Nephritic Syndrome

What happens in nephritic syndrome

Each kidney contains about a million glomeruli, tiny filters that clean the blood while keeping blood cells and protein in. In nephritic syndrome, inflammation damages the filter walls:

• red blood cells leak into the urine (hematuria), often forming red cell casts
• filtering slows, so salt and water build up, causing swelling and high blood pressure
• waste products such as creatinine rise in the blood
• some protein leaks, though less than in nephrotic syndrome

Nephritic vs nephrotic syndrome

Some diseases can cause features of both.

Causes

Post-infectious glomerulonephritis

Post-streptococcal glomerulonephritis typically affects children 1 to 2 weeks after strep throat or 3 to 6 weeks after a strep skin infection (impetigo). The immune response to the infection deposits immune complexes in the kidney. Most children recover completely. Adults can develop post-infectious glomerulonephritis after staphylococcal and other infections, sometimes during the infection.

IgA nephropathy

The most common glomerular disease worldwide. Visible blood in the urine often appears during or right after a cold. It can slowly progress to chronic kidney disease. IgA vasculitis (Henoch-Schönlein purpura) causes a similar kidney disease with a rash on the legs and buttocks, belly pain and joint pain, mostly in children.

Autoimmune diseases

• Lupus nephritis: in people with lupus
• ANCA-associated vasculitis: including granulomatosis with polyangiitis, often with sinus, lung and nerve symptoms
• Anti-GBM disease (Goodpasture syndrome): antibodies attack the kidney and lung filters, causing kidney failure and bleeding in the lungs

Other causes

• membranoproliferative glomerulonephritis, linked to hepatitis C and other infections
• infective endocarditis and infected shunts
• C3 glomerulopathy, related to complement system problems

Rapidly progressive glomerulonephritis

When kidney function falls over days to weeks, it is called rapidly progressive glomerulonephritis (RPGN), usually with crescents seen on biopsy. It is a medical emergency, most often caused by ANCA vasculitis, anti-GBM disease or lupus.

Symptoms

• dark, cola-, tea- or smoky-colored urine
• swelling of the face, especially around the eyes in the morning, and the legs
• reduced urine output
• high blood pressure, sometimes with headaches
• tiredness and feeling unwell
• shortness of breath from fluid build-up

Symptoms of the underlying cause may include a recent sore throat or skin infection, rash, joint pain, coughing blood or sinus problems.

Diagnosis

• Urinalysis and microscopy: blood, red cell casts and protein
• Urine protein-to-creatinine ratio
• Blood tests: creatinine and eGFR, electrolytes, blood count
• Immunology: complement levels (C3 and C4), antistreptolysin O (ASO) and anti-DNase B, ANA and anti-dsDNA, ANCA, anti-GBM antibodies, hepatitis B and C and HIV tests
• Kidney ultrasound
• Kidney biopsy: often needed to confirm the type and guide treatment, unless the picture is typical post-streptococcal disease in a child

Treatment

General measures

• blood pressure control, often with ACE inhibitors or ARBs, which also reduce protein leakage
• diuretics and salt restriction for swelling
• fluid restriction when urine output is low
• dialysis if kidney failure develops

Cause-specific treatment

• Post-streptococcal: supportive care; antibiotics if infection is still present
• IgA nephropathy: blood pressure and protein control, SGLT2 inhibitors, and newer targeted treatments or steroids for higher-risk disease
• Lupus nephritis and ANCA vasculitis: immunosuppression with steroids plus drugs such as cyclophosphamide, mycophenolate or rituximab
• Anti-GBM disease: urgent plasma exchange, steroids and cyclophosphamide

Complications

• acute kidney injury
• fluid overload and pulmonary edema
• hypertensive emergencies
• chronic kidney disease and kidney failure

Outlook

Children with post-streptococcal glomerulonephritis usually recover fully within weeks to months, though microscopic blood in the urine can persist for a year or more. Outcomes for autoimmune causes depend on how early treatment begins. Rapidly progressive disease needs urgent treatment to save kidney function.

Frequently asked questions

What is nephritic syndrome?

Nephritic syndrome is a set of signs caused by inflammation of the kidney's filters. It causes blood in the urine, swelling, high blood pressure, reduced urine output and falling kidney function. It has many causes, including infections and autoimmune diseases.

What is the difference between nephritic and nephrotic syndrome?

Nephritic syndrome is mainly inflammation, with blood in the urine, high blood pressure and kidney function decline. Nephrotic syndrome is mainly heavy protein leakage, with foamy urine, low blood albumin, high cholesterol and severe swelling.

What causes nephritic syndrome?

Common causes are post-infectious glomerulonephritis (often after strep throat or skin infection), IgA nephropathy, lupus nephritis, ANCA vasculitis and anti-GBM disease. A kidney biopsy often identifies the cause.

Can nephritic syndrome be cured?

Post-streptococcal glomerulonephritis in children usually resolves completely. Autoimmune causes can often be controlled with immunosuppressive treatment, though some people develop chronic kidney disease. Early diagnosis improves outcomes.

Why is my urine the color of cola?

Cola- or tea-colored urine can be caused by blood from inflamed kidney filters, muscle breakdown, liver problems or severe dehydration. It should be checked promptly with a urine test, especially after a recent sore throat or skin infection.