Upper gastrointestinal bleeding laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]

Overview

In patients with acute Upper GI bleeding who are unstable rapid assessment and resuscitation should be initiated even before diagnostic evaluation. Once hemodynamic stability is achieved, a proper clinical history, physical examination, and initial laboratory findings are crucial not only in determining the likely sources of bleeding but also in directing the appropriate intervention. In acute GI bleeding, initial hematocrit level measured will not accurately reflect the amount of blood loss. Laboratory findings of chronic upper GI bleeding include anemia, coagulopathy, and an elevated BUN-to-creatinine ratio.

Initial Laboratory Studies

• Common laboratory findings include anemia, coagulopathy, and an elevated BUN-to-creatinine ratio.
• The hematocrit level is used to identify the degree of blood loss and suggests the acuity or chronicity of blood loss.
• Serial complete blood count (CBC) tests are important for monitoring the presence of ongoing blood loss.
• Initial CBC may not fully reflect the actual degree of acute blood loss.
• Qualitatively, on peripheral blood smear prepared with Wright-Giemsa stain, normal erythrocytes should be smaller than the nucleus of a normal lymphocyte, and the central clear area should not be overly prominent.
• In iron-deficiency anemia associated with chronic blood loss, erythrocytes are smaller (microcytic) and appear lighter (hypochromic) than normal cells.
• Mild to moderate thrombocytopenia (>30 × 103/µL) does not usually result in spontaneous bleeding, although patients with a pre-existing lesion may bleed in the presence of even mild thrombocytopenia.
• Platelet count may rise in response to significant gastrointestinal bleeding and may fall with multiple blood transfusions.
• Low ferritin level is the most specific test for iron-deficiency anemia. This finding together with a low iron and high TIBC levels are helpful in diagnosing iron-deficiency anemia, a common complication of ongoing or significant UGIB.
• BUN level may be elevated out of proportion to any increase in the creatinine level in patients with UGIB, secondary to breakdown of blood proteins to urea by intestinal bacteria.
• In patients with esophageal varices, acquired coagulopathies are common due to cirrhosis.

NSG

• Determining whether blood is in gastric contents, either vomited or aspirated specimens, is surprisingly difficult. Slide tests are based on orthotolidine (Hematest reagent tablets and Bili-Labstix) or guaiac (Hemoccult and Gastroccult). Rosenthal found orthotolidine-based tests more sensitive than specific; the Hemoccult test's sensitivity reduced by the acidic environment; and the Gastroccult test be the most accurate. Cuellar found the following results:

Determining whether blood is in the gastric aspirate

Finding	Sensitivity	Specificity	Positive predictive value (prevalence of 39%)	Negative predictive value (prevalence of 39%)
Gastroccult	95%	82%	77%	96%
Physician assessment	79%	55%	53%	20%

Holman used simulated gastric specimens and found the Hemoccult test to have significant problems with non-specificy and false-positive results, whereas the Gastroccult test was very accurate. Holman found that by 120 seconds after the developer was applied, the Hemoccult test was positive on all control samples.