DTPA scan of hypertensive young lady is normal, USG shows small kidney on left side. Next investigation will be -

Hypertension in a young female is most probably due to renal artery stenosis (cause fibromuscular dysplasia) DTPA scan which shows the GFR comes to be normal because of increased renin activity. Digital subtraction angiography or Doppler U/S will show the stenosis. Now MRA (Magnetic resonance angiography) has replaced all previous modalities as the most sensitive (>95%) and specific test (95%) for the diagnosis of renal artery stenosis. But the most definitive diagnostic procedure is bilateral arteriography with repeated bilateral renal vein and systemic rennin determinations.