Can volume overload cause a decrease in creatinine (blood urea nitrogen) concentration?

Volume Overload and Its Effect on Creatinine Concentration

Yes, volume overload can cause a decrease in serum creatinine concentration due to dilution effects, which may mask underlying kidney dysfunction. 1

Mechanism of Dilution Effect

• Volume overload leads to dilution of serum components, including creatinine, resulting in falsely lower creatinine concentrations that may not accurately reflect true kidney function 1, 2
• This dilutional effect occurs because the same amount of creatinine becomes distributed in a larger fluid volume, reducing its measured concentration 2
• In heart failure patients, fluid retention and volume overload can cause significant hemodilution of serum markers 1

Clinical Significance

• Dilution from volume overload may mask deteriorating kidney function by artificially lowering serum creatinine values 1, 3
• In cirrhosis patients with ascites and volume overload, serum creatinine may appear normal despite significant reductions in glomerular filtration rate (GFR) 1
• Disproportionate elevation of blood urea nitrogen (BUN) relative to serum creatinine is a clinical indicator of reduced cardiac output and volume overload 3

Evidence in Different Clinical Scenarios

Heart Failure

• In acute decompensated heart failure, fluid overload can dilute serum creatinine, making it appear falsely improved 1
• When diuresis is initiated and fluid is removed, serum creatinine may paradoxically rise despite improving kidney function due to concentration effects 4
• Patients with tricuspid regurgitation often have volume overload that can affect creatinine measurements 1

Chronic Kidney Disease

• In CKD patients, volume overload is associated with disease progression, but the dilution effect may initially mask the decline in kidney function 5, 6
• When volume status is corrected in CKD patients with overhydration, serum creatinine may temporarily increase despite improved overall kidney health 6

Cirrhosis

• Patients with cirrhosis often have splanchnic vasodilation leading to effective arterial blood volume reduction and fluid retention 1
• This fluid retention can dilute serum creatinine, potentially delaying diagnosis of acute kidney injury 1

Clinical Implications and Management

• When assessing kidney function in patients with suspected volume overload, clinicians should consider the dilutional effect on creatinine 1
• Monitoring weight changes and other clinical signs of fluid status is important when interpreting changes in serum creatinine 4
• During diuretic therapy, rising creatinine may reflect concentration rather than worsening kidney function 4
• In patients receiving ACE inhibitors who develop volume depletion, serum creatinine may rise due to both hemodynamic effects and concentration effects as volume normalizes 1

Common Pitfalls

• Relying solely on serum creatinine to assess kidney function in volume-overloaded patients may lead to underestimation of kidney dysfunction 1, 2
• Failure to recognize that rising creatinine during appropriate diuresis may be due to concentration effects rather than worsening kidney function 4
• Not accounting for volume status when interpreting changes in creatinine during treatment with medications that affect renal hemodynamics (like ACE inhibitors) 1
• Overlooking that patients with chronic heart failure may have elevated intravascular volume without peripheral edema or rales, still causing dilutional effects 3