Post-Streptococcal Glomerulonephritis (PSGN)

What happens in PSGN

Group A Streptococcus bacteria cause strep throat and skin infections such as impetigo. In some people, the immune system's response to certain strep strains forms immune complexes that lodge in the glomeruli, the tiny filters in the kidneys. These trigger inflammation and activate the complement system, damaging the filters. As a result:

• blood and protein leak into the urine
• the kidneys filter less effectively
• salt and water are retained, causing swelling and high blood pressure

This pattern is called nephritic syndrome.

Who gets it

• Children aged 5 to 12 most often, though adults, especially older adults, can be affected
• More common in boys
• More common in areas with poor access to health care and crowded living conditions, where untreated skin infections are frequent
• Treating strep throat with antibiotics prevents rheumatic fever but does not reliably prevent PSGN

Symptoms

• Dark urine: cola-, tea- or rust-colored from blood (blood in urine)
• Swelling (edema): around the eyes in the morning, face, ankles and legs
• High blood pressure, which can cause headaches
• Reduced urine output
• Tiredness, nausea, loss of appetite
• Sometimes foamy urine from protein
• Some children have only abnormal urine tests and no symptoms

Diagnosis

• Urinalysis: blood, red blood cell casts (a strong sign of glomerular inflammation) and protein.
• Blood tests: kidney function (creatinine), electrolytes, and complement levels. Low C3 is typical and returns to normal within about 6 to 8 weeks.
• Evidence of recent strep infection: a throat or skin culture, or raised antibodies such as antistreptolysin O (ASO) after throat infection or anti-DNase B after skin infection.
• Blood pressure monitoring.
• Kidney biopsy: only if the course is unusual, such as worsening kidney function, nephrotic-range protein, C3 that stays low beyond 8 weeks, or no evidence of strep.

Treatment

There is no specific treatment to stop the inflammation, which settles on its own. Treatment supports the body during recovery:

• Salt and fluid restriction to reduce swelling and blood pressure
• Diuretics (water pills) to remove excess fluid
• Blood pressure medicines if pressure remains high
• Antibiotics if strep infection is still present, and to limit spread to close contacts
• Hospital care for severe high blood pressure, fluid overload or significant kidney injury. Dialysis is rarely needed, usually temporarily

Outlook

The outlook in children is excellent:

• Swelling and high blood pressure usually improve within 1 to 2 weeks
• Kidney function returns to normal within weeks
• C3 normalizes within about 6 to 8 weeks
• Microscopic blood in the urine may persist for months, up to 1 to 2 years
• Recurrence is rare

Adults, particularly older adults with other health conditions, have a higher risk of lasting kidney damage. Follow-up urine tests and blood pressure checks ensure full recovery.

Prevention

• Prompt treatment of strep throat and skin infections, and good hygiene to limit spread
• Keeping cuts, insect bites and eczema clean to prevent impetigo
• Handwashing and not sharing towels

Frequently asked questions

What is post-streptococcal glomerulonephritis?

It is inflammation of the kidney filters that develops weeks after a group A strep infection of the throat or skin. The immune response to the bacteria damages the filters, causing blood in the urine, swelling and high blood pressure. It mostly affects children and usually resolves completely.

How long after strep throat does glomerulonephritis occur?

It typically appears 1 to 3 weeks after strep throat and 3 to 6 weeks after a strep skin infection such as impetigo. This delay distinguishes it from kidney problems that occur during an active infection.

What are the symptoms of post-streptococcal glomerulonephritis?

The main symptoms are dark, cola-colored urine, puffiness around the eyes and swelling of the legs, high blood pressure with headaches, and passing less urine. Some children feel tired and lose their appetite. Mild cases may be found only on a urine test.

Is post-streptococcal glomerulonephritis curable?

Yes, in most cases. The inflammation resolves on its own within weeks, and most children regain normal kidney function. Treatment controls swelling and blood pressure during recovery. Adults have a higher chance of lasting kidney problems and need closer follow-up.