Can a Patient with a Single Kidney Take Aspirin?
Yes, a patient with a single kidney can generally take aspirin, but the decision depends critically on whether it's for primary versus secondary prevention of cardiovascular disease, and requires careful consideration of bleeding risk.
Clinical Decision Framework
For Secondary Prevention (History of MI, Stroke, or Known CVD)
Aspirin is indicated and should be given for secondary prevention in patients with chronic kidney disease, including those with a single functioning kidney 1. The major guidelines (NICE, KDIGO, and ACC/AHA/ASA) consistently recommend aspirin for secondary prevention, though with caution about increased bleeding risk 1.
- Recommended dose: 75-162 mg daily 1
- Key consideration: Monitor for bleeding complications, as the risk of major bleeding nearly doubles (RR 2.04) in patients with reduced kidney function 1
For Primary Prevention (No Prior Cardiovascular Events)
Aspirin should generally be avoided for primary prevention in patients with kidney disease 1. Current guideline recommendations explicitly state to avoid primary prevention with aspirin in CKD patients 1.
The evidence shows:
- No statistically significant reduction in major cardiovascular events (RR 0.92; 95% CI 0.49-1.73) 1
- Increased risk of major bleeding (RR 1.33; 95% CI 1.10-1.65) 1
- The bleeding risk may equal or outweigh uncertain benefits 1
Exception: ACC/AHA/ASA guidelines suggest aspirin may be considered for primary prevention if GFR is 30-45 ml/min/1.73 m², but this remains controversial 1
Important Caveats and Monitoring
Renal Function Considerations
- Having one kidney doesn't automatically contraindicate aspirin, but the functional status of that kidney is what matters 1
- At therapeutic doses (75-162 mg), aspirin has minimal effect on renal function in stable patients 1, 2
- However, aspirin can precipitate reversible acute renal failure in predisposed individuals with pre-existing chronic renal insufficiency 2
Bleeding Risk Assessment
The increased bleeding risk is substantial and dose-dependent:
- Major bleeding risk increases 33% overall in CKD patients on antiplatelet therapy 1
- Risk is particularly elevated if combined with anticoagulants (3-6 fold increase) 1
- Enteric coating does NOT reduce gastrointestinal bleeding risk 1
Contraindications to Consider
Avoid aspirin if the patient has 1:
- Active bleeding or bleeding tendency
- Concurrent anticoagulant therapy (requires extreme caution if combined)
- Recent gastrointestinal bleeding
- Clinically active hepatic disease
- Aspirin allergy
Pharmacodynamic Concerns
Patients with reduced kidney function may have impaired antiplatelet response to aspirin:
- High on-treatment platelet reactivity occurs more frequently (47% vs 22%) in patients with impaired renal function 3
- This may partially explain why aspirin is less effective in CKD patients 1
Body Weight Consideration
Patients with low body weight (<60 kg) and CKD have significantly increased cardiovascular risk with aspirin (HR 4.014) 4. If your patient weighs less than 60 kg, aspirin should be avoided unless there is compelling indication for secondary prevention.
Practical Monitoring Recommendations
If aspirin is prescribed:
- Establish baseline renal function (serum creatinine, eGFR) 1
- Monitor for signs of bleeding (gastrointestinal symptoms, bruising, epistaxis) 1
- Be aware that NSAIDs should be avoided concurrently, as they compound renal and bleeding risks 1
- Consider checking renal function periodically, particularly if other nephrotoxic medications are used 1
Bottom Line Algorithm
Does the patient have prior MI, stroke, or known cardiovascular disease?
- YES → Prescribe aspirin 75-162 mg daily with bleeding precautions 1
- NO → Proceed to step 2
Is this for primary prevention?
Check for contraindications (bleeding history, anticoagulants, body weight <60 kg) 1, 4
If prescribed, monitor for bleeding and renal function changes 1, 2