Lower 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

The essential blood work in diagnosing lower gastrointestinal bleeding includes a complete blood count, renal function and liver function tests, and coagulation studies. Although not diagnostic, a blood type and crossmatch should be done in patients who present with life-threatening bleeding.

Laboratory Findings

The essential blood work in diagnosing lower gastrointestinal bleeding includes a complete blood count, renal function and liver function tests, and coagulation studies. Although not diagnostic, a blood type and crossmatch should be done in patients who present with life-threatening bleeding.

Complete blood count

• Complete blood count may show a low hemoglobin level or a drop from a previous baseline level.
• In acute blood loss, the initial hemoglobin level may be normal but will fall with fluid resuscitation.
• Other abnormalities, such as thrombocytopenia, may point to a variceal source of bleeding.
• The presence of uremia or a history of aspirin or clopidogrel use should be noted, as both factors can significantly affect platelet function without causing thrombocytopenia.
• A raised leukocyte count may point to an infectious or inflammatory cause.

Renal function tests

• Abnormal values of renal function tests of may indicate underlying kidney disease, a condition associated with increased risk for gastrointestinal bleeding.
• A disproportionately raised urea nitrogen level may suggest bleeding from an upper gastrointestinal source or hemoconcentration.
• Intravenous contrast for angiograms must be administered with caution in patients with renal impairment to avoid the risk of contrast nephropathy.

Liver function tests

• Persons with an underlying liver disease are at increased risk of gastrointestinal bleeding, and bleeding may be more difficult to control due to coagulopathy associated with liver dysfunction.
• Abnormal liver function may suggest the presence of colorectal varices.

Coagulation studies

• An elevated INR may indicate anticoagulation with warfarin or may be evidence of severe liver dysfunction.
• A prolonged aPTT is seen in anticoagulation with heparin.

Blood type and cross match

• Identifies blood groups A, B, AB, O and Rhesus (Rh) factor.
• Essential in the management of hemodynamically unstable patients who may need a blood transfusion.

Blood in stools

Abdominal pain

Yes

No

Fever

Rectal pain

Yes

No

H/O of constipation

H/O of constipation

No

Yes

No

Yes

Weightloss

Diverticulosis

Hemodynamic status

Diverticulitis

No

Yes

Stable

Unstable

Polyps

Colon cancer

Ischemic colitis

Stool culture

Positive

Negative

No

Yes

Infectious colitis

Inflammatory bowel disease

Weight Loss

Anal fissure External Hemmrhoids

Yes

No

Rectal cancer Colon cancer

Angiodysplasia Polyps