Table 1.

Clinical Characteristics for all patients stratified by kidney disease.

Variables	No known kidney disease (n=28644, 56%)	Acute kidney injury without chronic kidney disease (n=16854, 33%)	Acute kidney injury with chronic kidney disease (n=3171, 6%)	Chronic kidney disease without acute kidney injury (n=853, 2%)	End stage renal disease (n=1935, 4%)
Age (years), Mean (SD)	53 (17)	57 (17)^a	62 (15)^a	65 (16)^a	53 (15)
Age >=65 years, n (%)	7864 (27)	6326 (38)^a	1491 (47)^a	493 (58)^a	481 (25)
Female sex, n (%)	15012 (52)	7658 (45)^a	11224 (39)^a	415 (49)	811 (42)^a
African-American ethnicity, n (%)	3345 (12)	1859 (11)	591 (19)^a	118 (14)	671 (35)^a
Rural area residency, n (%)	9277 (32)	5311 (32)	1008 (32)	274 (32)	534 (28)^a
Distance from residing neighborhood to hospital (km), Median (25th,75th)	52 (23, 117)	56 (27, 120)^a	57 (27, 120)	49 (23, 118)	76 (28, 171)
Population living in poverty in residing neighborhood, % (SD)	14.9 (8.4)	14.6 (8.1)^a	15.0 (8.4)	14.7 (8.1)	15.4 (8.6)^a
Primary Insurance, n (%)
Medicare	9310 (33)	7173 (43)^a	1897 (60)^a	560 (66)^a	1280 (66)^a
Medicaid	3835 (13)	2233 (13)	307 (10)^a	74 (9)^a	133 (7)^a
Private	12972 (45)	6343 (38)^a	879 (28)^a	204 (24) ^a	510 (26)^a
Uninsured	2527 (9)	1105 (7)^a	88 (3)^a	15 (2)^a	12 (1)^a
Emergent surgery, n (%)	10543 (37)	9545 (57)^a	1909 (60)^a	318 (37)	1276 (66)^a
Weekend admission, n (%)	3175 (11)	2940 (17)^a	533 (17)^a	89 (10)	378 (20)^a
Charlson-Deyo Comorbidity Score, n (%)
0	13297 (46)	4782 (28)^a	267 (8)^a	141 (17)^a	5 (0.3)^a
1	5420 (19)	3932 (23)^a	386 (12)^a	107 (13)^a	8 (0.4)^a
2	4898 (17)	3534 (21)^a	688 (22)^a	185 (22)^a	643 (33)^a
>=3	5029 (18)	4606 (27)^a	1830 (58)^a	420 (49)^a	1279 (66)^a
Comorbidities, n (%)
Hypertension	10953 (38)	7386 (44)^a	1781 (56)^a	550 (64)^a	1184 (61)^a
Cancer	5901 (21)	3553 (21)	455 (14)^a	171 (20)	72 (4)^a
Diabetes	3956 (14)	2863 (17)^a	968 (31)^a	268 (31)^a	728 (38)^a
Chronic Pulmonary Disease	3962 (14)	3247 (19)^a	694 (22)^a	165 (19)^a	235 (12)
Peripheral Vascular Disease	2427 (8)	2558 (15)^a	696 (22)^a	168 (20)^a	218 (11)^a
Cerebrovascular Disease	1786 (6)	1945 (12)^a	315 (10)^a	76 (9)^a	119 (6)
Congestive Heart Failure	984 (3)	1931 (11)^a	787 (25)^a	128 (15)^a	274 (14)^a
Myocardial Infarction	1276 (4)	1451 (9)^a	380 (12)^a	99 (12)^a	170 (9)^a
Liver Disease	871 (3)	1209 (7)^a	312 (10)^a	29 (3)	104 (5)^a
Surgery Type, n (%)
Cardiothoracic Surgery	2354 (8)	3329 (20)^a	842 (27)^a	114 (13)^a	251 (13)^a
Neurologic Surgery	5667 (20)	2340 (14)^a	240 (8)^a	112 (13)^a	63 (3)^a
Non-Cardiac General Surgery	5901 (22)	3799 (23)^a	646 (20)	196 (23)	439 (23)
Specialty Surgeries^b	10733 (37)	3469 (21)^a	613 (19)^a	350 (41)	120 (6)^a
Other Surgeries^c	3989 (14)	3917 (23)^a	830 (26)^a	81 (10)^a	1062 (55)^a
Admission Hemoglobin, g/dL, n (%)
Missing	10371 (36)	3268 (19)^a	564 (18)^a	291 (34)	374 (19)^a
<10	3201 (11)	3320 (20)^a	813 (26)^a	146 (17)^a	355 (18)^a
[10,12)	5912 (21)	4438 (26)^a	962 (30)^a	238 (28)^a	589 (30)^a
>=12	9160 (32)	5828 (35)	832 (26)^a	178 (21)^a	617 (32)
Chronic Kidney Disease, n (%)
Mild to moderate (eGFR≥30 ml/min per 1.73m²)	NA	NA	2022 (64)	787 (92)	NA
Severe (eGFR<30 ml/min per 1.73m²)	NA	NA	1149 (36)^d	66 (8)	NA

Abbreviations. SD, standard deviation; eGFR, estimated glomerular filtration rate.

p-value <0.05 for comparison with respect to no known kidney disease group using Bonferroni adjustment.

Specialty surgeries include orthopedic, gynecological, ear-nose-throat, urology and plastic surgeries.

Other surgeries include trauma, burn and transplant surgeries.

p-value <0.05 for comparison with respect to mild to moderate chronic kidney disease group.