Table 4. Univariable Cox regression analysis of predicting factors for renal function amelioration in 163 patients treated by retrograde flexible ureteroscopy and intracorporeal lithotripsy for intrarenal stones.

	Univariable
	p value	HR (CI)
Female gender (versus male)	0.251	1.7 (0.7- 4.1)
Age (continuous)	0.051	1.028 (0.99- 1.056)
Multiple stones (vs unique stone)	0.546	0.75 (0.29-1.9)
Cumulative stone diameter (continuous)	0.445	0.97 (0.9-1.05)
Stone free (vs stone persistence)	0.121	2.1 (0.82-5.35)
Multiple procedures	0.546	0.75 (0.295 - 1.9)
Preoperative stenting (vs. no stent)	0.765	0.872 (0.35-2.1)
Operation time (continuous)	0.311	1.006 (0.99-1.02)
Postoperative double pigtail stent (vs ureteral stent)	0.087	3. (0.85-10.6)

HR=Hazard ratio; CI=Confidence interval