This is a specialized test in urology which measures the urinary bladder pressure.
Why is this study done?
To answer this question, we need to understand how we urinate. Normal urination requires two conditions. One is adequate contractions of urinary bladder to expel urine. The second condition is unobstructed passage to the flow of urine. Both together are needed for normal urination. Even if one of them is impaired, the individual will experience problems in voiding. These symptoms are poor urine flow, difficulty in initiating urination, interrupted urine flow, straining to void, increased urinary frequency, sense of incomplete evacuation of urine, urgency , leakage of urine etc. When a patient comes to the doctor with these complaints, the urologist tries to decide whether these complaints relate to problem in the bladder or in the passage. Most of the times, based on history and physical examination, a diagnosis is easily made. In some situations, the diagnosis is made by carrying out tests like ultrasound abdomen and special x-ray studies. However in more complicated conditions it is very difficult to come to a conclusion. In such conditions UDS is done.
What is this test and how is it done?
This test measures the pressure generated in the urinary bladder and by using various nomograms it gives a relation between the pressure and the flow. The urologist then interprets these nomograms to know whether there is obstruction or weak bladder. This test also gives other information like the capacity of the bladder and the stretchability or compliance of the bladder. It also informs whether the bladder is hyper-excitable which leads to urgency and leakage of urine.
The test is done on an outpatient basis and doesn’t need anesthesia. A catheter is inserted in the bladder and another one in the rectum. Saline is infused through the bladder catheter and bladder pressure measurements are taken. At the end of the test, the patient is asked to pass urine in a measuring jar to test the force and quantity of urine. The entire process takes about 30 minutes and is painless. The report is given at the end of the study.
How is UDS useful?
It helps in making crucial decisions on the cause of urinary symptoms. It informs whether surgery is needed or not. It also provides information about treatment outcomes. For example, surgery for prostate enlargement may not result in expected outcomes if the bladder is damaged for some reason. This can be discussed with the patient beforehand so that one can have realistic expectations from surgery. In some cases surgery may not be useful at all. This too can be discussed with the patient and he is advised alternate treatment.