# AI instructs a diabetic patient to continue metformin during and after iodinated contrast administration without renal function check

- **ID:** `medical/contrast-hold-metformin`
- **Domain:** medical
- **Category:** data_error
- **Error Code:** `ACR-2024-MET`
- **Verification:** ai_generated
- **Fix Rate:** 82%

## Root Cause

Iodinated contrast can cause contrast-induced nephropathy (CIN), reducing renal clearance of metformin and precipitating lactic acidosis, a rare but fatal complication. Guidelines (ACR, ESUR) require checking eGFR before contrast; if eGFR <30 mL/min/1.73m², metformin must be held 48h before and after contrast; if eGFR 30-60, hold day of contrast and for 48h after.

## Workarounds

1. **Check eGFR before contrast. If eGFR >60 mL/min/1.73m²: continue metformin normally. If eGFR 30-60: hold metformin on day of contrast and for 48h after, then recheck eGFR. If eGFR <30: hold metformin 48h before and 48h after contrast, recheck eGFR before resuming.** (90% success)
   ```
   Check eGFR before contrast. If eGFR >60 mL/min/1.73m²: continue metformin normally. If eGFR 30-60: hold metformin on day of contrast and for 48h after, then recheck eGFR. If eGFR <30: hold metformin 48h before and 48h after contrast, recheck eGFR before resuming.
   ```
2. **For emergency contrast where pre-procedure eGFR is unavailable, hold metformin immediately, administer contrast, and check eGFR post-procedure. Resume metformin only if eGFR >30 and no evidence of CIN (creatinine rise <0.3 mg/dL).** (80% success)
   ```
   For emergency contrast where pre-procedure eGFR is unavailable, hold metformin immediately, administer contrast, and check eGFR post-procedure. Resume metformin only if eGFR >30 and no evidence of CIN (creatinine rise <0.3 mg/dL).
   ```

## Dead Ends

- **Assuming all diabetic patients on metformin need to stop before contrast regardless of renal function** — Overly cautious; patients with normal renal function (eGFR >60) can continue metformin safely. The decision depends on eGFR. (50% fail)
- **Telling patient to resume metformin immediately after contrast without checking post-procedure renal function** — If CIN develops, the reduced eGFR may still put the patient at risk; guidelines recommend waiting 48h and confirming renal function stable before resuming. (75% fail)
- **Using BUN or creatinine alone without calculating eGFR** — Creatinine alone is misleading in elderly or low muscle mass patients; eGFR (CKD-EPI equation) is the standard for metformin dosing decisions. (65% fail)