AKI & CKD Clinical Reference

KDIGO 2012 Definition (any of the following)

↑ SCr ≥ 0.3 mg/dL within 48 hours

↑ SCr ≥ 1.5× baseline within 7 days

UO < 0.5 mL/kg/h for ≥ 6 consecutive hours

Baseline SCr

Prior stable SCr (ideally within 3 months)
If unavailable: lowest SCr during hospitalization
Or: back-calculate using MDRD assuming eGFR = 75 mL/min/1.73m²

Key SCr Caveats

SCr lags GFR — may not rise until >50% nephron loss
Muscle mass affects baseline (elderly, malnutrition, cirrhosis → low SCr)
Cystatin C: less affected by muscle mass; emerging biomarker
NGAL, KIM-1, IL-18: early injury markers (not yet routine)

Distinction from CKD & Acute-on-Chronic

Feature	AKI	CKD	Acute-on-CKD
Onset	≤ 7 days	> 3 months	AKI criteria met on background CKD
Kidney size (US)	Normal / enlarged	Small, echogenic	Variable
Anemia	Not always	Normochromic, normo/microcytic	Both possible
PTH / Ca-PO₄	Not disrupted acutely	Elevated PTH, ↑ PO₄, ↓ Ca	Pre-existing abnormalities
Reversibility	Potentially full recovery	Irreversible loss	Partial recovery possible

KDIGO Staging (highest criterion applies)

Stage	SCr Criterion	UO Criterion	Clinical Severity
Stage 1	↑ ≥ 0.3 mg/dL or 1.5–1.9× baseline	< 0.5 mL/kg/h × 6–12 h	Mild; optimize hemodynamics, review nephrotoxins
Stage 2	2.0–2.9× baseline	< 0.5 mL/kg/h × ≥ 12 h	Moderate; consider nephrology consult
Stage 3	≥ 3× baseline or SCr ≥ 4.0 mg/dL or CRRT initiated	< 0.3 mL/kg/h × ≥ 24 h or anuria × 12 h	Severe; nephrology consult; consider RRT

Note: In patients < 18 years old, AKI stage 3 is also defined as eGFR < 35 mL/min/1.73m² or CRRT initiation.

Prognosis by Stage

Stage	30-day Mortality (ICU)	Risk of CKD progression
Stage 1	~10–15%	Low–moderate
Stage 2	~20–30%	Moderate
Stage 3	~40–60%	High; increased ESRD risk

Pre-renal

Volume depletion (hemorrhage, GI loss, burns)
↓ Effective circulating volume: HF, cirrhosis, sepsis
Renovascular: RAS, renal artery stenosis
Drugs: NSAIDs (↓ PGE₂), ACEi/ARB (↓ efferent tone), calcineurin inhibitors

FENa < 1% · FEUrea < 35% · UNa < 20 mEq/L · BUN:Cr > 20

Intra-renal

ATN (most common): ischemia, nephrotoxins
Glomerular: rapidly progressive GN, TTP/HUS
Interstitial: AIN (drugs, infection), sarcoid
Vascular: renal vein thrombosis, cholesterol emboli
Tubular: rhabdo, tumor lysis, cast nephropathy (myeloma)
Nephrotoxins: aminoglycosides, amphotericin B, contrast, cisplatin, vancomycin

FENa > 2% · Muddy brown casts (ATN) · WBC casts (AIN/GN)

Post-renal

Bladder neck obstruction (BPH, prostate Ca, clots)
Ureteral: stones, retroperitoneal fibrosis, external compression
Intrarenal: uric acid crystals (TLS), aciclovir, methotrexate

Post-void residual > 300 mL · Bilateral hydronephrosis on US

Common Urinalysis Findings by Cause

Finding	Suggests
Muddy brown granular casts + renal tubular epithelial cells	ATN
WBC casts + eosinophils (urine eos > 5%)	AIN
RBC casts + dysmorphic RBCs + proteinuria	Glomerulonephritis
Hyaline casts only	Pre-renal (concentrated urine)
Waxy / broad casts	Advanced CKD or severe AKI
Uric acid crystals	Tumor lysis syndrome
Free hemoglobin, no intact RBCs	Hemolysis / hemoglobinuria
Myoglobin (dipstick +blood, no RBCs)	Rhabdomyolysis

