Hemorrhagic Complications of Anticoagulant Therapy: Role of Multidetector Computed Tomography and Spectrum of Imaging Findings From Head to Toe Massimo Tonolini, MD, Sonia Ippolito, MD, Francesca Patella, MD, Marina Petullà, MD, and Roberto Bianco, MD Highly effective in preventing and treating thromboembolic conditions in acute and chronic settings, anticoagulant therapy is associated with a non-negligible risk of hemor- rhagic complications with a considerable clinical impact. Advanced age and comorbidities further increase the risk of bleeding during heparinization, treatment with low- molecular-weight heparins or long-term oral warfarin an- ticoagulation. Multidetector computed tomography repre- sents the mainstay diagnostic technique to image-suspected hemorrhages in anticoagulated patients, as it can quickly assess presence, site, and extent of hemorrhage, identify active bleeding, and possible underlying diseases. Cross- sectional imaging appearances of the wide spectrum of anticoagulant therapy–related bleeding complications are hereby presented, including peripheral and thoracic-ab- dominal wall muscular hematomas, intrathoracic, abdom- inal, retroperitoneal genitourinary, gastrointestinal, and brain hemorrhages. Prompt recognition and comprehen- sive diagnostic assessment with multidetector computed tomography allow clinicians to correctly choose treatment modification or withdrawal, surgery, or interventional pro- cedures as needed, with the aim to reduce the associated morbidity and mortality. Anticoagulant therapy (AT) is widely used nowadays to prevent or treat acute and chronic thromboembolic disorders. Although uncommon compared with the large number of treated patients, AT-related bleeding complications are increasingly encountered in clinical practice and associated with significant morbidity, hospitalization, and occasional mortality. 1-3 Virtually every organ system may be affected by hemorrhagic complications in anticoagulated patients. Although the bleeding site may sometimes be clini- cally obvious, physical findings and laboratory param- eters are insufficient to assess the true entity of the hematoma and the possible presence of ongoing hem- orrhage. 4 Widely available, thanks to its panoramicity and acquisition speed, multidetector computed tomogra- phy (CT) (MDCT) represents the diagnostic technique of choice to promptly image anticoagulated patients with suspected hemorrhagic complications, as it can assess presence, site, and extent of hematoma, identify active bleeding, and possible underlying diseases. 2,5,6 Anticoagulant Treatment Modalities The anticoagulant activity of heparin results from its ability to bind and activate antithrombin III, causing the inhibition of thrombin and other clotting factors of the intrinsic pathway of the coagulation cascade. Heparinization is useful to treat acute thromboembolic conditions, such as deep venous thrombosis or pulmo- nary embolism. The anticoagulant effect of heparin is generally short-term (6-8 hours), is monitored by means of the activated partial thromboplastin time, and may be reversed in selected occurrences by use of the protamine antidote. 7 Compared with unfractionated heparin, its recent derivates, low-molecular-weight heparins (LMWH) mainly inhibit factor Xa, have a longer plasmatic half-life, require limited surveillance, and are, therefore, highly suitable for treating lower-risk conditions and outpatients. 7 From the Department of Radiology, “Luigi Sacco” University Hospital, Milan, Italy. Reprint requests: Massimo Tonolini, MD, Department of Radiology, “Luigi Sacco” University Hospital, Via G.B. Grassi 74, 20157 Milan, Italy. E-mail: mtonolini@sirm.org. Curr Probl Diagn Radiol 2012;41:233-247. © 2012 Mosby, Inc. All rights reserved. 0363-0188/$36.00 + 0 http://dx.doi.org/10.1067/j.cpradiol.2012.05.001 Curr Probl Diagn Radiol, November/December 2012 233