Assessment of the order and interval between ^99mTc-DTPA renal scintigraphy and urinary system enhanced CT in affecting renal function

Objectives ^99mTc-DTPA dynamic renal scintigraphy and urinary system enhanced CT are routine preoperative examinations for patients in the department of urology. Previous studies suggested that, compared to the serum creatine, renal scintigraphy was more sensitive in reflecting renal function disorders. However, very few studies of CT contrast agent in affecting renal scintigraphy were reported. To avoid the potential but unclear effect, it was suggested that patients should take renal scintigraphy examination before or at least 48 hours after enhanced CT, which would affect the efficiency in clinical. The aim of this study was to compare the results of renal scintigraphy before urinary enhanced CT and after it within 48 hours,and to evaluate the influence of contrast agent on the results of renal scintigraphy.

Methods Till now, a total of 18 patients between 26 and 76 years old, with serum creatine less than 115umol/L, were enrolled in this study, including twelve men and six women. Informed consent forms were signed before the experiment. Each patient had ^99mTc-DTPA renal scintigraphy before urinary enhanced CT scan using contrast agent of loversol (80-90ml, iodine 320 mg/ml, with injection rate at 3ml/s). Within 48 hours, the patient received another ^99mTc-DTPA renal scintigraphy examination with the same condition as the first one. For both kidneys, paired t-tests were used in comparing the time to peak and glomerular filtration rate (GFR) based on each renal scintigraphy.

Results Before urinary enhanced CT scan, the average time to peak based on the renal scintgraphy is 4.9 minutes for the left kidney and 4.8 minutes for the right one; while the average time to peak is 5.9 minutes for the left kidney and 5.1 minutes for the right one after urinary enhanced CT scan (Table 1). No significant differences were found between them (P equals 0.128 and 0.555 for the left and right kidney separately). Based on each renal scintgraphy, the left kidney had an average GFR of 40.7 and 40.3 ml/min before and after urinary enhanced CT (P = 0.630); whereas the right one had 46.6 and 46.7 ml/min before and after (P = 0.935) .

Conclusions No significant different results of renal function from ^99mTc-DTPA renal scintigraphy were obtained before and after urinary enhanced CT scan. Therefore, no order or interval should be suggested between those two preoperative examinations.