Incidence of Contrast-Induced Nephropathy after Contrast-Enhanced Computed Tomography in the Outpatient Setting

Background and objectives: No prospective study has reported the incidence of contrast-induced nephropathy (CIN) or the associated morbidity and mortality after contrast-enhanced computed tomography (CECT) in the outpatient setting.Design, setting, participants, & measurements: We enrolled and followed a prospective, consecutive cohort (June 2007 through January 2009) of patients who received intravenous contrast for CECT in the emergency department of a large, academic, tertiary care center. Outcomes measured were as follows (1) CIN: An increase in serum creatinine ≥0.5 mg/dl or ≥25% 2 to 7 d after contrast administration; (2) severe renal failure: An increase in serum creatinine to ≥3.0 mg/dl or the need for dialysis at 45 d; and (3) renal failure as a contributing cause of death (consensus of three independent physicians) at 45 d.Results: The incidence of CIN was 11% (70 of 633) among the 633 patients enrolled. Fifteen (2%) patients died within 45 d, including six deaths after study-defined CIN. Seven (1%) patients developed severe renal failure, six of whom had study-defined CIN. Of the six patients with CIN and severe renal failure, four died, and adjudicators determined that renal failure significantly contributed to all four deaths. Thus, CIN was associated with an increased risk for severe renal failure and death from renal failure.Conclusions: CIN occurs in >10% of patients who undergo CECT in the outpatient setting and is associated with a significant risk for severe renal failure and death.Contrast-induced nephropathy (CIN) is a known complication of intravenous, iodinated contrast; is a common cause of renal failure in the inpatient setting (1–5); and is associated with both short- and long-term adverse outcomes (6,7). Previous reports indicated that CIN occurs in 4 to 20% of patients after intra-arterial administration after coronary angiography (5–9). In the outpatient setting, the use of intravenous contrast to enhance (contrast-enhanced computed tomography CECT]) imaging has increased sharply in recent years. Despite that >6% of all emergency department (ED) patients undergo CECT in the United States (10), no prospective data allow clinicians to estimate the rate of CIN or the associated morbidity and mortality after CECT in the outpatient setting in a heterogeneous population. Previous, retrospective work in outpatients who underwent CECT found the prevalence of CIN to be 5 to 13% (11–14) and indicates that patients without baseline renal insufficiency or chronic kidney disease may still be at risk for CIN in this population (11); however, these studies were limited by retrospective design and selection bias related to inclusion of inpatients with existing kidney disease (11–14). Thus, the absence of predicate literature required to estimate both the incidence and the clinical significance of CIN after CECT provided rationale for this work.In this study, we sought to define prospectively the incidence of CIN in an unselected, consecutive, heterogeneous population of ED patients who received low-osmolar, nonionic contrast for a CECT study of any body region. We tested the hypothesis that the incidence of CIN in the ED population exceeds 4% and that CIN is associated with a high rate of severe renal failure and death (5–9,11).