There are multiple indications for the use of ureteral stents (see Table 4.2). The primary purpose for these devices is to allow for the temporary relief of ureteral obstruction due to intrinsic or extrinsic sources of obstruction [5]. Intrinsic causes of obstruction commonly include ureteral stones, blood clots or tumors, ureteral strictures, and ureteropelvic junction (UPJ) obstruction. Extrinsic obstruction can result from malignancy (e.g., gynecologic, pelvic) outside of the ureter, retroperitoneal fibrosis, pelvic radiation, or other causes of external ureter compression [6] (see Fig. 4.2).

Ureteral stents may also be placed to promote healing of the ureter after reconstruction. This includes post-surgery for UPJ obstruction, renal transplantation, ureteroureterostomy, ureteroneocystostomy, cystectomy and urinary diversion, as well as after trauma, such as ureteral perforation during ureteroscopy. Following a cystectomy, ureteric stents can help reduce postoperative complications like extravastation, fistula formation and anastomotic stricture. Figure 4.3 shows ureteric stents coiled in the renal pelvis to prevent them moving out of place and protruding through the ileal conduit.

There are absolute indications for ureteral stent placement. These include relief of obstructing pyelonephritis, bilateral obstructing stones, obstruction of a solitary kidney, ureteric injuries (perforation/transections/avulsions) or after surgical repair of the ureter. Relative indications include the relief of pain from an obstructing stone, hydronephrosis or renal colic during pregnancy , significant ureteral edema after ureteroscopy, and before or after shock wave lithotripsy to aid in stone passage.

The ideal ureteral stent material should quickly improve or restore urinary flow, resist migration, be biocompatible, radiopaque, easy to insert, maintain its strength, be resistant to encrustation and infection, and cause little discomfort or distress to the patient [7]. Despite over 100 years of research into the design and creation of ureteral stents, modern stents that include all of the above criteria have not yet been developed.

Most modern ureteral stents are composed of synthetic proprietary polymeric biomaterial. One of the first synthetic polymers used for the creation of ureteral stents was polyethylene. Polyethylene is flexible and nonreactive in the body; however, long-term exposure to urine causes it to become brittle, which can lead to fragmentation [8]. Silicon stents, which are very biocompatible, were also developed early on, but are difficult to place due to high coefficients of friction and are easily occluded [9].

Manufacturers have produced synthetic compounds of various copolymers with differing strength, surface friction, radiopacity, and biodurability [10]. Table 4.3 summarizes the various stent materials developed and currently in use.

Recent advances in ureteral stent materials also include biodegradable stents. A biodegradable stent would allow for ureteral drainage without the need for secondary procedures to remove the stent. The Temporary Ureteral Drainage Stent (TUDS , Boston Scientific) completely dissolved in 84% of patients after 1 month; however, stent fragments persisted for more than 3 months in three patients requiring surgical removal [11, 12]. Due to the concern about retained fragments, the TUDS is no longer available. Biodegradable stents made of L lactide, glycolide are currently awaiting clinical trials, but appear to completely dissolve after 4 weeks in animal models [13].

Metallic stents were also developed to avoid encrustation, improve urinary flow despite malignant obstruction, and allow for longer dwell times. The Memokath 051 is a titanium-nickel alloy that expands into shape at body temperature. It has a bell shaped tip that helps keep the stent in place and is designed to be placed only at the site of the obstruction with minimal stent material in the bladder or kidney [14]. The resonance metallic stent looks like a standard double J stent, but does not have an inner hollow core. Flow occurs around the coils of the stent [15]. It is made of a corrosion-resistant, MRI-compatible, nickel-cobalt-chromium-molybdenum alloy and demonstrates very high tensile strength [16].

Every major stent manufacturer produces a double-J stent. Double-J stents range in diameter from 4.8 French (Fr) to 10 Fr and in lengths (measured between the start of the pigtails) from 10 centimeter (cm) to 30 cm. Each stent has end-holes and multiple side-holes that allow urine to drain freely from the kidney’s upper collecting system down through and around the stent, and into the bladder.

Multicoil stents allow for a single stent length for all patients (see Fig. 4.4b). Excess stent is coiled in the bladder to minimize irritation to the trigone. Multicoil stents also have similar diameters to standard double-J stents.

