Early observations and pilot data that first suggested a new direction
Contrast-induced nephropathy (CIN) was long considered a significant iatrogenic complication, with prevention protocols including IV hydration and N-acetylcysteine (NAC) widely adopted despite limited evidence. The magnitude and clinical relevance of contrast-associated AKI were questioned as observational studies with propensity-matched controls showed that most creatinine elevations after contrast exposure were not caused by the contrast itself but reflected baseline AKI risk and natural creatinine variation.
Landmark RCTs and pivotal trials that established the evidence base
The PRESERVE trial was the largest and most rigorous trial of CIN prevention. Among 5,177 high-risk patients scheduled for angiography, neither sodium bicarbonate over normal saline (4.4% vs 4.7%, p=0.62) nor NAC over placebo (4.6% vs 4.5%, p=0.88) reduced the composite of death, dialysis, or persistent kidney injury at 90 days. The trial was stopped early at a prespecified interim analysis for futility. This definitively showed that neither intervention was effective, overturning decades of clinical practice.
Follow-up studies, subgroup analyses, and real-world validation
The AMACING trial went further, questioning whether prophylactic IV hydration itself was necessary. Among 660 high-risk patients (eGFR 30-59 mL/min) undergoing contrast procedures, no prophylaxis was noninferior to standard IV hydration for CIN incidence (2.6% vs 2.7%). Additionally, 5.5% of hydrated patients had complications from the hydration itself. This challenged the assumption that IV hydration was the minimum standard of care, particularly for patients with moderate CKD receiving intravenous contrast.
Integration into clinical practice guidelines and recommendations
Radiology and nephrology guidelines have substantially de-escalated contrast prophylaxis requirements. The ACR updated guidance to recommend that IV hydration may not be necessary for patients with eGFR ≥30 mL/min receiving IV iodinated contrast, and NAC is no longer recommended. For intra-arterial contrast or eGFR <30 mL/min, IV hydration remains conditionally recommended. The emphasis shifted to using the lowest effective contrast volume and avoiding repeat contrast exposure within 48-72 hours.
ACR
IV hydration not routinely necessary for eGFR ≥30 with IV contrast; NAC not recommended; minimize contrast volume
KDIGO
Risk-benefit assessment; IV hydration for very high-risk patients; avoid unnecessary contrast; NAC not effective
Now
Current standard of care and ongoing research directions
The contrast-AKI paradigm has undergone a fundamental reassessment. PRESERVE dismantled the NAC and bicarbonate practices, and AMACING questioned routine prophylactic hydration. The emerging consensus is that contrast-associated AKI has been overestimated and over-treated, and that withholding necessary contrast-enhanced imaging due to CIN fears may cause more harm than the contrast itself. Prevention now focuses on avoiding unnecessary contrast, using minimal volumes, and reserving hydration for the highest-risk patients.
Is N-acetylcysteine (NAC) effective for preventing contrast nephropathy?+
No. The PRESERVE trial (5,177 high-risk patients) definitively showed NAC was no better than placebo (4.6% vs 4.5%, p=0.88) for the composite of death, dialysis, or persistent kidney injury at 90 days. NAC is no longer recommended by major guidelines for contrast-AKI prevention.
Is IV hydration needed before contrast-enhanced imaging?+
For most patients, routine IV hydration may not be necessary. The AMACING trial (660 patients with eGFR 30-59) showed no prophylaxis was noninferior to IV hydration for contrast nephropathy (2.6% vs 2.7%), and 5.5% of hydrated patients had complications from the hydration itself. IV hydration may still be considered for very high-risk patients (eGFR <30) or intra-arterial contrast exposure.
