contrast nephropathy (contrast-induced nephropathy, CIN)

Etiology

• contrast agents
  • intravenous contrast material is not responsible for most of the serum creatinine elevations after contrast-enhanced computed tomography
  • no evidence of contrast nephropathy from contrast agents used in computed tomography
    • no evidence for a harmful effect on kidney function of intravenous contrast administered for CT pulmonary angiography in an emergency setting
  • intravenous contrast not associated with increased risk of hemodialysis or death
  • low-osmolarity IV contrast not associated with acute kidney injury in critically ill patients
• patients at risk: (up to 27%)
  • patients with severe renal insufficiency
    • risk negligible if eGRR > 30 mL/min/1.73 m2
    • risk 0-17% for G4 & G5 renal failure
  • diabetic patients with mild renal insufficiency
  • hypotension
  • heart failure
  • intra-aortic balloon pump
  • age > 75-80
  • anemia
  • urgent or emergency procedure

Epidemiology

• up to 33% with angioplasty

Pathology

• vasoconstriction, obstruction & direct tubular toxicity
• acute tubular necrosis (ATN)
• hyperosmolarity of contrast agent may play role Clinical manifestasions
  • generally nonoliguric
    • only a few patients develop oliguric acute renal failure

Laboratory

• increase in serum creatinine
  • 24-48 hours after administration of contrast agent
  • increase in serum creatinine of 25% from baseline at 48 hours after contrast administration
• serum creatinine peaks in 3-5 days
• defined as 25% increase in serum creatinine
• return of serum creatinine to baseline within 1-2 weeks
• fractional excretion of Na+ (FENA) is < 1%
• urine osmolality is generally high
• urinalysis
  • muddy brown casts due to acute tubular necrosis (ATN)

Differential diagnosis

• acute tubular necrosis: - muddy brown casts in urine
• cholesterol emboli: blue toes, hypocomplementemia

Management

• prevention
  • prophylaxis not indicated if stable eGFR > 30-45 mL/min/1.73 m2
  • hydration:
    • 1 mL/kg/hr normal saline for 3-8 hours prior to contrast & 6-8 hours after contrast exposure for patients with G4 & G5 renal failure
    • isotonic sodium bicarbonate is alternative to normal saline
      • no benefit of sodium bicarbonate over normal saline
        • use normal saline (NEJM)
    • bioimpedance vector analysis promising non-invasive method to assess clinical hydration status
  • manage pharmacotherapy
    • not necessary to hold metformin
    • hold NSAIDS, diuretics unless volume overload
    • statins may reduce risk of contrast nephropathy in patients undergoing coronary angiography (relative risk = 0.58)
    • potassium nitrate (capsules) 1415 mg/day for 5 days starting the day prior to angiography
      • two beetroot shots/day (OTC) contains equivalent potassium nitrate
      • green leafy vegetables such as spinach also contain potassium nitrate but no specific dosage given
  • forced diuresis
    • high dose loop diuretics may aggravate contrast nephropathy
    • use of mannitol may increase risk
  • use of low or iso-osmolar iodinated contrast
    • use case with chronic renal failure G3b, eGFR= 32 mL/min/1.73 m2
  • N-acetylcysteine is effective; do not use (MKSAP) (NEJM)
  • neither bicarbonate nor N-acetylcysteine reduces contrast nephropathy relative to saline in patients undergoing coronary angiography
  • benefit uncertain, may benefit patients with serum creatinine > 1.2 mg/dL c 600 mg BID one day before & on the day of the procedure (4 doses)
    • of benefit
    • of marginal or no benefit {2 doses only; 1 hour prior to & 3 hours after}
  • 1200 mg IV prior to angioplasty, then 1200 mg PO BID for 2 days reduced contrast nephropathy 8% vs 33%
• efficacy of calcium channel blockers not established
• continuous venovenous hemofiltration of benefit in patients with chronic renal failure undergoing coronary angiography
• NaHCO3 154 mEq/L @ 3 mL/kg/hour for hour prior to contrast administration & @ 1 mL/kg/hour during & for 6 hours after procedure reduces contrast nephropathy (14% vs 2% vs normal saline)
  • further studies have failed to replicate this finding
  • not beneficial before computed tomography
  • use normal saline (NEJM)
• use of alternative imaging modality
  • non-contrast CT or MRI
  • ultrasonography
• generally low morbidity & mortality
• iodinated contrast is safe in patients on hemodialysis

More general terms

• nephropathy
• iatrogenic disease

More specific terms

• nephrogenic systemic fibrosis; nephrogenic fibrosing dermopathy (NSF/NFD)

Additional terms

• contrast agent