[Digital subtraction angiography and other non-invasive procedures for evaluating renal circulation and hypertension]

Nuclear medical techniques (such as isotope nephrograms, renal scintigrams) which are suitable as screening methods, have been unable to improve the diagnosis of reno-vascular hypertension. Amongst conventional procedures, the excretion urogram following a bolus injection was the most informative, particularly if performed together with nephro-tomography. Although ultrasound is of some use in evaluating the kidneys, the excretion urogram remains essential for the diagnosis of reno-vascular hypertension. Additional exposures and modifications (e.g. early phase urogram only add unnecessary radiation and cost without providing additional information. On the other hand, it would be useful to obtain digital subtraction angiograms of the renal arteries during the contrast injection. In this way, reliable information can be obtained on the cause of reno-vascular hypertension in more than 90% of patients. Similar results can be obtained by photographic subtraction (ISA). This should be used where DSA apparatus is not available. Angio-CT and sequential CT is not reliable for the diagnosis of renal artery stenosis. On the other hand, these methods provide density measurements or time-density curves of selected areas in the cortex or medulla of the kidney, which indicated abnormalities of the circulation and provide a comparison of the two sides.