Simple renal cyst and hypertension: cause or coincidence?

Hypertension and simple renal cysts are frequent clinical diagnoses. With the widespread use of new non-invasive diagnostic technics such as abdominal ultrasound and computer-assisted tomography renal cysts are diagnosed with increasing frequency. In patients 50 years or older renal cysts of various size may be found in nearly one third. Similarly, the incidence of hypertension increases with age. Thus, the coexistence of a simple renal cyst and hypertension in a patient may represent a pure coincidence or be a cause of high blood pressure. The effect of cyst removal upon hypertension has been documented in 22 patients in the literature. Surgical cyst removal or percutaneous cyst aspiration caused a significant fall in blood pressure in most patients. The drop in blood pressure was closely related to an activation of the renin angiotensin system in the involved kidney. Fifteen patients (68%) were considered cured and 2 improved after the intervention. All patients had large cysts. It is suggested that in patients with large renal cysts the lesion may, through local tissue and/or renal arterial compression, cause ischemia and in turn activate the renin angiotensin system. Since most of the renal cysts are 2 cm or less in diameter this may represent a very rare event. In patients with large renal cysts and hypertension percutaneous needle aspiration of the cyst and/or renal venous renin determination may be useful tools to determine a causal rather than a coincidental relation between the 2 lesions.