Iodine absorption in patients undergoing ERCP compared with coronary angiography

Background: Systemic absorption of iodinated contrast material occurs during endoscopic retrograde cholangiopancreatography (ERCP), the clinical significance of which has not yet been determined. Methods: Urinary iodine excretion was measured before and after coronary angiography (n = 20) and ERCP (n = 12). Thyroid hormone levels were determined before iodine load and after 6 and 24 weeks. Results: Before coronary angiography, iodine excretion was 101 +/- 38.3 mu mol/mol creatinine and increased to 865.10(5) +/- 721.10(5) mu mol/mol on the next day (p less than or equal to 0.001). After 6 weeks, it was still elevated (167 +/- 88.8 mu mol/mol, p < 0.01). Before ERCP, iodine excretion was 115 +/- 60.3 mu mol/mol and reached a peak of 5.3.10(5) +/- 4.9.10(5) mu mol/mol (p < 0.001). Six weeks later, it had returned to baseline. Two patients in the coronary angiography group but none in the ERCP group had suppressed thyrotropin after 6 weeks. Conclusions: The systemic iodine load during ERCP is approximately 0.6% of the iodine load during coronary angiography. Therefore routine measurement of thyroid hormones before ERCP is not recommended.