Sneha Patel, MD, Jellyana Peraza, MD, Aliaskar Hasani, MD, Sanjana Luther, MD, Rishika Chugh, MD, Aaron Tokayer, MD, FACG
Montefiore Medical Center, Bronx, NY
Introduction: The ratio of blood urea nitrogen (BUN) to creatinine can be used as a surrogate for identifying sources of upper gastrointestinal bleed (UGIB). The proposed mechanism of this “accelerated azotemia” is brisk bleeding above the ligament of Treitz, followed by blood protein breakdown and absorption in the upper GI tract in the setting of hypovolemia and subsequent kidney hypoperfusion. Several ratios have been described in the literature, with variable sensitivities and specificities, but there is no consensus on the ideal ratio for recognizing an UGIB. Our study seeks to expand upon a prior research study done at our institution to determine the sensitivity, specificity, and positive predictive value (PPV) of gradated BUN/creatinine ratios (20:1 to 100:1) in identifying an UGIB.
Methods: 1,194 patients were identified between 2008 and 2016 using “Looking Glass Clinical Analytics”™. Inclusion criteria were patients admitted with hematochezia, melena, or hematemesis, with a decrease in hemoglobin (Hb) of 1g/dL from baseline. Patients with chronic kidney disease stage 3 or greater were excluded. Demographic data and source of bleeding were collected. Hb, BUN, and creatinine values were collected at baseline, day 1, and day 2 of admission. Sensitivity, specificity, and PPV were calculated for each ratio. A receiver operating characteristic (ROC) curve was created for day 1 and 2 of admission.
Results: 604 patients had GI bleeding confirmed by endoscopy. Average age was 67 years, 50% (n=302) were female, and 76% (n=459) were Black or Hispanic. 62% (n=375) had a confirmed UGIB source. Median change in Hb from baseline was 3.0 g/dL. For a BUN/creatinine ratio of ≥ 20:1 on day 1, specificity was 66.67%, sensitivity was 73.32%, and PPV was 78.16%. Values for day 1 and 2 of hospital admission are listed in tables 1 and 2. ROC curve on day 1 (Figure 1) had an area of under the curve of 0.68 (CI=0.64-0.73).
Discussion: A BUN/creatinine ratio of ≥ 30:1 has a PPV of 84% and may be ideal for identifying an UGIB. Interestingly, as the ratio increases above 30:1, the PPV plateaus and the likelihood of UGIB does not increase further. The specificity of UGIB at 30:1 is high at 85%. The ROC curve shows that the BUN/creatinine ratio is an accurate test for predicting an UGIB. This indicates that in clinical practice, a patient presenting with GI bleeding and a drop in hemoglobin ≥ 1g/dL associated with an “accelerated azotemia” of ≥ 30:1 should first undergo upper endoscopy to localize a bleeding source.
Citation: Sneha Patel, MD, Jellyana Peraza, MD, Aliaskar Hasani, MD, Sanjana Luther, MD, Rishika Chugh, MD, Aaron Tokayer, MD, FACG. P1316 - FINDING THE IDEAL BUN TO CREATININE RATIO IN AN UPPER GI BLEED. Program No. P1316. ACG 2019 Annual Scientific Meeting Abstracts. San Antonio, Texas: American College of Gastroenterology.