I-131-orthoiodohippurate renal function test in detection of renal artery occlusion in aortic dissection

By use of I-131-orthoiodohippurate (I-131-OIH) comprehensive renal function test (CRFT), we studied 4 patients with aortic dissection and various degrees of renal artery obstruction and 39 patients without aortic dissection. Of the 39 patients, 3 had significant renal artery stenosis (RAS group) and 36 had normal renal arteriogram and renal function test (control group). Three of the 4 patients with aortic dissection had complicated renal artery occlusion (RAO group), one had independent RAS. The results indicate that: (1) In the RAO group, the difference in peak time (DPT) between the affected and contralateral kidneys was above 4 minutes: whereas that of the control group was 0-2 minutes (0.5 +/- 0.6 min). (2) In the RAO group, the percent difference of split effective renal plasma flow (%DSERPF) between the 2 kidneys were 29.6% and above or near 80% in patients with incomplete and complete RAO respectively; whereas that of the control group was below 22% (mean = 7.7 +/- 5.7%). In the RAS group, moreover, DPT was 0-2 minutes; and %DSERPF were above and below 22% in 1 case with marked (75% stenosis) and 2 with mild RAS (50-60% stenosis) respectively. The renogram curves were also evaluated. It was found that (1) In the RAO group, 2 cases with complete RAO showed flat shape in the affected kidney (similar to the background surve). The case with incomplete RAO showed markedly delayed rounding peak in phase 2 and slow descent in phase 3. The case with independent RAS showed only impaired phase 3 with saw-tooth waves and less steep slope. (2) In the RAS group, the 2 cases with mild RAS showed normal in one and slightly delayed peak with less steep descent in phase 3 in the other. The case with marked RAS showed reduced and delayed peak in phase 2, and less steep descent in phase 3 with saw-tooth waves and "cross-over" of the two kidney curves. It is concluded that use of I-131-OIH CRFT to evaluate DPT, %DSERPF and the renogram curve may help distinguish amongst RAO (with aortic dissection), RAS and the normal individual in most cases.