Effects of background substraction on differential kidney function measured by static scintigraphy with DMSA and dynamic scintigraphy with MAG 3

The aim of this study was to assess the influence of background subtraction (BS) on estimation of differential kidney function (DF) on the static scintigraphy with 99mTc dimercaptosuccinic acid (DMSA) and dynamic scintigraphy with 99mTc mercaptoacetyltriglicine (MAG3) and to establish possible differences between DF values estimated with these methods. Patients, methods: Patients (n = 106) were selected among those scheduled to static and dynamic scintigraphies within 3 months, with no interim clinical and laboratory changes, regardless the kidney pathology. DF was estimated according to the uptake ratio method. Four background regions of interest (ROIs) were applied, identical for both studies, and DF values were recalculated after BS. The corrected values were compared to the values before correction, separately for DMSA and MAG3, and between the studies. The results showed that ROIs used introduce variable results for the same patients, predominantly when noncorrected DF values were <45%. There were no significant differences between DF values (corrected and noncorrected) obtained from static and dynamic scintigraphy in all groups of patients. Since numerous reasons can bring to the errors in DF estimation when BS is used, the conclusions are that it would probably be more accurate to avoid BS, particularly when DF values are compared in a patient follow-up, and when kidney function is normal. BS should be used, but always in the same way, only when there is a significant difference in kidney size, or when DF is <25%, since background activity is then considerable. MAG3 and DMSA can be equally used for DF estimation and their results compared in patient follow-up.

Initial presentation of scintigraphic changes during the first episode of acute pyelonephritis in children

99mTc-DMSA scintigraphy is generally accepted as the method of choice for detecting renal parenchymal damage in pyelonephritis. 99mTc-MAG3 dynamic scintigraphy is not routinely used for this purpose. The aim of this study was to evaluate the MAG3 scintigraphic presentation in the acute phase of pyelonephritis in children and re-evaluate them at least 6 months later, as well as to establish whether a MAG3 in the parenchymal phase is as reliable and sensitive in the detection of a renal parenchymal damage as the DMSA. Patients, methods: The MAG3 scintigraphic pattern was evaluated during the first episode of acute pyelonephritis in 31 children (median age: 2.5 years) and compared to the DMSA scan. The scintigraphy was performed on the same day with both radiopharmaceuticals. After at least 6 months the whole procedure was repeated on 28 patients. A scoring system was designed to evaluate the parenchymal lesions, and categorize them as positive or equivocal. The findings on the initial scans were compared to those obtained in the follow up studies. Results: When all lesions (equivocal + positive) were analysed, MAG3 sensitivity was 98%, and specificity 78%, while for positive lesions only, the values were 83 and 100%, respectively. The average acute severity score was significantly lower for both MAG3 and DMSA then the follow up score (p <0.0001). These results corresponded to a clinical convalescence, which was observed in 26/28 children in the follow up. Conclusion: With the MAG3 scintigraphy a reliable semi quantitative and qualitative detection of the renal inflammatory lesions can be obtained in acute pyelonephritis, as well as their recovery, thus obviating the need for a DMSA scan. Moreover, the duration of the MAG3 procedure is shorter, enabling the visualization of the entire collecting system as well, while the radiation exposure is approximately a half of that delivered by the DMSA scan.

Effects of background substraction on differential kidney function measured by static scintigraphy with DMSA and dynamic scintigraphy with MAG 3

The aim of this study was to assess the influence of background subtraction (BS) on estimation of differential kidney function (DF) on the static scintigraphy with (99m)Tc dimercaptosuccinic acid (DMSA) and dynamic scintigraphy with (99m)Tc mercaptoacetyltriglicine (MAG3) and to establish possible differences between DF values estimated with these methods.

