What should the duration of anticoagulation be for a patient with idiopathic renal infarct?

Clinical Dilemma: 

David Garcia, MD: 

David A. Garcia, MD
Professor of medicine at the University of Washington School of Medicine in Seattle, Washington

This month, David Garcia, MD, advises on the length of anticoagulation in a patient with an idiopathic renal infarct.


I have a 32-year-old male patient with no cardiovascular risk factors who had what looks to be an idiopathic renal infarct. The radiologist feels that the infarct was likely arterial in origin, but no source of the clot has been found. Results from the CT angiography of the entire aorta and embolic work-up (including 48-hour Holter monitoring for atrial fibrillation) have been negative to date – so have the results from my APLA/PNH/MPN work-up.

In this instance, how long should anticoagulation last? I am unsure what duration to recommend because the infarct was arterial and idiopathic. Data for this circumstance seem to be scarce, and I have read that the duration should be anywhere from six to 12 months to indefinitely. While I am worried about recurrence – given he had this thrombosis at such a young age – I am also cognizant of the burden that lifelong anticoagulation will bring.


The plan you proposed is entirely reasonable, and I have very little to add to what you have already done for this patient. I presume the patient has had a trans-esophageal echocardiogram; if not, I would – in an abundance of caution – perform the test to exclude a cardiac source of embolism.

Also, if you have not already done it, I would check his serum homocysteine level. If these levels were very elevated (e.g., >15 Mmol/L), the threshold to extend anticoagulation (rather than switching to aspirin) might be lowered.

However, if, after an exhaustive search, you are unable to find any anatomic or “biochemical” reason for this man’s thrombosis, I agree that you should try to initiate antiplatelet therapy at some point. Committing him to lifelong anticoagulation based on a single event is difficult to justify. Of course, you should counsel him about and document the issues you have considered in making your recommendation.

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