Contrast-induced nephropathy

Contrast-induced nephropathy (CIN) is a purported form of kidney damage in which there has been recent exposure to medical imaging contrast material without another clear cause for the acute kidney injury. Despite extensive speculation, the actual occurrence of contrast-induced nephropathy has not been demonstrated in the literature. Analysis of observational studies has shown that radiocontrast use in CT scanning is not causally related to changes in kidney function. Given the increasing doubts about the contribution of radiocontrast to acute kidney injury, the American College of Radiology has proposed the name contrast-associated acute kidney injury (CA-AKI) (formerly referred to as post-contrast acute kidney injury; PC-AKI) because it does not imply a causal role, with the name contrast-induced acute kidney injury (CI-AKI) (formerly referred to as contrast-induced nephropathy; CIN) reserved for the rare cases where radiocontrast is likely to be causally related. There are multiple risk factors of contrast-induced nephropathy, whereof a 2016 review emphasized chronic kidney disease, diabetes mellitus, high blood pressure, reduced intravascular volume, and old age. European guidelines classify a pre-existing decreased kidney function to be a risk factor of contrast-induced nephropathy in the following cases: Estimated glomerular filtration rate (eGFR) < 45 ml/min/1.73 m2 of body surface area before intra-arterial administration with first-pass renal exposure (not passing lungs or peripheral circulation before kidneys), or in the intensive care unit eGFR < 30 ml/min/1.73 m2 before intravenous administration or intra-arterial administration with second-pass renal exposure Known or suspected acute kidney injury To calculate estimated GFR (a measure of kidney function) from creatinine, European guidelines use the CKD-EPI formula in adults ≥ 18 years, and the revised Schwartz formula in children. Swedish guidelines recommends no specific formula in children because of lack of evidence, but on the other hand recommends GFR based on cystatin C rather than creatinine in those with abnormal muscle mass, liver failure, or cirrhosis.