Original Research

Comparison of 99mTc-DMSA, 99mTc-DTPA and 99mTc-MAG3 Renal Scintigraphy in the Calculation of Relative Renal Function

10.4274/jus.galenos.2019.3107

  • Fadime Demir
  • Mustafa Demir

Received Date: 13.11.2019 Accepted Date: 24.11.2019 J Urol Surg 2020;7(2):130-133

Objective:

The aim of this study was to compare Tc-99m dimercaptosuccinic acid (99mTc-DMSA) renal cortical scintigraphy and Tc-99m diethylene triamine pentaacetic acid (99mTc-DTPA) and Tc-99m mercaptoacetyltriglycine (99mTc-MAG3) dynamic renal scintigraphy in the evaluation of relative renal function (RRF).

Materials and Methods:

Forty seven patients with renal cortical scintigraphy (with 99mTc-DMSA) and dynamic renal scintigraphy (with 99mTc-DTPA or 99mTc-MAG3) were included in this retrospective study. RRF obtained from 99mTc-DMSA, 99mTc-DTPA and 99mTc-MAG3 scintigraphies, clinical and demographic data were statistically analyzed.

Results:

There was a high correlation between 99mTc-DMSA renal cortical scintigraphy and dynamic renal scintigraphy (99mTc-DTPA or 99mTc-MAG3) in terms of RRF evaluation (r=0.981, p<0.001 and r=0.918, p=<0.001, respectively). While the Bland Altman plot showed an average difference of 3.30 between RRFs measured by 99mTc-DMSA and by 99mTc-DTPA, the difference between that with 99mTc-DMSA and 99mTc-MAG3 was 0.08.

Conclusion:

In conclusion, this study showed a high level of compliance between 99mTc-DMSA renal scintigraphy and dynamic renal scintigraphy (99mTc or 99mTc-MAG3) in the evaluation of RRF. Time loss, radiation exposed to the patients and economic losses are minimized with the use of a single method suitable for the purpose.

Keywords: Relative renal function, 99mTc-DMSA renal cortical scintigraphy, Dynamic renal scintigraphy

What’s known on the subject? and What does the study add?

Renal scintigraphies are frequently used tests to evaluate kidney parenchyma and collecting system. The relative renal function value can be calculated for both kidneys in each of these tests. This study shows whether there is a significant difference in the relative renal function calculation by comparing static renal scintigraphy (with DMSA) and the two most commonly applied dynamic renal scintigraphy (with DTPA and MAG3).


Introduction

Relative renal function (RRF) refers to the relative contribution rate of each kidney to total renal function. This rate is particularly important in patients with unilateral renal disorders and obstructive uropathies, as well as in terms of monitoring functional losses during follow-up. Kidneys with a RF value below 10% are unlikely to recover and nephrectomy is commonly recommended (1,2). In addition, it is known that RRF, calculated by scintigraphy, is a useful parameter in order to show whether the kidney function is improved or not from the early period of pyeloplasty (3). Likewise, it is used in the evaluation of the kidney donor’s renal function and to choose less functioning kidney. Therefore, radioisotopic RRF evaluation is a recommended test for the preoperative evaluation of potential renal donors (4).

Although recent studies on the calculation of RRF with computed tomography and magnetic resonance imaging have been published (5,6), the most commonly used method is scintigraphic imaging. Among these, Tc-99m dimercaptosuccinic acid (99mTc-DMSA) renal cortical scintigraphy is the most sensitive method to demonstrate parenchymal injury due to pyelonephritis and to collect data on RRF (7). 99mTc-DMSA is a radiopharmaceutical that binds to the proximal tubular cells in the renal cortex at a rate of 40-65% at 2 hours after the injection and allows visualization of the cortex (8). RRF can also be calculated by dynamic renal scintigraphies performed with Tc-99m mercaptoacetyltriglycine (99mTc-MAG3) and Tc-99m diethylene triamine pentaacetic acid (99mTc-DTPA). 99mTc-DTPA is the only radiopharmaceutical that is filtered by the glomerulus and can be used both for imaging the kidney and measuring the glomerular filtration rate. 99mTc-MAG3 is highly protein bound and the extraction rate is 40-50%. This ratio is more than twice that of 99mTc-DTPA. Therefore, 99mTc-MAG3 is preferred over 99mTc-DTPA in patients with suspected obstruction and renal dysfunction (9). There is no consensus on the interchangeability of these tests in the calculation of RRF.

