What is post-infectious glomerulonephritis?

Post-infectious glomerulonephritis (PIGN) is one of the 7 types of chronic glomerulonephritis (GN). They are all ‘autoimmune diseases’ where the immune (defence) system attacks normal tissue in the kidney (including the glomeruli). Why and how they occur is unclear.

So. What is post-infectious glomerulonephritis?

PIGN normally develops rapidly, and (classically) follows a streptococcal infection – typically a group A streptococcus, such as Streptococcus pyogenes – developing several weeks after infection. As a delayed immune response and consequence of group A strep infection, PSGN is not contagious.

PIGN can also occur with other micro-organisms: other bacterial infections; and infection with viruses, fungi, protozoans, and helminths. Infective endocarditis and ventriculoatrial shunt infection can also cause PIGN. Ventriculoperitoneal shunts are more resistant to treatment of infection.

Who gets PIGN?
PIGN previously affected mostly children, and it is still more common in this group in developing countries. Make: female = 2:1. However, the incidence has decreased in the developed world, likely reflecting the quicker and more widespread use of antibiotics. Hence PIGN is now significantly more common in adults and preferentially affects the elderly as well as patients with diabetes mellitus or high alcohol use.

When does it happen?
When it is caused by a streptococcus, the disease develops rapidly, usually 1-2 weeks after a streptococcal sore throat (‘strep throat’) or 2-3 weeks after streptococcal skin infection (impetigo). PIGN caused by a staphylococcus more commonly presents at the time of the infection.

Symptoms of post-infectious glomerulonephritis

90% of patients with PIGN present with a rapidly developing nephritic syndrome; shown by the classic triad of symptoms: oedema (swelling), hypertension (high blood pressure) and macroscopic haematuria (blood in the urine you can see):

Oedema (85% of patients; often pronounced facial and orbital oedema, especially on arising in the morning)
Hypertension (high blood pressure; 60-80%)
Macroscopic haematuria (blood in the urine you can see; 30-50%), with urine appearing dark, reddish-brown (like cola)
Proteinuria (protein in urine). This is usually mild and not in the nephrotic range
Non-specific: fever, lethargy, nausea, vomiting and anorexia (off food).

Even though impaired renal function is common, it is usually a mild acute kidney injury (AKI). Severe AKI is unusual (1-2%), but may progress to the need for dialysis. If so, dialysis is usually temporary. 50% of children have no symptoms.

Diagnosis of post-infectious glomerulonephritis

1. Blood tests.

Kidney function tests, i.e. urea and electrolytes (U+Es) – may show mild AKI
Increased antistreptolysin O (ASO; an antibody)) levels – are observed in 90% of patients after streptococcal throat infections and in up to 80% of patients after streptococcal skin infections. ASO remains elevated for several months. There is no specific blood test to identify staphylococcal infections except if it can be identified from a positive blood culture
Other antibodies – include anti-nicotinamide-adenine dinucleotidase (anti-NAD) which tends to rise following streptococcal sore throat. Other antibodies such as anti-DNAse B and anti-hyaluronidase (AHase) are usually elevated after both throat and skin infections.

Many patients have hypocomplementaemia (low complement, which is part of the immune system) due to complement activation – usually leading to low C3 levels, with normal or slightly low C4 levels.

2. Urine ACR. Low level proteinuria (protein in urine) is common. In 5% proteinuria is severe and they develop nephrotic syndrome.

3. Kidney biopsy. Biopsy is not usually done (if the diagnosis of PIGN is highly likely) and only considered in patients who do not recover renal function (e.g. dialysis dependent for more than 2 weeks) or have an abnormal presentation.

Typical abnormal glomerulus in a kidney biopsy in post-infectious glomerulonephritis, showing kidney inflammation. Renal biopsy may show other patterns including a ‘crescentic’ pattern of rapidly progressive glomerulonephritis.

Treatment of post-infectious glomerulonephritis

PIGN is a self-limiting condition [“that means it gets better!” CKDEx Ed] in most cases, and thus only symptomatic treatment is needed. Supportive treatment options aim to control complications such as oedema, hypertension and fluid overload (if present), which are prominent during the early phase of the disease

To do this, sodium and fluid restriction and loop diuretics may be needed. High blood pressure should be treated. In a small number of cases, temporary dialysis is required.

Patients should receive penicillin (preferably penicillin G). This will prevent spread of the strain to other people

Steroids can be considered in some patients with post infection glomerulonephritis and a very abnormal kidney biopsy (called rapidly progressive glomerulonephritis, RPGN); although the evidence for this treatment is not great (suggesting it may do not change outcomes and potentially increase risk, especially if there is an ongoing infection).

Prognosis (outlook) of post-infectious glomerulonephritis

The outlook for PIGN is good. Kidney function – as shown by blood creatinine and glomerular filtration rate (GFR) – usually returns to normal over 1-3 months, but proteinuria may persist for 6-12 months and microscopic haematuria (non-visible blood in the urine) for several years.

Long-term CKD is more common on patients with diabetes. The majority of children (90%) have complete recovery of their renal function. Recurrence of PIGN is rare.

Summary

We have described what is post-infectious glomerulonephritis. We hope it has been helpful.

Other resources

These are review articles for health professionals: Nassih, 2021, Rawla, 2022, CDC, 2022
What is chronic glomerulonephritis?
What is minimal change disease?
What is membranous nephropathy?
What is FSGS?
What is IgA nephropathy?
What is mesangiocapillary glomerulonephritis?
What is rapidly progressive glomerulonephritis?

Last Reviewed on 24 May 2024