General Approach — All AKI

Identify & treat underlying cause — pre-renal correction (fluids/vasopressors), relieve obstruction, remove nephrotoxins

Hemodynamic optimization — MAP ≥ 65 mmHg (≥ 80 in CKD/HTN); avoid both hypovolemia and fluid overload (target CVP 6–12 if mechanically ventilated)

Fluid resuscitation — Isotonic crystalloid (0.9% NaCl or balanced salt: PlasmaLyte/Ringer's Lactate) preferred over colloids (KDIGO 2012); Albumin only in hepatorenal or sepsis (ATTAIN, SMART trial data)

Drug dose adjustment — CrCl-based or eGFR-based adjustment; monitor drug levels (vanc, aminoglycosides); hold nephrotoxins

Metabolic management — Hyperkalemia, acidosis, fluid overload, hyperphosphatemia

Nutritional support — 0.8–1.0 g/kg/day protein (non-RRT); 1.0–1.5 g/kg/day if on RRT; avoid hypocaloric nutrition

Hyperkalemia Management

K⁺ (mEq/L)	Intervention
5.5–6.0	Low-K diet, kayexalate or patiromer, repeat labs
6.0–6.5 (no ECG Δ)	+ Furosemide if urine output present; kayexalate
> 6.5 or ECG changes	IV Ca-gluconate 10 mL 10% (membrane stabilization) → insulin 10U + D50W → NaHCO₃ → nebulized salbutamol → dialysis

Fluid Strategy by Stage

AKI Stage	Fluid approach
S1	Fluid challenge if volume-depleted; reassess at 30 min; avoid excessive IVF if euvolemic
S2	Conservative after resuscitation; daily I&O balance, weight; target neutral to −500 mL/day if stable
S3	Strict fluid restriction; consider UF if > 10% body weight fluid overload; prepare for RRT

Contrast-Induced AKI Prevention

Risk threshold: eGFR < 30 (intra-arterial) or eGFR < 45 with DM/CKD (intravenous iodinated contrast)

IV isotonic saline: 1–1.5 mL/kg/h × 3–12 h pre and 6–12 h post (KDIGO 2012)
Hold metformin 48 h pre/post if eGFR < 45
Use lowest volume of low-osmolar or iso-osmolar contrast
NAC: no benefit (PRESERVE trial 2018); not recommended
Avoid NSAIDs, ACEi/ARB day of procedure if high risk

Drug-Induced AKI — Key Offenders

Drug	Mechanism	Action
NSAIDs	↓ PGE₂ → afferent vasoconstriction	Stop; avoid in AKI/CKD eGFR <30
ACEi / ARB	↓ efferent tone → ↓ GFR	Hold in AKI; restart when stable
Aminoglycosides	Proximal tubular toxicity	Once-daily dosing preferred; drug levels
Vancomycin	Synergistic toxicity with pip-tazo	AUC-guided dosing; avoid pip-tazo combo
Amphotericin B	Tubular toxicity, afferent vasoconstriction	Use liposomal form; pre-hydration
Cisplatin	Proximal tubular DNA damage	Pre-hydration 1–2 L saline; amifostine not routine
Contrast media	Tubular toxicity + vasoconstriction	See CI-AKI section above

Emergent RRT Indications (AEIOU — any one sufficient)

A — Acidosis: refractory metabolic acidosis pH < 7.1–7.15 despite bicarbonate

E — Electrolytes: refractory hyperkalemia (K⁺ > 6.5 mEq/L) or symptomatic/ECG changes not responding to medical Rx

I — Intoxication: dialyzable toxins (methanol, ethylene glycol, lithium, salicylates, metformin)

O — Fluid Overload: pulmonary edema refractory to diuretics; > 10–15% body weight fluid accumulation

