Today we would like to introduce a new technology for measuring urethral pressures, three-dimensional high-resolution manometry. Two-dimensional and three-dimensional high-resolution manometry catheters are currently in clinical use in gastroenterology for measuring dynamic esophageal and anorectal pressures. Here we are looking at the 8 French two-dimensional catheter with a response rate of 25 milliseconds and evenly spaced pressure sensors along its length. Here is a schematic of the three-dimensional catheter. Using similar technology in a 12 French catheter with eight small circumferential pressure sensors like you see in the magnified sensor on the left, this catheter provides information about pressure direction as well as force over the 11 centimeter span of the catheter shown here. Now we will show you the display from these high-resolution manometry catheters and the types of pressure measurements we see in the female urethra. This is the pressure display using the three-dimensional high-resolution manometry catheter in a woman with stress incontinence. Right now we are only looking at the two-dimensional part of this high-resolution manometry system. First I will orient you to this display. Pressure is shown in terms of colors. Here is the color spectrum corresponding to pressures in millimeters of mercury. The lowest pressures are shown in blue, going up to the highest pressures, 200 millimeters of mercury in red. Resting urethral pressures are generally in the moderate yellow to green range. In this 2D color pressure display, the y-axis is distance along the catheter, which is about 26 centimeters long, and the x-axis is time. The catheter is in the bladder at the top of the screen, in the urethra in this area, and outside the subject's body in this section of the display. This area here is just artifact from my handling the catheter and can be ignored. During this one-minute section of the study, we see the urethral and bladder pressures at rest during three coughs and during three strain maneuvers. You can see here that the urethral pressures are green, or around 50 millimeters of mercury, and higher than the bladder pressures that are blue, around 5 millimeters of mercury. During a dynamic maneuver like this cough, the pressures increase in both the bladder and the urethra to around 130 millimeters of mercury, and this patient has stress urinary incontinence. Similarly, during the strain maneuver, the bladder and urethral pressures increase. Again, because the urethral pressures are now approximately the same as the bladder pressures, this patient has stress urinary incontinence. Now I would like to show you what the urethral and bladder pressures look like in three dimensions. The catheter is oriented such that the anterior portion of the catheter corresponds with the yellow line here and also is introduced into the urethra such that the catheter is oriented at 12 o'clock or anterior in the urethra. This white line in this pressure profile also signifies anterior or 12 o'clock in the urethra. The 3D sensing portion of this catheter spans from here to here, and in this image, the portion of the catheter is in the bladder, this portion is in the urethra, and this portion is outside the subject's body. If you take this 3D graph, cut it at the anterior white line, and open it up flat, it results in this display, which is a common way to look at 3D images. Think of it as though we cut a paper towel roll at the anterior point here and laid it out flat here. So it shows anterior, left, posterior, right, and back to anterior. And in this image, you also see bladder, urethral, and atmospheric pressures. What I will do now is scroll through a cough and strain maneuver in time to see what happens on these 3D pressure maps. Here we see the urethra at rest. As I scroll over the cough, pressures increase in the bladder and in the urethra. In the urethra, the pressures measured by this device are higher anteriorly, but there appears to be a path in the posterior and lateral urethra where the pressures in the bladder equal the pressures in the urethra, and this patient leaks. As I continue to scroll, she is back at rest, and the urethral pressures are again higher than they are in the bladder. A similar pattern is seen to the cough when I scroll through a strain maneuver with increase and equalization of the pressures between the bladder and the urethra. Now let's look at the 3D pressure measurements after midurethral sling surgery. In the two-dimensional display, you can see that all of the pressures in the urethra remain higher than the pressures in the bladder at rest and during cough, and she remains continent. On the 3D graph, you can see areas of higher pressure anteriorly near the distal urethra and posteriorly at the midurethra, possibly corresponding to the pubic symphysis and the midurethral sling. This patient is now continent. We see the same pattern during the strain maneuver with a high-pressure zone in the posterior urethra, possibly created by the midurethral sling. Using 2D data, we found that the pattern we just saw in the displays was consistent. After midurethral sling surgery, maximum urethral closure pressures at rest remained constant, but maximum urethral closure pressures increased markedly during cough and strain maneuvers. You can see this difference in the 2D pressures, the 3D graphs, and in this bar chart. In 21 post-midurethral sling patients, average resting pressures remained constant at approximately 50 centimeters of water, while average cough and strain pressures increased from about 30 to 90 centimeters of water. We have also started to look at the 3D pressure patterns in an effort to learn more about the physiology of the female urethra using this technology. A preliminary analysis of 44 subjects with no prior continence procedures showed that the most common pressure pattern was the pattern shown on the left, with the highest pressure zones in the anterior distal and posterior proximal urethra. During cough, nearly half of the subjects we studied showed this urethral pressure pattern. During strain maneuvers, the pressure pattern on the right, with the highest pressure zones in the anterior proximal and posterior distal urethra, was almost as common. Further work is ongoing to use this technology to improve our understanding of the continence mechanism of the urethra.

three-dimensional high-resolution manometry

urethral pressures

pressure sensors

stress incontinence

midurethral sling surgery