Urological and nursing-related predictors of unplanned hospital readmission after percutaneous nephrolithotomy: A prospective cohort study

Table 1 Sociodemographic characteristics presented for total, readmitted, and non-readmitted patients (n = 161), n (%)/mean ± SD¹

Sociodemographic variables	Total (n = 161)	Readmitted (n = 36)	Non-readmitted (n = 125)	P value
Sex
Male	97 (60.2)	25 (69.4)	72 (57.6)	0.138
Female	64 (39.8)	11 (30.6)	53 (42.4)
BMI
Underweight (< 18)	1 (0.6)	0 (0)	1 (0.8)	0.617
Normal weight (18-25)	101 (62.7)	24 (66.6)	77 (61.6)
Overweight (25-30)	47 (29.2)	11 (30.6)	36 (28.8)
Obese (> 30)	12 (7.5)	1 (2.8)	11 (8.8)
BMI	24.4 ± 2.8	24.1 ± 2.4	24.5 ± 2.9	0.430
Age group
From 20-39 years	63 (39.1)	17 (47.2)	46 (36.8)	0.091
From 40-59 years	78 (48.4)	12 (33.3)	66 (52.8)
From 60-65 years	20 (12.4)	7 (19.4)	13 (10.4)
Mean age (years)	44 ± 12.6	44.4 ± 12.7	43.9 ± 12.6	0.847
Marital status
Single	16 (9.9)	1 (2.8)	15 (12)	0.133
Married	141 (87.6)	35 (97.2)	106 (84.8)
Widow/widower	4 (2.5)	0 (0)	4 (3.2)
Occupation
Office work	37 (23)	7 (19.4)	30 (24)	0.372
Not working	124 (77)	29 (80.6)	95 (76)
Educational level
High	44 (27.3)	9 (25)	35 (28)	0.565
Secondary	33 (20.5)	9 (25)	24 (19.2)
Basic	30 (18.6)	5 (13.9)	25 (20)
Read and write	16 (10)	2 (5.5)	14 (11.2)
Illiterate	38 (23.6)	11 (30.6)	27 (21.6)
Residence
Urban	42 (26.1)	12 (33.3)	30 (24)	0.261
Rural	119 (73.9)	24 (66.7)	95 (76)
Special habits
Smoking	46 (28.6)	12 (33.3)	34 (27.2)	0.521
Use of excessive caffeine-containing beverages (café and tea)	66 (41)	16 (44.4)	50 (40)

¹χ² test used for qualitative data between the two groups and independent t-test used for quantitative data between the two groups.

BMI: Body mass index.

Table 2 Causes, timing, duration, and management of hospital readmission in patients with complications (n = 36), n (%)/mean ± SD

Variables
Frequency of readmission
Once	32 (88.9)
Twice	4 (11.1)
Causes of readmission
Inflammatory causes	20 (55.6)
Pyelonephritis	15 (41.7)
Other forms of UTIs	5 (13.9)
Hemorrhagic causes	4 (11.1)
Hematuria	2 (5.6)
Retroperitoneal hematoma	2 (5.6)
Combined inflammatory and hemorrhagic causes	4 (11.1)
Obstructive causes	5 (13.9)
Anuria	2 (5.6)
Acute urine retention	3 (8.3)
Extra urinary causes	3 (8.3)
Pulmonary complications	2 (5.6)
Gastric ulcers	1 (2.8)
Period from discharge to readmission
1-15 days after discharge	29 (80.6)
16-30 days after discharge	5 (13.9)
31-45 days after discharge	2 (5.6)
Mean length of hospital stay of readmission (day)	3.1 ± 2.8
Readmission management
Conservative treatment	30 (83.3)
Insertion of JJ	4 (11.1)
Insertion of both JJ and nephrostomy tube	2 (5.6)

UTI: Urinary tract infections; JJ: Double-J stent.

