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Case Presentation: A 65-year-old female with metastatic breast cancer, glioblastoma multiforme, bilateral pulmonary emboli diagnosed 4 days prior to admission started on enoxaparin, presented with syncope. On the day of admission the patient collapsed on the street suddenly without any prodrome. She reported abdominal pain for the prior 2-3 days, no other new symptoms, and no change in her baseline fatigue. On presentation to the emergency department (Figure presented) she was afebrile with a blood pressure of 105/72, and a heart rate of 92. Her physical exam was notable for conjunctival pallor and a firm, very tender 6 centimeter mass right of the midline slightly inferior to the umbilicus. Fothergill's sign was present. Her hemoglobin was 5.7 gm/dl (it was 12 gm/dl 4 days prior to admission). On CT scan of the abdomen and pelvis a large rectus sheath hematoma (RSH) was found that extended into the preperitoneal space inferiorly, as well as into the pelvis. The patient was transfused, enoxaparin was stopped and she had a retrievable inferior vena cava (IVC) filter placed. Upon further questioning, the patient reported that she had been injecting herself with enoxaparin intramuscularly rather than subcutaneously. Discussion: RSH is an uncommon cause of abdominal pain and is usually not associated with hemodynamically significant hemorhage. It is caused by rupture of the epigastric arteries or trauma to smaller vessels in the rectus muscle often due to vigorous contraction of the abdominal wall muscles from coughing, retching or straining from constipation. In this case, repeated direct intramuscular trauma from needles as well as the effect of the enoxaparin caused the hematoma. Mortality is reported at 4% for RSH but increases to 25% when anticoagulation plays a role. The patient presented with Fothergill's sign which is a painful abdominal mass that does not cross the midline and remains palpable with rectus muscle contraction thus differentiating it from an intra-abdominal mass. In light of her short term contraindication to receiving anticoagulation, an IVC filter was placed (supported by ACC/AHA guidelines issued in April 2011). The indications for placement of IVC filters are not robustly supported by evidence with only one prospective randomized study and a large populationbased retrospective analysis serving as the basis for recommendations. Because the RSH was caused by incorrect injection of enoxaparin, I recommended attempting to reinitiate anticoagulation in a monitored setting and if tolerated, removal of the retrievable IVC filter. The patient remained hemodynamically stable with an unfluctuating hemoglobin level and was transferred to the hospital where she was receiving her oncological treatment. Conclusions: RSH is often associated with the use of anticoagulation and on occasion can cause significant hemorrhage. IVC filters have a role in protecting patients with known proximal deep venous thrombosis or pulmonary embolism who have a contraindication against the use of anticoagulation