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A renal cyst is a small pocket filled with fluid and located in the kidneys. Also known as kidney cysts, many renal cysts are benign, and people can live out their entire lives without any knowledge of a cyst. In other cases, they are a cause for concern, and a doctor may recommend follow up treatment which can include surgery to remove the cyst when one is identified in the course of a medical examination and medical testing.
Classically, renal cysts are identified on ultrasound, MRI, or another type of medical imaging study. In the case of a simple cyst, the cyst shows up as a fluid-filled pocket, and if the cyst is aspirated, it can contain clear to yellowish fluid, sometimes mixed with blood. Complex cysts, on the other hand, have irregularities such as calcification, meaning that there is solid material inside the cyst, or they develop internal walls. A complex renal cyst is a cause for concern because it can be associated with the development of kidney cancer.
Some people have one or more cysts on the kidneys at birth. In other cases, a cyst develops as a result of an obstruction somewhere in the kidney. Lymphatic obstructions and vascular disease can both contribute to the development of this type of cyst. Patients can also have a condition called polycystic kidney disease (PKD), a genetic condition in which numerous cysts develop in the kidneys, causing damage to the kidneys and surrounding organs.
In some cases, this type of cyst can cause flank or back pain, especially if it becomes enlarged. Patients can also experience more generalized abdominal pain or discomfort. Other cysts are asymptomatic, and may only be identified by accident or after a patient dies a natural death. When a cyst is identified, a doctor may recommend additional testing to determine the nature of the cyst and determine whether or not it is an issue. If the cyst is dangerous, it can be removed surgically, or monitored to see if it grows or causes complications for the patient.
Tapeworms can also cause renal cysts. If a patient has a tapeworm infection which is not addressed in a timely fashion, a doctor may recommend additional testing to determine whether or not the patient has complications such as cysts on the kidneys. Cysts caused by tapeworms can also appear in other organs of the body, and they are classically associated with a decline in organ function.