Post-Infectious Glomerulonephritis
Kidney inflammation that develops after an infection such as strep
Quick Facts
- Type: Kidney (glomerular) inflammation
- Common trigger: Strep throat or strep skin infection
- Key signs: Blood in urine, swelling, high blood pressure
- Outlook: Most children recover fully
Overview
Post-infectious glomerulonephritis is inflammation of the glomeruli, the tiny filtering units of the kidneys, that develops a week or more after an infection. The most common trigger is an infection with group A streptococcus bacteria, such as strep throat or a strep skin infection, in which case it is called post-streptococcal glomerulonephritis.
The condition is not caused by the bacteria attacking the kidneys directly. Instead, the immune system's response to the infection produces particles that lodge in the kidney filters and cause inflammation. It most often affects children and usually follows a self-limited course, with the large majority recovering kidney function fully, though adults and severe cases need closer monitoring.
Symptoms
Symptoms typically appear 1 to 3 weeks after a throat infection, or several weeks after a skin infection, and may include:
- Blood in the urine, which may look pink, red, or cola/tea-colored
- Reduced urine output
- Swelling (edema), especially around the eyes, face, and in the legs and ankles
- High blood pressure
- Fatigue and feeling generally unwell
Some people have only mild changes detected on a urine test. Severe cases can cause significant swelling, very high blood pressure, or signs of kidney strain, which need prompt medical evaluation.
Causes
Post-infectious glomerulonephritis is caused by the immune system's reaction to an infection rather than by direct kidney infection. Triggers include:
- Streptococcal infections: Strep throat and strep skin infections (such as impetigo) are the classic and most common causes.
- Other bacterial infections: Certain other bacterial infections can also trigger it.
- Some viral and other infections: Less commonly involved.
After the infection, immune complexes form and deposit in the glomeruli, causing inflammation that interferes with the kidneys' ability to filter blood and balance fluid.
Risk Factors
- A recent strep throat or strep skin infection
- Childhood, as the condition is most common in children aged roughly 5 to 12
- Crowded living conditions where strep spreads easily
- Untreated or undertreated bacterial infections
Diagnosis
Doctors diagnose the condition based on the history of a recent infection plus characteristic urine and blood findings:
- Urine tests: Detect blood and protein in the urine.
- Blood tests: Measure kidney function and look for evidence of a recent strep infection and changes in immune system proteins (such as complement levels).
- Kidney biopsy: Occasionally performed in unclear or severe cases to confirm the diagnosis.
Treatment
There is no specific cure; treatment is mainly supportive while the kidneys recover:
- Managing fluid and salt: Limiting salt and fluids helps control swelling and blood pressure.
- Blood pressure control: Medications, including diuretics to remove excess fluid, may be used.
- Treating any remaining infection: Antibiotics clear lingering strep infection, though they do not reverse the kidney inflammation already present.
- Monitoring: Regular checks of blood pressure, urine, and kidney function track recovery.
Most children recover fully within weeks. Severe cases with significantly reduced kidney function may need more intensive treatment in hospital.
Prevention
- Promptly diagnose and treat strep throat and strep skin infections
- Complete the full course of prescribed antibiotics
- Practice good hygiene, including regular handwashing
- Keep skin wounds clean to reduce strep skin infections
- Seek care for sore throats with fever or for spreading skin infections
When to See a Doctor
See a doctor if you or your child develops blood in the urine, swelling, or reduced urination, especially after a recent throat or skin infection. Seek prompt or emergency care for:
- Very little or no urine output
- Severe swelling or rapid weight gain from fluid
- Severe headache, vision changes, or confusion (which can signal dangerously high blood pressure)
- Difficulty breathing
Frequently Asked Questions
What causes post-infectious glomerulonephritis?
It is caused by the immune system's reaction to an infection, most often a strep throat or strep skin infection. Immune particles formed in response to the infection lodge in the kidney's filtering units and cause inflammation, rather than the bacteria infecting the kidneys directly.
What are the main symptoms?
Typical symptoms include blood in the urine (often pink, red, or cola-colored), swelling around the eyes and in the legs, reduced urine output, and high blood pressure. Symptoms usually appear one to three weeks after a throat infection or several weeks after a skin infection.
Do most people recover from it?
Yes, especially children, who usually recover kidney function fully within weeks with supportive care. Adults and severe cases may have a less predictable course and need closer follow-up to monitor kidney function and blood pressure.
How is it treated?
There is no specific cure, so treatment supports the kidneys while they heal. This includes limiting salt and fluids, controlling blood pressure, using diuretics for swelling, and treating any remaining infection with antibiotics. Severe cases may need hospital care.
When should I seek urgent care?
Seek prompt care for very low or no urine output, severe swelling, difficulty breathing, or signs of dangerously high blood pressure such as severe headache, vision changes, or confusion. These need immediate medical attention.
References
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Glomerular Diseases.
- Mayo Clinic. Glomerulonephritis — Symptoms and causes.
- MedlinePlus, U.S. National Library of Medicine. Post-streptococcal glomerulonephritis.
- Centers for Disease Control and Prevention (CDC). Group A Streptococcal Disease.