Indications for biopsy

1.     post-op anuria

2.     clinical rejection which does not respond to immunosuppressive therapy

3.     deteriorating renal function

4.     proteinuria

5.     following transplantation

Hyperacute Rejection

• usu develops within a few hours post-transplantation
• Cause: pre-existing Abs to HLA or ABO antigens
• Gross: Kidney cyanotic and soft
• MICRO:

1. leukocytosis
2. platelet and fibrin thrombi
3. stasis of erythrocytes
4. thrombosis and fibrinoid necrosis of arterioles and intralobular arteries
5. widespread cortical necrosis within 24 hrs

Acute Rejection

• 3^rd to 7^th day post-transplantation, usually
• can occur weeks to years later
• Two types: Cellular or Vascular

Acute Cellular Rejection (interstitial rejection)

• Gross: enlarged kidney
• Micro:

1.     diffuse interstitial mononuclear infiltrate

2.     edema

3.     infiltrate contains: small and large lymphs, immunoblasts, plasma cells, histiocytes

4.     migration of interstitial cells into the tubular epithelium

5.     glomerular changes usu minimal

Acute Vascular Rejection

• Gross: edema, hemorrhage, and parenchymal necrosis
• Micro:

1.     vascular changes: Endovasculitis – endothelial swelling, hyperplasia and mononuclear infiltrate of the intima

2.     necrosis and cellular infiltrates in the media

3.     thrombi formation as a result of endothelial injury

4.     tubular necrosis (consequence of vascular changes)

5.     edema and hemorrhage in the interstitium

6.     glomeruli: cells swollen, hyperplasia, sometimes necrosis and blood stasis

• multiple infarcts occur in the advanced stages of vascular acute rejection
• not all vessels are affected, so biopsies may not show lesions

Classification of Acute Rejection

Grade I                                    Mild to moderate acute cellular rejection

Grade II:A                                Severe acute cellular rejection

Grade II:B                                Mild to moderate acute vascular rejection

Grade III                                  Severe acute vascular rejection

Chronic Rejection

• slowly progressive deterioration of the renal function
• often, increased BP and proteinuria
• months – years
• Micro:

1.     vessels: intimal fibrosis and lumen becomes obliterated

2.     interstitial fibrosis

3.     atrophy of the tubules

4.     Glomeruli: thickening of the BM, increase in mesangium

The grade classification of chronic rejection is on the degree of interstitial fibrosis and tubular atrophy

Transplant Nephrotic Syndrome

• most common cause is transplant glomerulopathy
• most common type of glomerulonephritis in transplant patients is membranous glomerulonephritis

Cyclosporine Nephrotoxicity

• no specific pathological features
• tubular vacuolization
• arteriolar hyaline change

Tags: anuria, Cyclosporine Nephrotoxicity, edema, hemorrhage, Hyperacute, parenchymal necrosis, Transplant Nephrotic Syndrome

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