Perioperative predictors of urinary tract infections after percutaneous nephrolithotomy

Table 1 Sociodemographic characteristics of the studied patients (n = 157; Assiut, Egypt, 2026)

Variables	Values are represented as mean ± SD (range)/n (%)
Age (years)	47.37 ± 12.47 (20-65)
Age categories
20-29	19 (12.1)
30-39	40 (25.5)
40-49	38 (24.2)
50-59	40 (25.5)
60-65	20 (12.7)
Body mass index (kg/m2)	24.44 ± 2.84 (16.80-33.80)
Sex
Male	96 (61.1)
Female	61 (39.9)
Educational level
High education	42 (26.8)
Secondary education	32 (20.4)
Basic	30 (19.1)
Unable to read and write	53 (33.7)
Occupation
Working	36 (23)
Not-working	121 (77)
Marital status
Single	15(9.6)
Married	138 (87.9)
Widow/widower	4 (2.5)
Residence
Urban	39 (24.8)
Rural	118 (75.2)
Current smoker	46 (29.3)

Table 2 Comparison of the sociodemographic characteristics in both groups (n = 157; Assiut, Egypt, 2026)¹

Variables	Patients with UTI (n = 31)	Patients without UTI (n = 126)	P value
	Values are represented as mean ± SD (range), n (%)
Age groups
20-29	6 (19.4)	13 (10.3)	0.642
30-39	6 (19.4)	34 (27)
40-49	9 (29)	29 (23)
50-59	5 (16.1)	35 (27.7)
60-65	5 (16.1)	15 (12)
Mean age	42.13 ± 13.9	44.91 ± 12.1	0.273
Body mass index	24 ± 2.5	24.55 ± 2.9	0.344
Sex
Male	21 (67.7)	75 (59.5)	0.400
Female	10 (32.3)	51 (40.5)
Educational level
High	7 (22.6)	35 (27.8)	0.491
Secondary	5 (16.1)	27 (21.4)
Basic	9 (29)	21 (16.7)
Unable to read and write	10 (32.3)	43 (34.1)
Occupation
Office working	6 (19.4)	30 (23.8)	0.869
Not working	25 (80.6)	96 (76.2)
Marital status
Single	4 (12.9)	11(8.7)	0.224
Married	25 (80.6)	113 (89.7)
Widow/widower	2 (6.5)	2 (1.6)
Residence
Urban	7 (22.6)	32 (25.4)	0.745
Rural	24 (77.4)	94 (74.6)
Current smoker	10 (32.3)	36 (28.6)	0.686

¹χ² test for qualitative data between two or more groups.

UTIs: Urinary tract infections.

Table 3 Comparison of the preoperative data in patients with and without urinary tract infections (n = 157; Assiut, Egypt, 2026)¹

Variables	Patients with UTI (n = 31)	Patients without UTI (n = 126)	P value
	Values are represented as mean ± SD (range), n (%)
Previous urological surgery
Endourology	5 (16.1)	22 (17.5)	1.000
SWL	11 (100)	0 (0.0)	0.088
Open surgery	13 (41.9)	36 (28.6)	0.150
Comorbidity
Hypertension	4 (12.9)	19 (15.1)	0.759
Diabetes mellitus	5 (16.1)	6 (4.8)	0.026
Chronic kidney disease	2 (6.5)	2 (1.6)	0.124
Preoperative laboratory investigations
History of pyuria	23 (74.2)	61 (48.4)	0.010
Hemoglobin (g/dL)	13.19 ± 2.12	12.87 ± 2.24	0.489
Serum creatinine (mg/dL)	1.11 ± 0.59	1.17 ± 0.68	0.625
Preoperative imaging findings
Stone size (cm)	2.75 ± 0.9	2.2 ± 0.59	< 0.001
Hydronephrosis	16 (51.6)	56 (44.4)	0.473

¹χ² test for qualitative data between two or more groups.

SWL: Extracorporeal shockwave lithotripsy; UTI: Urinary tract infection.

Table 4 Comparison of the operative and postoperative variables for patients with and without urinary tract infections (n = 157; Assiut, Egypt, 2026)¹

Variables	Patients with UTI (n = 31)	Patients without UTI (n = 126)	P value
	Values are represented as mean ± SD (range), n (%)
Approach
Infracostal	26 (83.9)	113 (89.7)	0.363
Supracostal	5 (16.1)	13 (10.3)
Number of punctures
Single	5 (16.1)	63 (50)	0.001
Multiple	26 (83.9)	63 (50)
Site of puncture
Upper calyx	4 (12.9)	11 (8.7)	0.549
Middle calyx	11 (35.5)	37 (29.4)
Lower calyx	16 (51.6)	78 (61.9)
Operation time (minutes)	172.26 ± 35.47	153.10 ± 32.38	0.004
Intraoperative instrumentation
Double-J stent	11 (35.5)	22 (17.5)	0.027
Nephrostomy tube	30 (96.8)	100 (79.4)	0.021
Blood transfusion	27 (90)	88 (69.8)	0.024
Postoperative data
Residual stones	9 (29)	11 (8.7)	0.002
Urethral catheterization duration (days)	9.06 ± 5.63	6.29 ± 3.49	0.001
Length of hospital stay (days)	5.52 ± 3.53	4.43 ± 2.88	0.074

¹χ² test for qualitative data between two or more groups.

UTI: Urinary tract infection.

Table 5 Multivariate logistic regression analysis for the predictors (independent variables) of urinary tract infections after percutaneous nephrolithotomy (dependent variable) (n = 157; Assiut, Egypt, 2026)

Variables	OR1	95%CI	T2	VIF3	P value
Preoperative
Diabetes mellitus	0.15	(0.14-1.13)	0.85	1.18	0.019
History of pyuria	0.40	(0.14-1.13)	0.82	1.22	0.083
Stone size	2.15	(1.1-4.41)	0.55	1.82	0.036
Operative variables
Operation time	1.01	(0.99-1.02)	0.45	2.22	0.452
Multiple renal punctures	1.15	(0.44-3.02)	0.52	1.92	0.774
Blood transfusion	0.34	(0.09-1.3)	0.90	1.11	0.133
Intraoperative double-J placement	1.74	(0.38-7.86)	0.78	1.28	0.474
Nephrostomy tube insertion	0.14	(0.02-1.3)	0.70	1.43	0.084
Postoperative variables
Duration of urethral catheterization	1.1	(0.99-1.22)	0.81	1.23	0.062
Residual stones	0.16	(0.03-0.93)	0.65	1.54	0.041

¹Some odds ratios appear counterintuitive in direction (e.g., odds ratio < 1 for diabetes mellitus and residual stones despite being described as risk factors based on their P-values). This reflects coding direction in the regression model.

²Tolerance > 0.10 confirms the model is statistically sound.

³Variance inflation factor < 5 indicates that multicollinearity is not a concern.

CI: Confidence interval; OR: Odds ratio; T: Tolerance; VIF: Variance inflation factor.