© Springer International Publishing Switzerland 2015
Sutchin R. Patel and Stephen Y. Nakada (eds.)Ureteral Stone Management10.1007/978-3-319-08792-4_1010. Ureteral Stents
(1)
Department of Urologic Sciences, University of British Columbia, Level 6 – 2775 Laurel St., Vancouver, BC, V5Z 1M9, Canada
(2)
Department of Urologic Sciences, University of British Columbia, 2660 Oak St., Vancouver, BC, V6H 3C6, Canada
Keywords
UreterStentNephrolithiasisIntroduction
Ureteral stents are a common tool in urology and particularly for the treatment of ureteral stones. Ever since the introduction of the modern stent by Finney in 1978, stent designs have been similar but with various modifications [1]. Most stents are comprised of materials based on plastics such as polyurethane or ethylene vinyl acetate and various patented polymer mixes. Most stents are comprised of two pigtail curls to prevent the stent from migrating out of the renal pelvis and bladder. To date, there has not been any stent design or stent material that has proven to be more comfortable or superior to any other stent.
When to Stent
Stents provide drainage from the kidney to the bladder and keep the ureter open. The main reason to stent in the setting of acute presentation of a ureteral stone is for patients presenting with an obstructing ureteral stone and infection. This has shown to be equivalent in treating sepsis compared to insertion of a nephrostomy tube [2]. One study has identified a quicker time to defervescence in those treated with a nephrostomy tube but overall outcomes were fairly equivalent [2]. When looking at quality of life measures, it was fairly equivalent between the two groups, but stented patients had more voiding symptoms as would be expected [3]. Decompression of the infected system to allow drainage and antibiotic administration is highly recommended in this situation followed by delayed definitive treatment of the ureteral stone.
There is good evidence that ureteral stents are not necessary following successful uncomplicated ureteroscopy where there is complete stone fragmentation, no perforation or infection [4]. However, patients who did have ureteral stents had a slightly lower, albeit non-significant, rate of urologic complications following ureteroscopy [5]. Despite the vast literature supporting not stenting following ureteroscopy, there are still two large groups of surgeons who routinely stent and those who do not stent after uncomplicated ureteroscopy [6]. Stenting after use of a ureteral access sheath does decrease postoperative complications and emergency room visits [7, 8].
Stents can be placed in the acute setting to treat obstructing hydronephrosis and pain. While it is common to place a stent to temporize the patient until shockwave lithotripsy (SWL) can be performed, ureteral stents have been shown to hinder the passage of stone fragments following SWL [9, 10]. Therefore, placement of a ureteral stent prior to SWL does not improve the rate of stone passage nor does it significantly prevent the occurrence of steinstrasse. Stents should only be placed for reasons of infection, acute renal injury, and unrelenting pain. There is no evidence to place a stent prior to SWL to promote stone passage.
Methods of Stenting
The two main methods of inserting a ureteral stent involve placing a ureteral stent over a guidewire—either through a cystoscope or visually placing it using fluoroscopy only. There are slight modifications to these two techniques that will help in various situations. Below are two different techniques for ureteral stenting.
Stenting Through a Cystoscope
1.
Fluoroscopy is typically required to ensure that the stent is placed properly.
2.
Lightly diluted contrast can be placed into the kidney and renal pelvis to highlight that area and identify when the ureteral stent is in the correct position.
3.
A guidewire must be in placed in the kidney and confirmed by fluoroscopy.
4.
Examine the stent for markings to (a) ensure you are inserting the correct end if one end is tapered or if it is a dual durometer stent and one end is meant for the kidney and the other for the bladder and to (b) familiarize yourself with markings of where the distal bladder curl will occur so that you do not push the stent too far into the ureter.
5.
Place the stent over the guidewire and insert it through the working channel of the rigid cystoscope. The stent should be directly visualized through the cystoscope as it inserts over the guidewire into the ureteral orifice. Ensure that you do not insert the distal marker that delineates the bladder curl too far into the ureter. The proximal portion overlying the kidney should be visualized using fluoroscopy and as the stent enters the collecting system, the guidewire can be slowly withdrawn to allow the kidney portion to curl.
6.
The guidewire can then be removed while holding the pusher with the stent in the correct position and the stent is visualized within the cystoscope. A good bladder curl should be ensured with direct visualization.
TIP: To ensure a good renal coil, leave the suture string on during placement (even if you intend to remove it later). Leaving the string on the stent will give you the ability to bring the stent backwards as well as forwards to ensure good positioning. Once the guidewire has been slightly removed as the stent enters the renal collecting system, if a proper renal coil is not seen on fluoroscopy, gently pull on the string of the stent to move it backwards into the proximal ureter. Once the stent is there and has straightened here, use the pusher to push it back into the renal pelvis (without the guidewire being in the proximal curl) and this will allow the curl to coil nicely. To remove the string, ensure you can see the stent in proper position either cystoscopically or fluoroscopically, cut the string loop and pull the string out while holding the pusher to keep the stent in proper position. This should be monitored cystoscopically or fluoroscopically.
