kidney function

chronic kidney disease

Chronic kidney disease (CKD) means your kidneys are damaged and can’t filter blood the way they should. The main risk factors for developing kidney disease are diabetes, high blood pressure, heart disease, and a family history of kidney failure.

CKD statistics

• more common in women (14%) than men (12%)

• by age: 65+ 38%

end stage renal disease

• permanent kidney failure that requires dialysis or kidney transplant

• US overview:

  • 808,000 americans were being treated for ESRD in 2021

  • 69% on dialysis

ESRD key facts

• men are 1.6x more likely to develop ESRD than woman

• Black Americans are 4x more likely than white Americans

• Hispanic and native people more than 2x more likely

risk factors for ESRD

• Diabetes with poor blood sugar control

• Glomerular diseases (conditions affecting the kidney’s filtering units)

• Polycystic kidney disease (PKD)

• High blood pressure

• Tobacco use

• Race/Ethnicity: Black, Hispanic, Asian, Pacific Islander, or American Indian heritage

• Family history of kidney failure

• Older age

• Frequent use of kidney-damaging medications (e.g., certain pain relievers)

conditions that can lead to kidney disease

• major causes

  • type 1 or 2 diabetes

  • high bp

• kidney stones, enlarged prostate, recurrent kidney infections

key functions of renal system

• Excretes wastes from the body

• Maintains water balance

• Regulates electrolytes (e.g., sodium, potassium)

• Helps maintain acid–base balance

• Regulates blood pressure

  • Secretes renin, which activates the angiotensin pathway

• Produces erythropoietin, a hormone that stimulates red blood cell (RBC) production*

excretion

• Removal of metabolic wastes from the blood and elimination from the body

• Urine = water + wastes

  • Primarily urea, the main waste product formed from protein metabolism

chronic renal failure

• Chronic = gradual and ongoing process

• Failure = destruction of nephrons so the kidneys can no longer perform their essential functions

• Progressive = continues to worsen over time

common causes of CRF

• Diabetes – high blood sugar directly damages blood vessels

• Hypertension – high pressure damages blood vessels, especially glomeruli

• Less Common Causes

  • Congenital or acquired kidney diseases

  • Autoimmune conditions

  • Infections

nephrons unit

• glomerulus: a network of capillaries that filters blood in

• bowman’s capsule: surrounds the glomerulus and collects filtrate, conducting it into tubules

• tubules: where filtrate process occurs

• arterioles peritubular capillaries-venules: reabsorption

pathophysiology of CRF

• one functioning kidney is enough to sustain life

• however Chronic Kidney Disease causing illnesses damage both kidneys simultaneously

• over time, nephron loss drops below the threshold needed for normal kidney function

effects of chronic renal failure

• glomerular damage

  • impaired filtration = decreased ability to excrete waste, regulate water and electrolytes

• juxtaglomerular cell damage

  • impaired blood pressure regulation

• reduced erythropoietin production

  • leads to anemia

symptoms of CKD or CRF

• dry and itchy skin

• tiredness or weakness

• bubbly or foamy pee

• loss of appetite

• need to pee more often

CRF signs

• protein in urine

• blood test abnormalities (electrolytes)

• anemia Caused by reduced erythropoietin production from damaged kidney cells

CRF long term outcomes

• Uremia – buildup of metabolic wastes in the blood

• Can be fatal if untreated

• hyperkalemia – increased blood potassium

  • Can lead to cardiac arrest

• Fluid overload – excess blood volume

  • Normally, blood volume ≈ 5 L

  • Can cause heart failure

prevention of CKD/ESRD

• primary prevention (prevent disease before it occurs)

  • eat well, exercise, maintain healthy

• secondary prevention (early detection)

  • screening for kidney damage

  • identify and reduce risk factors early

• tertiary prevention (slow progression)

  • take medications

  • control BP and blood glucose

modifiable behaviors for kidney health

• Maintain healthy weight

• Eat a balanced diet

• Exercise regularly

• Keep cholesterol in a healthy range

• Avoid tobacco (smoking/chewing)

• Control blood sugar

• blood pressure

treatment for CRF/ESRD

• dialysis: mechanically removes wastes and excess waste\

  • hemodialysis: blood filtered through machine

  • peritoneal dialysis: blood filtered using peritoneal membrane

• kidney transplant: replaces failed kidney with healthy one

  • live or cadaveric doner

hemodialysis

• mechanism:

  • Blood passes over an artificial filter membrane with tiny pores, similar to glomerular capillaries

  • Filtration occurs via diffusion across the membrane

• control

  • dialysis fluid concentration can be adjusted

  • creates concentration gradient to remove or retain water molecules

hemodialysis challenges

2-4 hours per session, 3 times a week

• unnatural timing → blood volume fluctuates, may cause hypotension

• cannot miss sessions or waste buildup occurs

• if stopped patient survival is 1-2 weeks

peritoneal dialysis

can be done at home and performed 1-4 times a day

• advantages:

  • home based, flexible schedule,

• disadvantages:

  • requires daily commitment, risk of infection

kidney transplant

procedure: surgically place a new kidney in the patient

• sources of donor kidneys:

  • cadaveric donor (deceased)

  • living donor

kidney transplant function and longevity

• new kidney begins working immediately after transplant

• reaches normal function within 1-2 weeks

• longevity: 10-25 years, after they may need dialysis or a second transplant

cadaveric donors vs living donors

• cadaveric donors:

  • limited supply, best donors under 60

• living donors:

  • much larger supply, number of living donations has increased over time

immune recognition during transplants

the immune system identifies self-cells to avoid attacking them

major histocompatibility complex (MHC)

• genes coding for surface proteins that help immune system detect foreign substances

• Also called Human Leukocyte Antigen (HLA) system

• Two major types: Class I and Class II

• Genes are clustered on chromosome 6 • Each gene has a large number of alleles → rare for 2 people to have identical MHC

this determines donor compatibility

role of MHC in immune function

MHC helps the immune system recognize infected cells and also determines whether a transplanted organ will be accepted or rejected