Pathology Of Renal Failure

25.5.07

Renal function
• Blood supply 1250ml/min.
• GFR 150ml/min.
• Urine output 1ml/min.
• Filtration (glomerulus).
• Modification (PCT).
• Concentration (loop and DCT).
• Active processes.

Acute renal failure (ARF)
• Pre-renal - pump failure, volume loss, microvascular damage.
• Renal.
• Post-renal.

ARF: renal causes
• Ischaemia - worsened by crush injury.
• Toxins.
-Heavy metals.
-Solvents.
-Antibiotics.
-Venoms and mycotoxins.
-Bence Jones protein.

ARF: post-renal causes
• Obstruction from:
-Stones.
-Prostatic enlargement.
-Tumours.
-Ureteric stricture.
-[+Rarer causes.]

Features of ARF
• Anuria/Oliguria.
• Na+ <20mEq/L.
• High osmolality (ratio u/p >1.5).
• High urea and creatinine.
• May go on to acute tubular necrosis (ATN).

ATN
• Biochemical/laboratory features:
-Not anuric (may be polyuric).
-Urine Na+ >40mEq/L.
-Osmolality u/p <1.1:1.
-Numerous granular and cellular casts.

Chronic renal failure (CRF)
• Leakage of proteins (damage to filter).
• Na+ and water retained.
-Oedema and hypertension.
• Haematuria.
• Decrease in GFR.
-<20% abnormal (<5% = ESRF).
• Raised urea, creatinine, K+.
• Decreased Ca2+.

CRF: syndromes
• Nephritic:
-Decreased urine output.
-Modest proteinuria.
-Hypertension.
-Retention of Na+ and water.
-Haematuria.
• Nephrotic:
-Protein loss>3.5g/day.
-Hypoalbuminaemia.
-Oedema.
• Rapidly progressive renal failure.
-Generally with crescentic glomerulonephritis.

Membranous glomerulonephritis
• Nephrotic syndrome.
• Drugs, tumours, infections, SLE, DM.
• Thickened glomerular basement membrane diffusely and universally.
• Spikes (complexes) on silver stain.

Immune complex glomerulonephritis
• Circulating complexes trapped in glomeruli.
• Injury mainly due to complement binding.
• Tend to cause Membranoproliferative pattern of injury.
• See in e.g.
-SLE.
-HBV.
-HCV.
-HIV.
-Endocarditis.
-Chronic infections.
-Parasitic invasions.

Amyloidosis
• Abnormal amount of polymerised protein (β-pleated sheet).
• Plasma cell and inflammatory types.
• Trapped in glomeruli in filtration.
• Result in nephrotic syndrome.
• Stains brick red with Congo red dye.
• Apple green birefringence with Congo red.

Interstitial nephritis
• Pyelonephritis.
• Drug induced.
-NSAIDs.

Renal papillary necrosis
• Osmotic stress.
• DM.
• NSAIDs.
-Australia.
-Vultures.

Systemic hypertension
• Benign hypertension tends to have minimal effects on GFR.
• Risk increased in black people in USA.

Summary
• ARF.
• CRF.
-Polycystic.
-Systemic.
§DM, SLE, hypertension.
-Glomerular.
-Interstitial.
-Obstruction.