Space-occupying lesions of the kidney

Technetium-99m-L,L-ethylenedicysteine renal scan as a single-modality investigation for the evaluation of renal morphology and function: a comparative study with technetium-99m-dimercaptosuccinic acid*

AIM

To evaluate whether cortical scars can be detected using the summed images of technetium-99m-L,L-ethylenedicysteine (99mTc-L,L-EC) renal dynamic scan, and to compare the results with technetium-99m-dimercaptosuccinic acid (99mTc-DMSA) scan. To evaluate the inter-observer variability for 99mTc-L,L-EC and 99mTc-DMSA scan reporting.

METHODS

One hundred and three patients were initially included in the study; 21 were excluded, five due to a single functioning kidney and 16 due to impaired renal function (serum creatinine>2.5 mg.dl(-1)). Eighty-two patients (39 females, 43 males), including 31 children, with a mean age of 33.4+/-11.3 years (range, 4 months to 74 years), underwent both 99mTc-DMSA and 99mTc-L,L-EC scintigraphy within a period of 14 days. 99mTc-L,L-EC images were regrouped into 2 min image sets, and the initial 2 min summed image (cortical phase) was used for the evaluation of scars. Three independent observers analysed both images separately on different days without being aware of the identity and clinical details of the patients. Their 99mTc-L,L-EC findings were compared with the consensus 99mTc-DMSA scan findings taken as reference.

RESULTS

The overall sensitivity of 99mTc-L,L-EC scans was 93% and the specificity was 96%. The inter-observer variability was 0.91 for 99mTc-L,L-EC and 0.94 for 99mTc-DMSA scan reporting, using the weighted kappa analysis at P<0.05.

CONCLUSIONS

99mTc-L,L-EC is an excellent single-modality comprehensive investigational agent for renal morphology, function and outflow tract evaluation with the added advantages of lower cost, convenience and low radiation exposure to the patient.

An evaluation of the use of 99Tcm-dimercaptosuccinic acid (DMSA) as a static renal imaging agent

The clinical value of 99Tcm-dimercaptosuccinic acid, utilized as a static renal imaging agent, has been analysed in 366 patients. It proved to be diagnostically most useful in space occupying lesions of the kidney when equivocal on IVU and provided useful additional information when used in the determination of divided renal function or the distribution of intrarenal function. Its use is contraindicated in the determination of divided renal function in obstructed kidneys because of accumulation of significant amounts of DMSA that are excreted by glomerular filtration. When DMSA uptake at three hours after injection is compared with 99Tcm-DPTA uptake from 90 to 150 seconds after bolus injection, there is a good correlation between the two methods of determination of divided renal function.

Unsuspected renal tumors associated with renal cysts

A series of renal tumors associated with renal cysts is presented. Prior to surgical exploration appropriate diagnostic studies failed to indicate evidence of the presence of neoplastic lesions. The importance of surgical exploration of avascular "benign" renal masses is emphasized.

Magnification renal scintigraphy in the differential diagnosis of septa of Bertin

Eight consecutive patients, referred because intravenous urography (IVP) raised the question of hypertrophied septum of Bertin versus a pathologic mass, were examined using 99mTc labeled radiopharmaceuticals with magnification renal scintigraphy. The areas of concern showed a spectrum of activity, from normal to markedly increased, as compared to surrounding tissue. The activity correlated with the size of the mass effect on IVP. Increased resolution provided by pinhole magnification was important in evaluating these patients. We feel that magnification renal scintigraphy is valuable in the evaluation of intrarenal masses.

Combined use of ultrasound and nuclear medicine techniques in kidney disease

Combined ultrasound and nuclear medicine procedures in the evaluation of urinary-tract disease are essentially limited to the kidneys. They are useful in the evaluation of patients with masses, renal failure, unilateral nonfunctioning kidney, trauma, and transplants. In our experience the combined use of these techniques has increased diagnostic accuracy and in many cases has obviated the need for more complex procedures associated with higher radiation doses. This is an especially important factor in children and in adults in the childbearing age group. We have achieved success with these modalities because of the constant communication between the referring physicians and the ultrasound and nuclear medicine divisions.