Today, we will be discussing upper tract imaging techniques as well as ureteral stenting in the urogynecologic patient. I have no disclosures. Our training objectives will include discussion of the equipment required for stent placement, the use of retrograde pyelography and its interpretation, and techniques for ureteral stenting. First, we will discuss the necessary equipment required for ureteral access, retrograde pyelography and ureteral stenting. Open-ended or special open-ended ureteral catheters are designed for intubation of the ureteral orifice and passage into the ureteral lumen. They are typically five French in diameter with an internal lumen capable of accommodating a guide wire. Wires pass through ureteral catheters to allow for upper tract access. This follows the same principle as Seldinger technique. Ureteral access with the wire will allow for further instrumentation of the upper urinary tract. Guide wires themselves are floppy-tipped in nature and relatively atraumatic. The remainder of the wire is firm distal to the tip. Dilute iodinated contrast is the preferred agent for retrograde pyelography. It is considered a safe agent due to its lack of systemic absorption. Fluoroscopy or continuous x-ray imaging allows for real-time visualization during retrograde instrumentation, pyelography, and stent placement. It may be technician or surgeon operated. Appropriate precautions should be taken including the use of lead. As with all radiographic imaging, the principle of valara, as low as reasonably attainable, should be utilized during fluoroscopy. Double-J ureteral stents are commonly used as indwelling ureteral catheters. A proximal curl located in the renal pelvis and a distal curl located in the urinary bladder maintain the stent's position after placement. The stent includes an internal lumen as well as perforating side holes along the length of the stent to allow for maximum drainage and to prevent occlusion. Stents at 5-centimeter intervals are also present along the length of the stent to aid in appropriate placement. Next, we will discuss retrograde imaging of the upper urinary tract. Retrograde imaging obtained through the injection of dilute contrast into the upper urinary tract affords critical information regarding the patient's anatomy. It allows for detection of variant anatomy as well as pathology. It also serves as a roadmap for further instrumentation. To make appropriate use of this information and understanding of the location, size, orientation, and configuration of the renal anatomy is essential. First, we will discuss the relative location in an anatomically normal patient. Typically the left kidney resides higher in the retroperitoneum when compared to the right kidney. Spinal markings can be helpful for determining the relative location of each kidney. In general, the left renal pelvis is approximately at the level of L2. The right renal pelvis typically resides between L2 and L3. Next, it is important to note the relative size of the kidney and collecting system. For most patients, the renal anatomy will span approximately 3 to 3.5 vertebral bodies in length. To determine appropriate orientation, first identify the upper and lower poles of the kidney. By drawing a line between the two poles, the orientation of the kidney can be appreciated. This should run roughly parallel to the psoas muscle. Understanding the configuration of the upper tract is important, particularly if stent placement is required. In most patients, roughly 3 to 5 calyces should be visible on an adequately performed retrograde pylogram. Not all patients will fit the standard appearance of one ureter draining a single renal pelvis. If fewer than 3 calyces are present, consider the possibility of an upper tract duplication. If no upper pole is visible and only a laterally oriented lower pole system is present, this may indicate a duplication. This is classically called the drooping lily sign. In this representation on the right, an arrow indicates a laterally oriented right lower pole that fits this description. In these cases, a second ureteral orifice draining the upper pole system may be present. Next we will cover the techniques of retrograde imaging and ureteral stent placement. First we will discuss appropriate technique for ureteral access. As previously noted, intubation of the ureteral orifice with a wire should precede passage of a ureteral catheter into the distal ureter. Failure to do so may result in perforation of the distal ureter. Appropriate position of the wire within the distal ureter should be confirmed on fluoroscopy before advancement of the ureteral catheter. Here we demonstrate ureteral access from an endoscopic view. The ureteral catheter is maintained at the ureteral orifice until a guide wire is introduced into the distal ureter. Note that as the catheter is advanced over the wire, tick marks are visible along the length of the stent at 1 centimeter intervals. Now using fluoroscopic guidance, the ureteral catheter can be safely advanced over top the guide wire once the wire has been safely positioned in the renal pelvis. Now that ureteral access has been obtained, retrograde pylography can be performed. There are two techniques for performing a retrograde pylogram. First is through distal ureteral access. While maintaining ureteral catheter 2 to 3 centimeters past the ureteral orifice, slow injection of 10 milliliters of dilute contrast can be injected into the upper tract. This may be accomplished with a cone-tip catheter if only diagnostic imaging is required. Second, is called a pull-down retrograde pylogram. Ureteral catheter is positioned at the level of the ureteral pelvic junction. Dilute contrast is slowly injected while the ureteral catheter is withdrawn down to the level of the distal ureter. Here is an external view of a pull-down retrograde pylogram. In this case, the ureteral catheter has already been positioned at the level of ureteral pelvic junction. The catheter is slowly withdrawn through the ureter and dilute contrast is injected into the upper urinary tract throughout the process. Fluoroscopic images are taken during this time to fully define the upper tract. Next, we will discuss ureteral stenting. The objective is to place a ureteral stent in an atraumatic fashion over an existing access wire. The proximal curl should be positioned in the renal pelvis and the distal curl within the urinary bladder. Excessive redundancy within the bladder should be avoided. There are two methods of sizing ureteral stents. First, the measuring markers of a double open-ended ureteral catheter can be used to precisely measure the length of the ureter. A more expedient technique is using the following formula. Height in inches minus 42 equals stent length in centimeters. Standard stent diameter is 6 French. Here we demonstrate the loading of a ureteral stent over a guide wire from an external view. Stents are hydrophilic and notoriously difficult to handle, so using a ray tech may be helpful to maintain grip. After the stent has been fully loaded into the cystoscope, the stent pusher may be loaded over top of the guide wire behind the stent. With the cystoscope positioned at the bladder neck, the stent pusher should be advanced until the metal tip is visible just beyond the beak of the scope. This position should be maintained by the cystoscope operator while the guide wire is withdrawn until the stent is fully deployed. At this point, the stent pusher may be withdrawn. Here we demonstrate this from an endoscopic view. The ureteral stent is again shown as it is passed over the guide wire. Once it is fully loaded into the cystoscope, it may be further advanced with the assistance of the stent pusher. Tick marks on ureteral stents are visible at 5 centimeter intervals along the length of the stent. One mark indicates 5 centimeters, two indicates 10 centimeters, and so on. Once the stent has been fully advanced, the stent pusher tip will be visible just distal to the beak of the scope. The scope that should then be positioned at the bladder neck as the assistant withdraws the guide wire. Outlined are important aspects of appropriate technique during stent placement. During passage of a ureteral stent, the length marking should always be visible to the operator to avoid accidental passage of the entire stent into the distal ureter. Minor tension should be placed on the guide wire by the assistant to allow for easy passage of the stent. Additionally, fluoroscopic confirmation of the proximal curl in the renal pelvis should be obtained during withdrawal of the guide wire. The distal tip of the stent should be positioned at the bladder neck as the wire is fully withdrawn to ensure the stent fully deploys within the bladder. In conclusion, we believe an understanding of normal retrograde imaging in ureteral stenting is essential for all pelvic floor surgeons. Appropriate use of these techniques affords surgeons the ability to troubleshoot during operative cases and allows for timely intervention when warranted.

upper tract imaging techniques

ureteral stenting

urogynecologic patients

retrograde pyelography

renal anatomy