AKI Following Contrast-Enhanced Computed Tomography in Pediatric Patients

Contrast-induced nephropathy (CIN) is the development of acute kidney injury (AKI) following exposure to iodinated contrast material, with incidence of AKI following intravenous contrast administration estimated to range from 1% to 20%, depending on the definition of AKI and the patient cohort. Compared with patients who do not develop CIN, those that do experience a higher rate of need for renal replacement therapy and death.

Patients identified as at risk for CIN may have contrast-enhanced examinations and procedures delayed or avoided. However, according to Jennifer S. McDonald, PhD, and colleagues, severity of CIN may have been overestimated in previous studies due to the lack of control groups of patients not administered contrast, and the attribution of  all cases of postcontrast AKI in the contrast-exposed group in those studies to CIN rather than other potential causes of AKI.

Further, there are few data available on the risks of administration of iodinated contrast in pediatric patients; Dr. McDonald et al. identified only one study comparing pediatric patients who received contrast to a control group not administered contrast. They recently conducted a retrospective cohort study designed to examine the rates of postcontrast AKI, dialysis therapy, and death in pediatric patients who underwent contrast-enhanced computed tomography (CT). The rates were compared with those of clinically matched patients who underwent unenhanced CT. Results of the study were reported in the American Journal of Kidney Diseases [2018;72(6):811-818].

The study population included pediatric (<18 years of age) patients who underwent either contrast-enhanced or unenhanced CT at the Mayo Clinic, Rochester, Minnesota, between December 2001 and January 2016. A total of 2201 pediatric patients (1773 contrast and 428 noncontrast) met all inclusion criteria; of those, 1741 (1391 contrast and 350 noncontrast) had height data recorded around the time of the CT to calculate estimated glomerular filtration rate (eGFR) as a measure of pre-CT kidney function.

Nearly half of the contrast recipients were female (n=830; 47%), and 1495 (84%) were emergency department (ED) admissions or inpatients at the time of CT; 12% (n=213) were in the intensive care unit (ICU) at the time of CT. In the 7 days prior to CT, 231 patients (13%) had dehydration diagnosed, 210 (12%) had received a blood transfusion, and 65 (3.7%) had received vasopressors. In the 7 days prior to CT, 2.0% (n=36) had precontrast AKI, 2.0% (n=36) had pyelonephritis, and 2.9% (n=52) had sepsis.

Among the 1773 patients in the contrast group, the rates of postcontrast AKI and dialysis therapy were 3.3% (59/1773) and 0.1% (2/1773), respectively. The majority of postcontrast was classified as stage 1 (n=59; 3.3%); two patients were classified as stage 2 (0.1%), and six as stage 3 (0.3%). Forty-four patients (2.5%) died within 30 days of CT.

Compared with the noncontrast patients, those who had contrast-enhanced CT were more likely to have presented to the ED; more likely to be in the ICU until the time of CT; had lower rates of pre-existing comorbid conditions (diabetes, hypertension, chronic kidney disease, glomerulopathy, reflux nephropathy, and obstructive uropathy); had lower rates of acute conditions present immediately before CT (precontrast AKI and obstructing renal stones); and were less likely to have received potentially nephrotoxic medications immediately prior to CT. Contrast patients also had slightly better kidney function prior to CT (measured by either serum creatinine level or eGFR) compared with patients in the noncontrast group.

A subgroup of 610 patients (305 contrast; 305 noncontrast) was identified by one-to-one matching using eGFR as a covariate. Prior to propensity score adjustment using eGFR as a covariate, the rates of postcontrast AKI, dialysis therapy, and death were higher in the noncontrast group than in the contrast group. Outcome rates became similar after matching by propensity score. Results were similar when using serum creatinine level as a covariate in the propensity score model rather than eGFR.

Following CT, six patients in the contrast group and three in the noncontrast group had stage 3 AKI diagnosed. Three of the eight (two contrast and one noncontrast) underwent dialysis following CT. The researchers performed a chart review on the eight patients to assess whether other factors were present that would have led to postcontrast AKI. All patients had a variety of contrast-independent potential causes of the postcontrast AKI: nephrotoxic drug treatment, sepsis, tumor lysis syndrome, hypoperfusion, and precontrast AKI.

Limitations to the study cited by the authors included the small sample size of the cohort coupled with the low incidence rates of postcontrast AKI and dialysis therapy that underpowered the researchers’ ability to fully assess those outcomes and determine the effects of contrast administration on the outcomes; the possibility of unmeasured confounders that could affect study outcomes; the exclusion of patients who underwent CT but had insufficient pre- or postcontrast serum creatinine results; the small proportion of the study population with decreased kidney at the time of the CT; and the inability to compare outcomes between various iodinated contrast materials.

“In conclusion, rates of AKI, dialysis therapy, and death following contrast-enhanced CT were very low in this pediatric cohort. Although not detectably different, an effect of contrast on these outcomes could not be ruled out,” the researchers said.

Takeaway Points

  1. There are few data available on the risks of administration of iodinated contrast material in pediatric patients regarding contrast-induced nephropathy; researchers at the Mayo Clinic conducted a retrospective cohort study to assess the risks of postcontrast acute kidney injury (AKI), dialysis therapy, and death.
  2. In the group with contrast-enhanced computed tomography (CT), the rates of AKI and dialysis therapy were 3.3% (59/1773) and 0.1% (2/1773). Following adjustment for propensity score modeling, there were no differences in the risk for AKI, dialysis therapy, or death between the group with contrast-enhanced CT and the group without contrast.
  3. All patients with post-contrast stage 3 AKI (six contrast and two noncontrast) also had contrast-independent potential causes of AKI.

following exposure to iodinated contrast material, with incidence of AKI following intravenous contrast administration estimated to range from 1% to 20%, depending on the definition of AKI and the patient cohort. Compared with patients who do not develop CIN, those that do experience a higher rate of need for renal replacement therapy and death.

