Head to head comparison of [99mTc]Tc(CO)3(NTA) and [99mTc]Tc-MAG3 in patients with suspected obstruction

Purpose 99mTc-tricarbonyl-nitrilotriacetic acid, [99mTc]Tc(CO)3(NTA), is a new 99mTc-renal radiopharmaceutical with a clearance equal to that of 131I-ortho-iodohippuran, [131I]I-OIH. Our purpose was to compare the performance of [99mTc]Tc(CO)3(NTA) and [99mTc]Tc-MAG3 in patients with suspected obstruction. Methods [99mTc]Tc(CO)3(NTA) was prepared with commercially available NTA ligand and CRS Isolink kit, and isolated by HPLC. Eighteen adult patients referred for diuretic renography received an intravenous injection of approximately 40 mg of furosemide 15 min prior to either [99mTc]Tc(CO)3(NTA) or [99mTc]Tc-MAG3 (mean activity of 47 ± 4.4 MBq). Data were acquired for 24 min followed by an anterior image of the liver and gall bladder and a measure of voided volume. Patients received a second furosemide injection equal to one third of the original dose followed fifteen minutes later by administration of the alternate tracer, mean activity of 320 ± 34 MBq. Clearances were measured using a camera-based technique. Results The clearance of NTA was greater than that of MAG3, 331 ± 146 versus 271 ± 105 mL/min/1.73 m2, respectively, p < 0.0001. The kidney to background ratio for NTA was greater than that of MAG3 for both left and right kidneys, p < 0.001; the 20 min/maximum count ratio was significantly less, p < 0.0001. There was no significant difference in the voiding volumes following NTA and MAG3 administration, 598 ± 237 mL versus 498 ± 170 mL, respectively, p = 0.07. Gall bladder activity was not observed with NTA but was present in 6/17 MAG3 studies. Images and renogram curves were comparable except for two patients where the NTA study excluded obstruction but the MAG3 study suggested an indeterminate or obstructed kidney. Conclusions Unlike MAG3, NTA is not eliminated via the hepatobiliary track. Moreover, NTA has a higher kidney to background ratio and more rapid clearance than MAG3. These advantages should allow more robust camera-based clearance measurements and may lead to better discrimination between obstructed and non-obstructed kidneys.

Head to Head Comparison of 99mTc(CO)3(NTA) and 99mTc-MAG3 in Patients with Suspected Obstruction

Purpose 99mTc-tricarbonyl-nitrilotriacetic acid, 99mTc(CO)3(NTA), is a new 99mTc-renal radiopharmaceutical with a clearance equal to that of 131I-ortho-iodohippuran. Our purpose was to compare the performance of 99mTc(CO)3(NTA) and 99mTc-MAG3 in patients with suspected obstruction.Methods 99mTc(CO)3(NTA) was prepared with commercially available NTA and CRS Isolink kit, and isolated by HPLC. Eighteen adult patients referred for diuretic renography received an intravenous injection of approximately 40 mg of furosemide 15 min prior to either 99mTc(CO)3(NTA) or 99mTc-MAG3 (mean activity of 47 ± 4.4 MBq). Data were acquired for 24 minutes followed by an anterior image of the liver and gall bladder and a measure of voided volume. Patients received a second furosemide injection equal to one third of the original dose followed fifteen minutes later by administration of the alternate tracer, mean activity of 320 ± 34 MBq. Clearances were measured using a camera-based technique.Results The clearance of 99mTc(CO)3(NTA) was greater than that of 99mTc-MAG3, 331 ± 146 vs 271 ± 105 mL/min/1.73 m2, respectively, p < 0.0001. The kidney to background ratio for 99mTc(CO)3(NTA) was greater than that of 99mTc-MAG3 for both left and right kidneys, p < 0.001; the 20 min/maximum count ratio was significantly less, p < 0.0001. There was no significant difference in the voiding volumes following 99mTc(CO)3(NTA) and 99mTc-MAG3 administration, 598 ± 237 mL vs 498 ± 170 mL, respectively, p = 0.07. Gall bladder activity was not observed with 99mTc(CO)3(NTA) but was present in 6/17 99mTc-MAG3 studies. Images and renogram curves were comparable except for two patients where the 99mTc(CO)3(NTA) study excluded obstruction but the 99mTc-MAG3 study suggested an indeterminate or obstructed kidney.Conclusions Unlike 99mTc-MAG3, 99mTc(CO)3(NTA) is not eliminated via the hepatobiliary track. Moreover, 99mTc(CO)3(NTA has a higher kidney to background ratio and more rapid clearance than 99mTc-MAG3. These advantages should allow more robust camera-based clearance measurements and may lead to better discrimination between obstructed and non-obstructed kidneys.

