Acute Kidney Injury

[Age]-yo [M/F] with PMH of..., presenting with
days constant/intermitent *** progressively worsening/improving

  • CC: decreased urine output / generalized weakness / fatigue / poor PO intake / edema / SOB / confusion / nausea-vomiting

  • PP: recent dehydration, diarrhea/vomiting, poor intake, hypotension, sepsis, contrast exposure,

  • PN:denies chest pain, fever, dysuria, hematuria, severe abdominal pain

  • pertinent SHx: tobacco, EtOH, drug use

  • Etiology: pre-renal (dehydration/sepsis), intrinsic (ATN/AIN/glomerulonephritis), post-renal (obstruction/BPH)

  • initial DATA

    • CBC, CMP (BUN/Cr ratio often >20 prerenal), Mag, Phos, LFTs,

    • UA (Hyaline cast -> prerenal, ATN-> Muddy brown , GN->RBC cast ,AIN->WBC casts )

    • FeNa (Urine Na and Urine Cr)(<1% pre-renal, >2% ATN) Less specific in CKD and diuretic use, or FEUrea <35% (if on diuretics, suggest pre-renal) >50% → ATN,

    • serum CK** if c/f rhabdo,

    • renal US vs CTAP if c/f obstruction suspected

  • pending DATA:

  • MEDS: (NSAIDs, ACE/ARB, abx, anticholinergics, PPI, allopurinol)

  • meeting criteria : ↑ Creatinine ≥ 0.3 mg/dL in 48 hours or ↑ Creatinine ≥ 1.5× baseline within 7 days or Urine output < 0.5 mL/kg/hr for 6 hours

  • DDX:

    • Pre-Renal - hypovolemia, dehydration, decreased effective volume with CHF/cirrhosis, shock, change in renal dynamics with NSAIDs, ACEi/ARB;

    • Intrinsic - ATN MC (socks/toxins, muddy brown casts), then GN (Immune-mediated, post-infectious,RBC casts + protein), AIN (NSAIDs, PPIs, antibiotics, ifx, Fever + rash + eosinophilia, WBC casts) vascular;

    • Post-Renal - retention, obstruction (BPH, stones, tumors),

    • Can't Miss DDX: Glomerulonephritis - tea-colored urine; Vasculitis - rash, hemoptysis, arthritis, h/o autoimmune dx; Rhabdo (cause of ATN) - found down, seizure, muscle pain, proximal muscle weakness; AIN - new meds (NSAIDs, beta-lactams, sulfa, PPI, allopurinol); Complex Obstruction - cancer*

  • COURSE:

Plan:
-- f/u FeNa or FEUrea, Urine-Na, Urine Cr
-- trend electrolytes and replete
-- 500cc-1L IV fluid challenge if suspected to be prerenal (( If Cr improves to baseline in <48H then was likely pre-renal ))
-- 1/2 L LR -> 125 ml/hr (prerenal)
-- daily BUN, Creatinine, and BMP for hyperK, hyperPhos, acidosis, uremia
-- strict I/O,
-- avoid nephrotoxoc agents: NSAIDs, ACE/ARB, diuretics
-- if c/f Post-Renal etiology - place foley, give alpha-antagonists (tamsulosin) or 5-alpha-reductase inhibitors if BPH; perc nephrostomy if malignant obstruction
-- Nephrology consult for RRT (AEIOU)
-- if c/f AIN - stop the offending agent (NSAIDs, PPIs, antibiotics) Nephrology consult , pred 40-60mg daily for 1-2 weeks
-- ATN - Supportive care ONLY Optimize perfusion
-- c/f Glomerulonephritis Nephrology consult, Steroids (first-line in many GN) ± immunosuppressants