Background The incidence of contrast nephropathy (CIN) following coronary angiography or percutaneous coronary intervention (PCI) in patients with diabetes mellitus (DM) may be up to 30% and is associated with increased long term morbidity and mortality.

Methods We recruited 208 consecutive patients undergoing elective or urgent coronary angiography or PCI with known DM and chronic kidney disease (CKD) (defined as eGFR <60 ml/min). CIN was defined as a post procedure rise in creatinine at day 3 of >25% from baseline or an absolute rise of 44.5 μmol/l. Severity of coronary disease was assessed using the SYNTAX Score and risk of CIN using the Mehran risk score. We evaluated serum and urine neutrophil gelatinase-associated lipocalin (NGAL) and albuminuria for additional information about CIN risk. N-acetylcysteine and intravenous hydration were given to all patients with eGFR <50 ml in accordance with local guidelines.

Results Baseline characteristics are summarised in table 1. 116 patients underwent coronary angiography and 92 underwent PCI. 39 patients (18.8%) developed CIN. Contrast dose was similar in the CIN and non-CIN group (p=0.249). The Mehran risk score was strongly predictive of CIN development (p<0.001). The SYNTAX score did not differ between those who did or did not develop CIN (p=0.188). A significant rise in serum NGAL was seen as early as 2 h post procedure in the CIN arm (p=0.03) and this persisted at 4 h (p=0.007) and 12–24 h (p=0.0015). Urine NGAL levels did not change significantly during the first 24 h. Neither albumin:creatinine ratio (p=0.149) or protein:creatinine ratio (p=0.635) predicted development of CIN.

Conclusions The current gold standard for measuring CIN is a rise in serum creatinine but this is of limited value as it does not increase until 48–72 h post renal injury. Neither the SYNTAX score, nor urinary albuminuria or proteinuria are predictive of CIN development. A rise in serum NGAL levels within the first 12 h following coronary angiography or PCI appears to be a very promising marker in the early diagnosis of CIN.