Patients identified as at risk for CIN may have contrast-enhanced examinations and procedures delayed or avoided. However, according to Jennifer S. McDonald, PhD, and colleagues, severity of CIN may have been overestimated in previous studies due to the lack of control groups of patients not administered contrast, and the attribution of  all cases of postcontrast AKI in the contrast-exposed group in those studies to CIN rather than other potential causes of AKI.

Further, there are few data available on the risks of administration of iodinated contrast in pediatric patients; Dr. McDonald et al. identified only one study comparing pediatric patients who received contrast to a control group not administered contrast. They recently conducted a retrospective cohort study designed to examine the rates of postcontrast AKI, dialysis therapy, and death in pediatric patients who underwent contrast-enhanced computed tomography (CT). The rates were compared with those of clinically matched patients who underwent unenhanced CT. Results of the study were reported in the American Journal of Kidney Diseases [2018;72(6):811-818].

The study population included pediatric (<18 years of age) patients who underwent either contrast-enhanced or unenhanced CT at the Mayo Clinic, Rochester, Minnesota, between December 2001 and January 2016. A total of 2201 pediatric patients (1773 contrast and 428 noncontrast) met all inclusion criteria; of those, 1741 (1391 contrast and 350 noncontrast) had height data recorded around the time of the CT to calculate estimated glomerular filtration rate (eGFR) as a measure of pre-CT kidney function.

Nearly half of the contrast recipients were female (n=830; 47%), and 1495 (84%) were emergency department (ED) admissions or inpatients at the time of CT; 12% (n=213) were in the intensive care unit (ICU) at the time of CT. In the 7 days prior to CT, 231 patients (13%) had dehydration diagnosed, 210 (12%) had received a blood transfusion, and 65 (3.7%) had received vasopressors. In the 7 days prior to CT, 2.0% (n=36) had precontrast AKI, 2.0% (n=36) had pyelonephritis, and 2.9% (n=52) had sepsis.

Among the 1773 patients in the contrast group, the rates of postcontrast AKI and dialysis therapy were 3.3% (59/1773) and 0.1% (2/1773), respectively. The majority of postcontrast was classified as stage 1 (n=59; 3.3%); two patients were classified as stage 2 (0.1%), and six as stage 3 (0.3%). Forty-four patients (2.5%) died within 30 days of CT.

Compared with the noncontrast patients, those who had contrast-enhanced CT were more likely to have presented to the ED; more likely to be in the ICU until the time of CT; had lower rates of pre-existing comorbid conditions (diabetes, hypertension, chronic kidney disease, glomerulopathy, reflux nephropathy, and obstructive uropathy); had lower rates of acute conditions present immediately before CT (precontrast AKI and obstructing renal stones); and were less likely to have received potentially nephrotoxic medications immediately prior to CT. Contrast patients also had slightly better kidney function prior to CT (measured by either serum creatinine level or eGFR) compared with patients in the noncontrast group.

A subgroup of 610 patients (305 contrast; 305 noncontrast) was identified by one-to-one matching using eGFR as a covariate. Prior to propensity score adjustment using eGFR as a covariate, the rates of postcontrast AKI, dialysis therapy, and death were higher in the noncontrast group than in the contrast group. Outcome rates became similar after matching by propensity score. Results were similar when using serum creatinine level as a covariate in the propensity score model rather than eGFR.

Following CT, six patients in the contrast group and three in the noncontrast group had stage 3 AKI diagnosed. Three of the eight (two contrast and one noncontrast) underwent dialysis following CT. The researchers performed a chart review on the eight patients to assess whether other factors were present that would have led to postcontrast AKI. All patients had a variety of contrast-independent potential causes of the postcontrast AKI: nephrotoxic drug treatment, sepsis, tumor lysis syndrome, hypoperfusion, and precontrast AKI.

Limitations to the study cited by the authors included the small sample size of the cohort coupled with the low incidence rates of postcontrast AKI and dialysis therapy that underpowered the researchers’ ability to fully assess those outcomes and determine the effects of contrast administration on the outcomes; the possibility of unmeasured confounders that could affect study outcomes; the exclusion of patients who underwent CT but had insufficient pre- or postcontrast serum creatinine results; the small proportion of the study population with decreased kidney at the time of the CT; and the inability to compare outcomes between various iodinated contrast materials.

“In conclusion, rates of AKI, dialysis therapy, and death following contrast-enhanced CT were very low in this pediatric cohort. Although not detectably different, an effect of contrast on these outcomes could not be ruled out,” the researchers said.

Takeaway Points

  1. There are few data available on the risks of administration of iodinated contrast material in pediatric patients regarding contrast-induced nephropathy; researchers at the Mayo Clinic conducted a retrospective cohort study to assess the risks of postcontrast acute kidney injury (AKI), dialysis therapy, and death.
  2. In the group with contrast-enhanced computed tomography (CT), the rates of AKI and dialysis therapy were 3.3% (59/1773) and 0.1% (2/1773). Following adjustment for propensity score modeling, there were no differences in the risk for AKI, dialysis therapy, or death between the group with contrast-enhanced CT and the group without contrast.
  3. All patients with post-contrast stage 3 AKI (six contrast and two noncontrast) also had contrast-independent potential causes of AKI.