Introduction: Rectus sheath hematomas (RSH) generally occur due to damage to the inferior epigastric artery. They are rare causes of abdominal pain or acute blood loss anemia, but are an important diagnostic consideration because they can be cryptic and are potentially fatal.

Clinical Findings: An 85-year-old female who had been admitted to the hospital for 10 days with a myasthenia crisis was found to be abruptly hypotensive with a tender abdominal mass in the left lower quadrant subtly crossing midline. She was on prophylactic anticoagulation during her hospitalization.

Main diagnosis, therapeutics, interventions, and outcomes: The patient was initially stabilized with fluids and received one unit of packed red blood cells. A CT-angiogram of her abdomen and pelvis demonstrated a type III RSH. She underwent a percutaneous inferior epigastric artery embolization via interventional radiology. Unfortunately, she did not recover and was transitioned to hospice, dying one day after discharge.

Conclusion: Although classic teaching about RSHs includes an association with systemic anticoagulation and a physical exam notable for a mass not crossing the midline, it is important to recognize a wider range of presentations including an abdominal mass that crosses the midline, as demonstrated by our patient. Other important risk factors include frailty, immunosuppression, and possibly abdominal injections (particularly heparin).