Nephritic Syndrome

Overview

Nephritic syndrome is a collection of signs that appear when the tiny filtering units of the kidneys, called glomeruli, become inflamed. This inflammation lets red blood cells and protein leak into the urine and reduces the kidneys' ability to remove waste and excess fluid from the body.

The classic features are blood in the urine (which may turn it pink, red, or cola-colored), high blood pressure, and swelling, often around the eyes and in the legs. Nephritic syndrome can come on suddenly, sometimes a week or two after a throat or skin infection, and ranges from mild and self-limiting to severe. It is different from nephrotic syndrome, which causes much heavier protein loss and more pronounced swelling.

The severity of nephritic syndrome varies widely. Some people have only mild changes that settle quickly, while others develop a more aggressive form that can worsen kidney function over days to weeks. Careful follow-up and repeat testing allow doctors to track how the kidneys are recovering and to adjust treatment as needed.

Symptoms

• Blood in the urine, making it pink, red, brown, or cola-colored
• High blood pressure
• Swelling (edema), often around the eyes in the morning and in the legs and ankles
• Reduced urine output
• Foamy urine from some protein loss
• Fatigue, headache, or nausea if waste builds up in the blood

A sharp drop in urine output, severe swelling, or signs of dangerously high blood pressure warrant prompt medical attention.

Children with post-infectious nephritic syndrome may seem generally unwell, tired, and puffy-faced, and parents often first notice darker urine. Because symptoms can be subtle, any new swelling or change in urine color is worth reporting to a doctor.

Causes

Nephritic syndrome results from inflammation of the glomeruli, which has several possible triggers:

• Post-infectious glomerulonephritis: Inflammation following a streptococcal throat or skin infection, especially in children.
• Autoimmune disease: Conditions such as lupus or IgA nephropathy in which the immune system attacks the kidneys.
• Small-vessel vasculitis: Inflammation of blood vessels in the kidneys.
• Goodpasture syndrome: A rare disorder affecting the kidneys and lungs.

Risk Factors

• Recent strep throat or skin infection
• Autoimmune conditions such as lupus
• Family history of kidney disease
• Certain infections such as hepatitis B or C
• Blood vessel inflammation (vasculitis)

Diagnosis

Diagnosis combines urine and blood testing with the clinical picture:

• Urinalysis: Detects blood, protein, and abnormal cell clusters (casts) in the urine.
• Blood tests: Measure kidney function (creatinine and urea), immune markers, and signs of recent infection.
• Imaging: Ultrasound to assess the kidneys.
• Kidney biopsy: A small tissue sample to identify the exact cause and guide treatment in unclear or severe cases.

Doctors also review your recent health history, such as any sore throat, skin infection, or known autoimmune disease, because these clues help point to the underlying cause and guide which additional tests are most useful.

Treatment

Treatment targets the underlying cause and protects kidney function.

• Blood pressure control: Medicines and salt restriction to manage hypertension and reduce kidney strain.
• Fluid and salt management: Limiting salt and fluid, sometimes with diuretics, to reduce swelling.
• Treating the cause: Antibiotics if an infection is still present, or immune-suppressing medicines such as corticosteroids for autoimmune causes.
• Dialysis: Temporary support if the kidneys fail significantly.

Post-infectious nephritic syndrome in children often resolves on its own, while autoimmune causes may need longer treatment.

Close monitoring of blood pressure, weight, and urine output is an important part of care, helping the team judge whether the kidneys are improving and whether treatment needs to be adjusted over time.

While the kidneys recover, doctors may temporarily limit certain foods high in salt and, in some cases, protein or potassium, to ease the workload on the kidneys. Most people can return to a normal diet as kidney function improves.

Prevention

• Treat strep throat and skin infections promptly and completely
• Manage chronic conditions such as lupus under medical care
• Control blood pressure and avoid unnecessary use of kidney-stressing medicines
• Attend follow-up appointments to monitor kidney function after an episode

When to See a Doctor

See a doctor promptly if you notice blood in your urine, new swelling, or a marked drop in how much you urinate. Seek urgent care for:

• Severe swelling or sudden weight gain from fluid
• Very high blood pressure with headache or vision changes
• Little or no urine output
• Shortness of breath, which can signal fluid overload

Related Topics

Frequently Asked Questions

References

1. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Glomerular Diseases.
2. Mayo Clinic. Glomerulonephritis.
3. MedlinePlus, U.S. National Library of Medicine. Nephritic syndrome.
4. National Kidney Foundation. Glomerulonephritis.