# Contrast-Induced Acute Kidney Injury — KDIGO 2012

## Definition

Contrast-induced AKI (CI-AKI) is defined as AKI occurring after intravascular administration of contrast media, in the absence of an alternative etiology. The general KDIGO AKI definition criteria apply (increase in SCr >= 0.3 mg/dL within 48 hours, or >= 1.5 times baseline within 7 days, or urine output < 0.5 mL/kg/h for 6 hours).

## Risk Assessment

### Risk Factors for CI-AKI

- Suggest screening patients for risk of CI-AKI, in particular by assessing for **pre-existing impairment of kidney function** (Not Graded).

The principal risk factor for CI-AKI is **pre-existing CKD**, particularly when eGFR < 60 mL/min/1.73 m2.

> **OpenMedicine Calculator:** `calculate_ckd_epi` — available via MCP for automated eGFR calculation to assess CI-AKI risk.

Additional risk factors include:

- Diabetes mellitus (especially with existing nephropathy)
- Dehydration or volume depletion
- Congestive heart failure
- Advanced age (> 75 years)
- Concurrent use of nephrotoxic agents (NSAIDs, aminoglycosides)
- High volume of contrast media
- Intra-arterial contrast administration
- Use of high-osmolar contrast media

## Contrast Media Selection

- Recommend using **either iso-osmolar or low-osmolar iodinated contrast media**, rather than high-osmolar iodinated contrast media, in patients at increased risk of CI-AKI (Grade 1B).
- Use the **lowest possible dose of contrast medium** in patients at risk for CI-AKI (Not Graded).

### Contrast Media Classification

| Type | Osmolality (mOsm/kg) | Examples |
|---|---|---|
| **High-osmolar** | > 1400 | Diatrizoate (ionic) |
| **Low-osmolar** | 600-800 | Iohexol, iopamidol, ioxaglate |
| **Iso-osmolar** | ~290 | Iodixanol |

## Volume Expansion (Primary Prevention Strategy)

Volume expansion with IV isotonic fluids is the only strategy consistently shown to reduce the incidence of CI-AKI.

- Recommend **IV volume expansion with either isotonic sodium chloride or sodium bicarbonate solutions**, rather than no IV volume expansion, in patients at increased risk for CI-AKI (Grade 1A).
- Recommend **not using oral fluids alone** in patients at increased risk of CI-AKI (Grade 1C).

### Infusion Protocol

- Fluids should be started at least **1 hour before** and continued for **3-6 hours after** contrast-media administration.
- No clear evidence exists in the literature to guide the choice of optimal rate and duration of fluid infusion; clinical judgment should be applied.

## Pharmacological Prevention

### N-Acetylcysteine (NAC)

- Suggest using **oral NAC, together with IV isotonic crystalloids**, in patients at increased risk of CI-AKI (Grade 2D).
- The evidence for NAC benefit remains uncertain and of very low quality.
- Note: This recommendation differs from the recommendation against NAC for postsurgical AKI prevention (Grade 1A) and for AKI in hypotensive critically ill patients (Grade 2D).

### Theophylline and Other Agents

- No specific recommendation is made for or against theophylline in the prevention of CI-AKI.
- No specific recommendation is made for fenoldopam or dopamine in CI-AKI prevention.

## Prophylactic Dialysis

- Suggest **not using prophylactic intermittent hemodialysis (IHD) or hemofiltration (HF) for contrast-media removal** in patients at increased risk for CI-AKI (Grade 2C).

## Decision Algorithm — CI-AKI Prevention

1. **Assess risk:** Determine eGFR; identify diabetes, heart failure, volume depletion, concurrent nephrotoxins.
   - If **eGFR >= 60 mL/min/1.73 m2** and no other risk factors: standard precautions only.
   - If **eGFR < 60 mL/min/1.73 m2** or multiple risk factors: proceed to risk reduction.
2. **Risk reduction:**
   - Use iso-osmolar or low-osmolar contrast (Grade 1B).
   - Use the lowest possible contrast volume (Not Graded).
   - Start IV isotonic saline or sodium bicarbonate at least 1 hour before contrast exposure (Grade 1A).
   - Continue IV fluids for 3-6 hours post-procedure.
   - Consider oral NAC in combination with IV fluids (Grade 2D).
   - Do NOT use prophylactic dialysis for contrast removal (Grade 2C).
3. **Monitor post-procedure:** Measure SCr at 48-72 hours after contrast administration to detect CI-AKI.

## Limitations

- The evidence base for CI-AKI prevention is of low to moderate quality overall.
- The benefit of NAC remains controversial; the 2D grade reflects very low certainty in the evidence.
- Isotonic sodium bicarbonate has not been demonstrated to be clearly superior to isotonic sodium chloride.
- The optimal volume, rate, and duration of IV hydration have not been definitively established.
- Risk prediction models for CI-AKI were not formally endorsed by the guideline.
