The unilateral absence of excretion as shown by urography is particularly significant in the context of prior abdominal trauma. Of 23 such cases studied, 17 involved traumatic main renal artery occlusion; only 1 of these 17 kidneys was salvaged. Earlier diagnosis may improve surgical results. Urography should be abbreviated in favor of renal angiography to differentiate renal artery occlusion from other renal injuries, agenesis and preexisting renal disease. Clinical and plain radiographic features provide few clues. Renal venography, ultrasonography and retrograde ureteropyelography should be used only as secondary procedures. The role of renal scintiangiography remains to be determined.