Captopril enhanced GFR measurement raises the confidence in categorization of intermediate probability scans

Captopril Renogram is an accepted modality for screening of patients with Renovascular hypertension, however the renogram parameter changes are subtle and may not be evident in impaired renal function. There is always an uncertainty in categorizing such patients into a low or high probability group and most are categorized as intermediate probability. In such patients a noted absolute fall in GFR as measured by plasma sampling technique can be a sensitive parameter for the detection or ruling out of hemodynamically significant RVHT.

47 consecutive hypertensive patients; 29 male and 18 females with a median age of 25 years, were evaluated for hemodynamically significant RVHT with a Tc99m-DTPA Captopril enhanced renogram and GFR measurement by plasma sampling method.

33 patients had a low probability scan, 3 had high probability scan and 11 had an intermediate probability scan. After taking into account a fall in GFR (>20% was taken as significant fall) post-Captopril, out of the 11 patients in the intermediate probability 7 shifted to a low probability as there was no fall in GFR and 3 were put into high probability as a fall in GFR was noted. One patient continued to be in the intermediate probability group as only 13% fall in GFR was noted.

Captopril enhanced GFR measurement by plasma sampling method raises confidence in fitting patients with suspected RVHT with intermediate probability scans into a definitive category.