Can a blood clot to one kidney result in normal kidney function tests if the other kidney is functioning properly?

Blood Clot to One Kidney and Kidney Function Tests

Yes, a blood clot to one kidney can result in normal kidney function tests if the other kidney is functioning properly, as renal function tests primarily reflect overall kidney function rather than individual kidney status.

Pathophysiology of Unilateral Renal Vein Thrombosis (RVT)

• Renal vein thrombosis (RVT) may present as unilateral disease limited to the renal vein, in which case renal function should be normal because the opposite kidney is unaffected 1
• When only one kidney has reduced perfusion, overall kidney function tests may remain normal due to compensation by the unaffected kidney 2
• The anatomical differences between the left and right renal veins (left being longer at 6-10 cm versus right at 2-4 cm) can influence the presentation and management of unilateral renal vein thrombosis 3

Laboratory Findings in Unilateral Renal Vascular Occlusion

• Standard kidney function tests (creatinine, BUN, eGFR) primarily reflect the combined function of both kidneys rather than individual kidney performance 1
• In unilateral RVT without extension into the inferior vena cava (IVC), the contralateral kidney can maintain normal global renal function 1
• Patients with a single affected kidney may show normal estimated glomerular filtration rate (eGFR) if the contralateral kidney compensates adequately 2

Clinical Presentation of Unilateral Renal Vascular Occlusion

• Flank pain on the affected side, particularly in acute occlusion scenarios, is a common symptom of decreased renal perfusion to a single kidney 2
• Hypertension that is resistant to standard treatment, especially in patients with no prior history of difficult-to-control blood pressure, may occur due to activation of the renin-angiotensin-aldosterone system from the affected kidney 2
• Possible hematuria in cases of renal trauma with vascular injury can be a sign of reduced renal perfusion to a single kidney 2

Diagnostic Considerations

• Asymmetry in kidney size on ultrasound or other imaging modalities can be a diagnostic clue to reduced renal perfusion in one kidney, even when overall kidney function tests remain normal 2
• Contrast extravasation on CT scan in cases of trauma can indicate reduced renal perfusion to one kidney 2
• Arterial contrast extravasation on CT-scan in hemodynamically stable patients may indicate renal vascular injury requiring angiography and possible intervention 1

Important Clinical Pitfalls

• Assuming bilateral kidney involvement when only one kidney has reduced perfusion is a common pitfall in clinical practice 2
• Relying solely on serum creatinine or eGFR can miss significant unilateral kidney disease, as these tests reflect total kidney function 4
• Standard renal function prediction equations have limited accuracy for detecting mild to moderate decreases in GFR, particularly in patients with normal serum creatinine levels 4
• Even the most accurate renal function estimation formulas (Cockroft-Gault and Bjornsson equations) exhibit levels of error that make them suboptimal for detecting unilateral kidney disease 4

Management Considerations

• In unilateral RVT with normal kidney function tests, the decision to treat with anticoagulation should consider the risk of loss of kidney function versus the risk of bleeding 1
• For patients with unilateral renal vascular injury and active bleeding, angiography with super-selective angioembolization may be indicated even when kidney function tests are normal 1
• In cases of severe injury with main renal vein injury without self-limiting bleeding, surgical intervention rather than angioembolization is indicated 1

Long-term Outcomes

• Of patients with RVT who received anticoagulation, 25% developed chronic kidney disease at a median follow-up of 5.7 years, compared with 80% in the group that did not receive anticoagulation 1
• Median estimated GFR at a median follow-up of 4.7 years was 111 mL/min per 1.73 m² in the anticoagulation group compared with 75 mL/min per 1.73 m² in the group that did not receive anticoagulation for RVT 1
• Long-term follow-up showed good functional and morphological results in patients with single kidney after appropriate management 1