Is frothy urine a sign of kidney disease?

Frothy Urine and Kidney Disease

Frothy urine can be a sign of kidney disease, particularly when it indicates the presence of protein in the urine (proteinuria or albuminuria). While not all frothy urine indicates kidney problems, it warrants attention as a potential early warning sign of kidney damage.

Understanding Frothy Urine

• Approximately 22% of patients who complain of foamy urine have overt proteinuria, making it a clinically significant symptom that should not be ignored 1
• Frothy urine occurs when proteins in the urine lower the surface tension of the liquid, causing bubbles to form more easily and persist longer than normal 1
• The presence of protein in urine (proteinuria) is a principal marker of kidney damage according to the National Kidney Foundation 2

Clinical Significance and Evaluation

• Persistent proteinuria is considered the principal marker of kidney damage, with an albumin-creatinine ratio greater than 30 mg/g in spot urine samples usually considered abnormal 2
• When patients present with frothy urine, evaluation should include:
  • Urinary albumin-to-creatinine ratio (UACR) measurement in a random spot urine collection 2
  • Assessment of estimated glomerular filtration rate (eGFR) 2
  • Evaluation for other signs of kidney damage 2

Risk Factors Associated with Frothy Urine and Proteinuria

• Diabetes is a leading cause of chronic kidney disease (CKD) worldwide and the primary cause of end-stage kidney disease in the United States 3
• Hypertension is another frequent cause of CKD that can both cause kidney damage and result from kidney disease 3
• In patients with frothy urine, increased serum creatinine and phosphate levels are statistically significant risk factors for overt proteinuria 1
• Poor renal function, diabetes, and increased serum glucose are also associated with overt proteinuria in patients with foamy urine 1

When to Be Concerned

• Chronic kidney disease is diagnosed by the persistent elevation of urinary albumin excretion, low eGFR, or other manifestations of kidney damage for at least 3 months 2
• An active urinary sediment, rapidly increasing albuminuria, nephrotic syndrome, rapidly decreasing eGFR, or absence of retinopathy (in type 1 diabetes) suggests alternative or additional causes of kidney damage 2
• Individuals should be referred for evaluation by a nephrologist if they have continuously increasing urinary albumin levels, continuously decreasing eGFR, or if the eGFR is <30 mL/min/1.73 m² 2

Screening Recommendations

• Patients with diabetes should be screened annually for diabetic kidney disease 2
  • For type 1 diabetes: starting 5 years after diagnosis
  • For type 2 diabetes: starting from diagnosis
• Screening for albuminuria can be most easily performed by urinary albumin-to-creatinine ratio (UACR) in a random spot urine collection 2
• Due to variability in urinary albumin excretion, at least 2 specimens collected within a 3-6 month period should be abnormal before considering a patient to have crossed diagnostic thresholds 2

Important Caveats

• Not all frothy urine indicates kidney disease—other factors such as concentrated urine, rapid urination, or certain chemicals in the urine can cause foaming 4
• Exercise within 24 hours, infection, fever, congestive heart failure, marked hyperglycemia, menstruation, and marked hypertension may elevate UACR independently of kidney damage 2
• False-positive and false-negative results can occur with dipstick urinalysis, so confirmation with laboratory testing is important 4

If you notice persistent frothy urine, consult with a healthcare provider for proper evaluation, as early detection and treatment of kidney disease can prevent or delay adverse outcomes.