Determinants and impact of calcium oxalate crystal deposition on renal outcomes in acute kidney injury patients

Figures & data

Figure 1. Flow chart of the study.

Table 1. Baseline features of patients with acute kidney injury (AKI) and CaOx deposition.

Variables	CaOx (n = 32)	Non- CaOx (n = 20)	p Value
Age, year	53 ± 14	52 ± 14	0.75
Men, n (%)	27 (84)	11 (55)	0.03
Prior CKD, n (%)	3 (9)	0	0.15
AKI, n (%)
Stage 1/2/3	6 (19)/6 (19)/20 (63)	2 (10)/5 (25)/13 (65)	0.60
Etiologies of AKI, n (%)
Nephrotoxic drugs	21 (66)	7 (35)	0.05
Idiopathic induced by severe nephrotic syndrome	5 (16)	NA
concurrent with nephrotoxic drugs exposure	2 (6)	NA
Severe proliferative glomerulonephritis (EPGN or CrGN)	9 (28)	NA
Idiopathic tubulointerstitial nephritis	NA	6 (30)
Concurrent with nephrotoxic drugs exposure	NA	5 (25)
Acute tubular necrosis	NA	1 (5)
Comorbidities, n (%)
Diabetes mellitus	17 (53)	4 (20)	0.02
Hypertension	22 (69)	3 (15)	<0.001
Urolithiasis	5 (16)	1 (5)	0.13
Alcohol abuse	13 (41)	1 (5)	0.008
Infection	14 (44)	3 (15)	0.04
Malignancies	2 (6)	1 (5)	1.00
Rheumatologic diseases	3 (9)	0	0.28
Traditional predisposing factors to hyperoxaluria, n (%)	9 (28)	NA
Excessive intake of oxalate-rich food or vitamin C supplement	4 (13)	NA
Refractory diarrhea	5(16)	NA
Gastrectomy	2 (6)	NA
Chronic pancreatitis	1 (3)	NA
Pre-renal conditions to renal hypoperfusion, n (%)	28 (88)	12 (60)	0.04
RAASi	10 (31)	0	0.008
Diuretics	14 (44)	0	<0.001
NSAIDs	6 (19)	3 (15)	1.00
Hypoalbuminemia	10 (31)	1 (5)	0.04
Hypotension	3 (9)	1 (5)	1.00
BUN-to-sCr ratio >10	20 (63)
FeNa < 1%	4/16 (25)	0	0.12
BNP <100	9/24 (38)	7/12 (58)	0.30
Other conditions, n (%)
Antibiotic use within 2 months before biopsy	14 (44)	7 (35)	0.58
Other potential nephrotoxic drugs^a	17 (53)	7 (35)	0.26
Laboratory tests, median (P25, P75)
Biopsy sCr, μmol/L	349.7 (237.5, 587.0)	321.0 (192.8, 466.7)	0.24
Peak sCr, μmol/L	703.3 (465.2, 937.6)	337 (222.0, 618.4)	0.001
BUN-to-sCr ratio, mean ± SD	12.4 ± 5.8
Glycated hemoglobin, %	6.5 ± 1.0	6.1 ± 0.9	0.32
Serum albumin, g/L	36.1 (24.5, 41.2)	39.2 (35.9, 42.6)	0.13
BNP, pg/mL^b	256.5 (42.5, 448.8)	75.3 (25.3, 381.8)	0.44
Urinary pH	6.0 (5.0, 6.5)	6.5 (6.0, 6.9)	0.14
uA/C, g/g.cr	65.5 (15.9, 342.0)	87.8 (28.4, 1216.7)	0.63
uNAG /C, U/g; Increased uNAG, n (%)	28.3 (20.4, 101.8); 20 (74)	28.7 (21.1, 56.6); 13 (77)	0.78; 0.74
Urinary α1-MG /C, mg/g; Increased urinary α1-MG, n (%)	78.9 (28.8, 255.6); 24 (92)	196.5 (24.8, 337.1); 13 (81)	0.56; 1.00
Renal glycosuria, n (%)	17 (53)	11 (55)	1.00
Hematuria, n (%)	22 (69)	6 (30)	0.01
Leukocyturia, n (%)	17 (53)	6 (30)	0.15
Serum IgG, g/L, mean ± SD	12.5 ± 5.5	14.7 ± 4.9	0.22
CRP, mg/L	4.6 (1.2, 17.4)	10.0 (2.2, 17.4)	0.13
ESR, mm/h	45.0 (31.0, 78.5)	68.0 (7.0, 98.5)	0.30

