Clinical factors predicting ureteral stent failure in patients with external ureteral compression

Effect of ureteral stent length and implantation position on migration after implantation

BACKGROUND

Ureteral obstruction is a urinary system disease that causes urinary retention, renal injury, renal colic, and infection. Ureteral stents are often used for conservative treatment in clinics, and their migration usually results in ureteral stent failure. The migrations include proximal migration to the kidney side and distal migration to the bladder side, but the biomechanism of stent migration is still unknown.

METHOD

Finite element models of stents with lengths from 6-30 cm were developed. The stents were implanted into the middle of the ureter to analyze the effect of stent length on its migration, and the effect of stent implantation position on 6-cm-long stent migration was also observed. The stents' maximum axial displacement was used to assess the ease of stent migration. A time-varying pressure was applied to the ureter outer wall to simulate peristalsis. The stent and ureter adopted friction contact conditions. The two ends of the ureter were fixed. The radial displacement of the ureter was used to evaluate the effect of the stent on peristalsis.

RESULTS AND DISCUSSION

The maximum migration occurs in the positive direction for a 6-cm-long stent implanted at the proximal ureter (CD and DE), but in the negative direction at the distal ureter (FG and GH). The 6-cm-long stent demonstrated almost no effect on ureteral peristalsis. The 12-cm-long stent diminished the radial displacement of the ureter from 3-5 s. The 18-cm stent diminished the radial displacement of the ureter from 0-8 s, and the radial displacement within 2-6 s was weaker than other time. The 24-cm stent diminished the radial displacement of the ureter from 0-8 s, and the radial displacement within 1-7 s was weaker than other time.

CONCLUSION

The biomechanism of stent migration and ureteral peristalsis weakening after stent implantation was explored. Shorter stents were more likely to migrate. The implantation position had less influence on ureteral peristalsis compared with the stent length, which provided a reference for stent design aimed at reducing stent migration. Stent length was the main factor affecting ureteral peristalsis. This study provides a reference for the study of ureteral peristalsis.

Acute kidney injury due to bilateral malignant ureteral obstruction: Is there an optimal mode of drainage?

There is a well-known relationship between malignancy and impairment of kidney functions, either in the form of acute kidney injury or chronic kidney disease. In the former, however, bilateral malignant ureteral obstruction is a surgically correctable factor of this complex pathology. It warrants urgent drainage of the kidneys in emergency settings. However, there are multiple controversies and debates about the optimal mode of drainage of the bilaterally obstructed kidneys in these patients. This review addressed most of the concerns and provided a comprehensive presentation of this topic from the recent literature. Also, we provided different perspectives on the management of the bilateral obstructed kidneys due to malignancy. Despite the frequent trials for improving the success rates and functions of ureteral stents, placement of a percutaneous nephrostomy tube remains the most recommended tool of drainage due to bilateral ureteral obstruction, especially in patients with advanced malignancy. However, the disturbance of the quality of life of those patients remains a major unresolved concern. Beside the unfavorable prognostic potential of the underlying malignancy and the various risk stratification models that have been proposed, the response of the kidney to initial drainage can be anticipated and evaluated by multiple renal prognostic factors, including increased urine output, serum creatinine trajectory, and time-to-nadir serum creatinine after drainage.

Fluoroscopy-guided trans-urethral exchange of double-J ureteral stents

Background

For patients with malignant ureteral obstruction or stricture who require long-term internal drainage, plastic double-J stents (DJ stents) represent the mainstay of therapeutic strategies. DJ stents should be replaced at least once every 6 months to avoid infection or obstruction. Although DJ stents are generally replaced under cystoscopy, successful fluoroscopy-guided retrograde replacement of DJ stents in the interventional suite has been described in the literature.

Methods

Between April 2004 and May 2020, we exchanged 143 DJ stents in 19 male and 22 female patients under fluoroscopic guidance using Nelaton catheters, snare catheters, and 8F DJ stents. All procedures were performed with patients under sedation and local anesthesia. There were 39 patients with malignant ureteral obstruction and two patients with benign ureteral strictures. This study was approved by the Institutional Review Board. Technical success, clinical success, complications, procedure time, and mean interval between two procedures were retrospectively reviewed, and the factors affecting the success rate of the procedure were analyzed.

Results

Obstruction was detected at the abdominal ureter in 4 patients, pelvic ureter in 29 patients, and intravesical ureter in 8 patients. Twenty-six patients underwent two or more sessions of the procedures, whereas 15 patients underwent single-session procedures. Total 34 outpatient-based procedures and 109 inpatient-based procedures were performed. Technical success and clinical success were achieved in 94.4% (135/143) and 93.3% (126/135) procedures, respectively. Mean procedure time was 21.5 min (range 9–192 min). Mean procedure interval was 101.8 days (range 5–306 days). Technical success was negatively affected by male sex and obstruction at the pelvic ureter and was positively affected by previous successful exchange. Left-sided ureteral stent placement and old age negatively influenced clinical success. Septic shock occurred in one patient and was treated with antibiotics.

Conclusion

Fluoroscopy-guided trans-urethral exchange of DJ stents is an effective and less painful procedure.