Primary Kidney Disease

Primary vs secondary kidney disease

Both can lead to chronic kidney disease and kidney failure.

Types of primary kidney disease

Glomerular diseases

The glomeruli are tiny filters in the kidney. Damage lets protein and blood leak into urine.

• IgA nephropathy: the most common primary glomerulonephritis worldwide; often causes visible blood in the urine during or just after a cold or sore throat.
• Focal segmental glomerulosclerosis (FSGS): scarring in parts of the glomeruli; heavy protein loss.
• Membranous nephropathy: a common cause of nephrotic syndrome in adults, caused by antibodies (often anti-PLA2R).
• Minimal change disease: the most common cause of nephrotic syndrome in children; usually responds well to steroids.
• Post-infectious glomerulonephritis: after strep or other infections.

Glomerular diseases present as either:

• nephrotic syndrome: heavy protein in urine, low blood albumin, swelling and high cholesterol
• nephritic syndrome: blood in urine, high blood pressure, reduced kidney function

Inherited and cystic diseases

• Polycystic kidney disease: fluid-filled cysts enlarge the kidneys; autosomal dominant PKD is the most common inherited kidney disease.
• Alport syndrome: a collagen gene disorder causing blood in urine, hearing loss and eye changes.
• APOL1-associated kidney disease: gene variants more common in people of African ancestry raise the risk of FSGS and kidney failure.

Tubulointerstitial diseases

Affect the tubules and tissue around them: interstitial nephritis (often medicine-related), renal tubular acidosis, and reflux nephropathy.

Congenital abnormalities

Malformed, small or obstructed kidneys present from birth are a major cause of kidney disease in children.

Symptoms

Early kidney disease often causes no symptoms. Signs include:

• foamy urine (protein)
• pink, red or cola-colored urine
• swelling around the eyes, ankles or legs
• high blood pressure
• tiredness, poor appetite
• in advanced disease: nausea, itching, breathlessness, confusion, reduced urine

Diagnosis

1. Urine tests: dipstick, urine albumin-to-creatinine ratio, microscopy for red cells and casts.
2. Blood tests: creatinine and eGFR, electrolytes, albumin, cholesterol, and specific tests such as complement levels, anti-PLA2R antibodies, ANCA and hepatitis serology.
3. Kidney ultrasound: size, cysts, obstruction.
4. Kidney biopsy: the key test for most glomerular diseases, identifying the exact cause and guiding treatment.
5. Genetic testing: for suspected inherited kidney disease.

Treatment

Protect the kidneys

• blood pressure control, often targeting a systolic pressure below 120 to 130 mmHg as advised
• ACE inhibitors or ARBs to reduce protein leakage
• SGLT2 inhibitors, which slow kidney decline in many types of chronic kidney disease
• salt restriction, healthy diet and avoiding NSAIDs
• statins for cholesterol

Disease-specific treatment

• steroids and immunosuppressants (such as rituximab, tacrolimus, mycophenolate, cyclophosphamide) for minimal change disease, membranous nephropathy and some FSGS
• newer targeted treatments for IgA nephropathy, such as targeted-release budesonide and sparsentan
• tolvaptan to slow cyst growth in rapidly progressing polycystic kidney disease

Kidney failure

Dialysis or kidney transplantation when kidney function falls to very low levels. Some primary diseases, such as FSGS, can recur in a transplanted kidney.

Outlook

The outlook varies widely. Minimal change disease often goes into remission; IgA nephropathy and FSGS may progress slowly over decades; polycystic kidney disease often leads to kidney failure in middle age. Early detection and treatment substantially slow progression.

Frequently asked questions

What is primary kidney disease?

Primary kidney disease is kidney damage that starts in the kidneys, such as glomerulonephritis or polycystic kidney disease, rather than being caused by another condition such as diabetes or high blood pressure.

What are the most common primary kidney diseases?

IgA nephropathy, focal segmental glomerulosclerosis, membranous nephropathy and minimal change disease are common glomerular diseases. Autosomal dominant polycystic kidney disease is the most common inherited kidney disease.

What are the early signs of kidney disease?

Kidney disease is often silent early. Signs can include foamy urine, blood in the urine, swelling of the eyes or ankles and high blood pressure. Routine urine and blood tests are the best way to find it early.

Why is a kidney biopsy needed?

Many glomerular diseases look similar in urine and blood tests but need very different treatments. A biopsy examines kidney tissue under the microscope to identify the exact disease and how much damage is present.

Can primary kidney disease be cured?

Some types, such as minimal change disease, often go into remission with treatment. Others, like polycystic kidney disease, cannot be cured, but blood pressure control, medicines and lifestyle measures can slow progression, and dialysis or transplant are options for kidney failure.