Data are presented as n (percentage), mean ± SD or median (P₂₅, P₇₅); CKD: chronic kidney disease; AKI: acute kidney injury; NA: not available; RAASi: renin–angiotensin–aldosterone system inhibitor; NSAIDs: non-steroidal anti-inflammatory drugs; BUN: blood urea nitrogen; FeNa: fractional excretion of sodium; BNP: B type natriuretic peptide; sCr: serum creatinine; uA/C: urinary albumin-to-creatinine ratio; NAG: N-acetyl-β-D-glucosaminidase (reference: 0.3–12 U/L); α1-MG: α1-microglobulin (reference: <12 mg/L); uNAG/C: urinary NAG to urinary creatinine ratio; α1-MG/C: urinary α1-microglobulin to urinary creatinine ratio; CRP: C-reactive protein; ESR: erythrocyte sedimentation rate

Severe nephrotic syndrome is defined as the presence of edema, proteinuria >6 g/d, and serum albumin <15 g/L. Severe proliferative glomerulonephritis is defined as severe endocapillary proliferative glomerulonephritis and/or crescents observed in >50% glomerulus. Excessive intake of oxalate-rich food or vitamin C supplement is defined as patients receiving >2 g/d vitamin C infusion for >3 d before kidney biopsy or they reported excess oxalate precursor intake. Refractory diarrhea is defined as patient report of stool of Bristol VI or VII type for >3 months. Pre-renal conditions to renal hypoperfusion consists of the use of RAAS inhibitors or diuretics or NSAIDS, or the conditions of hypoalbuminemia or hypotension or BUN-to-sCr ratio > 10. FeNa and BNP are not included in the pre-renal conditions because of missing data.

^a Types of the potential nephrotoxic drugs were summarized in Supplementary Table 6.

^b Only 24 patients had available BNP data.

Figure 2. CaOx crystal cast and intrarenal depositions. Immunohistochemistry staining showed the expression of SLC26A6 transporter in (A and B) urinary sediments of a cast containing CaOx crystals. (C and D) Intraluminal and intracellular CaOx crystals (original magnification, ×5000). (E) Tubular expression of SLC26A6 transporter in a patient with severe oxalosis and (F) another patient with minimal change disease as the control (original magnification, ×200). (G) CaOx crystals under polarized microscopy (original magnification, ×200). (H) von Kossa staining showed calcium-containing crystals.

Table 2. Comparison of clinical features among AKI patients with oxalosis and non-oxalosis.

	AKI with oxalosis (n = 32)	AKI w/o oxalosis (n = 20)	p Value
AKI Stage 3, n (%)	62.5	65.0	0.86
sCr at biopsy, μmol/L	349.7 (237.5, 587.0)	356.9 ± 206.6	0.24
Urine output, mL	1769 ± 628	1850 (1500, 2400)	0.55
Urinary pH	6.0 (5.0, 6.5)	6.2 ± 0.7	0.39
24-h urine parameters, mmol/24 h
Sodium	109.6 ± 51.7	74.0 (45.0, 170.8)	0.78
Potassium	31.7 ± 15.5	41.1 ± 19.4	0.12
Chloride	100.4 ± 46.7	90.7 (32.0, 173.6)	0.69
Calcium	1.2 ± 0.7	0.7 (0.6, 2.1)	0.96
Phosphorous	12.2 ± 7.8	12.2 (6.5, 20.0)	0.84
Magnesium	2.9 ± 1.6	2.5 (1.8, 5.0)	0.84
Uric acid, mol/24 h	2109.5 ± 1064.0	2899.1 ± 1163.8	0.14
Urea nitrogen	217.3 ± 118.3	241.2 ± 119.5	0.67
Spot-urine parameters, mmol/L
Sodium	63.0 ± 22.1	53.2 ± 22.4	0.21
Potassium	17.0 (12.0, 25.5)	20.0 (13.0, 26.0)	0.37
Chloride	57.2 ± 20.5	55.9 ± 26.0	0.87
Calcium	0.8 ± 0.4	0.8 ± 0.5	0.96
Phosphate	7.2 ± 3.7	6.8 ± 4.2	0.82
Magnesium	1.8 ± 0.7	1.6 ± 0.6	0.46
Uric acid,	1144.7 ± 574.5	1364.0 (1242.7, 1926.4)	0.10
Urea nitrogen	110.3 ± 42.9	131.3 ± 47.2	0.32
Oxalate	0.2875 (0.2225, 0.3825)	0.1925 (0.1850, 0.2413)	<0.001
Citrate	0.4775 (0.3725, 0.7213)	0.6400 (0.3363, 0.8913)	0.29
Urinary Ox/Ci ratio	0.7110 ± 0.3972	0.4057 ± 0.2029	0.005
Urinary Ca/Crea ratio	0.7112 (0. 2059, 1.0104)	0.6661 (0.5244, 0.9157)	0.60
Kidney pathology
Tubular calcification index, n^a	11.00 (5.00, 17.00)	0.00 (0.00, 1.00)	<0.001
SLC26A6 staining score, %^b	0.18 ± 0.05	0.14 ± 0.04	0.009
Glomerular global sclerosis^c	1.50 (0, 3.00)	0 (0, 1.00)	0.01
AT	3.50 (2.25, 5.00)	2.00 (1.00, 5.00)	0.45
AI	1.00 (0.00, 2.00)	0.00 (0.00, 1.00)	0.002
ATI	4.00 (2.00, 5.75)	3.67 ± 3.16	0.010
CT	0.50 (0.00, 1.00)	1.00 ± 0.87	0.048^d
CI	0.00 (0.00, 1.00)	1.00 (0.00, 1.540)	0.14
CTI	0.50 (0.00, 2.25)	2.00 (0.00, 3.00)	0.008

