What is a cortical cyst of the kidney?

Cortical kidney cysts are one type of renal cyst that becomes more common as people grow older. While the incidence of renal cysts in children are rare, the condition is more likely to occur in individuals after age 50. Renal cortical cysts are simple interstitial fluid filled sacs near the outside region of the kidneys. They become more common as one grows older and usually grow to 10-15 centimeters or more. They can be found and located through an ultrasound. But usually not something to worry about, they are commonly benign.
Symptoms of Cortical kidney cysts
While some people with renal cysts may attribute lower back pain to the cyst, a simple cyst should not cause pain. If a person diagnosed with a complex cortical kidney cyst complains of pain in the lower back or groin area, or pain when urinating, it could be another condition. Constant pain could indicate the presence of a malignant mass, which means that any cancer present may already be in the later stages. Even if malignancy is determined not to be the cause of pain, a doctor generally orders a routine urinalysis and urine culture to make sure that groin or back pain is not due to infection or other medical condition.
The simple renal cyst is a benign non-neoplastic mass of unknown etiology arising in renal parenchyma (cortical cyst) or within the sinus region (parapelvic cyst). The uncomplicated cyst cavity is typically unilocular, usually filled with clear serous fluid and lined with a cuboidal epithelium with no communication to the renal collecting system. It's believed that these cysts arise from tubular or lymphatic obstruction. The incidence of renal cysts increases with age occurring rarely in neonates and the pediatric group, to over 50% in those over age 50.The simple renal cortical cyst or parapelvic cyst is discovered incidentally so it's important to differentiate it from a true renal neoplasm. Renal cysts account for 60-65% of all renal masses. Large cortical cysts can show up as a palpable flank mass and parapelvic cysts can be detected producing extrinsic compression or mass effect on the collecting system on an intravenous pyelography (IVP) exam.