Acquired Cystic Kidney Diseases in Dialysis Patients

EPIDEMIOLOGY

The incidence of acquired cystic disease increases progressively with the duration of renal replacement therapy—hemodialysis or peritoneal dialysis. However, ACKD can occur in some patients even before dialysis is initiated. In one study of 130 patients with advanced kidney disease or ESKD, the incidence of multiple cysts was noted to be 7% in those with chronic kidney disease (CKD) and 22% in those on maintenance dialysis (2). The duration of dialysis was 15 months in patients with no cysts, 28 months in those with one to three cysts, and 49 months in those with acquired cystic disease (2). Fifty percent to 80% of patients are affected after 10 or more years on dialysis (3–5). In a similar study of 48 patients with ESKD on continuous ambulatory peritoneal dialysis (CAPD), the incidence of both solitary and multiple renal cysts was noted to be 52% in patients on CAPD for 23 ± 16 months (6). The frequency however may be underestimated on the basis of imaging studies alone. In a single-center study in which most renal transplant patients undergo ipsilateral native nephrectomy at the time of transplant surgery, the prevalence of ACKD was reported to be at 33% based on strict pathologic criteria, which may still be lower than the true incidence given that only one kidney was removed (7) (FIGURE 33.1).

RISK FACTORS

Researchers have shown that time spent on hemodialysis was the most important risk factor for the development of ACKD (8). Men and African Americans have been reported to be at much higher risk than women or Caucasians (8,9).

PATHOGENESIS

The exact pathogenesis of ACKD in humans is not known, but its understanding has been aided by available in vivo and in vitro animal models. The slow progressive loss of functioning renal tissue in ESKD promotes initial compensatory hypertrophy and later hyperplasia of the residual nephrons (3,9). The cysts being confined to the kidneys suggest that local intrarenal events are of primary importance (9). Analysis of the cyst fluid, which is thought to derive from ultrafiltrate secreted into the cyst, typically has a composition similar to that in the plasma; this finding plus the presence of a brush border on the luminal membrane on microdissection studies suggests that the cysts arise primarily from proliferation of proximal tubular epithelial cells (3,9).

Compensatory renal hypertrophy is influenced by many factors, the most important of which is activation of oncogenes and release of growth factors, which, over a prolonged period of time, promote progressive tubular hyperplasia and cyst formation (10,11). Alternatively, other provoking factors might emerge, such as environmental chemicals, transforming viruses, or male sex hormones, that lead to the transition of the proliferative process into malignant growth.

CLINICAL MANIFESTATIONS

ACKD is usually asymptomatic and discovered incidentally during imaging studies. In one review, for example, only 14% of patients developed symptoms, with hematuria being most common, followed by pain and urinary tract infection. Some may manifest with potential complications of ACKD such as cystic hemorrhage that may present with or without hematuria, cyst rupture with consequent perinephric or retroperitoneal hemorrhage, and cyst infection or abscess formation or erythrocytosis.

COMPLICATIONS

Renal Cell Carcinoma

As with ACKD, the incidence of renal cell carcinoma (RCC) as a complication of ACKD varies in different reports (8,12,13). Two prospective studies found an incidence of 4% (2 of 57) and 7% (2 of 30) over a 7- to 10-year period. A review of published reports estimated an incidence of 0.18% per year, compared with 0.008% in the general population in the United States.

Most reports, however, may misrepresent the true prevalence of RCC because they primarily rely upon screening radiography for detection. A single-center study in which most renal transplant patients underwent ipsilateral native nephrectomy at the time of transplant surgery showed that RCC was found in 4.2% of 260 nephrectomies, which may still be lower than the true incidence given that only one kidney was removed (7).

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