99mTc-L, L-EC – Role of Delayed Imaging in Impaired Functioning Kidney

Introduction: Renal Dynamic Scintigraphy(RDS) is a Nuclear Medicine imaging technique for evaluating the renal physiology and function. The three commonly used radiotracers for RDS include ^99mTc-Diethylene Triamine Penta-acetic Acid (^99mTc-DTPA), ^99mTc-Mercapto-acetyl Triglycine (^99mTc-MAG3) and ^99mTc-L,L,ethylenedicysteine (^99mTc-L, L-EC). Amongst these, L,L-EC is the agent preferred in the developing nations due to its lower cost and better availability and at least non-inferior tracer kinetics to MAG3. Timely diagnosis of renal outflow obstruction from non-obstructed drainage system is of paramount importance as its management decision can drastically impact on the patient outcome.

Methods: Impaired functioning kidney does not handle the radiotracer in a similar fashion to a normally functioning kidney. In patients with impaired renal function, the clearance of radiotracer from the kidney to the collecting system can be sluggish due to a variety of upstream causes and thus remains equivocal in the conventionally used scanning time of 20 minutes. However, delayed imaging at a later time point can aid in these equivocal cases. In this exhibit, we wish to discuss interesting case findings of RDS with special emphasis on the added value of delayed imaging in impaired renal function.

Results: Pictorial demonstration of concepts of the radiochemistry and imaging protocol of Renal Dynamic Scan would be provided along with a series of functional imaging of cases with impaired renal function. The key headings would include: Overview of Renal Dynamic Scan, Key difference in the 3 commonly used tracers, Clinical cases utilizing ^99mTc-L, L-EC scan in patients with impaired renal function and discussion of pertinent findings and pitfalls.

Conclusions: In this exhibit, we present the case based examples of the role of delayed time point imaging in ^99mTc-L, L-EC Renal Dynamic Scan in cases of impaired renal function.