Grooved stents were developed to improve extraluminal stent drainage. In most cases, stent drainage occurs intraluminally (through the hollow portion of the stent) and around the stent (see Fig. 4.4c). A small groove made on the outside of the stent was designed to increase extraluminal flow.

Tail stents/Dual durometer stents are used to minimize patient discomfort by removing the coil from the bladder portion of a double-J ureteral stent (see Fig. 4.4d) [18, 19]. The proximal or renal side of a tail stent is configured like a standard double-J stent, though the bladder or distal end tapers into thin 3 Fr closed tip tails [19]. The distal portion of the stent is also occluded in order to decrease urinary reflux up the catheter with voiding. The tails are kept long to aid in easy retrieval if proximal migration occurs and the stents only come in one length [18].

The Polaris™ stent is a combination of a tail stent and dual durometer stents . Dual durometer stents are made of two different materials. Firmer biomaterials are used on the proximal or renal side, while softer biomaterials are at the bladder end. Despite these properties, patients reported only mildly improved stent-related symptoms [18, 20]. Endopyelotomy stents are used for upper tract drainage after incising the ureteropelvic junction (UPJ) (see Fig. 4.4e). These stents taper from a large caliber diameter (usually 10–14 Fr) to a smaller distal (bladder) diameter (7–8 Fr) (see Fig. 4.4f). In order to minimize ureteral tissue ingrowth on the stent during healing after endopyelotomy, no side drainage holes are present on the proximal or renal portion of the stent [4].

Open ended or universal catheters have no coils and are long enough to allow for external drainage (see Fig. 4.4g). These long straight hollow tubes are temporary catheters that can be used to perform retrograde pyelograms, collect urine or specimens from the upper tracts, and aid in the placement of guidewires for endourologic procedures. They are also frequently placed in the ureter prior to complex pelvic surgery in order to aid in the identification of the ureter during surgery and avoid inadvertent ureteral injury. The open-ended type catheter has an opening at the tip of the catheter. The universal or Pollock catheter has a rounded atraumatic tip with a side exit hole. This design allows for atraumatic placement in the upper tract without the need for a guidewire.

Single J ureteral stents have a single pigtail coil on the proximal or renal end, and a long straight segment. These are generally used for external drainage or drainage of the upper tract after urinary diversion surgery.

Stent placement : The standard double-J stent is usually placed during cystoscopic examination of the bladder. General anesthesia is often necessary for placement. After cystoscopic examination of the bladder, the ureteral orifice is identified. A small wire is then advanced into the orifice. Confirmation that the wire is in the appropriate position in the kidney can be accomplished with fluoroscopic or ultrasonic images. Usually an open-ended catheter is then advanced over the wire into the kidney. Contrast dye is gently injected to fill and outline the collecting system. The wire is then replaced back into the upper tract. Using fluoroscopic guidance, the ureteral stent is advanced into the appropriate location and coiled. An adequate coil can be directly visualized in the bladder through the cystoscope.

There are several alternative methods for placing ureteral stents including using only fluoroscopic guidance without direct cystoscopic visualization . This method can be performed over a guidewire or in some cases, assisted with an 8–10 Fr dilator. The 10 Fr portion of the dilator is left in position in the ureter as the stent is advanced through the 10 Fr portion. The technique allows for less buckling of the stent in the bladder as it is being advanced. Since these methods rely on fluoroscopic guidance for correct stent placement, care must be taken to avoid pushing the ureteral stent too far proximally and beyond the ureteral orifice into the distal ureter.

Stent removal : Internal ureteral stents can be removed via two methods. For patients who need a temporary stent (<1 week), a long nylon suture is tied to the distal tip of the stent. This suture—referred to as an “extraction string”—is brought out through the urethra and secured externally with tape to the penis or pubic region. During stent removal, the suture is gently pulled until the entire stent is removed. The stent is often removed in the office by an advanced practice provider (nurse practitioner or physician assistant) or the urologist. In some cases, patients may remove the stent at home. A systematic review of ureteric stents on extraction strings by Oliver and colleagues [21] found that the strings are easy for patients to self-remove and can reduce the stent dwell time for patients, resulting in less morbidity and undue burden. While this technique does not require a cystoscopic examination of the bladder to remove the stent, it should only be performed for stents that will be removed quickly (<1 week), since the external string can be prone to inadvertent stent dislodgement.

