Extreme D-dimer Elevation and Hemodynamic Collapse Due to Splenic Rupture in an Anticoagulated Patient.

D-dimer is commonly used in acute medicine to evaluate suspected venous thromboembolism (VTE), but markedly elevated levels lack specificity and may also occur in serious non-thrombotic conditions. We report a case of an 83-year-old woman on anticoagulation who presented with a two-week history of left-sided pleuritic chest pain and a profoundly elevated D-dimer (>10,000 ng/mL). Initial CT pulmonary angiography excluded pulmonary embolism, and she was admitted for observation and empirical antibiotics. Later the same day, a repeat D-dimer test showed an increase to >14,000 ng/mL. Overnight, she developed hypotension and a rapid hemoglobin drop from 119 to 77 g/L, accompanied by abdominal distension and tenderness. Urgent CT abdomen and pelvis revealed a large hemoperitoneum with suspected splenic rupture. Anticoagulation was reversed, and she underwent emergency laparotomy, confirming splenic rupture with successful hemostasis. Post-operative recovery was uncomplicated. Histology revealed an underlying vascular neoplasm, which may have contributed to splenic fragility but did not alter the acute diagnostic challenge. This case illustrates the difficulty of interpreting extreme D-dimer elevations and emphasizes that sudden hemodynamic deterioration in anticoagulated patients may indicate life-threatening hemorrhage rather than thromboembolism. Clinicians should maintain a broad differential diagnosis and repeat clinical assessment when initial investigations are unrevealing, ensuring timely recognition of rare but critical causes of collapse, such as splenic rupture.