How long is too long? “I forgot that I had a ureteral stent”

Many people have ureteral stents placed to prevent or treat urinary tract obstruction, and if you happen to be one of these people, it’s likely that you’re familiar with some of the symptoms of having a stent.  However, it can be easy to forget that you have a stent in place, particularly if you’re experiencing minimal discomfort from your stent.  Generally, it is recommended that stents be removed or exchanged before every 3-4 months.  But what happens if you have it in place longer than this or if your stent is forgotten?

Abdominal xray of a patient with a forgotten stent that had been in place for three years.

One of the most common things that may happen to ureteral stents is encrustation, in which calcifications form around the placed stent.  This phenomenon occurs to a minor degree in many patients and is usually of little consequence.  It is most extensive when the stent is left in place for too long, and urinary tract obstruction and infection may occur as a result of encrustation.  The amount of stent encrustation is directly related to how long a ureteral stent has remained in place.  One study found that 9.2% of stents became encrusted when in place for less than 6 weeks, while 47.5% of stents that remained in place for 6 to 12 weeks were encrusted and 76.3% of stents were encrusted after 12 weeks (El-Faqih et al, 1991).  The length of time a stent remains in place is in fact the greatest risk factor for stent encrustation.  Other risk factors include the composition of the stent used, a history of stone formation, urinary infections, alkaline urine, and pregnancy.  Because of the physiologic changes accompanying pregnancy that predispose these patients to more profound indwelling ureteral stent encrustation, it is recommended that stents are removed or exchanged every 6-8 weeks in pregnant women (Kavoussi et al, 1992).

Xray illustration of retained left ureteral stent. Stent highlighted red. Surrounding stone highlighted blue.

Proximal stent migration and fragmentation are two other complications of indwelling ureteral stents.  The hardening and degradation of stent polymers may lead to fragmentation, particularly if the stent is left in place for longer than 6 months (Monga et al, 1995).  Uncommonly, a stent may perforate the ureter or erode through the ureter and form an abnormal connection between the ureter and adjacent structures.  The occurrence of these complications is associated with an increased amount of time that the stent is in place.

If a retained ureteral stent is suspected, your doctor will likely obtain imaging of your urinary tract to determine stent location, the extent of encrustation and to help quantify stone burden, a prognostic indicator that helps to determine correct surgical management.  Because the composition of the encrustation is typically calcium-based, most can be seen on a plain film x-ray of the kidneys, ureters, and bladder.  CT scans or ultrasonography are other useful imaging modalities, particularly if the stones are composed of uric acid and cannot be seen on an x-ray.  Radionucleotide studies may be necessary if the stone burden is high to assess kidney function.  Depending on the extent of encrustation, the stent may be removed in a retrograde fashion by cystoscopy with or without extracorporeal shock wave lithotripsy (ESWL).  If more extensive encrustation is present, transurethral cystolitholapaxy, retrograde ureteroscopy and laser lithotripsy, or antegrade nephroscopy and ureteroscopy may be preformed.  In some cases, multiple sessions are required to completely remove the stent and stones.  Antibiotics may be given if an infection is present.

Recognizing the temporary nature of an indwelling ureteral stent and the need for timely follow-up with your urologist is the best way to prevent the complications associated with stent retention.  The management of retained ureteral stents is associated with a 6.9-fold increase in financial burden compared to the average cost of timely stent extraction (Sancaktutar et al, 2011).  Recently, the development of electronic stent registries at some hospitals to monitor stent placement and removal has shown to significantly reduce the number of forgotten stents (Lynch et al, 2007).

Xray image of a retained left ureteral stent with an associated staghorn kidney stone.

Xray illustration of left retained stent. Stent colored red. Stone colored blue.

References

El-Faqih, S. R., Shamsuddin, A. B., Chakrabarti, A., Atassi, R., Kardar, A. H., Osman, M. K., and Husain, I. Polyurethane internal stents in treatment of stone patients: morbidity related to indwelling times. J. Urol., 146: 1487, 1991.

Kavoussi, L. R., Albala, D. M., Basler, J. W., Apte, S., and Clayman, R. V. Percutaneous management of urolithiasis during pregnancy. J. Urol. 148: 1069-1071, 1992.

Lynch, M. F., Ghani, K. R., Frost, I., and Anson, K. M. Preventing the forgotten ureteral stent: implementation of a web-based stent registry with automatic recall application. Urol. 70: 426-426, 2007.

Monga, M., Klein, E., Castaneda-Zuniga, W. R., and Thomas, R. The forgotten indwelling ureteral stent: a urological dilemma. J. Urol. 153: 1817-1819, 1995.

Sancaktutar, A. A., Soylemez, H., Bozkurt, Y., Penbegul, N., and Atar, M. Treatment of forgotten ureteral stents: how much does it really cost? A cost-effectiveness study in 27 patients. Urol. Res.; DOI: 10.1007/s00240-011-0409-3, 2011.

Vanderbrink, B. A., Rastinehad, A. R., Ost, M. C., Smith, A. D. Encrusted urinary stents: evaluation and endourologic management. J. Endourol., 22(5): 905-912, 2008.