Acute Glomerulonephritis (Post-Streptococcal) – Causes, Symptoms, Diagnosis & Treatment

Acute Glomerulonephritis (AGN), particularly Post-Streptococcal Glomerulonephritis (PSGN), is a kidney disorder that follows an untreated streptococcal infection, typically of the throat or skin. It is characterized by inflammation of the glomeruli, the tiny filtering units of the kidney, leading to impaired kidney function. This condition is most common in children and young adults but can affect individuals of any age.

Understanding the pathology, clinical features, and interventions is crucial for early detection and effective management.

Pathology of Post-Streptococcal Glomerulonephritis

The disease develops due to an immune-mediated response following a Group A beta-hemolytic streptococcal infection. The pathological sequence can be summarized as follows:

1. Untreated strep infection (throat or skin).

2. The immune system forms antigen-antibody complexes about 1–2 weeks after infection.

3. These complexes become trapped in the glomeruli.

4. Trapping leads to inflammation and scarring.

5. This results in decreased glomerular filtration rate (GFR) and kidney dysfunction.

It’s important to note: The strep bacteria itself does not damage the kidneys. Instead, the immune complexes formed due to infection trigger the inflammation.

Signs and Symptoms

Patients often present with a combination of urinary, systemic, and laboratory findings:

Hematuria – Blood in the urine, often giving a cola-colored appearance.

Azotemia – Excess nitrogenous waste in the blood.

Malaise & Fatigue – Due to toxin buildup.

Headache – Often linked to hypertension.

Proteinuria (mild) – Loss of protein in urine.

Hypoalbuminemia – Low albumin levels from protein loss.

Decreased GFR – Reduced kidney function.

Oliguria – Low urine output (<400 mL/day).

Edema – Especially around the face and eyes, due to sodium and water retention.

Hypertension – Elevated blood pressure from fluid overload.

Increased BUN & Creatinine – Indicating impaired kidney function.

Increased Urine Specific Gravity – Due to concentrated urine.

Positive ASO (Antistreptolysin O) Titer – Evidence of recent streptococcal infection.

Interventions and Management

Treatment focuses on addressing the underlying cause, managing symptoms, and preventing complications:

1. Eliminate the Cause

• Treat the underlying streptococcal infection with appropriate antibiotics (usually penicillin).

2. Dietary Modifications

• Fluid restriction – Prevents fluid overload.
• Sodium restriction – Reduces hypertension and edema.
• Protein restriction – Minimizes further kidney stress.
• Increased carbohydrate intake – Provides energy and prevents excessive protein breakdown.

3. Monitoring

• Daily intake and output charting – Ensures proper fluid balance.
• Daily weight monitoring – Detects fluid retention. (A gain of 1 kg ≈ 1,000 mL of retained fluid).

4. Bed Rest & Supportive Care

• Encouraged to reduce stress on kidneys.
• Monitor blood pressure regularly.
• Use antihypertensives and diuretics as required.

Diagnostic Values

Urinalysis – Presence of RBCs, mild proteinuria, high specific gravity.

Serum Tests – Elevated BUN, creatinine, decreased GFR.
ASO Titer – Indicates recent streptococcal infection.
Renal Biopsy (if needed) – Confirms glomerular immune complex deposits.

Prognosis

• Children: Usually recover completely within weeks to months.
• Adults: Higher risk of chronic complications.
• Untreated cases may lead to chronic kidney disease (CKD) or end-stage renal failure.

Frequently Asked Questions (FAQ)

Q1: What is the main cause of acute post-streptococcal glomerulonephritis?

It is caused by immune complex deposition in the glomeruli following a Group A beta-hemolytic streptococcal infection.

Q2: How soon after a strep infection does AGN develop?

Usually 10–14 days after throat infection or skin infection.

Q3: Why is urine dark in AGN patients?

The presence of red blood cells in urine gives it a cola or tea-colored appearance.

Q4: Can acute glomerulonephritis be prevented?

Yes, by prompt treatment of streptococcal infections with antibiotics.

Q5: What lab tests confirm AGN?

Urinalysis (RBCs, protein), blood tests (BUN, creatinine), and ASO titers are the most common diagnostic tests.