He has been in good health with the only medical problem in his history being depression.
He is taking sertraline. On exam, his blood pressure is 100/60, and his pulse is 100, both while lying down. His blood pressure while standing is 90/60 and his pulse while standing is 130. The rest of his exam is normal. His lab values include hemoglobin of 10, hematocrit of 30, white blood cell of 4.6, platelet count of 175,000, sodium of 142, chloride of 100, bicarbonate of 24, potassium of 3.8, blood urea nitrogen (BUN) of 38, and creatinine clearance (Cr) of 1.1.
Dr. Paauw
What is the most likely source of his bleeding?
A. Gastric ulcer
B. Meckel’s diverticulum
C. Arteriovenous malformation
D. Diverticulosis
E. Hemorrhoids
What makes the most sense
The most likely cause of this patient’s maroon stool is an upper gastrointestinal bleed, so it would make the most sense for a gastric ulcer to be the source of his bleeding. The clue here is the very high BUN/Cr ratio.
We were all taught early in our training that a high BUN/Cr ratio represented volume depletion. This is certainly the most common cause, but very high BUN/Cr ratios (over 30) can represent causes beyond volume depletion.
Witting and colleagues studied factors that predicted upper GI bleeding in patients presenting without hematemesis. They found that the three strongest predictors were black stool (odds ratio, 16.6), BUN/Cr ratio greater than 30 (OR, 10), and age greater than 50 (OR, 8.4).1
Srygley and colleagues reviewed high-quality studies of factors associated with upper GI bleeding.2 Factors that were found to increase the likelihood of an upper gastrointestinal bleed were Melenic stool on exam (likelihood ratio, 25), blood or coffee grounds on nasogastric aspiration (LR, 9.6), and BUN/Cr ratio greater than 30 (LR, 7.5).
Very high BUN/Cr ratios can indicate problems other than UGI bleeding and volume depletion. High BUN/Cr ratios are seen in patients with heart failure.
Zhang and colleagues studied if a high BUN/Cr ratio helped distinguish heart failure from asthma and chronic obstructive pulmonary disease (COPD).3 They found that, compared with those in the asthma group, the BUN/Cr ratios were significantly increased in the heart failure group (P < .05), whereas no significant differences in BUN/Cr ratios were found between the asthma and COPD groups.
Cheang and colleagues conducted their own study, as well as a meta-analysis, looking to see if high BUN/Cr ratios predicted increased mortality in patients with acute heart failure.4 In the meta-analysis of 8 studies (including their own), they found that the highest BUN/Cr ratio category was associated with an 77% higher all-cause mortality than the lowest category (hazard ratio, 1.77; 95% confidence interval, 1.52-2.07).
High dose corticosteroids can raise BUN levels, especially in patients with chronic kidney disease, and cause unexpectedly high BUN/Cr ratios.
Pearl
Very high BUN/Cr ratios (greater than 30) can signify upper GI bleeding, heart failure, or high-dose corticosteroid use.
Dr. Paauw is professor of medicine in the division of general internal medicine at the University of Washington, Seattle, and he serves as third-year medical student clerkship director at the University of Washington. Contact Dr. Paauw at dpaauw@uw.edu.
References
1. Am J Emerg Med. 2006 May;24(3):280-5.
2. JAMA. 2012;307(10):1072-9.
3. Comput Math Methods Med. 2022 Jul 21. doi: 10.1155/2022/4586458.
4. Cardiorenal Med. 2020;10:415-28.