Fresh rectal bleeding and haemoglobin drop in a 70-year-old man on rivaroxaban and naproxen

A 70-year-old man is admitted with a two-day history of fresh rectal bleeding and light-headedness. He has atrial fibrillation, diagnosed three months ago, for which he was started on rivaroxaban 20 mg once daily eight weeks ago. He also has osteoarthritis of the knee, managed with naproxen 500 mg twice daily for the last four weeks. His other regular medications are lisinopril 10 mg once daily for hypertension and metformin 500 mg twice daily for type 2 diabetes mellitus. He reports no previous history of gastrointestinal bleeding. He recalls a self-limiting episode of fresh red blood per rectum six weeks ago, which he did not seek medical attention for. That episode occurred two weeks after starting rivaroxaban and before naproxen was commenced. He has no known allergies.

On admission, he is pale and clammy. Blood pressure is 90/60 mmHg, heart rate 110 beats per minute and regular. Rectal examination reveals fresh blood. Laboratory results show haemoglobin 90 g/L (previously 130 g/L three months ago), platelet count 180 x 10^9/L, International Normalised Ratio 1.1, and normal activated partial thromboplastin time. Renal function and liver function tests are within normal limits. An urgent colonoscopy is performed after resuscitation. It shows no active bleeding or ulceration, and a few sigmoid diverticula without stigmata of recent haemorrhage. There is no sign of malignant disease.

Both rivaroxaban and naproxen are withheld on admission. He receives intravenous fluids, an intravenous proton pump inhibitor (pantoprazole 40 mg twice daily), and a transfusion of two units of red blood cells. The rectal bleeding stops within 24 hours of drug withdrawal. His blood pressure and heart rate normalise, and haemoglobin is stable at 95 g/L after transfusion. He is not rechallenged with either drug, because the risk of further haemorrhage is considered high. The clinical team considers the differential diagnosis: bleeding from sigmoid diverticulosis, NSAID-induced mucosal injury, or anticoagulant-related bleeding. The earlier bleeding episode before naproxen was started makes rivaroxaban the more likely cause. A decision is made to restart anticoagulation after discussion with the haematology and cardiology teams, using a different agent, and to avoid NSAIDs permanently.