The aim of this study was to compare 99mTc-DMSA scintigraphy and 99mTc-DTPA and 99mTc-MAG3 scintigraphy in the evaluation of RRF.


Materials and Methods


Patient Preparation

A total of 47 patients, who underwent renal cortical (with 99mTc-DMSA) and dynamic renal scintigraphy (99mTc-DTPA or 99mTc-MAG3) for several reasons between 2015 and 2019, were included in this retrospective study. Twenty-eight patients underwent 99mTc-DMSA and 99mTc-DTPA renal scintigraphy and 19 patients underwent 99mTc-DMSA and 99mTc-MAG-3 renal scintigraphy. Inclusion criterion was a time interval of less than one month between static and dynamic renal scintigraphy. Single kidney and horseshoe kidney patients were excluded from the study.


Dynamic and Static Renal Scintigraphy

99mTc-DMSA scintigraphy imaging was performed two hours after the injection (recommended dose according to age and weight is 1-5 mCi) in the  supine position using a dual head gamma-camera (E-CAM, Siemens, Germany) with low-energy parallel-hole collimator. RRF (%) was calculated by using manually drawn regions of interests (ROIs) around the kidney for the right and left kidneys and for background activity extraction (Figure 1A).

Dynamic renal scintigraphy was performed just after injection (recommended doses according to age and weight is between 1-5 mCi) in the supine position using a dual head gamma-camera (E-CAM, Siemens, Germany) with low-energy all-purpose parallel-hole collimator. Routine diuretic injection was performed at 15 min in dynamic renal scintigraphy. RRF (%) rates were calculated by using manually drawn ROIs around the kidney for the right and left kidneys and for background activity extraction (Figure 1B). RRF was measured on a composite image (2-3 min after the injection).


Statistical Analysis

Continuous variables are reported as mean ± standard deviation, whereas categorical variables are presented as absolute numbers. Spearman’s correlation coefficient was used for correlation analysis. A p value of less than 0.05 was considered statistically significant. All analyses were performed using the SPSS software (version 20.0). The Bland-Altman analysis was used with R software to assess the degree of agreement between RRF values.


Results

A total of 47 patients (18 male, 29 female) with the mean age of 18.21±19.83 (1-68 years) were included in the study. Renal scintigraphy was performed in 22 (46.8%) patients due to infection, in 12 (25.5%) due to  hydronephrosis and 13 (27.7) for other diagnoses.

The correlation between 99mTc-DMSA and dynamic scintigraphy (99mTc-DTPA and 99mTc-MAG3) was significantly high (p=0.934). The correlation between 99mTc-DMSA and 99mTc-MAG3 was higher than the correlation between 99mTc-DMSA and 99mTc-DTPA (Table 1, Figure 2).

Bland Altman plot between RRFs (%) measured using 99mTc-DMSA and 99mTc-DTPA showed a mean difference of 3.30 [95% confidence interval (CI) = (5.72; 0.88)]. The limit of agreement ranged from 14.28 to -7.67.

On the other hand, Bland Altman plot for between RRFs (%), measured by 99mTc-DMSA and 99mTc-MAG3 showed a mean difference of 0.08 [95% confidence interval (CI) = (1.92; -1.75)]. The limit of agreement ranged from 8.61 to -8.44 (Figure 3).


Discussion

In this study, measurements of RRF obtained by 99mTc-DMSA, 99mTc-DTPA and 99mTc-MAG3 renal scintigraphy were found to be highly compatible with each other. The agreement between 99mTc-DMSA and 99mTc-MAG3 measurements was much better than with 99mTc-DTPA.

RRF is an important parameter used for determination and monitoring of changes in renal function. Scintigraphy methods are often used to evaluate relative function. 99mTc-DMSA scintigraphy allows the imaging of renal cortical structure and thus it is a recommended test for evaluating infection and RRF (10). In their study, Momina et al. (11) compared RRF calculated with 99mTc-DMSA and 99mTc-DTPA scintigraphy and found a positive correlation between the two methods (r=0.996, p<0.001). In a similar study, Yalcin et al. (12) compared RRF values calculated by 99mTc-DTPA with those calculated by 99mTc-DMSA and reported that 99mTc-DTPA was also a good method for calculating RRF.

