radiocontrast - induced nephropathy ( rin ) can lead to acute renal failure ( arf ) , which may require dialysis therapy . arf increases treatment cost due to sepsis , hemorrhage , respiratory failure , and a long hospitalization.[13 ] rin is an important cause of hospital - acquired arf and is responsible for 12% of cases . renal medullary hypoxia and the direct toxic effects of iodinated contrast agents on renal tubules are possible mechanisms responsible for the pathophysiology of rin . identified specific risk factors for rin are current renal insufficiency , diabetes mellitus , and high contrast volume , dehydration , advanced age ( > 70 years ) , congestive heart failure ( chf ) , and nephrotoxic drug use ( angiotensin converting enzyme inhibitor and nonsteroidal antiinflammatory drugs ) . patients at risk for radiocontrast nephropathy are recommended to use nonionic iso - osmolar or nonionic low osmolar contrast agents . increases in serum creatinine levels are useful for detecting rin . in the majority of patients , plasma creatinine levels rise within the first 2448 h after administering the radiocontrast agent , reach a peak within 35 days , and return to normal after 13 weeks . recent studies have reported that urine levels of il-18 ( a pro - inflammatory cytokine ) , kidney injury molecule-1 , and neutrophil gelatinase - associated lipocalin ( ngal ) levels are important for early detection of rin . some reports have shown that il-18 levels start to increase within 46 h and peak at 12 h in patients with acute renal injury . in this study , we aimed to compare the plasma creatinine levels with spot urine il-18 levels following radiocontrast administration . twenty patients ( 11 males and 9 females ) underwent diagnostic and therapeutic contrast - enhanced examinations at the department of internal medicine from january 2009 to march 2009 . the study was approved by the institute ethics committee and written consent was obtained from the selected patients based on a low mehran risk score ( 5 ) . patient demographic characteristics a precontrast - enhanced examination of serum blood urea nitrogen ( bun ) , creatinine , na , k , cl , ca , p , creatinine clearance was analyzed and they were repeated at 24 , 48 , and 72 h following contrast administration . spot urine il-18 levels were measured before and 6 and 24 h after radiocontrast administration with a human il-18 elisa kit ( biosource invitrogen human il-18 , california ) . intravenous iopromid ( 623 mg / ml , 1.5 ml / kg ; ultravist 300 ) , a three - way oral and rectal contrast material for abdominal ct scans , and 650 mg / ml meglumine diatrizoate ( urovist , 100 ml ) were used for every patient . glomerular filtration rate was calculated using the cockcroft 1 h before the procedure , 8.4% nahco3 plus 5% dextrose ( 3 ml / kg / h ) with 1200 mg / day n - acetylcysteine was given to all patients prophylactically . after radiocontrast agent administration , the same prophylactic treatment was continued ( 1 ml / kg / h ) for 6 h. during this time , hydration and urine output were followed by monitoring the intake and release of fluids . patients with no history of kidney disease , plasma creatinine values < 1.2 mg / dl , gfr60 ml / min , nondiabetic , no urinary infection , and no decompensated heart failure were included . urinary il-18 levels were measured with a human il-18 elisa kit ( biosource invitrogen human il-18 , carlsbad , ca , usa ) . the statistical analysis was performed with the ncss pass 2007 and 2008 statistical software ( kaysville , ut , usa ) . serum creatinine levels increased after radiocontrast administration compared with precontrast levels , although the result was not statistically significant [ table 2 ] . a slight increase in creatinine levels occurred at 48 h after radiocontrast administration but they fell to precontrast values at 72 h. a slight increase in plasma creatinine levels at 24 and 48 h following radiocontrast administration was observed compared with precontrast values , but it was not statistically significant ( p=0.052 and p=0.285 , respectively ) [ table 2 ] . plasma creatinine levels in patients before and after radiocontrast agent administration compared with precontrast urine spot il-18 levels , postcontrast 6 and 24 h urinary levels of il-18 increased significantly ( p=0.048 and p=0.028 , respectively ; table 3 ) . a tendency for postcontrast 24-h urinary il-18 levels to increase was observed compared with 6 h , but the increase was not statistically significant ( p=0.808 ; table 3 ) . spot urine il-18 levels in patients before and after radiocontrast agent administration plasma creatinine levels and spot urine il-18 were weakly but positively correlated with those during the precontrast period , although this finding was not statistically significant ( r=0.246 , p=0.126 ) . similarly , postcontrast 24-h plasma creatinine levels