U — Uremia: encephalopathy, pericarditis, bleeding diathesis; BUN alone not a threshold (typically > 100–130 mg/dL in context)

RRT Modality Comparison

Feature	IHD (Intermittent HD)	CRRT	SLED / Hybrid
Hemodynamic stability	Less stable	Most stable	Intermediate
Solute clearance	Rapid, efficient	Slow, continuous	Intermediate
Preferred setting	Stable patients, dialyzable toxin	Hemodynamically unstable, ICP ↑, fluid overload	Intermediate, resource-limited
Anticoagulation	UFH or none	Regional citrate (preferred) or UFH	UFH or none
Drug clearance	Rapid removal — risk underdosing	Continuous — different dosing tables	Moderate
Nursing burden	Moderate	High (24h circuit)	Intermediate

Initiation Timing

STARRT-AKI (2020) & IDEAL-ICU (2018): Early vs. standard RRT initiation — no survival benefit from early initiation in the absence of AEIOU criteria. Initiate when indicated, not prophylactically.

CRRT Dose

KDIGO 2012: effluent dose ≥ 20–25 mL/kg/h
Prescribe 25–30 mL/kg/h to account for downtime
Higher dose (RENAL, ATN trials): no survival benefit above 25 mL/kg/h

Recovery Definition & Timing

Category	Definition
Full recovery	SCr returns to within 125% of baseline within 90 days
Partial recovery	SCr improved but > 125% baseline at 90 days
Non-recovery	Dialysis dependence at 90 days → classified as ESRD
AKD (Acute Kidney Disease)	AKI or GFR < 60 for < 90 days (KDIGO 2012 extension concept)

AKI → CKD Progression Risk

AKI survivors have 8–10× higher risk of developing CKD vs matched controls
Risk ↑ with: stage 3 AKI, pre-existing CKD, diabetes, older age, incomplete recovery
Each episode of AKI = independent risk factor for CKD progression

KDIGO 2012 Follow-up guidance: All AKI patients → SCr at 3 months post-discharge. If SCr remains elevated: manage as CKD; if resolved: counsel on increased CKD/CVD risk.

Post-AKI Discharge Checklist

Restart ACEi/ARB only when SCr stable (typically ≥ 7 days post-AKI resolution)

Resume metformin when eGFR > 45 mL/min/1.73m²

Review all medications for renal dose adjustments

Avoid NSAIDs and nephrotoxins

Follow-up SCr, urine ACR, BP at 3 months

Nephrology referral if eGFR < 60 or proteinuria persists at 3 months

Sources: KDIGO AKI Guidelines 2012; STARRT-AKI NEJM 2020; IDEAL-ICU NEJM 2018; RENAL NEJM 2009; ATN NEJM 2008. Thai CPG for AKI: not available as a separate document — KDIGO 2012 is used as primary reference at Songklanagarind Hospital.

KDIGO 2012 Definition

Abnormalities of kidney structure or function, present for > 3 months, with implications for health — defined by either ↓ GFR < 60 mL/min/1.73m² or markers of kidney damage (albuminuria, urinary sediment, histology, imaging, transplant history)

Markers of Kidney Damage

Albuminuria (ACR ≥ 30 mg/g or AER ≥ 30 mg/24h)
Urinary sediment abnormalities (RBC casts, WBC casts)
Electrolyte or other tubular disorders (e.g., Fanconi, RTA)
Structural abnormalities on imaging (polycystic kidneys, scars)
Renal transplant history

GFR Estimation (CKD-EPI 2021)

CKD-EPI 2021 (race-free) preferred over MDRD
Single measurement insuffiicient — must persist > 3 months
Cystatin C-based eGFR: confirmatory when SCr-based is uncertain (extreme muscle mass, pregnancy, cirrhosis)
Measured GFR (iohexol, inulin clearance): rarely needed; transplant workup, clinical trials

CKD vs AKI vs Acute-on-Chronic

Duration criterion	Kidney Disease Category
< 7 days	AKI
7–90 days	AKD (Acute Kidney Disease)
> 90 days	CKD

GFR Categories (G1–G5)

