Renal cysts can be classified as simple or complex. Simple renal cysts are common in normal kidneys, and their incidence increases with age. These cysts are benign, asymptomatic lesions that rarely require treatment. Simple renal cysts may be solitary or multiple and bilateral. Usually it does not cause symptoms and signs. The clinical significance of simple renal cyst is not entirely clear. Most nephrologists believe that simple renal cysts are of little significance. However, in a study involving 1948 potential healthy kidney transplant donors, age and sex adjusted cysts greater than or equal to 5mm were associated with higher albumin secretion, hypertension and high filtration. Other studies have also reported its association with hypertension, but no such finding has been found in a series of studies involving more than 1,000 patients. This study showed that the incidence of hypertension, low back pain, hematuria and proteinuria in cystic patients did not increase compared with matched control groups without cysts.
If there is no obstruction, simple renal cyst will not cause renal function damage. However, limited evidence suggests that younger patients with simple renal cysts may have a slight decrease in renal function (but still within the normal range).
Simple renal cyst can be accompanied by rupture, hematuria, pain, abdominal mass, infection and/or hypertension in very few cases:
Simple rupture of renal cyst can cause hematuria and/or low back pain. One of the largest case series included 25 patients with simple renal cyst rupture, 21 with hematuria and 17 with low back pain. 21 cases were spontaneous cyst rupture, 4 cases were caused by blunt abdominal contusion or iatrogenic injury (during medical operation). The ruptured cysts of 11 patients closed spontaneously after communicating with the collecting system, while 2 patients persisted.