Stenting Using Fluoroscopy
1.
Lightly diluted contrast can be placed into the kidney and renal pelvis to highlight that area and identify when the ureteral stent is in the correct position. Be careful not to inject highly concentrated contrast as it makes the proximal curl of the stent difficult to visualize on fluoroscopy.
2.
A guidewire should be in placed in the kidney and its position confirmed by fluoroscopy.
3.
Insert the stent over the guidewire and use the pusher to advance the stent into the patient’s ureter.
4.
Maintain fluoroscopic surveillance of the bladder portion to ensure the stent does not coil up inside the bladder (which also leads to losing your guidewire access). Ensure the pusher end with the radiopaque marker is inserted first and look for this mark on fluoroscopy. A general rule of thumb is that this marker should be at the lower limit of the pubic symphysis for females and at the mid pubic symphysis for males to ensure that the stent is not inserted too far into the ureter. Be careful to adjust your landmarks in females with cystoceles: the limit is then much lower than the bottom portion of the pubic symphysis. These stents can almost be inserted just visually to the urethral meatus and then pushed into the bladder using a rigid cystoscope or Foley catheter given the short female urethra.
5.
Once the stent pusher is inserted to the proper level, fluoroscopy of the kidney should be performed to ensure that the stent is in the renal pelvis. Slightly withdraw the guidewire to allow the renal coil to curl in good position. If it does not coil properly, use the string to wiggle the stent backwards into the proximal ureter and then use the pusher again to push it into the kidney and it should curl nicely. (Remember not to hold the string while you are advancing the stent with the pusher, as these two opposing forces will not result in good stent positioning). If there is concern regarding the status of the proximal ureter (e.g. perforation), then care must be taken if the stent is pulled back into this area. If there is a known perforation, this technique should not be employed and the stent should not be pulled back into this area for fear that it may exit out the perforation.
6.
Direct fluoroscopy over the bladder and observe that the stent pusher marker is in the correct position (mid symphysis for males, bottom of the symphysis for females) and then cut one end of the string (if you are going to remove it) and pull it out while holding the stent in place using the stent pusher. Continuous fluoroscopy should be used here to ensure the stent is not being pushed too far. Be sure to hold the end of the pull-string that contains the knot so that the whole suture can be removed smoothly through the stent hole. Remove the entire guidewire and the stent should curl nicely in the bladder.
7.
If the bladder curl does not coil and is in the urethra, apply gentle suprapubic pressure which will often pull the stent into the bladder. Using the rigid cystoscope or a Foley catheter will also help move the bladder curl end of the stent into the correct position. If that fails, then direct visualization with cystoscopy is necessary to find the stent and push it or grasp it if needed and position the coil inside the bladder. Stents that are left across the bladder neck and sphincter will result in total urinary incontinence and are poorly tolerated requiring repositioning.
Problem: The Stent Is Too Short!
1.
If the kidney coil is in good position, but the distal coil marker is well within the ureter (as seen through a cystoscope) or the stent pusher marker is above the desired location on fluoroscopy, the chosen stent length is too short. This is another reason to leave the string on the stent as it can simply be pulled back over the wire and exchanged for a longer stent. If a string is not present, the entire guidewire and stent can be pulled back as one unit to try and remove the stent. Cystoscopy and a grasper may be necessary to remove the stent. If this is done, remove the stent to the urethral meatus and pass another guidewire through it to preserve ureteral access.
2.
To date, many measurements have been attempted to try and determine a surrogate marker that correlates well with ureteral length. These include height, torso length, CT length of the ureter [11–20]. The results appear to be mixed and the truest measurement is to use a ureteral catheter with graduated markings to directly measure the length of the ureter, although some of the other measurements (particularly CT) seem promising [12].
Problem: The Distal End of the Stent Is Pushed into the Ureter
1.
Radiation Exposure to the Patient and the Urologist
Shock Wave Lithotripsy for the Treatment of Ureteral Stones
Selecting the Appropriate Treatment Modality for Ureteral Calculi
Semirigid Ureteroscopy for Ureteral Calculi
Tips and Tricks in the Treatment of Ureteral Stones
Adjunctive Equipment for Ureteral Stone Management
If the stent is too short or a proper length stent is inserted too far into the ureter and nothing is visible within the bladder, this should be dealt with at the time of surgery rather than delaying repositioning. Such stents may not drain properly and may result in severe bladder symptoms from irritation of the ureterovesical junction. In some cases, it can result in severe hydronephrosis and if there is any ureteral or renal perforation, may lead to a urinoma.
Related posts:
Radiation Exposure to the Patient and the Urologist
Shock Wave Lithotripsy for the Treatment of Ureteral Stones
Selecting the Appropriate Treatment Modality for Ureteral Calculi
Semirigid Ureteroscopy for Ureteral Calculi
Tips and Tricks in the Treatment of Ureteral Stones
Adjunctive Equipment for Ureteral Stone Management
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