Cystic Diseases of the Kidney

Although 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: 807