Category	eGFR (mL/min/1.73m²)	Description
G1	≥ 90	Normal or high (only CKD if damage marker present)
G2	60–89	Mildly decreased
G3a	45–59	Mild-moderately decreased
G3b	30–44	Moderately-severely decreased
G4	15–29	Severely decreased — prepare for RRT/transplant workup
G5	< 15	Kidney failure (add D if on dialysis: G5D)

Albuminuria Categories (A1–A3)

Category	ACR (mg/g)	AER (mg/24h)	Description
A1	< 30	< 30	Normal to mildly increased
A2	30–300	30–300	Moderately increased (microalbuminuria)
A3	> 300	> 300	Severely increased (macroalbuminuria / nephrotic range > 2000)

KDIGO Risk Matrix (GFR × Albuminuria)

GFR ↓ / ACR →

A1 <30

A2 30–300

A3 >300

G1 ≥90

Low

Moderate

High

G2 60–89

Low

Moderate

High

G3a 45–59

Moderate

High

V.High

G3b 30–44

High

V.High

G4 15–29

V.High

G5 <15

V.High

Risk = risk of CKD progression, AKI, and cardiovascular events. Monitor frequency matches risk category (Low: annual; Mod: 1–2×/yr; High: 2–3×/yr; V.High: ≥4×/yr).

Common Causes Globally & in Thailand

Rank	Cause	Key Features
1	Diabetic Nephropathy (DKD)	Most common worldwide; microalbuminuria → macroalbuminuria → ESRD; requires DM dx ≥ 5–10 yr usually; absent retinopathy → consider biopsy
2	Hypertensive Nephrosclerosis	Often bland UA; small echogenic kidneys; may co-exist with DKD
3	Glomerulonephritis	IgA nephropathy (most common GN), FSGS, membranous, MPGN; hematuria + proteinuria
4	Obstructive/Reflux Uropathy	BPH, recurrent UTI/VUR in childhood
5	ADPKD	Most common hereditary; large bilateral cysts; flank pain, hematuria, HTN; tolvaptan slows progression in rapidly progressive cases
6	Lupus Nephritis	ISN/RPS classification; class III/IV most severe; treat with MMF or cyclophosphamide
7	Other	Chronic pyelonephritis, myeloma kidney, NSAID nephropathy, analgesic nephropathy

Targets (KDIGO 2024 CKD Update)

Parameter	Target	Comment
Blood pressure	< 120 mmHg SBP (KDIGO 2024, standardized measurement)	Based on SPRINT; individualize in elderly, orthostatic hypotension, eGFR <30
Proteinuria	ACR < 30 mg/g (or maximum reduction achievable)	RAAS blockade first-line for proteinuric CKD
HbA1c	≤ 7.0% (individualize: relax to 7.5–8.0% in comorbid/elderly)	Tight control slows DKD progression; monitor for hypoglycemia
LDL-C	< 70 mg/dL (CKD G3–G5 = high CVD risk)	Statin ± ezetimibe; no new statin in G5D (SHARP trial)
eGFR decline	< 5 mL/min/1.73m²/year	Rapid loss: >10 mL/min/year or >25% in 5 years → investigate

Disease-Modifying Pharmacotherapy (KDIGO 2024)

Drug Class	Agent / Dose	eGFR Initiation	Key Benefit
ACEi or ARB First-line (proteinuric CKD)	Enalapril 5–40 mg/day Losartan 50–100 mg/day	Any eGFR; tolerate SCr rise ≤ 30%	↓ proteinuria, ↓ ESRD (RENAAL, IDNT)
SGLT2i First-line (DKD or proteinuric CKD)	Dapagliflozin 10 mg OD Empagliflozin 10 mg OD	eGFR ≥ 20 to initiate; continue until dialysis (DAPA-CKD, EMPA-KIDNEY)	↓ ESRD, ↓ hospitalization for HF, ↓ CV death
Finerenone Non-steroidal MRA (DKD)	Finerenone 10–20 mg OD	eGFR ≥ 25; K⁺ < 5.0 mEq/L at initiation	↓ CKD progression + CV events in DKD (FIDELIO-DKD, FIGARO-DKD)
GLP-1 RA DKD with DM or obesity	Semaglutide 0.5–1 mg SC/wk	Any eGFR; no renal dose adjustment	↓ proteinuria, ↓ CV events (FLOW trial 2024: renal outcomes in CKD)
Statin ± Ezetimibe	Rosuvastatin 10–20 mg ± Ezetimibe 10 mg	G3–G5 (non-dialysis); de novo statin in G5D not recommended (SHARP)	↓ CVD events (SHARP trial)
Dietary protein	0.6–0.8 g/kg/day (non-dialysis non-diabetic)	G3b–G5	↓ progression (MDRD study); monitor nutritional status

