage problems are tracked to facilitate a correct diagnosis.

 Rick Fields-Gardner