Introduction
The kidney has millions of tiny units known as nephrons that filter the blood and remove the waste from the body through urine. Each unit connects to the glomeruli. When the glomerulus becomes swollen or inflamed due to infection, it is called post-infectious glomerulonephritis. The condition is a common cause of developing acute nephritic syndrome in children.
What Is Acute Post-infectious Glomerulonephritis?
Acute post-infectious glomerulonephritis is a kidney disorder that develops in some children after an infection in the throat or skin. It is because the immune system fighting the infection mistakenly targets the kidneys. Therefore, damaging the kidneys reduces their ability to filter blood until the condition heals completely. The developing disease is termed acute post-infectious glomerulonephritis (PIGN). Acute post-infectious glomerulonephritis has a slight male predominance.
Children between 5 to 12 years are susceptible to developing acute post-infectious glomerulonephritis. However, the incidence of developing acute post-infectious glomerulonephritis has decreased in high-income countries owing to improved socio-economic status, hygiene, and the widespread use of antibiotics.
Among adults, the risk factors for developing acute post-infectious glomerulonephritis are diabetes, malignancy, HIV (Human Immunodeficiency Virus), alcoholism, and intravenous drug use.
What Causes Post-infectious Glomerulonephritis to Develop?
Bacteria, parasites, and viruses could cause post-infectious glomerulonephritis to develop. Streptococcus bacteria are a common cause of developing glomerulonephritis infection among children. Other bacterial causes are pneumococcus, gram-negative bacteria, chlamydia, and mycoplasma. Viral causative agents include herpes simplex, cytomegalovirus, Epstein-Barr virus, mumps, influenza, and hepatitis B. Parasitic causes are toxoplasma and Plasmodium malaria.
Non-streptococcal organisms have developed as the primary etiological agent for producing acute post-infectious glomerulonephritis in high-income countries. The infection tends to develop one to two weeks after streptococcal throat infection and three to six weeks following streptococcal skin infection. The presentation, symptoms, and management of non-streptococcal cases are similar to Streptococcus-induced acute post-infectious glomerulonephritis.
What Is the Pathogenesis of Acute Post-infectious Glomerulonephritis?
During initial infection, Streptococcus bacteria or antigens enter the bloodstream and localize within the glomerulus. After a few days, antibodies specific to the antigen tend to form. The antigen with glomerulus interacts with antibodies to form immune complexes. Some of the immune complexes deposit within the glomeruli. Complement activation and inflammatory response have a role in producing kidney injury. All these factors together cause acute post-infectious glomerulonephritis.
What Are the Signs and Symptoms of Post-infectious Glomerulonephritis?
The clinical course of acute post-infectious glomerulonephritis follows a subclinical, acute nephritic syndrome, nephritic syndrome, or rapidly progressive glomerulonephritis pattern. The subclinical course of the disease is typical.
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Hematuria (Blood in Urine): The symptom commonly appears in post-infectious glomerulonephritis. The presentation could range from asymptomatic microscopic hematuria to gross hematuria with other signs. The urine appears dark, similar to tea or cola. Hematuria is a result of glomeruli damage, which leaks blood into urine.
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Edema (Body Swelling): Among children, the swelling begins around the eyes when the child wakes up. Swelling may also develop in other body parts, such as ankles or bellies. It is a result of fluid building up in those areas. It swells when the body retains too much water and salt and produces insufficient urine. In severe cases, the individual may experience difficulty breathing as fluids enter the lungs.
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Hypertension (High Blood Pressure): Salt and water buildup in the body can be mild or severe, which increases blood pressure. Very high blood pressure could cause problems in the brain or heart of an affected individual.
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Proteinuria (Protein in Urine): Although urine protein levels in post-infectious glomerulonephritis are not high enough to cause problems in some individuals, it induces body swelling. The body's inability to maintain equilibrium due to excessive protein loss in the urine results in insufficient protein levels. Consequently, it causes swelling and leaks fluid into the incorrect body areas.
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Acute Kidney Injury (Decreased Kidney Function): As kidneys cannot adequately filter blood, it produces acute kidney injury. The kidney injury develops quickly and lasts for a short time. The developing acute kidney injury can be mild or severe.
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Henoch-–Schonlein Purpura: It is an atypical presentation among individuals with streptococcal acute post-infectious glomerulonephritis. The diagnosis of the condition is affirmed with a biopsy.
How Is Acute Post-infectious Glomerulonephritis Diagnosed?
The doctor will perform a complete physical exam, which includes measuring blood pressure. The physician records any prior Streptococcus or disease history. Diagnosing acute post-infectious glomerulonephritis is easier, based on clinical symptoms and blood and urine test results. Serological markers for identifying streptococcal infection, which triggers acute post-infectious glomerulonephritis, are anti-streptolysin O titer and depression of serum complement C3 level. The depression of serum C3 level preceded hematuria.
The individual’s blood or urine is also analyzed. Microscopic analysis of the blood can reveal hematuria. Testing the urine of the affected patients demonstrates the presence of protein, RBC (red blood cell), and cast cells. Other diagnostic laboratory tests are CBC (complete blood count), basic metabolic panel, serum albumin, C3, C4, throat culture, and random urine creatinine. Patients with worsening symptoms or uncertain diagnoses will need a kidney biopsy.
How Is Acute Post-infectious Glomerulonephritis Treated?
Mild cases of acute post-infectious glomerulonephritis do not require treatment. Such individuals must eat less salt until the infection improves and the kidney heals. A low-salt diet prevents body swelling and edema. High blood pressure and swelling are controlled with supportive therapy such as medication. A positive throat culture for Streptococcus is treated with antibiotics.
Individuals with severe swelling and high blood pressure require hospital monitoring and oral or intravenous administration of medications. However, severe acute post-infectious glomerulonephritis is rare and may require short-term dialysis. An individual is considered recovering when the fluid overload is reduced spontaneously or pharmacologically, along with normalization of blood pressure and resolution of hematuria and proteinuria.
There is no specific therapy to cure the condition. Most individuals affected by acute post-infectious glomerulonephritis have their symptoms resolved within 1 to 2 weeks. However, a trace amount of blood can be found in urine for several months. Follow-ups and repeated blood tests are required for monitoring the condition. Most individuals will have complete recovery of their kidney function.
Conclusion
Post-infectious glomerulonephritis remains a concern for children between 5 to 12 years. The non-streptococcal etiology for the condition has been rapidly increasing in high-income countries. Streptococcal antigens and immunological complex formation are factors responsible for developing renal injury. Although there is no specific treatment, management of hypertension and body swelling can help with recovery.
