What is the Clinical significance of Contrast induced nephropathy?
Contrast induced nephropathy is defined as an increase in the pre-contrast baseline serum creatinine within 48 to 72 hours following contrast administration.
Most studies have defined Contrast induced nephropathy as an elevation of serum creatinine of >0.5 mg/dL or >25% of baseline value.
Some studies now define using the AKIN criteria of >0.3 mg/dL.
CIN has been shown to be associated with an increase in hospital and long-term morbidity and mortality.
It is noted as the third leading cause of Acute Kidney Injury for inpatients with retrospective studies showing its incidence varying between 3% and 30% depending on contrast volume, concomitant risk factors, and whether the contrast is given intravenously or arterially.
Lower incidences are seen with venous administration. The in-hospital mortality rates in a large retrospective analysis were 1.1% without Contrast induced nephropathy, 7.1% in CIN not requiring dialysis, and 35.7% for those with Contrast induced nephropathy requiring dialysis; fortunately,
Contrast induced nephropathy requiring dialysis is rare (typically representing less than 2% of Contrast induced nephropathy). Although Contrast induced nephropathy is usually reversible and rarely requires renal replacement, studies have shown that Contrast induced nephropathy requiring dialysis has a 2-year survival rate of less than 40%.
This high mortality rate is difficult to interpret and difficult to solely contribute to CIN, as these patients tend to have confounding comorbidities that also place them at higher mortality risk.
Contrast induced nephropathy also has been shown to be an independent risk factor for subsequent chronic kidney disease (CKD), as noted in many retrospective studies.
There has been an association between Contrast induced nephropathy and mortality, but a causal relationship has never been truly established. Several retrospective studies have shown that less than one-third of patients with Contrast induced nephropathy will have some permanent loss of kidney function following an episode of Contrast induced nephropathy.