Renal cysts are sacs of fluid that occur on or within the kidneys. They are usually not a cause for concern and are generally left untreated. A renal cyst is more commonly referred to as a simple kidney cyst.
Definition & Facts
Most renal cysts are benign and do not impact kidney function. Renal cysts can form on one or both kidneys. They are markedly different from the cysts associated with polycystic kidney disease (PKD), a genetic disorder where numerous cysts grow on the kidneys and impair their function resulting in kidney failure. Simple kidney cysts are more common in people aged 50 and over.
Symptoms & Complaints
Changes in urinary habits may be a symptom of simple renal cysts and patients experiencing the following changes should consult their physician to determine the exact cause of these symptoms:
There may also be a relationship between high blood pressure and simple kidney cysts although it is not well understood. There are some cases where blood pressure returns to a normal range following the drainage of a large cyst. High blood pressure as a symptom is typically seen in patients with PKD and a sign that normal kidney function is being affected by the presence of cyst clusters.
Not that much is known about the exact causes of simple renal cysts. Studies show that they do not appear to be inherited. Age seems to be the major risk factor. It is estimated that up to half of people age 50 and over have at least one renal cyst and that one-third of people age 70 and older have one. Age also increases the chances that more cysts will grow and become larger.
Renal cysts form when the tube of a nephron begins to enlarge and fill with fluid. It is also believed that obstruction of tubules within the kidneys or a blood supply deficiency to the kidneys may also cause cysts to form. In some cases diverticula, which are small sacs that form on the tubules, may detach and later become a cyst. The cysts that form as a result of PKD tend to form in clusters and have a more severe impact on kidney function versus that of a simple kidney cyst.
Diagnosis & Tests
Since simple renal cysts do not typically cause symptoms on their own they are most often discovered during tests for other conditions. One of the following methods can be performed by a trained professional to determine the severity of the cysts and whether or not they are indicative of a more severe condition.
- Abdominal ultrasonography and pelvic ultrasound- An ultrasound uses a transducer to bounce sound-waves off internal organs to produce an image. This gives a view of the kidneys and cysts and determines if they are filled with fluid or not.
- Pelvic or Abdominal CT scan. A CT scan may be performed in conjunction with an ultrasound and may be done with or without contrast dye. This helps doctors distinguish benign cysts from possible tumors.
- MRIs. Like a CT scan this may be done with or without contrast dye injection. An MRI gives a more detailed image of the kidneys and helps identify cysts or tumors. Blood tests and urine testing may also be performed to determine whether kidney function is being impaired by cysts.
Treatment & Therapy
In most cases, no action is taken beyond monitoring of symptoms. If the cysts are found to be putting pressure on surrounding organs or impairing kidney function the following treatment options may be utilized:
- Puncturing and draining the cyst. A physician will insert a long needle through the skin to the cyst using ultrasound guidance. The cyst will be punctured and drained. A solution of alcohol will then be injected into the cyst to harden the tissue and shrink the size of the cyst. This is typically an outpatient procedure.
- Surgical removal. Larger and more problematic cysts require surgical removal. A surgeon makes a small incision and accesses the cysts with a device called a laparoscope to better view the cyst and kidneys. The cyst is then drained and the outer tissue is removed or burned away to prevent future cysts from forming. This procedure may require a 1-2 day hospital stay.
Prevention & Prophylaxis