Proteinuria (Protein in Urine)
Protein in the urine is one of the most important early markers of kidney disease. Healthy kidneys allow only tiny amounts of protein to pass into the urine. When the filtering apparatus is damaged, larger amounts leak through. Persistent proteinuria is not a disease in itself, but it is a strong signal that something needs investigating.
Dr Rory McQuillan provides specialist assessment of proteinuria, identifying the underlying cause and starting treatment to protect long-term kidney function.
How proteinuria is measured
Protein in the urine is measured by:
- Urine dipstick (a screening tool, useful but imprecise)
- Urine albumin-to-creatinine ratio (ACR), the standard quantitative test
- Urine protein-to-creatinine ratio (PCR)
- 24-hour urine collection (occasionally used for very high levels)
Causes of proteinuria
- Diabetes (the most common cause in adults)
- High blood pressure
- Glomerulonephritis (IgA nephropathy, membranous, FSGS, minimal change, lupus, others)
- Chronic kidney disease from any cause
- Pre-eclampsia in pregnancy
- Multiple myeloma and other plasma cell disorders
- Heart failure
- Transient causes including fever, exercise, and dehydration
When proteinuria matters most
Heavy proteinuria (ACR above 70, or in the nephrotic range above 220) is more likely to indicate significant kidney disease. Proteinuria associated with reduced kidney function, hypertension, swelling, or signs of systemic illness should prompt early specialist input.
Specialist investigation
Investigation depends on the level of proteinuria and the clinical context. Tests may include:
- Confirmation of persistent proteinuria with repeat testing
- Quantification with ACR or PCR
- Blood tests including kidney function, full blood count, glucose, lipids, and immunology
- Hepatitis B, C, and HIV serology where appropriate
- Renal ultrasound
- Kidney biopsy in selected cases
Treatment principles
Reducing proteinuria slows progression of kidney disease and reduces cardiovascular risk. The main treatments are:
- ACE inhibitors or ARBs (which reduce protein leakage)
- Blood pressure optimisation
- Glycaemic control in diabetes
- SGLT2 inhibitors for diabetic and non-diabetic proteinuric kidney disease
- Specific therapy for the underlying glomerular disease where indicated
Appointments
Appointments are arranged through GP referral.
Frequently Asked Questions
An ACR below 3 mg/mmol is normal. ACR 3-30 is moderately increased (microalbuminuria). ACR above 30 is significantly increased and warrants investigation.
Not always. Small amounts can be transient and harmless. Persistent or significant proteinuria, however, is an important sign of kidney damage and should be investigated.
Yes. ACE inhibitors, ARBs, SGLT2 inhibitors, and treatment of the underlying cause can all reduce proteinuria and slow the rate of kidney decline.
Many patients with proteinuria do not need a biopsy. It is recommended when the level is high, the cause is uncertain, or when the result will change treatment.
Have a Question?
If you’d like more information about Dr. McQuillan’s services or need assistance from the practice team, please get in touch below.
Please note: Appointments are arranged via GP referral.