PREDICTIVE VALUE OF TECHNETIUM TC 99M-LABELED RED-BLOOD-CELL SCINTIGRAPHY FOR POSITIVE ANGIOGRAM IN MASSIVE LOWER GASTROINTESTINAL HEMORRHAGE

PURPOSE: This study was performed to evaluate whether the time interva l from injection of technetium Tc 99m (Tc-99m)-labeled red blood cells to the time of a radionuclide ''blush'' (positive scan) can be used t o improve the efficacy in predicting a positive angiogram. METHOD: A r etrospective review revealed 160 patients who received Tc-99m-labeled red blood cell scintigraphy for evaluation of massive lower gastrointe stinal hemorrhage between 1989 and 1994. Patients were included who de monstrated signs of shock on admission, had an initial decrease in hem atocrit of greater than or equal to 6 percent, or required a minimum t ransfusion of two units of packed red blood cells. Scanning duration w as 90 minutes, with imaging every 2 minutes. Time interval from inject ion to a positive scan was analyzed to determine predictability of a p ositive angiography. RESULTS: Of 160 patients, 86 demonstrated positiv e scans, of whom 47 underwent angiography. These 47 patients were divi ded into two groups according to scan results. Group 1 (n = 33) had im mediate appearance of blush; Group 2 (n = 14) had blush after two minu tes. In Group 1, 20 of 33 patients had a positive angiogram, yielding a positive predictive value of GO percent (P = 0.033). Of the 14 patie nts with negative angiograms (13 from Group 1, and 1 with a negative s can), 6 had radiographic occlusion of the inferior mesenteric artery a nd 1 had spasm of the right colic artery, with scans that blushed in t he respective distributions. Excluding these seven patients yielded a positive predictive value of 75 percent (P = 0.0072) for angiography. In patients with a delayed blush (Group 2), 13 of 14 had negative angi ograms, yielding a negative predictive value of 93 percent (92 percent excluding those with nonvisualization of the inferior mesenteric arte ry). Twenty of 21 (95 percent) positive angiograms occurred in Group 1 patients. Of the 27 patients with negative angiograms, 13 were Group 2 patients. CONCLUSION: Patients with immediate blush on Tc-99m-labele d red blood cell scintigraphy required urgent angiography. Patients wi th delayed blush have low angiographic yields. These data suggest that patients with delayed blush or negative scans may be observed and eva luated with colonoscopy.