Dietary & Lifestyle Targets

Parameter	Recommendation
Sodium	< 2 g/day (= 5 g NaCl/day)
Potassium	Restrict if K⁺ > 5.0 mEq/L; patiromer/sodium zirconium cyclosilicate for chronic hyperkalemia
Phosphate	Restrict dietary phosphate in G3b+ with hyperphosphatemia; CaCO₃ or sevelamer as phosphate binders with meals
Protein	0.6–0.8 g/kg/day in G4–G5 (non-dialysis); 1.0–1.2 g/kg/day on HD
Exercise	≥ 150 min/week moderate aerobic; resistance training 2×/wk
Smoking	Cessation strongly recommended (accelerates progression)
NSAID	Avoid in eGFR < 30; caution in G3b

Drug Dose Adjustment by eGFR — Key Drugs

Drug	eGFR 30–59	eGFR 15–29	eGFR <15 / Dialysis
Metformin	Reduce dose; caution	Contraindicated	Contraindicated
Enoxaparin	Normal; monitor anti-Xa	0.75 mg/kg Q24h (DVT/PE Rx)	UFH preferred
Apixaban	Normal	Use with caution	Avoid (or use in CrCl ≥15 AF only)
Rivaroxaban	Normal (AF: 20→15 mg)	15 mg in AF; avoid VTE Rx	Avoid
Dabigatran	Reduce dose	Avoid	Avoid
SGLT2i	Continue (eGFR≥20)	Continue (eGFR≥20)	Stop at eGFR <20 for glycemic; continue cardio-renal if started
Allopurinol	100–200 mg/day	50–100 mg/day	50 mg OD or after each dialysis session
Digoxin	0.0625–0.125 mg/day; monitor levels	Avoid or very careful monitoring	Avoid

CKD-Mineral Bone Disease (CKD-MBD)

Begins at G3a; worsens progressively

Abnormality	Mechanism	Management
↑ Phosphate	↓ GFR → ↓ renal PO₄ excretion	Dietary restriction; CaCO₃ / sevelamer with meals
↓ Calcium	↓ calcitriol → ↓ GI Ca absorption	Calcitriol 0.25–0.5 mcg/day; correct Ca
↑ iPTH (2° HPT)	↓ Ca → ↑ PTH stimulus	Target iPTH 2–9× ULN in G5D; cinacalcet in dialysis; parathyroidectomy if refractory
↓ Vitamin D	↓ 1α-hydroxylase activity	Native Vit D3 → calcitriol (active form) in G4–G5

Renal Anemia

Hb typically < 11 g/dL in G4–G5; earlier in DKD

Cause: ↓ EPO production (principal) + iron deficiency + shortened RBC survival
Exclude iron deficiency first: TSAT < 20%, ferritin < 100–200 ng/mL
IV iron (Ferric carboxymaltose / Iron sucrose): TSAT < 30%, ferritin < 500 — treat before/instead of ESA
ESA (Epoetin / Darbepoetin): initiate when Hb < 10 g/dL after iron repletion; Hb target 10–11.5 g/dL; avoid Hb > 13 g/dL (↑ CV/stroke risk: TREAT trial)
HIF-PHI (Roxadustat, Daprodustat): oral alternative; approved in G3–G5 and dialysis; monitor BP and thrombosis

