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Cystic Diseases of the KidneyAlthough not all cysts of the kidney are congenital, all types of cysts are discussed here for convenience. Cystic diseases of the kidney are a heterogeneous group comprising hereditary, developmental but nonhereditary, and acquired disorders. As a group, they are important for several reasons: (1) they are reasonably common and often represent diagnostic problems for clinicians, radiologists, and pathologists; (2) some forms, such as adult polycystic disease, are major causes of chronic renal failure; and (3) they can occasionally be confused with malignant tumors. A useful classification of renal cysts is as follows:[9] 1. Cystic renal dysplasia 2. Polycystic kidney disease a. Autosomal-dominant (adult) polycystic disease b. Autosomal-recessive (childhood) polycystic disease 3. Medullary cystic disease a. Medullary sponge kidney b. Nephronophthisis 4. Acquired (dialysis-associated) cystic disease 5. Localized (simple) renal cysts 6. Renal cysts in hereditary malformation syndromes (e.g., tuberous sclerosis) 7. Glomerulocystic disease 8. Extraparenchymal renal cysts (pyelocalyceal cysts, hilar lymphangitic cysts) Only the more important of the cystic diseases are discussed below. Table 20-2 summarizes the characteristic features of the principal renal cystic diseases. CYSTIC RENAL DYSPLASIA This sporadic disorder is due to an abnormality in metanephric differentiation characterized histologically by the TABLE 20-2-- Summary of Renal Cystic Diseases Inheritance Pathologic Features Clinical Features or Complications Typical Outcome Diagrammatic Representation Adult polycystic kidney disease Autosomal dominant Large multicystic kidneys, liver cysts, berry aneurysms Hematuria, flank pain, urinary tract infection, renal stones, hypertension Chronic renal failure beginning at age 40–60 yr Childhood polycystic kidney disease Autosomal recessive Enlarged, cystic kidneys at birth Hepatic fibrosis Variable, death in infancy or childhood Medullary sponge kidney None Medullary cysts on excretory urography Hematuria, urinary tract infection, recurrent renal stones Benign Familial juvenile nephronophthisis Autosomal recessive Corticomedullary cysts, shrunken kidneys Salt wasting, polyuria, growth retardation, anemia Progressive renal failure beginning in childhood Adult-onset medullary cystic disease Autosomal dominant Corticomedullary cysts, shrunken kidneys Salt wasting, polyuria Chronic renal failure beginning in adulthood Simple cysts None Single or multiple cysts in normalsized kidneys Microscopic hematuria Benign Acquired renal cystic disease None Cystic degeneration in end-stage kidney disease Hemorrhage, erythrocytosis, neoplasia Dependence on dialysis persistence in the kidney of abnormal structures—cartilage, undifferentiated mesenchyme, and immature collecting ductules—and by abnormal lobar organization. Most cases are associated with ureteropelvic obstruction, ureteral agenesis or atresia, and other anomalies of the lower urinary tract. Dysplasia can be unilateral or bilateral and is almost always cystic. In gross appearance, the kidney is usually enlarged, extremely irregular, and multicystic ( Fig. 20-6A ). The cysts vary in size from microscopic structures to some that are several centimeters in diameter. On histologic examination, they are lined by flattened epithelium. Although normal nephrons are present, many have immature ducts. The characteristic histologic feature is the presence of islands of undifferentiated mesenchyme, often with cartilage, and immature collecting ducts ( Fig. 20- 6B ). When unilateral, the dysplasia is discovered by the appearance of a flank mass that leads to surgical exploration and nephrectomy. The function of the opposite kidney is normal, and such patients have an excellent prognosis after surgical removal of the affected kidney. In bilateral renal dysplasia, renal failure may ultimately result. Date: 2016-04-22; view: 971
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