Data are reported as number and percentage, mean ± SD or median (P₂₅, P₇₅). p Value, by Wilcoxon signed rank tests.

sCr: serum creatinine; uOx: urinary oxalate; uOx/C: urinary oxalate (mmol/L) to creatinine (mmol/L) ratio; uCi: urinary citrate; uCi/C: urinary citrate (mmol/L) to creatinine (mmol/L) ratio; uCa urinary calcium concentration; uCa/C, urinary calcium (mmol/L) to creatinine (mmol/L) ratio; uCi/C x uCa/C, uCi/C multiply by uCa/C; uCa/uCi: urinary calcium (mmol/L) to citrate (mmol/L); N/A: not available. AT: acute tubular injury score; AI: acute interstitial injury score; ATI: acute tubulointerstitial injury score (calculated as: AT + AI); CT: chronic tubular injury score; CI: chronic interstitial injury score; CTI: chronic tubulointerstitial score (calculated as: CT + CI)

^aPositive von Kossa-stained crystal amounts were calculated per piece of renal tissues; ^bSLC26A6 transporter expression was shown as the percentage of the number of positive renal tubules to total tubules (%) under 400× microscope. ^cPercent of globally sclerosed glomeruli (score 0, <5%; score 1, 5–10%; score 2, 11–20%; score 3, >20%; if a specific glomerulopathy such as diabetic nodular glomerulosclerosis or focal segmental glomerulosclerosis (FSGS), was identified, the score defaulted to 3). ^d p Value within the range of 0.045–0.050 was expressed up to three significant decimal places.

Table 3. Univariable regression analysis of risk factor to oxalosis.

