Vasculature: Kidneys rely on constant supply of oxygenated blood in order to function properly and survive.

A) Lesion-Related Vascular Changes:

• Kidney perfusion could be negatively affected by renal cancer, infection, or trauma.

B) Age-Related Vascular Changes:

• The kidneys are highly vascularized, making them vulnerable to vascular damage with aging.
• Common change: Arteriosclerosis (loss of elasticity) leading to narrowed blood vessels.

C) Disease- and Lifestyle-Related Vascular Changes

• Other Risk Factors for vascular changes:  Atherosclerosis (build up of fatty plaques) also leads to narrowed blood vessels and can contribute to increased blood pressure, which can lead to further development of atherosclerosis and narrowing of blood vessels.
• Risk Factors for the development of atherosclerosis include: Type I and II diabetes mellitus, hypertension, sedentary behaviour, smoking, diet high in fats and/or sugars, genetics, biological sex, and age.

Impact of Narrowed Blood Vessels:

• Reduced blood supply causes ischemia in the kidney tissue.
• Kidneys do not have a backup blood supply, making them quite susceptible to ischemia.
• Consequences:
  • Rapid damage to renal tissue, leading to decline in kidney function.

Kidney’s Response to Decreased Blood Flow:

1. Kidneys secrete renin in response to low perfusion. (Memory Trick:  Low Blood Flow stimulates RAAAS Renin-Angiotensin II-ADH-Aldosterone-Sympathetic).
2. Increased renin activates angiotensin II, which:
   • Causes vasoconstriction, raising blood pressure, and
   • Stimulates aldosterone and ADH release from adrenal gland cortex and pituitary gland respectively.
3. Actions of aldosterone and ADH (anti-diuretic hormone):
   • Promote salt and water retention by nephrons, reducing salt and water in urine.
   • Increase blood volume, further elevating Blood Pressure (BP).
4. This creates a vicious cycle:
   • Hypertension worsens vessel narrowing (due to reflexive constriction of afferent arteriole as well as development of systemic atherosclerosis).
   • Further reduces blood flow, causing more damage.

Progression to Chronic Kidney Damage:

1. Persistent high blood pressure damages vessel walls in the kidney.
2. Nephrosclerosis develops (thickening and hardening of the walls of renal arterioles and small arteries), narrowing blood vessel lumens contributing to ischemia.
3. Vascular injury also contributes to development of atherosclerosis and arteriosclerosis.
4. Narrowed lumens reduce renal blood flow, leading to nephron loss, fibrosis, and scarring.
5. Atrophy: The kidney shrinks over time with fibrotic tissue replacing healthy tissue.
6. Loss of nephron function: can lead to Chronic Kidney Failure if not treated
   • Kidneys fail to filter blood waste effectively.
   • Accumulation of waste products in blood causes uremia.

Treatments:

• Control hypertension:  Using antihypertensive drugs (e.g., diuretics, beta-blockers).
• Manage underlying conditions:  e.g. Proper diabetes control
• Lifestyle modifications:
  • Reduced sodium intake.
  • Healthy diet and regular exercise.

Summary:

Chronic vascular damage from hypertension and atherosclerosis leads to renal ischemia, nephron loss, fibrosis, and kidney atrophy. Without intervention, progressive damage results in end-stage renal failure, characterized by accumulation of waste products, with dialysis or transplant as potential treatments. Preventing vascular damage through blood pressure control and lifestyle changes is essential.