99mTc-MAG3 Diuretic Renography: Intra- and Inter-Observer Repeatability in the Assessment of Renal Function

The aim of the present study is to evaluate the intra- and inter-observer agreement in assessing the renal function by means of 99mTc-MAG3 diuretic renography. One hundred and twenty adults were enrolled in the study. One experienced and one junior radiographer processed the renograms twice by assigning manual and semi-automated regions of interest. The differential renal function (DRF, %), time to maximum counts for the right and left kidney (TmaxR-TmaxL, min) and time to half-peak counts (T1/2, min) were calculated. The Bland–Altman analysis (bias±95% limits of agreement), Lin’s concordance correlation coefficient and weighted Fleiss’ kappa coefficient were used to assess agreement. Based on the Bland–Altman analysis, the intra-observer repeatability results for the experienced radiographer using the manual and the semi-automated techniques were 0.2 ± 2.6% and 0.3 ± 6.4% (DRF), respectively, −0.01 ± 0.24 and 0.00 ± 0.34 (TmaxR), respectively, and 0.00 ± 0.26 and 0.00 ± 0.33 (TmaxL), respectively. For the junior radiographer, the respective results were 0.5 ± 5.0% and 0.8 ± 9.4% (DRF), 0.00 ± 0.44 and 0.01 ± 0.28 (TmaxR), and 0.01 ± 0.28 and −0.02 ± 0.44 (TmaxL). The inter-observer repeatability for the manual method was 0.6 ± 5.0% (DRF), −0.10 ± 0.42 (TmaxR) and −0.05 ± 0.38 (TmaxL), and for the semi-automated method −0.2 ± 9.1% (DRF), 0.00 ± 0.31 (TmaxR) and −0.05 ± 0.40 (TmaxL). The weighted Fleiss’ kappa coefficient for the T1/2 assessments ranged between 0.85–0.97 for both intra- and inter-observer repeatability with both methods. These findings suggest a very good repeatability in DRF assessment with the manual method—especially for the experienced observer—but a less good repeatability with the semi-automated approach. The calculation of Tmax was also operator-dependent. We conclude that reader experience is important in the calculation of renal parameters. We therefore encourage reader training in renal scintigraphy. Moreover, the manual tool seems to perform better than the semi-automated tool. Thus, we encourage cautious use of automated tools and adjunct validation by manual methods where possible.

Modified Whitaker test: a novel diagnostic for nephroptosis

A 77-year-old woman presented with right flank pain radiating to the ipsilateral groin and associated nausea, consistent with renal colic. In the emergency department, a non-contrast CT scan revealed severe right-sided hydronephrosis but failed to demonstrate a calculus or ureteropelvic obstruction. The patient improved with fluids and followed up with a community urologist. Initial work-up with cystoscopy and ureteroscopy, voiding cystourethrogram and diuretic renography failed to deduce a diagnosis. At our hospital, we used a modified dynamic (supine and upright) Whitaker test in a novel fashion to diagnose nephroptosis, a rare hypermobility condition of the kidney.

Pyeloplasty for pelviureteric obstruction junction obstruction

Pelviureteric junction obstruction (PUJO) is a common clinical presentation. Patients require investigation with biochemistry and imaging in the form of computed tomography and diuretic renography. The gold-standard pyeloplasty treatment is minimally invasive pyeloplasty. Here we discuss a typical presentation of PUJO and discuss key questions in the investigation, management and follow-up of this condition, including a review of the treatment options. Level of evidence: 3a

Ureterocolic fistula detected by mercaptoacetyltriglycine (MAG-3) diuretic renography including single photon emission CT and low-dose CT (SPECT–CT)

We describe the case of a 60‐year‐old man with a ureterocolic fistula following laparoscopic sigmoid resection. The fistulous tract between the left ureter and sigmoid colon was detected by mercaptoacetyltriglycine diuretic renography including single photon emission CT with low-dose CT. Ureteroneocystostomy was successfully performed.