Metabolic Acidosis

Typical onset G3b–G4; target serum HCO₃⁻ ≥ 22 mEq/L
Sodium bicarbonate 0.5–1 mEq/kg/day PO (divided doses) — first-line (KDIGO 2024)
Veverimer: novel Cl⁻/HCO₃⁻ exchanger; not yet widely available
Correction slows CKD progression (BASE pilot, BICARB trial data)

Hyperkalemia

K⁺ > 5.0 mEq/L: dietary restriction, optimize acidosis
K⁺ > 5.5: patiromer 8.4–25.2 g OD or sodium zirconium cyclosilicate 10 g TID × 2 days → 5 g OD maintenance
Avoid stopping RAAS/SGLT2i for hyperkalemia — use potassium binders instead (allows continuation of renoprotective therapy)

Cardiovascular Risk

CKD is an independent cardiovascular risk factor. All G3+ patients should be considered at high–very high CVD risk. Major cause of death in CKD (exceeds ESRD mortality in G3–G4).

Statin: indicated in all CKD G3–G5 non-dialysis (SHARP trial LDL target < 70 mg/dL)
Aspirin: per CVD indication; not routine for primary prevention in CKD alone
SGLT2i: dual renal + cardiac benefit; prescribe for all CKD G2–G4 A2–A3 regardless of DM status (DAPA-CKD: non-DM benefit shown)
BP target: SBP < 120 mmHg (KDIGO 2024); individualize in frailty/orthostatic hypotension

Nephrology Referral Criteria (KDIGO 2012)

eGFR < 30 mL/min/1.73m² (G4–G5) — prepare for RRT

ACR > 300 mg/g (A3) persisting > 3 months

eGFR decline > 25% or > 5 mL/min/1.73m²/year

Refractory hypertension (≥ 3 drugs at max dose)

Hematuria + proteinuria → possible GN (biopsy consideration)

Unexplained AKI; suspected rare/hereditary kidney disease

RRT Modality Comparison

Feature	Hemodialysis (HD)	Peritoneal Dialysis (PD)	Kidney Transplant
Setting	In-center or home	Home (most)	Surgical; outpatient FU
Access	AV fistula (preferred), graft, or tunneled catheter	Peritoneal catheter	Deceased or living donor
Frequency	3×/wk (4 h); or daily nocturnal HD	CAPD: 4 exchanges/day; APD: nightly	Continuous; lifelong immunosuppression
Survival	Comparable to PD in first 1–2 years	May have early survival benefit; equivalent long-term	Best survival of all modalities
Residual renal function preservation	Faster loss	Better preserved	Restored
Contraindications	Poor vascular access, hemodynamic instability	Prior abdominal surgeries, adhesions, obesity, hernia	Active malignancy, active infection, severe CVD

Timing of RRT Initiation in CKD G5

IDEAL Trial (Cooper et al., NEJM 2010): Early start (eGFR 10–14) vs late start (eGFR 5–7 or uremic symptoms) — no survival difference. Initiate RRT based on clinical indication, not eGFR threshold alone.

Symptomatic uremia (encephalopathy, pericarditis, nausea/vomiting, wasting)
Fluid overload refractory to diuretics
Refractory hyperkalemia or acidosis
eGFR < 6 (practical floor even if asymptomatic)

AV Fistula Preparation Timeline

Refer vascular surgery when eGFR < 20 mL/min (CKD G4) or eGFR decline trajectory → ESRD within 12 months
AVF maturation: 6–12 weeks minimum before HD use
Preserve forearm veins (no antecubital IV in dominant arm)

Sources: KDIGO CKD 2012, KDIGO CKD 2024 Update (JASN), SHARP (Lancet 2011), DAPA-CKD (NEJM 2020), EMPA-KIDNEY (NEJM 2023), FIDELIO-DKD (NEJM 2020), FIGARO-DKD (NEJM 2021), FLOW (NEJM 2024), IDEAL (NEJM 2010), TREAT (NEJM 2009). Thai CPG for CKD: no current standalone CPG — KDIGO guidelines used as primary reference.