Acute Kidney Injury
at the bedside
definition (KDIGO)
- creatinine ≥1.5× baseline within 7 days
- or creatinine rise ≥26.5 µmol/L within 48 h
- or urine output <0.5 mL/kg/h for ≥6 h
KDIGO stages
- stage 1: creatinine 1.5–1.9× baseline, or a rise of ≥ 26.5 µmol/L; urine output < 0.5 mL/kg/h for 6–12 h
- stage 2: creatinine 2.0–2.9× baseline; urine output < 0.5 mL/kg/h for ≥ 12 h
- stage 3: creatinine ≥ 3× baseline, or ≥ 353.6 µmol/L, or starting dialysis; urine output < 0.3 mL/kg/h for ≥ 24 h, or anuria for ≥ 12 h
Stage determines investigation intensity, monitoring frequency, and nephrology timing. Stage 3 or any urgent indication: same-day nephrology.
review
- vitals · fluid balance
- urine output · weight trend
immediate actions
- ECG if hyperkalemia suspected
- stop nephrotoxins
- urinary catheter if obstruction suspected
escalate now if
- hyperkalemia
- pulmonary edema
- severe metabolic acidosis
- uremic encephalopathy
- uremic pericarditis
focused check
HPI
- volume depletion: vomiting, diarrhea, poor oral intake, diuretics, bleeding
- sepsis: fever, chills, infectious symptoms
- obstruction: LUTS, urinary retention, flank pain, anuria
- nephrotoxins: NSAIDs, ACEi / ARBs, contrast, aminoglycosides, vancomycin
- intrinsic renal: dark urine, hematuria, foamy urine, rash, arthralgia, hemoptysis
examination
- volume status: dry mucous membranes, orthostatic hypotension, JVP, peripheral edema
- cardioresp: pulmonary edema, heart failure
- abdomen: distended bladder, flank tenderness
- skin: rash, vasculitic lesions
send now
initial
- CBC · U&E
- calcium · magnesium · phosphate
- CK if rhabdomyolysis suspected
- VBG / ABG if unwell
urine
- urinalysis · microscopy
- urine ACR / PCR if indicated
imaging
- bladder scan if retention suspected
- renal ultrasound if obstruction suspected
- CT KUB if stones suspected or obstruction unclear on US
contrast media
- IV isotonic crystalloid: only intervention with consistent evidence for high-risk contrast studies
- NAC not recommended: PRESERVE (2017) and ACT (2011) showed no benefit; ACR 2024 moved away from KDIGO 2012’s weak suggestion of oral NAC
- do not delay necessary contrast imaging for AKI alone; if elective, agree timing and hydration with radiology
calculator FENa · MDCalc ↗︎
treat
general
- treat underlying cause
- stop nephrotoxins, renally adjust meds
- strict input / output charting · daily weight
hypovolemic
- balanced crystalloid bolus 250 to 500 mL, reassess after each
- repeat until euvolemic, then maintenance
obstructive
- bladder scan · Foley catheter
- relieve obstruction (catheter, nephrostomy, or stent)
- post-obstructive diuresis: if UOP >200 mL/h (>2 h) or >3 L/24 h, replace fluids and monitor closely
fluid overload
- restrict fluids to ~1 L/day (or urine output + ~500 mL insensible)
- IV loop diuretic, e.g. furosemide 40 to 80 mg IV (higher if CKD)
- diuretics treat overload, not AKI: no “flushing the kidneys”, never in hypovolemia
dialysis: AEIOU (an urgent indication, not a number)
- A acidosis (refractory; pH thresholds vary by protocol, commonly around 7.1)
- E electrolytes (refractory hyperkalemia)
- I intoxications (dialyzable)
- O overload (refractory to diuretics)
- U uremia (encephalopathy, pericarditis)
recheck
- creatinine and urine output per KDIGO stage: more often at higher stages
- daily weight and fluid balance while AKI active
- potassium after any correction or medication change
before leaving
- document: KDIGO stage, suspected cause, interventions, trend
- pending: repeat U&E, urine studies, or imaging sent
- hand over: current creatinine/urine-output trend, dialysis-indication watch, who to call
if not improving / further escalation
- urgent nephrology: dialysis indication (AEIOU), refractory hyperkalemia or acidosis, fluid overload unresponsive to diuretics, rapidly progressive GN or suspected vasculitis
- urgent urology: obstructed + infected system (pyonephrosis/urosepsis), bilateral obstruction or single functioning kidney, retention not relieved by catheter
MOC pearl
most inpatient AKI comes down to three questions: is the patient dry, overloaded, or obstructed?
evidence
| source | type |
|---|---|
| KDIGO AKI staging criteria | international guideline |
| PRESERVE trial 2017, ACT trial 2011 (contrast-AKI, N-acetylcysteine) | major peer-reviewed trials |
| ACR Manual on Contrast Media, 2024 edition (current NAC/hydration guidance) | specialty-society guidance |
Verify indication, dose, allergies, interactions, renal/hepatic function and local protocols before prescribing.
free the on-call checklist covers the whole shift on one printable page.
More clinical resources in the MOC+ Library →
reviewed Jul 2026updated Sep 2026file lab/rft-acute-kidney-injury