	Moderate-to-severe oxalosis (<5 [reference] vs.$\ge$5 crystals per high-power field)		Severe oxalosis (≤10 [reference] vs. >10 crystals per high-power field)
	OR (95%CI)	p Value	OR (95% CI)	p Value
Peak sCr ($\mu$ mol/L)	1.002 (1.000, 1.004)	0.04	1.001 (0.999, 1.003)	0.21
nadir eGFR (mL/min/1.73 m^2)	0.896 (0.810, 0.991)	0.03	0.891 (0.788, 1.007)	0.07
sCr at biopsy ($\mu$ mol/L)	1.002 (0.999, 1.004)	0.24	1.002 (0.999, 1.005)	0.13
eGFR at biopsy (mL/min/1.73 m^2)	0.942 (0.887, 1.000)	0.05	0.9678 (0.914, 1.026)	0.28
RAASi	2.585 (0.665, 10.039)	0.17	3.437 (0.834, 14.165)	0.09
Diuretics	7.700 (2.063, 28.742)	0.002	3.889 (1.038, 14.566)	0.04
NSAIDs	0.670 (0.151, 2.974)	0.60	1.371 (0.298, 6.318)	0.69
24-h urine parameters, mmol/24 h
Sodium	0.949 (0.750, 1.201)	0.66	0.994 (0.961, 1.028)	0.73
Potassium	1.085(0.343, 3.426)	0.89	0.926 (0.834, 1.028)	0.15
Chloride	0.773 (0.633, 0.994)	0.01	0.991 (0.958, 1.024)	0.58
Calcium	0.413 (0.017, 10.200)	0.59	1.450 (0.237, 8.889)	0.69
Phosphorous	4.967 (0.484, 50.980)	0.18	1.054 (0.841, 1.321)	0.65
Magnesium	1.978 (0.046, 85.286)	0.72	2.375 (0.553, 10.167)	0.25
Uric acid (per 10^3 increase)	1.006 (1.001, 1.012)	0.03	1.000 (0.998, 1.001)	0.77
Urea nitrogen	1.198 (1.025, 1.400)	0.02	1.012 (0.990, 1.035)	0.29
Spot-urine parameters
Sodium (mol/L)	1.006 (0.985, 1.026)	0.59	0.994 (0.969, 1.021)	0.67
Potassium (mol/L)	1.001 (0.998, 1.004)	0.63	0.999 (0.995, 1.003)	0.57
Chloride (mol/L)	1.005 (0.987, 1.023)	0.60	0.996 (0.973, 1.018)	0.71
Calcium (mol/L)	1.005 (0.981, 1.029)	0.70	0.997 (0.970, 1.025)	0.83
Phosphate (mol/L)	1.001 (0.994, 1.009)	0.73	1.000 (0.992, 1.008)	0.96
Magnesium (mol/L)	1.000 (0.995, 1.004)	0.84	0.999 (0.993, 1.005)	0.70
Uric acid (mol/L)	0.997 (0.993, 1.002)	0.28	0.996 (0.990, 1.002)	0.22
Urea nitrogen (mol/L)	0.997 (0.991, 1.003)	0.32	0.999 (0.993, 1.005)	0.68
uOx (mmol/L)	1.719 (0.243, 12.179)	0.59	0.557 (0.029, 10.764)	0.70
uCi (mol/L)	0.999 (0.998, 1.001)	0.47	0.996 (0.992, 1.000)	0.03
uOx/C (mmol/mmol, per 0.01 increase)	1.047 (0.980, 1.118)	0.17	0.925 (0.808, 1.060)	0.26
uCi/C (mmol/mmol, per 0.01 increase)	0.997 (0.972, 1.002)	0.83	0.905 (0.822, 0.996)	0.04
uCa/C (mmol/mmol, per 0.01 increase)	0.988 (0.975, 1.001)	0.07	0.998 (0.990, 1.006)	0.64
uOx/uCi (mmol/mmol, per 0.01 increase)	1.023 (1.004, 1.042)	0.02	1.026 (1.006, 1.047)	0.01
uCa/uCi (mmol/mmol)	0.998 (0.983, 1.013)	0.76	1.006 (0.992, 1.020)	0.40
Kidney pathology
SLC26A6 %^a (per 1% increase)	1.401 (1.102, 1.780)	0.006	1.181 (0.963,1.447)	0.11
Tubular calcification index^b	1.320 (1.105, 1.575)	0.002	1.065 (1.002, 1.132)	0.04
Glomerular global sclerosis^c	2.026 (1.233, 3.330)	0.005	1.194(0.727, 1.960)	0.48
AT	1.030 (0.725, 1.462)	0.87	1.305 (0.740, 2.301)	0.36
AI	0.850 (0.699, 1.079)	0.18	1.297 (0.870, 1.935)	0.20
ATI	0.934 (0.800, 1.090)	0.38	1.194 (0.911, 1.565)	0.20
CT	1.510 (0.758, 3.007)	0.24	1.006 (0.422, 2.287)	0.99
CI	1.355 (0.869, 2.113)	0.18	0.907 (0.577, 1.479)	0.70
CTI	1.209 (0.915, 1.596)	0.18	0.967 (0.709, 1.319)	0.83

