Acute postinfectious glomerulonephritis (APIGN) is a kidney condition that develops following an infection. It involves inflammation of the glomeruli, which are the tiny filtering units within the kidneys responsible for removing waste and excess fluid from the blood. This inflammation can hinder the kidneys’ filtering function. The term “acute” signifies that the onset of this kidney injury is rapid and typically resolves within a relatively short period. APIGN represents a temporary but significant disruption to kidney health, particularly in children.
How Acute Postinfectious Glomerulonephritis Develops
APIGN arises from the body’s immune response to a prior infection, rather than the infection directly invading the kidneys. Certain infections, most commonly those caused by specific strains of Streptococcus bacteria, such as strep throat (pharyngitis) or skin infections like impetigo, can trigger this reaction. While strep bacteria were historically the primary culprits, other bacteria, viruses, fungi, and parasites can also lead to APIGN.
After the initial infection, the immune system produces antibodies. In APIGN, these antibodies, or immune complexes, can settle in the glomeruli. This deposition activates the body’s immune defenses within the kidney filters, leading to inflammation of the glomeruli. This process occurs after a latency period, usually 6 to 21 days following the initial infection.
Recognizing the Signs of Acute Postinfectious Glomerulonephritis
The inflammation and damage to the kidney’s filtering units can lead to several symptoms. One of the most common signs is hematuria, or blood in the urine, which can make the urine appear dark, like tea or cola. Sometimes, the blood is not visible to the naked eye but can be detected through laboratory testing.
Another frequent symptom is swelling, known as edema, which often begins around the eyelids. This fluid retention can also appear in other areas, such as the ankles or abdomen. High blood pressure (hypertension) is also common, resulting from the kidneys’ reduced ability to regulate fluid and salt balance. Individuals may also experience fatigue or a decrease in urine output, reflecting the kidneys’ impaired filtering capacity.
Diagnosis and Management
Diagnosing APIGN involves clinical evaluation and laboratory tests. A doctor performs a physical examination, including checking blood pressure. Urine tests detect blood and protein, which are indicators of glomerular damage. Blood tests assess kidney function by measuring waste products like creatinine and urea, and look for markers of a recent streptococcal infection, such as antistreptolysin O (ASO) titers or anti-DNase B antibodies. In some complex or atypical cases, a kidney biopsy may be necessary to confirm the diagnosis and assess glomerular injury.
Management of APIGN is primarily supportive, focusing on alleviating symptoms and supporting kidney function while the body recovers. This includes managing blood pressure with antihypertensive medications to prevent complications. Fluid and salt intake may be restricted to reduce swelling, and diuretics may be prescribed to eliminate excess fluid. If the initial infection is still active, antibiotics may be administered to eradicate the bacteria. Most individuals with APIGN see their condition resolve with this supportive care as the kidneys heal.
Outlook and Recovery
The prognosis for individuals with APIGN is favorable, with most children and many adults making a full recovery. Kidney function improves over weeks to months, and symptoms like blood in the urine and swelling gradually resolve. Regular follow-up appointments with a healthcare provider are important to monitor kidney health and ensure complete recovery of kidney function.
While full recovery is the most common outcome, a small percentage of adults may experience progression to chronic glomerulonephritis. In rare instances, individuals can develop severe complications such as acute kidney failure requiring dialysis. However, these long-term complications are uncommon, and most affected individuals regain normal kidney function without lasting problems.