HP infographic
Chronic Kidney Disease (CKD)
progressive, irreversible loss of renal architecture and function lasting over 3 months, marked by a decline in Glomerular Filtration Rate (GFR <60mL/min/1.73m^2) or persistent albuminuria (high levels of albumin in the blood)
Risk Factors: Diabetes mellitus (diabetic nephropathy complication) and hypertension
• Glomerular Damage: High levels of sugar in the blood cause the tiny blood vessels in the glomeruli to become narrow, hardened, and scarred.
• Basement Membrane Thickening: The filtering walls (glomerular basement membrane) thicken, and cells become inflamed, allowing vital proteins like albumin to leak out of the blood and into the urine.
• Nerve and Bladder Damage: Diabetes can harm the nerves that control the bladder. When you cannot feel a full bladder, urine pressure builds up and causes secondary damage to the kidneys.
• Vicious Cycle of High Blood Pressure: Damaged kidney blood vessels trigger or worsen high blood pressure, which places even more strain and destruction on the remaining healthy kidney tissue
In a healthy body, the kidneys function as the body's master filtration plant:
Balanced Nephrons: Each kidney contains about 1 million healthy functional filtering units called nephrons.
Stable Filtration Pressure: Blood enters each nephron through an input blood vessel (afferent arteriole) and leaves through an output vessel (efferent arteriole). Blood pressure inside the delicate capillary filter (the glomerulus) is kept at a precise, safe level.
Controlled Waste Removal: Healthy nephrons filter out metabolic waste (urea, creatinine) into urine while keeping essential proteins (like albumin) in the blood.
Negative Feedback in Action: If total blood pressure drops or rises slightly, the kidneys auto-regulate their blood vessel diameters to keep the Glomerular Filtration Rate (GFR) steady at around 120 \text{ mL/min/1.73m}^2.
When initial kidney injury occurs (due to diabetes, high blood pressure, or inflammation), a portion of nephrons die off permanently. To keep the person alive, the body triggers a compensatory adaptation:
Loss of Capacity: Instead of 2 million working nephrons, the body might only have 1 million left.
The Body's Emergency Response: To prevent metabolic waste from instantly building up in the blood, the remaining healthy nephrons work overtime: The afferent arteriole (inflow) dilates to let more blood surge in. The efferent arteriole (outflow) constricts under the influence of Angiotensin II to build up back-pressure inside the filter.
Hyperfiltration: This mechanical trick forces single nephrons to filter double or triple their normal workload (Single-Nephron Hyperfiltration).
Pseudo-Homeostasis: On standard lab tests, total kidney filtration (GFR) looks surprisingly normal because surviving nephrons are compensating for their dead neighbors
destructive positive feedback loop (vicious cycle):
Mechanical Wall Damage: Kidney capillary filters are fragile. Persistent high hydraulic pressure (glomerular hypertension) creates intense physical shear stress against filter walls.
Podocyte Injury & Protein Leakage: The protective filtering cells (podocytes) tear off under the high pressure. Large proteins like albumin start leaking into urine (proteinuria).
Glomerulosclerosis (Scarring): Chronic inflammation and protein leakage cause irreversible scar tissue to replace healthy capillaries.
The Positive Feedback Trap:
- High pressure causes nephron scarring
- Scarred nephrons die permanently
- Fewer surviving nephrons remain
- The remaining nephrons must work at even higher pressure to compensate
- Accelerated death of remaining nephrons.
