BUN CREATININE RATIOS - AID TO DECISION-MAKING ABOUT DELAYED IMAGING IN TC-99M RED-BLOOD-CELL SCANS FOR GASTROINTESTINAL HEMORRHAGE/

In patients with gastrointestinal hemorrhage, delayed or late scans wi th Tc-99m labeled red blood cells are readily performed and have progn ostic impact when early images are negative. Nevertheless, there have been no indicators for the likelihood of detecting bleeding on such im ages. In a review of all gastrointestinal bleeding scans over an 8-yea r period, 73 patients had delayed images (> 3 hours) following early n egative exams. For these patients, determinations of serum blood urea nitrogen (BUN) and creatinine (Cr) were evaluated as the BUN/Cr ratio and were compared against delayed scan findings and confirmed diagnose s. Patients with significant renal failure were excluded from analysis . There were 34 late positive (46%) and 39 late negative (54%) studies . Mean BUN/Cr was 26.5 and 20.0 in patients with late positive and lat e negative scans, respectively (p < 0.05). Occurrence of late positive scans was 38% (19/50) for BUN/Cr < 25.0 vs. 65% (15/23) for BUN/Cr > 25.0 (p < 0.05). Patients with early negative images and a BUN/Cr rati o of 25 or greater have a greater likelihood of a positive delayed ima ge. Late imaging should be encouraged in patients with elevated BUN/Cr and early negative scintigraphy.