Clinical and Laboratory Predictors of Positive CT Angiography in Patients With Lower Gastrointestinal Bleed

Abstract

Introduction: Acute gastrointestinal (GI) hemorrhages are responsible for 1-2% of all hospitalizations nationwide, amounting to over 30,000 admissions annually. CT Angiography (CTA) is being increasingly utilized as a first-line study for the diagnosis of acute lower GI bleed, with reported high sensitivity and specificity rates. However, CTA is also a relatively expensive resource and carries the potential for contrast and radiation related complications. We aim to identify clinical and laboratory parameters, which may help improve the diagnostic yield of CTA. Methods: From January 2012 to 2017, a total of 202 patients underwent CTA for work-up of suspected acute GI bleed at Einstein Medical Center. The primary outcome (CTA scan positive for active bleed) was determined upon review by a board-certified interventional radiologist. Clinical parameters (blood transfusion requirement, tachycardia (>100bpm), hypotension (systolic blood pressure<90, diastolic blood pressure<60), medications (antiplatelet or anticoagulant) and coagulopathy (INR>1.5, thrombocytopenia<150,000) were evaluated for potential associations with positive CTA scan. Chi-squuare test was used to determine the statistical significance (P value<0.05). Results: Among the 202 patients who underwent CTangiography, a total of 49 (24.3%) had a CTA scan positive for active bleed. On analysis of clinical variables, no significant associations were found between positive CTA scan and hypotension (p=0.38), need for blood transfusion (p=0.97), use of antiplatelet agents (p=0.93), thrombocytopenia (p=0.78), or elevated INR >1.5 (p=0.39). However, an association was observed with the use of anti-coagulant medications, in as much as 27% of patients with positive CTA scan were therapeutically anticoagulated, versus only 14% of patients with negative CTA (p=0.05). A weaker trend was also witnessed between the presence of tachycardia and CTA findings (p=.087). Conclusion: Patients on therapeutic anticoagulation have a higher likelihood of positive diagnosis of active GI bleed on CT Angiography. Based on the modest sample size, no other significant clinical or laboratory parameters proved to be effective predictor for positive CTA. Thus the importance of clinical judgement in deciding the need of CTA in the work up of patients with lower GI bleed remains of utmost importance.