In situations where the stent is left “without a string,” a cystoscopy must be performed to retrieve the stent. The stent is seen in the bladder and grasped with an alligator forceps or basket and gently removed. This is most commonly performed in the office with local anesthesia. A magnetically tipped stent was developed to make retrieval easier and to avoid a cystoscopy; however, since 20% of the stents could not successfully be removed without a cystoscopy, the product has been removed from the market [22]. Recent updates in magnetic tip design have shown promising results, and magnetic retrieval of ureteral stents may be available in the future [23, 24].

After stent removal , the patient may experience some transient discomfort or ureteral spasm. This is often mild and controlled with non-steroidal anti-inflammatory drugs (NSAIDs) or narcotics. In most cases, stent-related symptoms will resolve within a day or two after stent removal. Follow-up imaging after stent removal depends on the procedure performed and may include renal bladder ultrasounds, renal scans and cross sectional imaging with magnetic resonance imaging (MRI) or computed tomography (CT) scans.

Stent-related problems are extremely common. More than 85–90% of all patients who have an indwelling ureteral stent will report some complication after placement [25, 26]. Complications include irritative voiding symptoms (frequency, urgency, nocturia, and dysuria), flank pain, suprapubic pain, and hematuria. Joshi et al. [27] developed and validated a Ureteral Stent Symptoms Questionnaire (USSQ) to report stent-related pain, urinary symptoms, sexual dysfunction, and decreased work productivity. This tool has helped standardize knowledge of stent-related complications and allowed for validated assessments of interventions that can improve stent-related issues. The following details stent-related complications :

Stent pain/voiding symptoms : More than 80% of patients report significant stent-related pain affecting daily activities, while 78% will report irritative voiding symptoms [25, 28, 29]. Stent-related flank pain (25%) is likely due to the reflux of urine up the stent during increased intravesical pressures while voiding [30, 31]. As pressure is transmitted up the stent, intrarenal pressures rise, causing pain and discomfort in the flank. This phenomenon is sometimes called the “water hammer .” Pain associated with the stent may also be related to the movement of the stent within the kidney, ureter, and/or bladder [32]. Stent removal can result in flank pain, as well as lower urinary tract symptoms (LUTS), urgency, frequency, and incontinence, due to the irritation of the bladder mucosa [33, 34].

A number of studies have looked at ways to improve stent-related pain and voiding dysfunction, which is also likely due to trigonal irritation [33, 34]. Patients with the distal coil crossing the midline of the bladder report more pain, voiding symptoms, decreased work performance, worsening sexual function, and more analgesia requirements than patients with more appropriately placed stents [35, 36]. Overall, stents that cross the bladder midline, have longer amount of time in-situ, develop urinary tract infections (UTIs), and have all been associated with patient pain and discomfort due to the caliceal position of the upper renal coils [37, 38].

Stent diameter does not appear to influence the severity of stent-related symptoms. A larger sized diameter stent does not appear to cause more symptoms of pain, hematuria, or irritative voiding complaints. A number of studies have compared various stent sizes ranging from 4.8 Fr up to 14 Fr endopyelotomy stents, and have shown that stent-related symptoms do not improve even when smaller diameter stents are used [39–41].

Various studies have also examined the effects of stent materials on urinary scores and discomfort. While many of these studies suggest that stents created from softer materials may be better tolerated, no single stent material appears to have a distinct advantage over other stents in terms of minimizing renal pain and dysuria [7, 20, 42, 43].

Despite appropriately placing and sizing the stent, patients will still experience stent-related urinary symptoms and pain. A number of medications have been studied to reduce overall stent-related symptoms. While NSAIDS and narcotics can help alleviate stent-related pain, voiding symptoms are not improved with these medications [44]. Alpha blockers are the only medications in a number of randomized controlled trials that have been shown to significantly decrease the rates of stent-related pain, LUTS and sexual dysfunction, and improve overall general health scores [45]. Both alfuzosin and tamsulosin have been extensively studied for their positive effects on stent-related discomfort, but any alpha blocker would likely be associated with a decrease in stent-related LUTS and pain [40, 45–48].