and spot urine il-18 levels were weakly but positively correlated , although this result was also not statistically significant ( r=0.254 , p=0.276 ) . there was no difference between pre- and postcontrast values of serum blood urea nitrogen ( bun ) , creatinine , na , k , cl , ca , p , and creatinine clearance . the most common definition of rin is plasma creatinine levels of 0.5 mg / dl or higher 72 h after contrast administration or 25% higher than the basal plasma creatinine level . plasma creatinine levels began to rise within 24 h in 80% of the patients with rin , peaking at 4872 h , and returning to baseline after 2 weeks . the first 24 h remains unclear in patients with acute renal injury , but il-18 levels start to increase within 46 h , peaking at 12 h. additionally , plasma creatinine is affected by age , body weight , total body volume , gender , race , drug use , muscle mass , and protein intake so researchers are looking for a diagnostic marker for rin that can be measured easily and is not affected by nonrenal factors . most studies related to these parameters include serum and urine cystatin c , serum and urine ngal , and urine il-18 in the analysis . as proinflammatory cytokine il-18 levels increase in urine , tubular inflammation , such as ischemia , reperfusion injury , allograft rejection , cisplatin toxicity , and endotoxemia occur . parikh et al . , found that 72 patients with acute tubular necrosis and delayed graft reaction have significantly higher il-18 levels than other kidney diseases ( urinary tract infection , chronic renal failure , nephrotic syndrome , or prerenal azotemia ) . reported that il-18 generally showed a low sensitivity but high specificity , respectively , for assessing an acute kidney injury diagnosis and risk classification . in our study , we examined spot urinary il-18 levels in comparison with plasma creatinine levels . a weak positive correlation was found between precontrast creatinine and urine il-18 levels , although it was not statistically significant . furthermore , we also found a weak positive correlation between postcontrast 24 h creatinine and urine il-18 levels , although this was not statistically significant either . a slight increase in plasma creatinine levels at 24 h and 48 h following radiocontrast administration was observed compared with precontrast values , but it was not statistically significant which was regressed to precontrast values at 72 h. a statistically significant increase in the level of spot urinary il-18 levels at 6 and 24 h postcontrast was observed , compared with precontrast spot urine il-18 levels and difference between 6 and 24 hour levels were not statistically significant . one of the limitations of this study is that there are other early biomarkers of acute kidney injury such as ngal and kim-1 . another limitation is that urine il-18 measurement was indexed to serum creatinine instead of urine creatinine since serum creatinine is considered to be a better and commonly used marker in the diagnosis of acute kidney injury . in conclusion , spot urine il-18 levels at sixth hour following radiocontrast administration suggesting that it may be an earlier parameter for identifying kidney injury .
radiocontrast administration is an important cause of acute renal failure . in this study , 
 compared the plasma creatinine levels with spot urine il-18 levels following radiocontrast administration . 
 twenty patients ( 11 males , 9 females ) underwent radiocontrast diagnostic and therapeutic - enhanced examinations . 
 the rin mehran risk score was low ( 5 ) . 
 the radiocontrast agents used were 623 mg / ml iopromid ( 1.5 ml / kg ) , and 100 ml of 650 mg / ml meglumine diatrizoate as three - way oral and rectal contrast material for abdominal computed tomography ( ct ) scans . 
 serum blood urea nitrogen , creatinine , na , k , cl , ca , p , creatinine clearance , and spot urine il-18 levels were analyzed before and repeated at 24 , 48 , and 72 h after radiocontrast administration . 
 six and 24-h urinary il-18 levels were measured with a human il-18 elisa kit following radiocontrast administration . 
 an increase in plasma creatinine 24 and 48 h following radiocontrast administration was observed compared with precontrast values , but it was not statistically significant ( p=0.052 and p=0.285 , respectively ) . a statistically significant increase in il-18 levels was observed at 6 and 24 h , compared with precontrast values ( p=0.048 and p=0.028 , respectively ) . 
 a tendency for postcontrast 24-h urinary il-18 levels to increase was observed compared with 6 h , but the increase was not statistically significant ( p=0.808 ) . 
 our results show that plasma creatinine starts to increase at 24th hour ; however , spot urine il-18 levels go up at 6th hour following radiocontrast administration implying urine il-18 to be an earlier parameter for kidney injury .