There are different diuretic administration protocols. Some of those are F + 20, F-15 and F-0 protocols. In a study comparing 99mTc-DTPA and DMSA scintigraphy in terms of RRF;  F +10 diuretic application in DTPA scintigraphy  provided more compatible results compared to F0 protocol (13). In our study, diuretic injection was performed in all the dynamic studies at 15 min. 

In a study by Aktas and Inanir (14) comparing 99mTc-DMSA and 99mTc-MAG3, it was found that RRF estimations with both methods showed significant correlation with good reproducibility in children with hydronephrosis. In a study by Othman et al. (15) comparing 99mTc-DMSA and 99mTc-MAG3 to evaluate renal cortex and RRF; it was reported that 99mTc-MAG3 scintigraphy provided adequate imaging for renal cortex evaluation and RRF. Ritchie et al. (16) reported that there was no significant difference between 99mTc-DMSA and 99mTc-MAG scintigraphy in terms of RRF and cortical evaluation. As a result, if the RRF is normal and there is no evidence of scar in the renal cortex on 99mTc-MAG3 scintigraphy, 99mTc-DMSA scintigraphy is not necessary.

In our study, we compared 99mTc-DMSA with 99mTc-DTPA and 99mTc-MAG3 to calculate RRF. We found a high correlation between 99mTc-DMSA and dynamic scintigraphies. However, the correlation between 99mTc-DMSA and 99mTc-MAG3 was a little better than with 99mTc-DTPA. In addition, in the Bland Altman analysis, the mean difference value of 99mTc-DMSA with 99mTc-MAG3 was very low. In a similar study,  Dostbil et al. (17) reported that the RRF calculated by 99mTc-DMSA, 99mTc-DTPA and 99mTc-MAG3 were compatible with each other and any of these techniques could be used. In their study of rabbits with unilateral ureteral obstruction, Lee et al. (18) compared renal function measurements obtained using 99mTc-DMSA with that by 99mTc-MAG3, and 99mTc-DTPA and found no significant difference. They concluded that 99mTc-MAG3, and 99mTc-DTPA could be used in place of the static image of 99mTc-DMSA.

A study performed with 99mTc-DMSA, 99mTc-DTPA and 99mTc-MAG3 in newborns and children showed that the kidney was the highest radiation-absorbed organ in the body and the radiation dose was the highest in 99mTc-DMSA, and least in 99mTc-MAG3 (19). In a study by Marcia et al. (20) the total radiation dose absorbed to the kidney was 0.00466 and 0.00339 mGy.MBq–¹ in renal scintigraphy with 99mTc-DTPA and 99mTc-MAG3, respectively. Total absorbed radiation dose to the kidney in dynamic renal scintigraphy  consists of the radiopharmaceutical activity in the kidney and in the bladder. In 99mTc-DMSA scintigraphy, the absorbed dose to the kidney was 0.17881 mGy.MBq–¹. Total absorbed radiation dose to the kidney in DMSA renal scintigraphy consists of the radiopharmaceutical activity in the kidney, bladder, spleen and liver. According to these results, the lowest radiation dose was determined in 99mTc-MAG3 study.


Conclusion

In conclusion, this study suggests that there is a high level of correlation between 99mTc-DMSA renal scintigraphy and dynamic renal scintigraphy (99mTc-MAG3 and 99mTc-DTPA) in terms of RRF evaluation. For this reason, any of these tests (the most appropriate for the clinical purpose) can be selected in the RRF evaluation. In this way, radiation, time loss and economic losses are minimized by a single measurement method.


Ethics

Ethic Committee Approval: This study was supported by Gaziosmanpaşa University Research Fund (project number: 19-KAEK-109).

Informed Consent: This was not necessary for retrospective study.

Peer-review: Externally peer-reviewed.

Authorship Contributions

Concept: F.D., Design: F.D., M.D., Data Collection or Processing: F.D., M.D., Analysis or Interpretation: F.D., M.D., Literature Search: F.D., M.D., Writing: F.D., M.D.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: No institutional or financial support was received. No animal or human studies were carried out by the authors for this article.

Images

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