Phenazopyridine HCl (a urinary tract analgesic) and anticholinergic medications such as oxybutynin and tolterodine have not definitively shown a trend towards improving pain or LUTS associated with stents. A randomized trial of phenazopyridine versus oxybutynin ER versus a placebo showed no difference in stent-related pain or irritative voiding symptoms between the groups [49]. A second trial comparing alfuzosin and tolterodine showed improved pain and urinary frequency symptoms compared to a placebo [50]. Nocturia and urgency were also significantly improved in the tolterodine group, but overall health, sexual performance, and work performance did not differ between the groups. The combination of terazosin and tolterodine significantly improved irritative symptoms, analgesic use, quality of life (QOL), and flank pain compared to a placebo, while tolterodine monotherapy improved some voiding parameters [51]. A combination of solifenacin and tamsulosin showed some improvement in stent-related symptoms, but these trials lacked randomization and the use of a placebo [52–54, 55]. Overall, the effects of anticholinergic medications on stent-related symptoms are likely small and may only improve stent-related urgency, frequency and nocturia.

Various intravesical treatments have also been used in attempts to improve stent-related discomfort. Intravesical instillation of oxybutynin, alkalized lidocaine, ketorolac or 0.9% normal saline immediately after stent placement has shown no major difference in pain related events after installation [56]. Interestingly, injection of the local anesthetic ropivacaine in the ureteral orifice after stent placement did not improve LUTS or stent-related pain; however, a small dose of onabotulinumtoxinA (BTX) injected in three sites around the ureteral orifice did improve postoperative pain and decreased analgesia use [57, 58]. Symptom reductions were noted immediately after the injection, suggesting that BTX may have some immediate analgesia effects in the bladder and ureter. However, most of these studies suffer from the lack of placebo use and small sample sizes. Further research is needed to see if intravesical therapies are beneficial.

Stent pain and lower urinary tract symptoms (LUTS) are common and often unavoidable. In order to minimize some of these effects, the stent should be sized appropriately so that it does not cross the midline of the bladder and should be placed in the renal pelvis. Small diameter stents, as well as specialty stents (floppy tail, etc.) may only slightly improve some of these symptoms. As previously stated, alpha-blockers do appear to be effective in reducing some symptoms and should be considered if appropriate after stent placement. Anticholinergic medications may improve irritative voiding symptoms, but are not effective in managing stent-related pain. Phenazopyridine and other intravesical or intraureteral agents may also provide some benefit, but the data supporting their use is limited.

Sexual dysfunction associated with an indwelling ureteral stent is also a common, if under-reported or under-recognized, issue found in 32–86% of patients with an indwelling stent [59]. Females are more likely to report sexual dysfunction due to the distress of having a foreign body in the bladder [60]. The International Index of Erectile Function and the Female Sexual Function Index decline significantly following stent placement. Similar to stent-related pain and voiding dysfunction, alfuzosin appears to significantly reduce pain with sexual intercourse and improve overall satisfaction with sexual activity in both men and women [46].

Hematuria or gross hematuria, immediately after stent placement is also common and usually self-limiting, while microscopic hematuria may be present while the stent remains in place. Hematuria may be a sign of a UTI or anticoagulation therapy. Ureteroarterial fistula is an extremely uncommon but severe complication of ureteral stenting. It often presents with intermittent gross hematuria and massive hemorrhage during stent exchange. Predisposing factors for fistula formation include having an indwelling stent for >1 year (even with routine changes), previous pelvic surgery, radiation therapy, and underlying vascular disease [61]. Treatment includes embolization, vascular stenting, or open repair [61, 62].

Stent-related urinary tract infections are reported in 20–30% of patients after stent placement, and will often occur despite the use of prophylactic antibiotics [63–66]. They are difficult to diagnose because of the similarities between symptoms of routine stent discomfort and UTIs [64]. The biggest risk factor for the development of bacteriuria and colonization of the ureteral stent is dwell time, with bacteria rates of <20% in most series at 1 month rising to >40% after 3 months [64, 66–68]. Rates of colonization were much higher than bacteriuria and also increased precipitously with longer dwell times. No colonization was found with dwell times less than two weeks [68]. Thus, it would be prudent to change stents more frequently in patients who are having recurrent UTIs.

Infections and bacterial colonization are caused by the formation of biofilms and encrustation on the stent [69, 70]. These processes provide bacteria with an environment protected from antibiotics [70]. Dwell time, a history of diabetes, female gender, chronic renal failure, and pregnancy were also risk factors for the development of bacteria and colonization [68, 71]. The most frequent organisms associated with stent-related infection include enterococcus, Staphylococcus aureus, pseudomonas, and Escherichia coli [72]. Treatment should be tailored to the individual organism; however, in some cases the stent may be colonized with a completely different organism [63]. If a stent becomes severely encrusted, it can lose flexibility and may be more prone to fracture. Removal or replacement of the stent is necessary if the infection cannot be cleared with antibiotics or if the dwell times are long.

