Imaging Studies for patients with Polycystic Kidney Disease (PKD) on Hemodialysis
Imaging Studies of PKD can provide accurate and reproducible markers of progression of renal disease in patients with polycystic kidney disease. PKD is a genetic disorder characterized by the growth of numerous cysts in the kidneys. When cysts form in the kidneys, they are filled with fluid. PKD cysts can profoundly enlarge the kidneys while replacing much of the normal structure, resulting in reduced kidney function and leading to kidney failure.
In most cases of autosomal dominant PKD, patients have no symptoms and their physical condition appears normal for many years, so the disease can go unnoticed. Physical checkups and blood and urine tests may not lead to early diagnosis. Because of the slow, undetected progression of cyst growth, some people live for many years without knowing they have autosomal dominant PKD.
In individuals with positive family history, the diagnosis of ADPKD is usually established by radiologic imaging studies and demonstration of kidney extensive and bilateral cystic changes throughout the kidneys, which are typically enlarged and have a moth-eaten appearance due to cysts that displace functional tissue. These changes develop with age and are less often present or obvious in younger patients.
The most common form of diagnostic kidney imaging is ultrasound, but more precise studies, such as computerized tomography (CT) scans or magnetic resonance imaging (MRI) are also widely used. In autosomal dominant PKD, the onset of kidney damage and how quickly the disease progresses can vary. Kidney imaging findings can also vary considerably, depending on a patient's age.
Once cysts have grown to about one-half inch, however, diagnosis is possible with imaging technology. Ultrasound, which passes sound waves through the body to create a picture of the kidneys, is used most often. Ultrasound imaging does not use any injected dyes or radiation and is safe for all patients, including pregnant women. It can also detect cysts in the kidneys of a fetus, but large cyst growth this early in life is uncommon in autosomal dominant PKD.
More powerful and expensive imaging procedures such as CT scans and MRI also can detect cysts. Recently, MRI has been used to measure kidney and cyst volume and monitor kidney and cyst growth, which may serve as a way to track progression of the disease. CT and MRI are very useful to define the extent of PLD and the presence of complications.
These measurements predict risk of progression to chronic kidney disease and end-stage renal disease, often before changes in routine laboratory studies. For example, cyst size and kidney size predict 8 year risk of chronic kidney disease more accurately than age, degree of proteinuria, or serum BUN, or creatinine.
Criteria for Diagnosing PKD:
Current screening criteria states:
- Two or more cysts as diagnostic for individuals ages less than 59
- A minimum of four cysts in each kidney for older at-risk individuals.
The finding of fewer than two cysts in each kidney is sufficient to exclude the disease in people who are 30 or older.
Disclaimer: The UCLA Health System cannot guarantee the accuracy of such information. The information is provided without warranty or guarantee of any kind. Please speak to your Physician before making any changes.