Presentation
Recent diagnosis of hypertension and stroke. US shows a small left kidney but no RAS. Left renal bruit. ? RAS.
Patient Data
TECHNIQUE
Tc99m-MAG3 was administered via IV cannula for baseline study.
20mg of oral catopril given. IV Tc99m-MAG was then administered 1 hour post catopril.
Dynamic and planar imaging was performed.
FINDINGS
Patient was adequately hydrated with at least 500 ml of oral fluid before each phase.
Baseline (pre captopril) study
Reduced uptake of radiotracer within the mid and upper pole of the left kidney during perfusion imaging. The right kidney demonstrates normal perfusion and uptake of radiotracer. Radiotracer is identifiable within the renal pelves at 180 seconds (bilaterally) with normal emptying of the upper urinary tract. The mean cortical transit times are 21 minutes on the left, and 10 minutes on the right. The differential renal function at 2-3 minutes is 30% on the left and 70% on the right.
Post captopril study
There is a rising renogram on the left suggestive of decreased urine flow and washout (cortical retention). The washout of the right kidney remains normal. The differential function is overall unchanged in the pre and post-captopril study.
COMMENT
- High probability of left sided renovascular hypertension.
- Normal study of the right kidney.
- Further investigation may be warranted to assess for photopenic region in the upper pole of the left kidney.
Case Discussion
Captropril studies are reported according to the probability of RAS, with high probability findings being:
- unilateral parenchymal retention of MAG3
- deterioration in the renogram curve +/- relative function of the affected kidney following captopril compared to baseline
- prolongation of time to peak of 120s
- change in split function >10%
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