Role of 99mTc-DTPA Captopril Renal Scintigraphy in the Diagnosis of Renal Fibromuscular Dysplasia: A Case Report.

Fibromuscular dysplasia (FMD) represents the most common non-inflammatory and non-atherosclerotic cause of renal artery stenosis (RAS), frequently manifesting as resistant renovascular hypertension (RVH). While anatomical imaging can identify structural abnormalities such as the classic "string-of-beads" pattern, 99mTc-DTPA captopril renal scintigraphy provides essential physiological data by demonstrating a measurable drop in the glomerular filtration rate (GFR) when the compensatory renin-angiotensin-aldosterone system is disrupted. This case report details a 33-year-old male with severe hypertension (190/140 mmHg) and secondary hyperaldosteronism whose diagnosis was supported by baseline and post-captopril scintigraphy, showing a reduction in differential renal function. Subsequent renal angiography confirmed a 50% stenotic lesion. Balloon angioplasty was complicated by distal dissection, necessitating stent placement, and the patient subsequently achieved symptom resolution with discontinuation of antihypertensive therapy. With a reported sensitivity of 83-93% and a specificity of 90%, 99mTc-DTPA scintigraphy serves as a highly effective, non-invasive diagnostic tool that captures the functional significance of renal lesions, potentially avoiding more invasive procedures while guiding early intervention to prevent permanent kidney injury.