Incidence of Contrast-induced Nephropathy in Kidney Transplant Recipients

• Contrast induced nephropathy (CIN) is characterized by the development of acute kidney injury (AKI) after the administration of intravascular iodinated radio-contrast in the absence of any other etiology of AKI. Incidence of CIN for those without pre-existing renal impairment ranges from 0.6%–2.3%, however, risk increases to 12–26% for those with risk factors for CIN. Common risk factors are pre-existing renal impairment, DM, advanced age, peri-procedural intravascular volume-depletion, congestive heart failure and concomitant use of other nephrotoxic drugs. Patients who develop CIN have high morbidity and mortality in the short and long term.
• We proposed that Kidney transplant recipients (KTRs) may be at higher risk of CIN, due to high prevalence of CKD, DM, CVD and the concurrent use of a nephrotoxic calcineurin-inhibitor (CNI) for immunosuppression. CNI are used in more than 95% of KTR. Very little information is available about incidence of CIN in KTRs. To our knowledge, only 4 studies (all retrospective) exist and were published in 1975, 1983 and 2000. Only one of these studies was done after the introduction of CNIs. There are no prospective studies of CIN in KTRs.
• As such, we felt the need to explore this area in the CNI era. Important contrast based testing is often avoided in KTR for fear of CIN. We found that the risk of CIN is not elevated, despite being on calcineurin inhibitors, in patients with relatively high GFR. This finding will hopefully reassure the clinicians and help perform important testing that may involve contrast in a selective group of KTR.

Contrast-induced nephropathy (CIN) is responsible for one-third of acute kidney injuries (AKI) in the hospital setting. The incidence of CIN varies from 3% to 30%, depending on the preexisting risk factors, with higher incidence noted with diabetes mellitus, chronic kidney disease, and older age. Though CIN risk factors are common in kidney transplant recipients (KTRs), data about incidence of CIN in this population are sparse.MethodsWe retrospectively analyzed 124 consecutive patients transplanted at our center between January 2002 and December 2013 and received iodinated intravascular contrast with stable kidney function prior to contrast administration. CIN was defined as either an absolute rise in serum creatinine of ≥0.5 mg/dL or a ≥25% drop in estimated glomerular filtration rate (eGFR) after contrast administration.ResultsSeven of 124 (5.64%) patients developed CIN. Kidney function returned to baseline in 5 of the 7 patients within 3 weeks. In 2 patients serum creatinine remained elevated due to recurrent AKI episodes from other causes. Dialysis was not required in any patient. Calcineurin inhibitors (CNIs) were being used in 95% patients at the time of contrast administration. Diabetes mellitus, baseline serum creatinine, age, race, gender, and the use of ACE inhibitor, angiotensin receptor blocker, diuretic, or prophylaxis with intravenous hydration ± N-acetylcysteine did not affect the incidence of CIN.ConclusionIncidence of CIN in KTRs was low in our study (5.6%), much less than previously reported. This low incidence may be related to the high baseline eGFR (>70 mL/min/1.73 m2) and use of hypo-osmolar contrast in our patients. In KTRs with baseline eGFR >70 mL/min, the incidence of CIN is low despite the concurrent use of nephrotoxic CNI.