While there are no currently available methods or materials that avoid biofilm formation and encrustation , early stent removal and use of prophylactic antibiotics can help reduce the risk of infections in patients who are at high risk for infection or encrustation. In general, however, antibiotics should not be used prophylactically for all patients [73]. Patients with diabetes, chronic renal failure, and pregnancy should be monitored closely and scheduled for shorter stent dwell times or removal. Overall, the most successful method to reduce stent-related infection is removal of the stent as early as possible.

Stent encrustation is one of the most complicated challenges of ureteral stents. Encrustation occurs as a result of the development of biofilms on a stent’s surface. Biofilms consisting of albumin, Tamm–Horsfall proteins and various other urinary proteins can cover the stent surface almost immediately after stent placement [70, 74, 75]. These films support the aggregation and precipitation of various magnesium or calcium based crystals. Bacteria can also become trapped in the biofilm leading to further crystallization, encrustation, and potentially to symptomatic UTIs that are difficult to treat because of the protective nature of the biofilm [70]. Encrustation can occur on the outside and intraluminal cavity of the stent, leading to stent failure and obstruction.

Longer dwell times are the biggest risk factor for stent encrustation [76]. After six weeks, 9.2% of stents are encrusted, compared to 76.3% of stents at twelve weeks. Other risk factors include a history of urolithiasis, chemotherapy, bacteriuria or infection, and pregnancy [76]. In these patients, stents should be closely monitored and changed frequently. Overall, standard stent material should be removed or replaced every 2–4 months, depending on an individual patient’s tendency towards encrustation.

Managing the “forgotten” severely encrusted stent can be extremely challenging. Often the stone burden on the stent is massive, covering both the proximal and distal curls of the stent as well as, the entire ureteral length. Various methods for removing such stents have been employed, including shock wave lithotripsy, ureteroscopy and combined ureteroscopy, and percutaneous approaches [76–80]. Often multiple procedures are required to remove the entire stent and stone burden. Increased dwell time in the ureter can also lead to stent degradation and brittleness which in turn leads to stent fracturing and increases the complexity and difficulty of extraction. In some rare cases, patients will present with a fractured stent [81].

The best method to prevent stent encrustation and the complex procedure needed to remove a forgotten stent is to simply avoid the complication. This can be achieved by close patient monitoring after stent placement. Some programs employ computerized tracking and retrieval systems that notify the physician when a stent is overdue or needs to be removed [82]. These systems have resulted in significant declines in the percentage of forgotten stents.

Stent failure can be a major complication of an indwelling ureteral stent. Stent failure can occur in the absence of stent encrustation and in patients with intrinsic or extrinsic obstruction [83]. While most cases of intrinsic obstruction can be successfully managed with stent replacement or definitive repair of the underlying problem, extrinsic or malignant obstruction is more commonly associated with stent failure [84, 85]. Patients with malignant causes for obstruction should be closely monitored for worsening hydronephrosis since worsening pain may be related to the underlying disease process and changes in serum creatinine may be misleading if the patient has a normal contralateral kidney. Renal ultrasounds or other cross section imaging to assess for hydronephrosis and periodic routine stent changes can help avoid the risk of permanent renal injury [86, 87]. If a stent fails due to extrinsic malignant obstruction, management options include increasing the diameter of the stent, placing two parallel stents, using metal stents or placing a percutaneous nephrostomy tube [86, 88–90].

Since the introduction of the double-J stent in the early 1970s, stent migration has become an uncommon problem, with a reported incidence of less than 2–8% [91, 92]. Stent migration that occurs distally is easily managed by replacing the stent. Proximal stent migration is less common with an incidence of 1–4%, but more difficult to manage [92]. Risk factors for proximal stent migration include smaller diameter stents (4.8 Fr stents are more likely to migrate or dislodge compared to 6 Fr stents) [41], dwell time, shorter length, inadequate curl or improper stent positioning [91–93].

Proximal stent migration can be managed by ureteroscopic retrieval with either a stone basket, alligator forceps or three-pronged graspers. An alternative retrieval method entails placing ureteral dilating balloons next to the stent or within the lumen of the stent, and slightly inflating the balloon to increase friction and pull the stent down [94–96].