Clinical application of normalized residual activity as a semiquantitative adjunct in assessing renal emptying in pediatric diuretic scans

Background@#The most recent pediatric diuretic imaging guidelines recommend the use of normalized residual activity (NORA) as a semiquantitative index of renal tracer drainage. It is defined as the ratio of post-void renal counts to 1-2 minute post-injection renal counts, with values less than 1 indicative of good drainage. We present two instances where NORA calculation was adjunctive in the evaluation of obstructive uropathy. @*Case Presentation@#The first patient was a 3-month-old male with left-sided congenital hydronephrosis. On dynamic imaging, the diseased kidney showed adequate perfusion and parenchymal extraction; moderate to severe pelvicalyceal tracer retention exhibited good response to diuretic. The pre-diuretic NORA of 1.62 declined to 0.28 after furosemide challenge, concordant with imaging findings that were negative for obstruction. The second patient was a 7-week-old male, also with congenital hydronephrosis of the left kidney. Dynamic images showed the diseased kidney with diminished perfusion and function, as well as pelvicalyceal tracer retention which became more severe after the diuretic was given. The pre-diuretic NORA was 1.81, which became 1.18 post-diuretic. This inadequate decline supplemented imaging findings pointing to significant obstruction. Other semiquantitative parameters have preceded NORA; however, clearance half-time is not validated as a marker of obstructive uropathy in infants and children, and output efficiency requires specialized software to calculate. Standardization of NORA determination is largely provided for by the guidelines recommending a perirenal background region of interest, as well as minimizing the interval between starting camera acquisition and injecting the tracer. @*Conclusion@#Semiquantitative analysis through NORA calculation gives relevant supporting information in the reporting of renal tracer drainage among pediatric patients. Further studies are needed to ascertain its applicability among adults and its diagnostic value in a larger sample of affected Filipino children.

Bowel Activity Caused by Free Tc-99m Pertechnetate Mimicking Urine Leaks during Tc-99m MAG3 Renal Scintigraphy / 대한핵의학회잡지

A 43-year-old woman with diabetic nephropathy underwent a Tc-99m MAG3 renal scintigraphy for the evaluation of renal function. Posterior images at 60 minutes demonstrated a migration of radiotracer activity beyond the lower pole of the left kidney, which might be incorrectly interpreted as urine leaks. However, the increased activities were moving along the bowel lumens over time. Another ring-like radioactivity was also seen in the suprasplenic region, and increased with time. These radioactivities were in the gastric fundus and gastrointestinal tract and caused by free Tc-99m pertechnetate.

Infarction of Renal Transplant with Extrarenal Excretion of Tc-99m MAG3 Demonstrated by Renal Scintigraphy / 대한핵의학회잡지

A 38-year-old woman with end stage renal disease received a living related donor-renal transplant to the right iliac fossa. She developed anuria a week later. Tc-99m MAG3 renal scintigraphy demonstrated no perfusion, uptake, or excretion of the radioactive tracer from the renal transplant. The expected area of the renal allograft appeared as a photopenic area with increased rim activity. The gallbladder and bowel activities were observed on delayed images at 24 hours. There was no blood flow within the renal artery on renal doppler examination. This case shows total absence of perfusion and function in the infarcted renal transplant with extrarenal excretion of Tc-99m MAG3 caused by acute renal artery thrombosis.

Animal model of renal ischemic injury, and chlorpromazine protector effect, evaluate by tc-99m-mag3 dynamic renal scan

Acute tubular necrosis (ATN) is a major complication of kidney transplantation, so as of urologic and vascular surgeries. In transplantation, although organ perfusion with proper solution are feasible and at least partially effective, new approaches remains needed to avoid lost of graft function due to ischemic insults, and by this way, chlorpromazine may play this hole. Sixteen male rats were evaluated by scintigraphy (dynamic renal scan with Tc-99m-MAG3), before and after surgically promote ischemia of left kidney. Animals were divided in 3 groups: Group A (control) without ischemic insult; Group B (ischemia without chlorpromazine) and Group C (ischemia with chlorpromazine). Group B demonstrated marked decreased of left renal function, compared with itself (right kidney; p 0,001) and compared with groups A and C (both p 0,001). No statistically observations was noted in group A, that makes sure of non-error source of surgical procedure lonely (p 0,05). Nevertheless mild decrease of left renal function was observed in some animals of group C, these appointments were not statistically significant (p 0,05). Further studies may prove, in the future, its usefulness in humans, specially concerning kidney transplantation.

Tc-99m MAG3 SPECT on Transplanted Kidney / 대한핵의학회잡지

PURPOSE: This study was designed to evaluate the usefulness of a technetium-99m mercaptoacetyltriglycine (Tc-99m MAG3) single photon emission computed tomography (SPECT) performed on transplanted kidney. MATERIALS AND METHODS: Thirty renal transplant patients were included in this study. Planar scan was performed for 30 minutes using 555 MBq Tc-99m MAG3. A post-voiding SPECT scan was acquired on the third, seventh, fourteenth and twenty eighth day after transplantation. RESULTS: SPECT scan showed interpretable image quality in 26 of 30 patients (86.7%) and 84 in 120 scans (70%). Fourteen of 26 patients with interpretable SPECT image showed decreased or increased radioactivity, but only 5 had abnormal findings on the planar scan. Focal SPECT defects were seen in allografts with normal function (n=3), acute tubular necrosis (n=3), and acute rejection (n=2). The defects are thought to reflect focally underperfused renal parenchyme or, in normal allografts, an artifact from uneven radioactivity distribution. Four of 10 patients with renal arterial variation showed focally decreased radioactivity and SPECT helped guide further studies that confirmed the exact cause. Five of 10 patients with acute tubular necrosis or acute rejection showed focally decreased radioactivity, but its relation to the patients' clinical course was not clear. Focally increased radioactivity was observed in 5 allografts with normal function and 1 with double ureter in which local clearance delay was observed. CONCLUSION: Tc-99m MAG3 SPECT renal scan can detect additional focal abnormalities compared to planar scan. Further study is necessary to elucidate the exact clinical significance of the SPECT findings.

Tc-99m MAG3 Renal Scan in Children: A Comparative Study with I-131 Hippuran Renal Scan / 대한비뇨기과학회지

To investigate the efficacy of Tc-99m MAG3 for renal scan, the images and renograms of Tc-99m MAG3 were compared to those of I-131 hippuran. Tc-99m MAG3 diuretic renal scan and I-131 hippuran diuretic renal scan were undertaken in 16 children with upper urinary tract anomalies within the time interval of 2 to 3 days. Their ages ranged from 1 week to 11 years old, and the male-to-female ratio was 14 to 2. Of these patients, 9 patients were less than 1 year old. The spectrum of upper urinary tract anomalies were unilateral ureteropelvic junction obstruction in 7 cases, bilateral ureteropelvic junction obstruction in 5 cases, bilateral non-obstructing non-refluxing megaureter, unilateral non-obstructing non-refluxing megaureter, bilateral obstructing megaureter and unilateral ulticystic dysplastic kidney in 1 case respectively. The images of Tc-99m MAG3 showed better resolution than those of I- 131 hippuran. The parameters of the Tc-99m MAG3 renogram in total functioning renal units, such as time to peak renal activity(r=0.98), half-time clearance to peak(r=0.88), half-time clearance after diuretic injection(r=0.96) and relative renal function(r=0.90), were correlated well with those of I-131 hippuran. In conclusion, Tc-99m MAG3 diuretic renal scan is considered to have a high potential to replace I-131 hippuran in routine radionuclide renal studies as well as renal tubular function test.