Nephrosis (Proteinuria)

What is Nephrosis (proteinuria)?

Nephrosis, often referred to as proteinuria, is a condition in which abnormal amounts of protein leak from the blood into the urine. In a healthy kidney, the glomeruli (tiny filtering units) retain protein while allowing waste products to pass into the urine. When the glomerular filter is damaged or overly permeable, proteins—most commonly albumin—escape into the urine.

Proteinuria is not a disease by itself; it is a sign that the kidneys are not functioning properly. The level of protein loss can range from a barely detectable increase (microalbuminuria) to massive protein loss (>3 g per day), which may lead to swelling (edema), low blood protein levels (hypoalbuminemia), and eventually chronic kidney disease (CKD) if untreated.

Sources: Mayo Clinic; National Kidney Foundation (NKF) ¹.

Common Causes

Proteinuria can arise from many different kidney diseases, systemic illnesses, medications, or temporary conditions. Below are the most frequently encountered causes.

• Minimal change disease (MCD) – the most common cause of nephrotic syndrome in children; the glomeruli look normal under a light microscope.
• Focal segmental glomerulosclerosis (FSGS) – scarring in scattered parts of some glomeruli; can be primary or secondary to obesity, HIV, or drug use.
• Membranous nephropathy – immune complex deposits on the outer side of the glomerular membrane, often linked to infections, malignancy, or auto‑immune disease.
• Diabetic nephropathy – chronic high blood sugar damages glomeruli; the leading cause of CKD worldwide.
• Hypertensive nephrosclerosis – long‑standing high blood pressure injures small blood vessels in the kidney.
• Lupus nephritis – systemic lupus erythematosus (SLE) can cause immune complexes to deposit in the kidneys.
• IgA nephropathy (Berger disease) – IgA deposits in the glomeruli, often following an upper‑respiratory infection.
• Infections – hepatitis B/C, HIV, malaria, and streptococcal infections can trigger glomerular injury.
• Medications & toxins – non‑steroidal anti‑inflammatory drugs (NSAIDs), certain antibiotics (e.g., aminoglycosides), gold salts, and heavy metals.
• Orthostatic (postural) proteinuria – a benign condition in adolescents where protein appears in urine only when standing.

Associated Symptoms

Protein loss itself may be silent, but it often co‑exists with other signs that reflect the underlying kidney disease or the systemic effects of protein depletion.

• Edema – swelling of the ankles, feet, lower legs, or around the eyes, especially after waking.
• Foamy or frothy urine – a classic visual clue that protein is present in the urine.
• Fatigue & weakness – due to low blood protein and anemia.
• Weight gain – primarily from fluid retention.
• Loss of appetite or nausea.
• High blood pressure – both a cause and a consequence of kidney disease.
• Decreased urine output or changes in urine color/clarity.
• Elevated blood cholesterol & triglycerides – kidney disease can impair lipid metabolism.

When to See a Doctor

Because proteinuria can be an early warning sign of serious kidney disease, it is important to seek medical evaluation promptly if you notice any of the following:

• Foamy or bubbly urine that persists for more than a few days.
• Swelling in the feet, ankles, or around the eyes.
• Unexplained weight gain (especially rapid).
• Persistent high blood pressure (>140/90 mm Hg) or newly diagnosed hypertension.
• History of diabetes, autoimmune disease, or recent severe infection.
• Any change in urinary frequency, pain, or blood in the urine.

Early detection often leads to better outcomes and may prevent progression to chronic kidney disease.

Diagnosis

Diagnosing proteinuria involves a combination of simple urine tests, blood work, imaging, and sometimes a kidney biopsy.

1. Urine Tests

• Urine dipstick – a rapid bedside test that can detect protein ≥30 mg/dL.
• Spot urine albumin‑to‑creatinine ratio (ACR) – quantifies albumin loss; <10 mg/g is normal, 30–300 mg/g is microalbuminuria, >300 mg/g indicates overt proteinuria.
• 24‑hour urine collection – measures total protein excretion; >3 g/day is classic for nephrotic syndrome.

