Acquired Cystic Kidney Disease in ESRD.(end stage renal disease)

Bilateral nephrectomy was commonly practiced 20-30 years ago in end stage renal disease (ESRD) patients beginning chronic dialysis. Nephrectomy was done to assist in the control of blood pressure and in preparation for future kidney transplantation. Since nephrectomy is no longer considered essential prior to transplantation and since more effective antihypertensive medications are available, greater than 90% of dialysis and transplant patients retain their native kidneys (Matson & Cohen, 1990). Cystic changes in the retained native kidneys of ESRD patients have been detected at autopsy (Dunnill, Millard, & Oliver, 1977). Since that time, acquired cystic kidney disease (ACKD) has been incidentally noted on diagnostic examinations using ultrasonography (US) and computerized tomography (CT) in ESRD patients on chronic dialysis.

Many questions have been raised regarding the clinical significance of ACKD in ESRD patients. Prior studies have documented that increased patient age and extended duration of dialysis are directly associated with development of ACKD (Gehrig, Gottheiner, & Swenson, 1985; Miller, Soffer, Nassar, & Kutner, 1989). Recent ESRD mortality statistics have documented that the average age of dialysis patients is increasing and that patient survival on dialysis is increasing (United States Renal Data System [USRDS], 1997). With improved patient survival and an older ESRD population, ACKD will likely become more prevalent.

The development of ACKD in patients on dialysis is usually of little clinical consequence; however, certain risks can be associated with cyst development that may lead to higher morbidity (Daugirdas & Ing, 1994). This article will discuss the etiology, prevalence, screening implications, and interdisciplinary management of ACKD. Two case studies of patients that illustrate complications related to ACKD will also be presented.

ACKD Defined

The development of ACKD in ESRD was first described from autopsy studies (Dunnill et al., 1977). ACKD has been defined based on several different parameters. A general definition includes the formation of multiple cysts (five or more) ranging from 0.2 to 2.5 cm in diameter in both kidneys. Medullary and cortical cyst development in kidneys that were previously free of cysts is synonymous with the diagnosis of ACKD. In a study that evaluated 155 patients at autopsy, the cysts were found to be filled with clear, serous, or hemorrhagic fluid, and kidney weight ranged from 150 to 350 grams (Miller et al., 1989). Patients nearing ESRD have been shown to lose kidney volume or mass, but once on dialysis and over a period of time, kidney mass appears to increase. This increased mass has been linked with development of ACKD (Scanlon & Karasick, 1983).

Complications

While most cysts remain benign and patients remain asymptomatic during their development, severe complications can arise. ACKD has been associated with cyst infection, cyst hemorrhage, retroperitoneal hemorrhage, and spontaneous rupture of the kidney. ACKD may undergo malignant transformation leading to the development of adenomas or renal cell carcinomas (Sarasin, Wong, Levey, & Meyer, 1995).

Patients remain asymptomatic until acute problems occur in the cyst such as: (a) cyst infection resulting in pyelonephritis, (b) cyst hemorrhage, or (c) spontaneous rupture of the kidney requiring emergent surgical nephrectomy. The greatest and most feared threat is malignant cystic transformation. Overall, ESRD patients have an 80% higher risk of developing renal, cancer than the average nonrenal failure population (Miller et al., 1989). The rate of occurrence for ACKD affects peritoneal and hemodialysis patients equally, but there does seem to be a marked difference in the frequency of malignant cystic transformation (Matson & Cohen, 1990). In a study of 353 continuous ambulatory peritoneal dialysis (CAPD) patients monitored over 10 years, none developed renal cancers (Katz, Sombolos, & Oreopoulos, 1987).

Adult polycystic kidney disease (APKD) differs from ACKD in that cysts occur prior to the development of chronic renal failure (see Figure 1). Many APKD patients have hepatic cysts in conjunction with renal cysts. Patients with APKD frequently have very large palpable kidneys and have a strong family history of APKD (Hricak & White, 1996). APKD typically leads to development of ESRD with the eventual need for renal replacement therapy. Simple renal cysts are another type of benign renal cysts that are frequently present in adults over the age of 50 years, even in the presence of normal renal function (see Figure 2). In a broad-based study of people with normal renal function, 50% of adults 50 …