Blood pressure and kidney health are intimately related to one another.^1,2 It is thought that high blood pressure, or hypertension, and kidney function have a two-way relationship: hypertension can cause decline in kidney function, but kidney disease can also cause hypertension.

How Does Kidney Disease Affects Blood Pressure?  

Before diving into how kidney disease can affect blood pressure, it is helpful to look at what the kidney does. The kidney is a part of the renal system that consists of the kidneys, ureters, bladder, and urethra.³ It plays an important role in filtering and regulating the amount of water and electrolytes in the blood, stimulating red blood cell production, maintaining acid-base balance, and regulating blood pressure. The kidney regulates blood pressure through maintaining sodium and electrolyte balance in the blood.⁴ A crucial system in blood pressure homeostasis is the “RAAS”, shortened for the renin-angiotensin-aldosterone system.⁵ Simply put, the kidney cells recognize changes in blood pressure and secrete a protein called “renin” which triggers a cascade of events that cause a systemic response to normalize blood pressure. In the normalization of blood pressure, the kidneys either increase or decrease reabsorption of sodium into the blood, which affects fluid retention, and hence blood pressure. 

Given the critical role kidneys play in blood pressure regulation, diseases of the kidney can directly affect blood pressure.⁴ Studies have shown that lowered kidney function is associated with significantly higher systolic and diastolic blood pressures. Experts also note that cardiovascular diseases (ie, diseases of the heart and blood vessels) are much more common in individuals with chronic kidney disease (CKD) and that CKD is associated with worse cardiovascular outcomes.⁶

How Does High Blood Pressure Affect Kidney Health?

Kidney plays an integral part in regulating blood pressure, but blood pressure also has a significant impact on kidney function.⁴ Hypertension is a well-known risk factor for decline in kidney function, notably associated with chronic kidney disease progression.¹ It is also an independent risk factor for developing end-stage kidney disease, previously known as kidney failure.^1,2

Blood pressure greatly affects kidney health because of the renal system’s structural and functional dependence on vasculature.² For instance, the glomerulus is an important structure in the kidney consisting of bundles of capillaries, or small blood vessels.⁷ These structural units play a major role in filtering and regulating electrolytes in the blood by allowing molecules of certain size and charge to pass, but not allowing others, and are highly dependent on blood pressure. Although the kidneys can maintain stable blood pressure and flow in the renal system across a broad range of systemic blood pressure under normal conditions, chronic hypertension can cause damages to the kidneys.² Hypertension can result in renal microvascular (ie, small blood vessel) damages by mechanically stretching glomerular capillaries and cells within the kidneys, which can ultimately impair the kidney’s ability to properly filter and regulate electrolytes and molecules.