Kidney blood supply. Coloured angiogram (X-ray) showing the blood supply in a healthy human kidney. The kidney is grey. Leading to, and entering, the kidney from centre left is the renal artery (purple). This artery branches into a network of smaller blood vessels, which in turn form tiny specialised capillary structures called glomeruli (not seen). The kidneys filter waste products from the blood, excreting them as urine. Hence the blood supply is intricate. An angiogram is produced by injecting a radio-opaque dye into the patient's bloodstream and then taking an X- ray. An angiogram can be used to diagnose blood vessel disorders.