Does the kidney's primary response to hypertension involve hyperfiltration?

From the Guidelines

Yes, it is true that the kidneys' primary response to elevated blood pressure is hyperfiltration. When blood pressure increases, the higher pressure in the renal arteries leads to increased filtration pressure in the glomeruli, resulting in a higher glomerular filtration rate (GFR) [ 1 ]. This hyperfiltration is part of the kidneys' attempt to maintain homeostasis by increasing sodium and water excretion through a process called pressure natriuresis. The increased filtration allows the kidneys to eliminate more sodium and water, which helps reduce blood volume and subsequently lower blood pressure back toward normal levels.

Key Points to Consider

• The mechanism of hyperfiltration is a crucial negative feedback system for blood pressure regulation [ 1 ].
• However, chronic hyperfiltration due to persistently elevated blood pressure can eventually damage the kidneys, leading to glomerular injury, proteinuria, and progressive kidney dysfunction [ 1 ].
• Uncontrolled hypertension is a major risk factor for chronic kidney disease, as the initially adaptive hyperfiltration response becomes maladaptive over time [ 1 ].
• The use of ACE inhibitors or ARBs can reduce the level of albuminuria and the rate of progression of renal disease in hypertensive patients with diabetes [ 1 ].

Clinical Implications

• The primary response of the kidneys to elevated blood pressure is indeed hyperfiltration, which can have both adaptive and maladaptive consequences depending on the duration and severity of the hypertension [ 1 ].
• It is essential to manage hypertension effectively to prevent the progression of kidney disease, particularly in patients with diabetes or those at risk of developing chronic kidney disease [ 1 ].

From the Research

Kidney Response to Elevated Blood Pressure

• The kidneys' primary response to elevated blood pressure is not solely hyperfiltration, as the relationship between hypertension and kidney function is complex 2.
• Renal hyperfiltration, defined as an increased glomerular filtration rate above normal values, is associated with early phases of kidney disease in various conditions, such as obesity and diabetes 3.
• When the kidney is subjected to acute increases in blood pressure, renal blood flow and glomerular filtration rate are observed to remain relatively constant due to mechanisms like tubuloglomerular feedback and the myogenic response 4.

Hyperfiltration and Its Implications

• Renal hyperfiltration is associated with a higher risk of cardiovascular disease and all-cause mortality 3.
• High sodium intake can lead to glomerular hyperfiltration, increased tubular energy expenditure, and protein catabolism in patients with essential hypertension 5.
• The combination of angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers with calcium channel blockers has been shown to provide better benefits on metabolic, renal, and cardiovascular outcomes in hypertensive patients, which may help mitigate the effects of hyperfiltration 6.

Mechanisms of Renal Autoregulation

• The myogenic response is thought to protect the kidney against the damaging effects of hypertension, rather than solely regulating renal excretory function 4.
• Additional mechanisms, such as redundant and compensatory mechanisms, may exist to maintain ambient levels of renal blood flow and glomerular filtration rate within normal range, despite chronic alterations in blood pressure 4.