PATIENTS, METHODS

Patients (n=106) were selected among those scheduled to static and dynamic scintigraphies within 3 months, with no interim clinical and laboratory changes, regardless the kidney pathology. DF was estimated according to the uptake ratio method. Four background regions of interest (ROIs) were applied, identical for both studies, and DF values were recalculated after BS. The corrected values were compared to the values before correction, separately for DMSA and MAG3, and between the studies. The results showed that ROIs used introduce variable results for the same patients, predominantly when noncorrected DF values were <45%. There were no significant differences between DF values (corrected and noncorrected) obtained from static and dynamic scintigraphy in all groups of patients. Since numerous reasons can bring to the errors in DF estimation when BS is used, the conclusions are that it would probably be more accurate to avoid BS, particularly when DF values are compared in a patient follow-up, and when kidney function is normal. BS should be used, but always in the same way, only when there is a significant difference in kidney size, or when DF is <25%, since background activity is then considerable. MAG3 and DMSA can be equally used for DF estimation and their results compared in patient follow-up.

Initial presentation of scintigraphic changes during the first episode of acute pyelonephritis in children: simultaneous evaluation with MAG3 and DMSA

99mTc-DMSA scintigraphy is generally accepted as the method of choice for detecting renal parenchymal damage in pyelonephritis. 99mTc-MAG3 dynamic scintigraphy is not routinely used for this purpose. The AIM of this study was to evaluate the MAG3 scintigraphic presentation in the acute phase of pyelonephritis in children and re-evaluate them at least 6 months later, as well as to establish whether a MAG3 in the parenchymal phase is as reliable and sensitive in the detection of a renal parenchymal damage as the DMSA.

PATIENTS, METHODS

The MAG3 scintigraphic pattern was evaluated during the first episode of acute pyelonephritis in 31 children (median age: 2.5 years) and compared to the DMSA scan. The scintigraphy was performed on the same day with both radiopharmaceuticals. After at least 6 months the whole procedure was repeated on 28 patients. A scoring system was designed to evaluate the parenchymal lesions, and categorize them as positive or equivocal. The findings on the initial scans were compared to those obtained in the follow up studies.

RESULTS

When all lesions (equivocal + positive) were analysed, MAG3 sensitivity was 98%, and specificity 78%, while for positive lesions only, the values were 83 and 100%, respectively. The average acute severity score was significantly lower for both MAG3 and DMSA then the follow up score (p < 0.0001). These results corresponded to a clinical convalescence, which was observed in 26/28 children in the follow up.

CONCLUSION

With the MAG3 scintigraphy a reliable semi quantitative and qualitative detection of the renal inflammatory lesions can be obtained in acute pyelonephritis, as well as their recovery, thus obviating the need for a DMSA scan. Moreover, the duration of the MAG3 procedure is shorter, enabling the visualization of the entire collecting system as well, while the radiation exposure is approximately a half of that delivered by the DMSA scan.

Resistance and pulsatility indices in acute renal obstruction

PURPOSE

The aim of this study was to evaluate the reliability of Doppler waveform alterations in diagnosing acute unilateral renal obstruction.

METHODS

From December 1993 to January 1996, 54 patients with unilateral renal obstruction were prospectively examined by conventional and duplex Doppler sonography. Seventy-eight patients with nonrenal abdominal problems comprised the control group. Doppler signals were obtained from interlobar arteries and arcuate arteries at the corticomedullary junction. From the waveform analysis, we calculated resistance (RI) and pulsatility (PI) indices. We also used the differences in RI and PI between the 2 kidneys in the same examinee (delta RI and delta PI) for further statistical analysis.

RESULTS

The mean RI and PI (+/- standard deviation) in the patients without renal impairment were 0.64 +/- 0.04 and 1.14 +/- 0.14, respectively. The mean delta RI and delta PI were 0.02 +/- 0.01 and 0.07 +/- 0.05, respectively. Both the RI and PI were significantly correlated with age (r = 0.74 and 0.69, respectively; p < 0.01). Acute renal obstruction significantly (p < 0.01) elevated the mean RI (0.72 +/- 0.04), delta RI (0.09 +/- 0.04), PI (1.42 +/- 0.17), and delta PI (0.33 +/- 0.18). Significant decreases in RI and delta RI were noted after relief of the obstruction. The best accuracy in diagnosing acute unilateral renal obstruction was achieved with the combination of delta RI > or = 0.06 and/or delta PI > or = 0.20, which had a sensitivity of 94% and specificity of 99%.

CONCLUSIONS

Renal Doppler indices are reliable parameters in the sonographic diagnosis of acute unilateral obstructive uropathy.