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Dx: Ultrasound-Guided Catheter Placement
Easy enough, right? The patient has a large, distended bladder that requires a Foley for decompression. Unfortunately, once you pull down the patient’s diaper to examine his genitals, you realize that the case isn’t going to be as straightforward as you thought. His urethral stricture is covered with a crusting cellulitis and all attempts to pass a catheter are met with resistance, bleeding, and a slew of cursing (mostly from the patient).
You have your intern call the urologist on call, while you head over to the supply closet to gather the equipment you know you will need. As anticipated, your intern tells you that the Urologist wants you to get everything set up for a suprapubic catheter and to page him when you are ready to go. Once he arrives, you use your bargaining power to get the urologist to let your intern do the procedure. You know your team has only one shot to do it right, so you show your intern how she can use bedside ultrasound to guide the catheter placement. Like a pro, she anesthetizes the patient, inserts a needle under direct ultrasound guidance, and then places a suprapubic catheter into the bladder via the Seldinger technique. You beam with pride as you see the catheter on ultrasound entering the bladder lumen (Image 1).
You drain 1500 mL of urine and watch as your patient’s demeanor and vital signs normalize. To your surprise, the urologist thanks you for the consult and for showing him a “neat ultrasound trick” that he plans to use the next time he places a suprapubic catheter. After your senior resident’s run of bad luck with procedures, it was nice to see your intern nail one on the first try.
Tips & Tricks for Performing Bladder Ultrasonography
01 Ultrasound can be used to assess bladder volume prior to performing a suprapubic aspiration or placement of a suprapubic catheter. The formula to estimate bladder volume is (A)(B)(C)/2, where A, B and C are the height, depth and width of the bladder measured with the ultrasound calipers.
02 Bladder scans should be performed with a low frequency curvilinear or phased array transducer. Remember that lower frequency transducers allow you to visualize deeper structures at the expense of resolution.
03 Obtain both longitudinal and transverse views of the bladder, and map out surrounding structures.
04 Use ultrasound to determine how deep the bladder lies below the skin’s surface. Ensure that you have a needle long enough to puncture through the anterior bladder wall.
05 Ultrasound can be used to guide needle insertion during the placement of a suprapubic catheter.
06 Once the needle has been visualized entering the bladder lumen, withdraw a sufficient amount of urine to relieve some of the intraluminal pressure. Leaving a small amount of urine within the bladder can make it easier to pass a suprapubic catheter.
07 In order to avoid creating a false passage, use ultrasound to guide the suprapubic catheter into the bladder lumen. The catheter will appear as a hyperechoic structure within the anechoic bladder lumen.
08 With bedside ultrasound, there is no substitute for experience. The more scans you do, the better you will be able to differentiate abnormal from normal, even when you may not be sure exactly what the abnormality is. An image library of normal and abnormal ultrasounds helps immensely, and you can find out in the ultrasound section of www.epmonthly.com.
09 For more information on how ultrasound can save your day, check out the ultrasound app “SonoSupport”. Available now for smartphones and tablets.
Brady Pregerson (@TheSafetyDoc) manages a free online EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more info visit EMresource.org.
Teresa S. Wu (@TeresaWuMD) is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa EM Program in Phoenix.