Table 3 Comparison of the preoperative clinical variables between the readmitted and non-readmitted groups of patients (n = 161), n (%)/mean ± SD

Variables	Readmitted (n = 36)	Non-readmitted (n = 125)	P value
Comorbidities
Hypertension	5 (13.9)	19 (15.2)	0.542
Diabetes mellitus	2 (5.6)	9 (7.2)	0.537
Chronic kidney disease	1 (2.8)	3 (2.4)	0.641
Nutrition and fluid assessment
Normal diet	27 (75)	100 (80)	0.331
Specific diet (diabetic, salt-free)	9 (25)	25 (20)
Average fluid intake (2-3 L/day)	28 (77.8)	102 (81.6)	0.383
Fluid intake > 3 L/day	8 (22.2)	23 (18.4)
Previous urological procedures
Endourologic surgery	4 (11.1)	23 (18.4)	0.222
Open surgery	13 (36.1)	36 (28.8)	0.260
ESWL	2 (5.6)	9 (7.2)	0.537
Laboratory investigations
Pus cells in urine analysis	29 (80.6)	58 (46.4)	0.001
Mean serum creatinine (mg/dL)	1.24 ± 0.8	1.12 ± 0.6	0.321
Mean hemoglobin level (g/dL)	13.14 ± 2.3	12.9 ± 2.2	0.557
Mean prothrombin time (second)	12.4 ± 0.8	12.2 ± 0.7	0.095
Preoperative findings in computed tomography
Mean stone size (cm)	2.64 ± 0.71	2.31 ± 0.68	0.012
Solitary kidney	4 (11.1)	5 (4)	0.114
Stone location
Right kidney	22 (61.1)	55 (44)	0.052
Left kidney	14 (38.9)	70 (56)
Preoperative hydronephrosis	26 (72.2)	48 (38.4)	0.001
Presence of preoperative JJ	8 (22.2)	23 (18.4)	0.383

¹χ² test used for qualitative data between the two groups and independent t-test used for quantitative data between the two groups.

ESWL: Extracorporeal shockwave lithotripsy; JJ: Double-J stent.

Table 4 Comparison of the operative and postoperative variables between the readmitted and non-readmitted groups of patients (n = 161), n (%)/mean ± SD

Variables	Readmitted (n = 36)	Non-readmitted (n = 125)	P value1
Operative variables
Approach
Infracostal	31 (86.1)	112 (89.6)	0.555
Supracostal	5 (13.9)	13 (10.4)
Number of punctures
Single	6 (16.7)	63 (50.40	< 0.001
Multiples	30 (83.3)	62 (49.6)
Target calyx of puncture
Upper calyx	4 (11.1)	12 (9.6)	0.671
Middle calyx	9 (25)	41 (32.8)
Lower calyx	23 (63.9)	72 (57.6)
Type of disintegrators
Ultrasonic	2 (5.6)	4 (3.2)	0.403
Pneumatic	34 (94.4)	121 (96.8)
Academic qualification of the main operator
Professor	16 (44.4)	51 (40.8)	0.665
Assistant professor	0 (0)	2 (1.6)
Lecturer	19 (52.8)	63 (50.4)
Assistant lecturer	1 (2.8)	9 (7.2)
Patient position
Supine	2 (5.6)	20 (16)	0.167
Prone	34 (94.4)	105 (84)
Operative time
Total operation time (minute)	182.5 ± 34.7	150.72 ± 31.3	0.001
PNL procedural time (minute)	158 ± 27.3	130 ± 29	< 0.001
Ureteral JJ
Number of patients	12 (33.3)	21 (16.8)	0.033
Duration	43.3 ± 19	59.6 ± 25.5	0.062
Indications
For residual stone	10 (27.8)	16 (12.8)	0.082
For other causes	2 (5.6)	5 (4)
Nephrostomy tube
Number of patients	33 (82.4)	103 (82.4)	0.136
Removal before discharge	33 (91.7)	92 (73.6)	0.146
Removal after discharge (within 3 days)	1 (2.8)	10 (8)
Postoperative Variables
UOP at the 1st postoperative 24 hours (mL)	925 ± 210.95	956.80 ± 267.48	0.512
Pain degree
No pain	20 (55.6)	75 (60)	0.172
Mild	1 (2.8)	15 (12)
Moderate	8 (22.2)	23 (18.4)
Sever	7 (19.4)	12 (9.6)
Discharge with urethral catheter and its duration (day)
Discharge with urinary catheter	24 (66.7)	54 (43.2)	0.011
2-7	18 (50)	85 (68)	0.014
8-13	10 (27.8)	32 (25.6)
14-20	8 (22.2)	8 (6.4)
Mean duration with catheter	9.5 ± 6	6.4 ± 3.7	< 0.001
Complications
Pneumothorax	5 (13.9)	7 (5.6)	0.100
Intraperitoneal fluid collection	10 (27.8)	6 (4.8)	< 0.001
Postoperative urinary tract infection	13 (36.1)	20 (16)	0.011
Received pre-discharge instructions
Instructions about wound care	16 (44.4)	70 (56)	0.150
Instructions about medications	25 (69.4)	81 (64.8)	0.379
Activity daily living instructions	12 (33.3)	65 (52)	0.048
Instructions about urethral catheter care	7 (19.4)	55 (44)	0.005
Diet instructions	8 (22.2)	27 (21.6)	0.550
Follow-up appointment	19 (68.2)	63 (50.4)	0.475
Education on warning signs	18 (50)	57 (45.6)	0.390
Hospital stay (day)	5.1 ± 3.8	4.6 ± 2.9	0.370

