Lecture 17 - Renal failure Flashcards
What are the functions of the kidneys?
- Elimination of waste products.
- Control of fluid balance.
- Regulate acid/base balance.
- Produce hormones.
- Regulation of electrolytes.
What is GFR?
Glomerular filtration rate - the rate at which the blood is cleared of waste products. Normal rate is >120ml/min.
How is GFR measured?
- Inulin clearance - inject a person with inulin (completely untouched by the kidneys - not absorbed) and measure their urine and compare it to their blood.
- eGFR - measure a persons creatinine as creatinine is completely cleared by the kidneys.
Define AKI?
Acute Kidney Injury - rapid decline of GFR (hours to days) and is potentially reversible.
Define CKD?
Chronic Kidney Disease - gradual decline of GFR (>3months) and is progressive and irreversible.
How do we asses an AKI?
- Serum creatinine.
2. Urine output.
What is stage 1 of an AKI
- 1.5-1.9 x baseline of serum creatinine OR >26micromol/L.
2. Urine output <0.5ml/kg/hr for 6-12 hours.
What is stage 2 of an AKI?
- 2.0-2.9 x baseline of serum creatinine.
2. Urine output <0.5ml/kg/hr for >12 hours.
What is stage 3 of an AKI?
- 3 x baseline of serum creatinine OR >354 micromol/L.
2. Urine output <0.3ml/kg/hr for >24 hours OR anuria >12 hours.
Describe a pre-renal AKI?
It is anything before the kidneys that is causing there to be decreased perfusion to them.
What can cause a pre-renal AKI?
- Intra-renal vasoconstriction - there is something which is causing there to be less blood in the kidneys e.g. meds (NSAIDs, ACEi, Diuretics).
- Systemic vasodilation - the vessel size has increased so BP has decreased/less blood to the kidneys. It can be due to sepsis or neurogenic shock.
- Volume depletion - there is less blood going to the kidneys, could be due to: diuretic overdose; osmotic diuresis (DKA).
Describe an intra-renal AKI?
This is injury to the inside of the kidney:
- Glomerular.
- Interstitial.
- Tubular.
- Vascular.
What can cause an intra-renal AKI?
- Meds.
- Infections.
- Ischaemia.
- Nephrotxins.
Describe a post-renal AKI?
This is an extra-renal obstruction.
What can cause a post-renal AKI?
- Prostate hypertrophy.
- Neurogenic bladder.
- Retroperitoneal fibrosis.
- Bladder, prostate and cervical cancer.
What are the risk factors for an AKI?
- CKD.
- Past history of AKI.
- > 75yo.
- Diabetes mellitus.
- Congestive heart failure.
- Liver failure.
- Hypotension.
- Sepsis.
- Hypovolaemia.
- High EWS.