^aSLC26A6 transporter expression was shown as the percentage of the number of positive renal tubules to total tubules (%) under 400 × microscope. ^bPositive von Kossa-stained crystal amounts were calculated per piece of renal tissues. ^cPercent of globally sclerosed glomeruli(0, <5%;1, 5–10%; 2, 11–20%; 3, >20%;If a specific glomerulopathy such as diabetic nodular glomerulosclerosis or focal segmental glomerulosclerosis (FSGS), was identified, the score defaulted to 3).

uOx: urinary oxalate; uOx/C: urinary oxalate to creatinine ratio; uCi; urinary citrate; uCi/C: urinary citrate to creatinine ratio; uCa/C: urinary calcium concentration to creatinine ratio; uOx/uCi; urinary oxalate to citrate ratio; uCa/uCi; urinary calcium to citrate ratio; SLC26A6%: the percentage of SLC26A6 expression

Table 4. Comparison between AKI patients having CaOx deposition (having no severe glomerulonephropathy) with a 3-month eGFR <15 and ≥ 15 mL/min/1.73 m².

	eGFR (mL/min/1.73 m^2) at 3-month
	<15 (or KFRT) (n = 5)	$\ge$15 (n = 17)	p
Nadir eGFR (mL/min/1.73 m^2), median (P25, P75)	6.2 (5.0, 9.0)	6.2(3.5, 10.4)	0.70
AKI stage 3 (%)	5 (100)	7 (41)	0.14
Diabetes (%)	2 (40)	11 (65)	0.61
Hypertension (%)	4 (80)	12 (71)	1.00
Urolithiasis (%)	2 (40)	5 (29)	1.00
CaOx deposition ≥ 5/HPF (%)	3 (60)	12 (71)	1.00
CaOx deposition >10/HPF(%)	1 (20)	9 (53)	0.32
Tubular calcification index	17 ± 11	11 (4.50, 35.00)	0.54
SLC26A6 % (mean ± SD)	17 ± 8	18 ± 4	0.60
uOx,mmol/L (mean ± SD)	0.40 ± 0.20	0.27 ± 0.06	0.22
uOx/C^a, median (P25, P75)	0.04 (0.01, 0.46)	0.27 (0.22, 0.33)	0.80
uCi mmol/L, median (P25, P75)	0.50 (0.32, 1.71)	0.45 (0.34, 0.62)	0.62
uCi /C^b, median (P25, P75)	0.25 (0.01, 0.40)	0.06 (0.03,0.20)	0.68
uCa/C^c, median (P25, P75)	0.35 (0.12, 1.75)	0.90 (0.29,1.03)	0.43
uOx/uCi^d, median (P25, P75)	0.88 ± 0.68	0.61 ± 0.29	0.44
uCa/uCi^e, median (P25, P75)	3.28 (0.37, 149.60)	8.32 (2.57, 42.36)	0.56
uA/C, mg/g	1719 (963, 1766)	27 (14, 105)	0.03
uA/C to uα1-MG	2.15 (1.42, 5.94)	0.48 (0.18, 2.27)	0.19
uNAG/C, U/g, median (P25, P75)	68 (43, 85)	27 (15, 57)	0.31
uα1-MG /C, mg/g, median (P25,P75)	297 (237, 571)	66 (44, 104)	0.009
Pathological scores
Glomerular active index			0.14
No GN	1 (20)	11 (65)
Mild-to-moderate activity	4 (80)	6 (35)
Glomerular sclerosis^f	3.0 (1.0, 3.0)	1.0 (0, 3.0)	0.22
AT	4.0 (3.0, 4.0)	1.0 (1.0, 3.0)	0.01
AI	2.0 (1.0, 2.5)	1.0 (0, 2.0)	0.34
ATI^f	6.0 (4.0, 7.0)	4.0 (1.0, 4.0)	0.12
CT	1.0 (0, 2.0)	0.0 (0, 1.0)	0.52
CI	2.0 (0, 4.5)	1.0 (0, 2.0)	0.32
CTI^g	3.0 (0, 6.5)	2.0 (0, 3.0)	0.36

Data are presented as n (percentage), mean ± SD, or median (P₂₅, P₇₅).

^aExpressed as the ratio of urinary oxalate (mmol/L) to urinary creatinine (mmol/L); ^bexpressed as the ratio of urinary citrate (mmol/L) to urinary creatinine (mmol/L); ^cexpressed as the ratio of urinary calcium (mmol/L) to urinary creatinine (mmol/L); ^dexpressed as the ratio of urinary oxalate (mmol/L) to urinary citrate (mmol/L); ^eexpressed as the ratio of urinary calcium (mmol/L) to urinary citrate (mmol/L); ^fATI = AT + AI; ^gCTI = CT + CI.

