Indwelling stents after ureteroscopy
Authors: Colin H Wilson, David A Rix
Journal: BMJ (2007)

In this week's BMJ, Nabi and colleagues1 present a meta-analysis of randomised controlled trials of the insertion of indwelling stents after uncomplicated ureteroscopy. During the past quarter of a century the development and use of endoscopic equipment in urology has increased. Semirigid and flexible instruments have been developed with working channels to allow passage of biopsy forceps, baskets, and laser fibres. Stones in the ureter, and even within the pelvis and peripheral calyces of the kidney, can now be fragmented and extracted. Upper tract transitional cell carcinomas can be diagnosed and, where indicated, treated endoscopically.

There remains controversy, however, about whether indwelling stents should be routinely inserted after these procedures. Balloon dilatation of the ureteric orifice, stone fragmentation and basket retrieval of fragments, biopsy, and destruction of mucosal lesions can all cause trauma to the ureter. In patients without stents this trauma can result in postoperative obstruction of the ureter, which requires emergency upper tract decompression. As an alternative to an indwelling stent, postoperative drainage of the upper tract can temporarily be achieved with a fine bore catheter. This avoids the need for a second procedure to remove the stent, but does require the patient to be admitted overnight at least.

Nabi and colleagues found that people who had stents inserted were significantly more likely to have haematuria (relative risk 2.18, 95% confidence interval 0.72 to 6.61), and lower urinary tract symptoms (dysuria: 2.25, 1.14 to 4.43; frequency and urgency: 2.00, 1.11 to 3.62) than people without stents.2 For the outcome of flank pain, significant heterogeneity between trials precluded pooling of results. No significant difference was seen in stone passage, stricture, formation, readmission rates, or emergency surgery. The review highlights the paucity of well designed trials, the heterogeneity of the procedures performed, and the lack of definition of the label “uncomplicated ureteroscopy.” It also found a lack of evidence for the use of any particular size or composition of ureteric stent with regard to outcome.

Pain from stents is usually related to mechanical bladder irritation and is felt in the suprapubic and genital area. Alternatively, pain may be felt over the kidney itself. In our own meta-analysis3 of the use of stents in recipients of renal transplants, pain was not an important feature of their use. This may be because the transplanted kidney has no connection to the recipient's nervous system, and the ureteric orifice of the transplant is high on the anterior wall, away from the sensitive trigone.4 Interestingly, Nabi and colleagues found no significant difference in flank pain between the groups with and without stents.

Another problem is that stents can be forgotten, which can result in blocked kidneys, intractable infections, or unpleasant urinary symptoms. Fail safe systems must be in place to record the details of patients with stents in situ. In a randomised controlled trial of the use of stents in India, 7% of patients discharged with stents either failed to attend for routine follow-up or their stents were forgotten and they presented late with encrustation and infection.5 In such cases, open stent removal may be needed. At least two cases of nephrectomy have been reported when stents became blocked and could not be separated from the ureter.6

So what should clinicians do in the light of the available evidence? The decision to insert a stent at the end of a ureteroscopic procedure is a balance between the known morbidity of stents and the perceived risk of ureteric obstruction if a stent is not inserted. As Nabi and colleagues point out, the spectrum of ureteric trauma after ureteroscopy is wide. An accepted grading system, based on operative and radiological findings, would greatly improve the ability of clinicians to compare results and techniques, and ultimately to produce validated guidelines for the use of stents. However, such a grading system may prove difficult to define and has hitherto eluded the urological community.

As technology advances, we may be able to reduce the trauma of ureterorenoscopy and potentially reduce the need for stent insertion and its associated morbidity. Further well designed trials in people with stones of various size and anatomical position, assessing retrieval methods with different sizes and materials of stents should help guide future practice.