Gross & microscopic appearance	Pathologic basis of disease	Clinical correlation	
Gross:
•	Kidneys are small & hard.
•	Symmetrical atrophy thinning of the cortex.
•	Poor demarcation of cortex from medulla.

Microscopic:
•	Widespread replacement of glomerular tufts by avascular, acellular hyaline material.
•	Cortical tubules become shrunken & atrophic.
•	Expanded interstitial spaces undergo fibrosis.
•	Some atrophic tubules may become cystically dilated with casts of inspissated proteinaceous material which is highly eosinophilic.	Etiology:
•	Primary renal disease: bilateral chronic pyelonephritis & chronic glomerulonephritis (less common).
•	Essential hypertension.

Pathogenesis:
•	Marked by significant loss of functioning renal tissue.
•	Primary renal disease causes vascular damage & renal ischemia leading to progressive renal damage.
•	Essential hypertension results in renal arteriolar vasoconstriction & renal ischemia.
•	Endothelial cell damage leads to platelet thrombosis, hyalinization & fibrosis.
•	Progressive effects of functional failure are uraemia & its complications.

Functional abnormalities:
•	Polyuria: reduced glomerular filtration rate & a greater reduction in reabsorption.
•	Urine of fixed specific gravity: inability to concentrate urine & failure of selective reabsorptive mechanisms.
•	Acidosis: inability of damaged tubules to form ammonia.

Causes of acute renal failure:
•	Organic vascular obstruction
•	Severe glomerular disease
•	Acute tubulo-interstitial nephritis
•	Massive infection, especially with papillary necrosis
•	Disseminated intravascular coagulation
•	Acute tubular necrosis	Uraemia:
•	Result from retention of  waste produces & failure to control fluid & electrolyte balance.
•	Lethargy
•	Anorexia
•	Nausea & vomiting
•	Mental confusion
•	Muscle twitchings
•	Convulsions & death if condition is not alleviated. 

Complications:
•	Hypertension: leads to left ventricular hypertrophy, cardiac failure & strokes.
•	Fibrinous exudates, e.g. fibrinous pericarditis, ‘uraemic pneumonitis’ with pleural exudate, uraemic colitis.
•	Hemorrhagic ulcers of the gastrointestinal tract.
•	Anemia: depression of bone marrow due to deficient erythropoietin production by the kidney.
•	Depression of immunological reaction: infections are common.