2. Blood Tests

• Serum creatinine & estimated GFR (eGFR) – assess overall kidney function.
• Serum albumin – low levels (<3.5 g/dL) suggest significant protein loss.
• Lipid panel – hyperlipidemia is common in nephrotic syndrome.
• Autoimmune markers (ANA, dsDNA, complement levels) if lupus is suspected.
• Infectious serologies for hepatitis B/C, HIV when indicated.

3. Imaging

• Renal ultrasound – evaluates kidney size, cysts, obstruction, or scarring.
• CT or MRI – reserved for complex cases or to rule out structural lesions.

4. Kidney Biopsy

When the cause remains unclear after non‑invasive testing, a biopsy provides a definitive diagnosis by allowing microscopic examination of glomerular structure. It is essential for conditions such as FSGS, membranous nephropathy, or lupus nephritis.

References: Cleveland Clinic; National Institutes of Health (NIH) ².

Treatment Options

Treatment is directed at three main goals: (1) stop or reduce protein loss, (2) control underlying disease, and (3) manage complications such as edema and hyperlipidemia.

Medical Therapies

• Angiotensin‑converting enzyme inhibitors (ACE‑Is) or Angiotensin II receptor blockers (ARBs) – lower glomerular pressure and reduce proteinuria in diabetic and non‑diabetic kidney disease.
• Immunosuppressive agents – corticosteroids, calcineurin inhibitors (cyclosporine, tacrolimus), mycophenolate mofetil, or rituximab for primary glomerulonephritides (MCD, FSGS, membranous nephropathy).
• Diuretics (e.g., furosemide) – alleviate edema by promoting fluid excretion.
• Statins – treat hyperlipidemia often seen in nephrotic syndrome.
• Anticoagulation – considered in severe nephrotic syndrome (protein loss >5 g/day) due to increased risk of thrombosis.
• Antidiabetic agents – tight glycemic control (HbA1c <7 %) slows progression of diabetic nephropathy.
• Blood pressure control – target <130/80 mm Hg (KDIGO guideline).

Home & Lifestyle Measures

• Low‑salt diet (≤2 g sodium/day) to reduce fluid retention.
• Protein‑moderate diet – 0.8 g/kg body weight; avoid excessive restriction that could worsen malnutrition.
• Fluid management – for severe edema, doctors may recommend a fluid restriction of 1.5–2 L/day.
• Weight monitoring – daily weigh‑ins help track fluid balance.
• Regular exercise – improves blood pressure and insulin sensitivity.
• Smoking cessation – reduces cardiovascular risk, which is high in kidney disease.

All medication changes should be made under physician supervision; abrupt discontinuation of ACE‑Is or steroids can worsen proteinuria.

Prevention Tips

While some causes (genetic, autoimmune) cannot be avoided, many risk factors are modifiable:

• Maintain optimal blood pressure (<130/80 mm Hg) via diet, exercise, and medication when needed.
• Control blood sugar tightly if you have diabetes; use glucose‑lowering agents and regular monitoring.
• Adopt a heart‑healthy diet rich in fruits, vegetables, whole grains, and low in saturated fats and processed foods.
• Limit use of nephrotoxic drugs (NSAIDs, certain antibiotics). Always discuss alternatives with your doctor.
• Stay hydrated but avoid excessive fluid intake if you have significant protein loss or edema.
• Get routine screening for proteinuria if you have risk factors (diabetes, hypertension, family history of kidney disease). A simple dipstick urine test once a year is often sufficient.
• Avoid smoking and excessive alcohol, both of which accelerate kidney damage.
• Vaccinate against hepatitis B and influenza to reduce infection‑related kidney injury.

Emergency Warning Signs

Prompt evaluation can prevent irreversible kidney damage and reduce the risk of life‑threatening complications.

Sources: 1. Mayo Clinic. “Proteinuria.” https://www.mayoclinic.org/; 2. National Institutes of Health. “Kidney Disease.” https://www.nih.gov/; 3. KDIGO Clinical Practice Guideline for the Management of Glomerular Diseases, 2023; 4. Cleveland Clinic. “Nephrotic Syndrome.” https://my.clevelandclinic.org/; 5. National Kidney Foundation. “Kidney Disease Overview.” https://www.kidney.org/.