Migration of forgotten stent into renal pelvis

Abstract

Stent migration is a well recognized complication of forgotten stents, but migration into the renal pelvis is rarely documented. We present a case of migration and coiling of a forgotten stent in the renal pelvis, and discuss briefly, the etiological factors for the phenomenon and associated problems in management.

CASE REPORT

A 51-year-old male patient presented with history of recurrent episodes of left loin pain of four years duration. He had undergone Double J stenting followed by extracorporeal shock wave lithotripsy in a different hospital seven years back. Ultrasonography showed a hydronephrotic left kidney with good parenchyma, a 2 cm pelvic stone, with multiple lower calyceal stones, along with stent coils. A plain radiograph [Figure 1] revealed a completely coiled stent in the left pelvicalyceal system with encrustations and stones around it. The patient was not aware of the presence of the stent.

Figure 1.

Encrusted stent coiled in the renal pelvis

A retrograde urogram revealed complete cut-off at the level of pelviureteric junction due to the pelvic stone. The stent and stones were retrieved by a percutaneous nephrostomy tract under combined ultrasonographic and fluoroscopic guidance. Despite irregular encrustations and adherence to the renal calyces at various points, the stent could be removed intact, along with complete stone clearance. Restenting was done because of extensive manipulation of the pelvicalyceal system [Figure 2].

Figure 2.

Post operative: stent removal, stone clearance and restenting

DISCUSSION

An indwelling ureteral stent is a necessary evil in urological practice because of its extensive utility but significant associated morbidity. Encrustation, migration, and fragmentation form the triad of complications of forgotten stents (>6 months).[1] Migration into renal pelvis is infrequently documented.[2] Proximal migration of stent occurs in 0.6 to 3.5% of cases.[3] Significant risk factors for migration are the duration of stenting, a low stent-to-ureter length ratio (a stent too short for the ureter), proximal curl in the superior calyx as opposed to renal pelvis, inadequate distal curl (<180°), and the ‘jack’ phenomenon wherein a ureteric stone alongside the stent acts like the jack of a car, allowing only proximal migration and preventing distal movement during respiration.[4]

Management can be complicated, often requiring a combination of multiple procedures including ureteroscopy, percutaneous nephroscopy, lithotripsy (endoscopic/shock wave), or open procedures.[1] It is also wrought with the risk of devastating complications—sepsis and renal failure.[5] In most cases, the distal end of migrated stent lies in the ureter and can be removed by ureteroscopy.[3] However, percutaneous access may be required in the rare event of complete coiling in the pelvis, which occurred in this case.

Migration can be prevented by choosing appropriate length and material of the stent and with proper placement. Breau and Norman[6] advocated direct measurement of ureteric length from the X-ray for selecting optimal stent length. They postulated that the optimal stent-to-ureter length ratio is 1.04, which reduces migration as well as bladder irritation. Migration can also be prevented by adding a retrieval suture to the distal end, frequent stent changes when longer indwelling times are required,[6] and usage of polyurethane stents, which fragment and migrate less readily than silicone stents but encrust more rapidly.[1] Patient education and accurate documentation are important and are the responsibilities of the urologist.[1,5] Mobile phone services can improve communicability with patients and should help to reduce this complication further. This is especially very important in developing countries like India where the level of awareness can be low.