What is nephritis?

Nephritis means inflammation of the kidneys. It's not a single disease but a category of conditions — all involving the immune system attacking or damaging kidney tissue. The inflammation can affect different parts of the kidney, which is why there are several types of nephritis with different names.

Nephritis can come on suddenly (acute) or develop slowly over years (chronic). Some types cause rapid kidney failure if not treated promptly; others cause gradual damage over decades.

Types of nephritis

Glomerulonephritis (GN) — Inflammation of the glomeruli, the tiny filtering units inside each kidney. The most common type of nephritis. Can be caused by infections, autoimmune diseases (like lupus), or conditions like IgA nephropathy.
Lupus nephritis — Kidney inflammation caused by systemic lupus erythematosus (SLE), an autoimmune disease. About half of people with lupus develop kidney involvement.
IgA nephropathy (Berger's disease) — The most common glomerular disease worldwide. IgA antibodies deposit in the kidney causing inflammation. Often presents with blood in the urine after a cold or infection.
Interstitial nephritis — Inflammation in the spaces between kidney tubules, often caused by medications (especially NSAIDs, antibiotics, or proton pump inhibitors like omeprazole).
Pyelonephritis — Kidney inflammation caused by a bacterial infection (a kidney infection). Usually begins as a urinary tract infection that travels up to the kidneys.

Symptoms

Symptoms vary by type but may include:

  • Blood in the urine — may appear pink, red, or cola-colored, or detected only on lab tests
  • Foamy or frothy urine (protein leaking into urine)
  • Swelling of the face, hands, feet, or ankles
  • High blood pressure
  • Reduced urine output
  • Fatigue
  • For kidney infections: fever, chills, back pain, painful urination

Diagnosis and treatment

Diagnosis typically involves blood tests (eGFR, complement levels, specific antibodies), urine tests (proteinuria, blood), and often a kidney biopsy — a procedure where a tiny sample of kidney tissue is taken with a needle and examined under a microscope to identify the specific type of nephritis.

Treatment depends on the specific cause:

  • Immunosuppressants — For autoimmune nephritis (steroids, mycophenolate, cyclophosphamide, rituximab)
  • Blood pressure medications — ACE inhibitors or ARBs to reduce proteinuria and protect kidneys
  • Antibiotics — For bacterial kidney infections
  • Stopping the offending medication — For drug-induced interstitial nephritis
  • Targeted therapies — Newer treatments like sparsentan for IgA nephropathy
Blood in the urine — even if it goes away — should always be evaluated by a doctor. It can be an early sign of nephritis that, if caught early, can be treated before significant kidney damage occurs.