KFRT: kidney failure requiring replacement therapy; GN: glomerulonephritis; uOx: urinary oxalate; uCi: urinary citrate; uCa: urinary calcium; uNAG/C: urinary N-acetyl-β-D-glucosaminidase to urinary creatinine ratio; α1-MG/C: urinary α1-microglobulin to urinary creatinine ratio; AT: acute tubular injury score; AI: acute interstitial injury score; CT: chronic tubular injury score; CI: chronic interstitial injury score

Table 5. Univariate regression analysis of poor long-term kidney outcome (eGFR < 15 mL/min/1.73 m² or on KFRT vs. eGFR ≥ 15 mL/min/1.73 m² [reference] at 3 months) in patients having no glomerulonephritis.

	OR (95% CI)	p
Nadir eGFR (mL/min/1.73 m^2)	0.985 (0.751, 1.291)	0.91
Diabetes	0.364 (0.047, 2.817)	0.33
Hypertension	1.667 (0.147, 18.874)	0.68
Urolithiasis	1.600 (0.202, 12.694)	0.66
History of medications
RAASi	7.333 (0.661, 81.365)	0.11
Diuretics	1.600 (0.202, 12.694)	0.66
NSAIDs	7.000 (0.791, 61.977)	0.08
CaOx deposition ≥ 5/HPF	0.625 (0.079, 4.959)	0.66
CaOx deposition >10/HPF	0.222 (0.020, 2.424)	0.22
SLC26A6 % (per 1% increase)	0.922 (0.695, 1.223)	0.57
Tubular calcification index	1.006 (0.939, 1.079)	0.86
uOx ($\mu$ mol/L)	1.011 (0.998, 1.025)	0.11
uOx/C^a (per 0.01 increase)	1.048 (0.974, 1.127)	0.21
uCi ($\mu$ mol/L)	1.001 (0.999, 1.003)	0.26
uCi /C^b (per 0.01 increase)	1.001 (0.974,1.028)	0.97
uCa/C^c (per 0.01 increase	0.998 (0.986, 1.010)	0.75
uOx/uCi^d (per 0.01 increase)	1.016 (0.991, 1.041)	0.22
uCa/uCi^e	1.009 (0.993, 1.025)	0.30
uA/C, g/g	1.086 (0.695, 1.697)	0.72
uNAG/C (U/g)	1.007 (0.986, 1.028)	0.53
uα1-MG /C (mg/g)	1.007 (1.000, 1.013)	0.04
Pathological scores
Glomerular active index
No GN	reference
Mild-to-moderate activity	7.333 (0.661, 81.365)	0.11
Glomerular global sclerosis^f	1.731 (0.718, 4.173)	0.22
AT	3.524 (1.012, 12.272)	0.48
AI	1.086 (0.631, 1.869)	0.77
ATI^f	1.303 (0.890, 1.908)	0.17
CT	1.758 (0.553, 5.590)	0.34
CI	1.669 (0.820, 3.397)	0.16
CTI^g	1.344 (0.858, 2.105)	0.20

^a The ratio of urinary oxalate (mmol/L) to urinary creatinine (mmol/L); ^bthe ratio of urinary citrate (mmol/L) to urinary creatinine (mmol/L); ^cthe ratio of urinary calcium (mmol/L) to urinary creatinine (mmol/L); ^dthe ratio of urinary oxalate (mmol/L) to urinary citrate (mmol/L); ^ethe ratio of urinary calcium (mmol/L) to urinary citrate (mmol/L); ^fATI = AT + AI; ^gCTI = CT + CI.

KFRT: kidney failure with replacement therapy; RAASi: renin–angiotensin–aldosterone system; NSAIDs: non-steroidal anti-inflammatory drugs; GN: glomerulonephritis; uOx: urinary oxalate; uCi: urinary citrate; uCa: urinary calcium; uNAG/C: urinary NAG to urinary creatinine ratio; α1-MG/C: urinary α1-microglobulin to urinary creatinine ratio; AT: acute tubular injury score; AI: acute interstitial injury score; CT: chronic tubular injury score; CI: chronic interstitial injury score

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.