Vesicoureteral Reflux Detected on Post-void Image of ^99mTc MAG3 Renal Scintigraphy

Abstract

^99mTc MAG3 scintigraphic scan is sensitive at depicting focal parenchymal abnormalities and can be used for the measurement of overall renal function. We experienced a 5-year-old boy presenting with bilateral flank fain, intermittent urinary stream and dysuria. On the post-void delayed image of ^99mTc MAG3 scintigraphic scan vesicoureteral reflux was detected in left non-functioning kidney, which was missed on voiding cystourethrography.

Introduction

Vesicoureteral reflux (VUR) may be diagnosed by both voiding cystourethrography (VCUG) and radionuclide cystourethrography.[1,2] Although the results of both methods did not show a significant difference, radionuclide cystourethrography offers a high sensitivity in the younger age group.[3,4] Continuous monitoring during and absence of body background allows radionuclide cystourethrography to demonstrate reflux which could well be intermittent and of small volume.[5] These facts could have led VCUG to miss VUR.[4]

Conventional renal scan is not usually used for diagnosis of VUR. We present a case of unilateral VUR demonstrated on renal scintigraphy, missed on VCUG.

Case Report

The present case report is about a 5-year-old boy presented with bilateral flank pain with intermittent urinary stream, dysuria for 2 days and an episode of hematuria. Ultrasonogram abdomen showed bilateral moderate hydronephrosis with ureteric dilatation and distended urinary bladder [Figure 1]. VCUG revealed normal urethral caliber with no evidence of VUR [Figure 2]. Diuretic-augmented renal scintigraphy using ^99mTc MAG3 was performed with a standard protocol to evaluate renal function which showed functional asymmetry. Right kidney appeared to be fair functioning with incomplete outflow clearance whereas left kidney could not be visualized on initial dynamic images. Post-void delayed image of ^99mTc MAG3 scintigraphic scan acquired at 20 min after dynamic study, showed appearance of left kidney and ureter which indicate VUR [Figure 3].

Figure 1.

Ultrasound abdomen shows left kidney 7.5 cm with moderate to gross hydronephrosis

Figure 2.

Voiding cystourethrography showing no evidence of urethral stricture and vesicoureteral reflux

Figure 3.

^99mTc MAG3 renal scintigraphy showing fair functioning hydronephrotic right kidney with partial outflow clearance whereas left kidney is not visualized in dynamic images. Post-void image showing appearance of left kidney and ureter indicative of vesicoureteral reflux

Discussion

Dynamic renography using ^99mTc MAG3 in combination with furosemide challenge has been widely used to determine the differential function of the kidneys, occurrence of reflux as well as the patency of the outflow tract in this context.[6] Renal scans can also be important in monitoring individual renal function during conservative management of many renal disorders. Although VUR shown by radionuclide cystography has been reported, its demonstration during dynamic renography is unusual.[7,8] Conventional ^99mTc MAG3 scintigraphy can work as indirect cystography to detect reflux.[9,10] We could demonstrate the reflux by this without conventional VCUG by acquiring additional data after micturition and hence that analysis of the kidneys can be undertaken when the bladder is empty.[11] Post-void image is essential at the end of the diuretic renogram if outflow clearance is incomplete, to calculate residual urine volume and to better evaluate drainage from the collecting system, as it allows comparison with sequential studies.[12] Bladder catheterization has been advocated in children undergoing diuretic renography to maintain an empty bladder throughout the procedure. Using the post-void Images, bladder catheterization is not recommended.

This case illustrates the presence of VUR in the of non-functioning renal tissue on post-void image which was not detected on VCUG as VUR is known to be a somewhat variable phenomenon with different conditions of hydration, bladder volume and pressure. It might be expected that different techniques attempting to diagnose VUR from two separate episodes of voiding would reveal some discrepancy in diagnostic results.[13]

The case described, demonstrates the value of acquiring post-void image in diuretic renography which would help the physician in making appropriate management decisions. A careful review of the post-void image established the correct diagnosis, obviating the need for further investigation.