Renal failure Flashcards
(34 cards)
What are the functions of the kidneys?
Homeostasis
Metabolic/endocrine
What is the homeostatic function of the kidneys?
Elimination of waste
Water homeostasis
Electrolyte homeostasis
Acid base homeostasis
Blood pressure control
What is the metabolic/endocrine function of the kidneys?
Synthesis of hormones:
Vitamin D
Erythropoietin - for RBC production.
Renin
What is chronic kidney disease?
Usually slowly progressive and irreversible.
Commonly due to diabetes and hypertension.
Reduce the risk factors to reduce the risk of further kidney damage.
What is acute kidney disease?
Rapid onset - hours to days.
Usually caused by systemic illness
e.g. an infection which affects the whole body - shock and BP falls.
Reversible with treatment.
Who develops acute kidney injury?
Older Age
Diabetes mellitus
Hypertension
Heart disease
Liver disease
Chronic Kidney
Disease
Who develops chronic kidney disease?
It is associated with diabetes mellitus and hypertension.
Multiple drugs, especially NSAIDs - aspirin and ibuprofen, are toxic in large quantities over a long time.
The elderly - more exposure to risk factors.
Can be genetic - polycystic kidneys.
What happens if salt and water homeostasis by the kidneys fails?
Inability to concentrate urine - loss of diurnal rhythm of urine excretion.
Inability to excrete water - oedema.
Sodium retention - causes hypertension, and CNS dysfunction, and brain function - drowsy then unconscious.
What is oedema?
Fluid movement out of vasculature into tissues, mainly when albumin concentration falls.
Can have fluid in the lungs, and peripherally.
What happens if potassium homeostasis by the kidneys fails?
There is large functional reserve of K+ in cells, but failure to excrete can cause hyperkalaemia.
K+ is needed to regulate the heart function - high K+ causes cardiac arrythmias.
Alterations in membrane excitability.
What is the acid base homeostasis of the kidneys?
CO2 + H2O <–> H2CO3 <–> H+ + HCO3-
Failure to excrete H+ causes systemic acidosis.
This causes increases CO2, which is then removed by the lungs to maintain pH.
What happens if the acid base homeostasis by the kidneys fails?
Systemic acidosis
Symptoms of breathlessness to low the CO2 concentration.
Physiological systems begins to fail as enzyme function depends on pH, can cause confusion then death.
Cardiac muscle contraction is reduced.
Hyperkalaemia.
What happens if erythropoietin is not made by the kidneys?
The kidneys make EPO (erythropoietin), which is a hormone that drives RBC production.
Can become anaemia, as harder to carry around oxygen.
What are the symptoms of anaemia?
Impaired cognition
Transfusion requirement, or given synthetic EPO.
Iron overload.
Blood-borne infection.
Increased risk of left ventricular hypertrophy.
Increased cardiovascular disease in patients with chronic kidney disease.
What happens if metabolic waste products are not excreted by the kidneys?
Accumulation of toxic waste products:
Creatinine
Nitrogenous waste in urea - causes confusion and heart problems.
Retention of urate - joint problems (gout).
Retention of phosphate - cardiovascular disease.
What is the role of the kidneys in drug metabolism?
Many drugs are excreted by the kidney.
Metabolism of drugs may be impaired by renal failure.
Increased risk of toxicity due to accumulation of drug.
What drugs may be impaired by renal failure?
Insulin
Opiates
Antibiotics
Sedatives
Digoxin
Treatment is to give drugs less often to avoid accumulation - increased dosing interval.
What are the complications due to loss of kidney function?
Anaemia
Hypertension
Disturbed Ca2+ homeostasis - bone abnormalities.
Disturbed phosphate homeostasis.
Cardiovascular disease.
Abnormal metabolism of drugs.
Immune suppression
Bleeding
Complications of treatment
What is the relationship of kidney disease, CVD and diabetes?
Chronic kidney disease is often caused by cardiovascular disease, and diabetes.
Kidney disease worsens CVD
Diabetes causes CVD
Lots of overlap of diseases
Treating diabetes mellitus, reduces kidney injury, which improves CVD.
When is renal replacement therapy needed?
For acute or chronic kidney disease, if unable to maintain:
Water homeostasis
Electrolyte homeostasis
Acid/base homeostasis
Excrete metabolic waste products
Without treatment it is a terminal illness.
What are the forms of renal replacement therapy?
Dialysis - replaces kidney function except for EPO production.
Transplantation - replaces all kidney function.
Palliative care.
What is dialysis?
Dialysis is an extracorporeal (outside of body) therapy where fluid and solutes are added or removed to the patients’ blood.
It works by separating the patient’s blood and the dialysis fluid with a semipermeable membrane.
It is not as good as own kidneys, GFR is 15ml/min compared to 120mil/mol.
What is peritoneal dialysis?
Blood is next to the dialysis fluid, separated by a semipermeable peritoneal membrane.
This draws out the excess ions and water from the blood, and provides HCO3-, by equilibrium.
What is the peritoneal fluid?
Contains water molecules and dextrin molecules - which keep osmotic pressure high, so water moves into peritoneal cavity.
Low Na+, K+, H+ and urea concentrations in dialysis fluid so they leave the blood by concentration gradient.
HCO3- enters to buffer H+.
