Multichannel urodynamics enhances diagnostic capabilities in the bladder

Howard B. Goldman, MD, FACS

Urology Times® is celebrating its 50th anniversary in 2022. To mark the occasion, we are highlighting 50 of the top innovations and developments that have transformed the field of urology over the past 50 years. In this installment, Howard B. Goldman, MD, FACS, discusses the development of multichannel urodynamics testing. Goldman is a professor of urology and vice chair of the Glickman Urologic Institute at Cleveland Clinic.

Could you provide an overview of the development of multichannel urodynamics?

The whole concept of measuring urine flow and bladder physiology, so to speak, initially started in the 1800s. There were some scientists and physicians who were trying to figure out what was going on in the bladder, using primarily animal models, putting little tubes in the bladder and trying to measure pressures. In around the 1930s, physicians started to look at using bladder pressure measurements in humans, as a way of learning about the physiology of the bladder, but also trying to get an understanding of how voiding occurs and looking for abnormalities in urination.

The term urodynamics was first used in probably around the 1950s. The idea of urodynamics, in general, is testing that describes the function and movement of urine in the lower urinary tract, primarily the bladder, and as it goes through the urethra. Originally, what was utilized was called single-channel cystometry. What that means is there's a single tube put in the bladder and you measure the events going on in the bladder. The challenge with that, and where multichannel urodynamics has made a huge difference, is you really can't figure a lot of things out with just that 1 snapshot of what's going on in the bladder itself through that 1 pressure monitor. For instance, if you see a rise in the bladder pressure on a pressure monitor in the bladder, it could be because the patient is pushing or it could be because the patient is having a bladder spasm. But with just that monitor in the bladder alone, you don't really know.

What was then developed was a second pressure measurement, and that's why they call it multi channel. Single channel is just the bladder. But if you have a second pressure monitor that's measuring abdominal pressure—and this is typically placed either in the rectum or the vagina—you can now differentiate between when someone's just coughing or pushing, or when it's actually a bladder muscle contraction. You can essentially compare the two and subtract one from the other and get what the actual bladder muscle is doing. That's multichannel urodynamics.

But it's gotten to be much more, because another element you then combine that with is measuring someone's urinary flow. So while they're urinating, or if they're having incontinence, you can measure how much urine they're producing. You can relate changes in bladder pressure and you know if it's really the bladder or just pushing or something, to how fast the flow is. Let's say someone has trouble urinating. Is it because the bladder is not squeezing well, or is it squeezing very well, but there's some blockage? By relating bladder pressures to flow, you can get much more understanding. Then you go to the next level—people have actually put in a little EMG monitor, so you can measure what the pelvic floor muscles are doing. The final element, which is often called fluoro urodynamics, or video urodynamics, is where we do fluoroscopy at the same time. By instilling contrast dye in the bladder, instead of just water or saline, you can actually not only see what the bladder is doing, what the flow is, what the muscles are doing, but if you do it under X ray, you can actually see the physical outline of the bladder. Is it going other places it shouldn't when they urinate, how does it flow, are things opening and closing at the right time?

Basic multichannel urodynamics, just to go back to the beginning, is having the 2 separate pressure monitors so you can differentiate between a true bladder contraction vs just the abdominal pressure pushing on the bladder, because the total bladder pressure is a combination of the abdominal pressure and the detrusor muscle pressure. So if you know the total bladder pressure by the catheter that's in the bladder, and you know the abdominal pressure by the catheter that's in, let's say, the rectum and you subtract one from the other, you're left with just the true bladder muscle pressure. That's what multichannel urodynamics is all about. What made it so important is you're able to diagnose things much better; you're able to have a much better understanding of what's actually going on. And then of course, as I mentioned earlier, you now add these other things on—the flow, the EMG, the fluoroscopy. But it all comes down to the multichannel urodynamics. This was first introduced in the 1950s, but there were a lot of technical issues. It wasn't that easy in the office to have different catheters and pressure monitors and all that. So even though it sounded very good, I think a lot of people quickly went back to just doing the single-channel urodynamics, because multichannel was technically difficult to do. As time went on, different companies came out that really were able to integrate all this together, where we just had 1 machine with 2 little tubes. It wasn't like you're working in a laboratory by yourself trying to do this, you could actually get a machine that can do all this. I would say that at least in the developed world, probably the vast majority of all urodynamics done today are of the multichannel variety.