¹χ² test used for qualitative data between the two groups and independent t-test used for quantitative data between the two groups.

JJ: Double-J stent; UOP: Urine output; PNL: Percutaneous nephrolithotomy.

Table 5 Postoperative complications and their grades and management (n = 52)

Complications	Frequency	Number of readmitted patients	Treatment regimen (number of patients)	Modified Clavein grade
Obstructive complications
Anuria	2	2	JJ placement (2)	IIIa
Acute urinary retention	3	3	Urethral catheterization (3)	II
Renal pain/colic	8	0	Medical expulsive (8). Antimicrobial therapy (3)	II, II
Genitourinary infections
Acute pyelonephritis	18	15	JJ placement (4) with percutaneous nephrostomy (2). Antimicrobial therapy (18)	IIIa, II
Other infection1	5	5	Antimicrobial therapy	II
Hemorrhagic complications
Gross hematuria	5	2	Blood transfusion, intravenous fluids, and anti-bleeding measures (2). Antibleeding measures only (3)	II, II
Retroperitoneal hematoma	3	2	Blood transfusion (1). Antimicrobial/antibleeding therapy (3)	II
Combined infections and hemorrhage	4	4	Blood transfusion (1). Antimicrobial therapy (4). Angioembolization (1)	II, II, IIIa
Extraurologic
Pneumonia	3	2	Antimicrobial therapy (3)	II
Peptic ulcer	1	1	Upper GIT endoscopy and medical therapy	IIIa
Total	52	36		42 II and 10 IIIa

¹They included infected perinephric collections in three cases and combined acute epididymo-orchitis with gross pyuria in two cases. Six cases of infected, neglected gauze or encrustations at the nephrostomy tube site were not included here; they required no treatment other than local cleansing.

GIT: Gastrointestinal tract, JJ: Double-J stent.

Table 6 Multivariate logistic regression analysis of the predictors of post-percutaneous nephrolithotomy hospital readmission

Potential predictors	OR	95%CI	P value
Preoperative predictors
Positive pus cells in urine analysis	5.8	(1.7-19.5)	0.004
Stone size	0.6	(0.23-1.5)	0.282
Preoperative hydronephrosis	1.43	(0.41-5)	0.575
Intraoperative predictors
Total operation time (minute)	1	(0.92-1.04)	0.434
PNL procedural time (minute)	1.1	(1-1.15)	0.084
Multiple renal punctures	2.9	(0.8-10.8)	0.103
Insertion of a double-J stent	0.25	(0.06-1.1)	0.060
Occurrence of intraoperative injuries	15	(3-75)	0.001
Postoperative predictors
Postoperative urinary tract infections	0.58	(0.43-9.91)	0.554
Discharge with urethral catheter	1.1	(1-1.3)	0.076
Duration of urethral catheterization	1.13	(1-1.3)	0.110
Inadequate activity daily living instructions	0.12	(0.14-1.26)	0.123
Inadequate urethral catheter care instructions	0.25	(0.08-0.9)	0.035

PNL: Percutaneous nephrolithotomy.

Table 7 Risk score for the independent predictors based on the multivariate logistic regression

Item	Risk score
Predictors
Positive pus cell in preoperative urine analysis	5
Intraperitoneal injuries	8
Inadequate catheter care instructions	4
Total score	17
Categorized score
Low risk	0–4
Moderate risk	5–9
High risk	10–17