Acute Kidney Injury - Hospitalist Approach (KDIGO)

Algorithm Steps

1. ▶

   Start

   Acute Kidney Injury Identified

   Rising creatinine or decreased UOP

   1. ●

      Action

      KDIGO AKI Staging

      Classify severity

      • STAGE 1:
      • - Cr 1.5-1.9x baseline, OR
      • - Cr increase ≥0.3 mg/dL, OR
      • - UOP <0.5 mL/kg/hr x 6-12h
      • STAGE 2:
      • - Cr 2.0-2.9x baseline, OR
      • - UOP <0.5 mL/kg/hr x ≥12h
      • STAGE 3:
      • - Cr ≥3x baseline, OR
      • - Cr ≥4.0 mg/dL, OR
      • - UOP <0.3 mL/kg/hr x ≥24h, OR
      • - Anuria x ≥12h, OR
      • - Initiation of RRT
      1. ◆

         Decision

         Determine Etiology

         Pre-renal vs Intrinsic vs Post-renal

         1. ●

            Action

            Pre-renal AKI (Most common)

            Decreased renal perfusion

            • CAUSES:
            • - Hypovolemia (bleeding, dehydration)
            • - Hypotension (sepsis, cardiac)
            • - Decreased effective circulating volume
            • (CHF, cirrhosis, nephrotic)
            • - Renal artery stenosis
            • - ACEi/ARB in CKD
            • LABS:
            • - FENa <1%
            • - BUN/Cr ratio >20:1
            • - Urine Na <20 mEq/L
            • - Bland sediment
            1. ●

               Action

               Workup

               Diagnostic tests

               • BASIC:
               • - BMP, Mg, Phos, CBC
               • - UA with microscopy (sediment)
               • - Urine electrolytes (Na, Cr)
               • - Renal ultrasound (if not recent)
               • CALCULATE:
               • - FENa = (UNa × PCr)/(PNa × UCr) × 100
               • IF INTRINSIC SUSPECTED:
               • - Consider nephrology consult
               • - Complement (C3/C4)
               • - ANA, ANCA, anti-GBM
               • - Serum/urine protein electrophoresis
               1. ●

                  Action

                  Management Principles

                  General approach

                  • 1. TREAT UNDERLYING CAUSE
                  • 2. OPTIMIZE VOLUME STATUS:
                  • - Fluids if hypovolemic
                  • - Diuretics if overloaded
                  • 3. STOP NEPHROTOXINS:
                  • - NSAIDs, aminoglycosides
                  • - Hold ACEi/ARB temporarily
                  • 4. ADJUST DRUG DOSES for GFR
                  • 5. AVOID CONTRAST if possible
                  • 6. MONITOR I/Os, daily weights
                  • 7. NUTRITION: Avoid excessive protein
                  1. ⚠

                     Warning

                     Dialysis Indications (AEIOU)

                     When to call nephrology urgently

                     • A - Acidosis (pH <7.1, refractory)
                     • E - Electrolytes (K+ >6.5, refractory)
                     • I - Intoxication (lithium, methanol, etc)
                     • O - Overload (pulmonary edema, refractory)
                     • U - Uremia (encephalopathy, pericarditis)
                     • ALSO CONSIDER:
                     • - Rapidly rising Cr without clear cause
                     • - Oliguria/anuria >24h despite resuscitation
                     1. ✓

                        Outcome

                        Outcomes

                        Monitoring and prognosis

                        • Monitor Cr daily until stable
                        • Recovery: Days to weeks depending on cause
                        • Prerenal: Usually recovers quickly if treated
                        • ATN: May take 1-3 weeks to recover
                        • Increased CKD risk after AKI episode
                        • Follow-up with nephrology if severe
         2. ●

            Action

            Intrinsic AKI

            Damage to kidney itself

            • ATN (most common intrinsic):
            • - Ischemic (prolonged prerenal)
            • - Nephrotoxic (contrast, aminoglycosides)
            • - Muddy brown casts
            • - FENa >2%
            • AIN (Interstitial nephritis):
            • - Drug-induced (NSAIDs, PPIs, abx)
            • - WBC casts, eosinophils
            • GLOMERULONEPHRITIS:
            • - RBC casts, proteinuria
            • - Systemic symptoms
         3. ●

            Action

            Post-renal AKI

            Obstruction

            • CAUSES:
            • - BPH (most common in men)
            • - Malignancy
            • - Nephrolithiasis (bilateral/solitary)
            • - Retroperitoneal fibrosis
            • DIAGNOSIS:
            • - Renal US: Hydronephrosis
            • - Bladder scan: Retention
            • TREATMENT:
            • - Foley catheter (lower)
            • - Nephrostomy tube (upper)