Renal Function Flashcards
Describe the gross anatomy of the kidneys
- 2 retroperitoneal organs
- receive 25% of cardiac output
- right is slightly lower than the liver
Main functions of the kidneys
- excretion of waste
- maintain EFC volume & composition
- endocrine function
Briefly describe urine formation
- glomerulus forms filtrate and tubules process the filtrate to form urine
Describe kidney disease
- heterogenous disorder
- usually destruction of complete nephrons
- acute kidney injury
How do we assess a patient with kidney disease ?
- through clinical examination
- laboratory investigations
- urinalysis
- GFR
- urea & electrolytes
Signs & symptoms of renal failure
- symptoms of Uraemia
- disorders of Micturition
- disorders of urine volume
- alterations in urine composition
- pain
- oedema
Define symptoms of Uraemia
nausea , vomiting , lethargy
Define disorders of micturition
- frequency
- nocturia
- retention
What are some biochemical tests for renal function?
- Urinalysis = appearance, pH, glucose, protein, sediment
- proteinuria
- measurement of GFR = clearance tests, plasma creatinine
Describe GFR
- Glomerular Filtration Rate
- essential to normal function
- quantity of filtrate formed each minute
How do you work out clearance ?
Clearance = (U x V) /P
What does U stand for in clearance equation?
U = urinary conc. of substance
What does V stand for in the clearance equation?
V = rate of urine formation (mL/min)
What does P stand for in the clearance equation ?
P = plasma conc. of a substance
What is normal for GFR?
100ml/min
What are some direct measurements of GFR?
- insulin clearance
- EDTA clearance
- creatinine clearance
What are some estimated assessments of GFR?
- Cockroft & Gault
- MDRD formula
- CKD-EPI
Describe Creatinine Clearance
- fairly straightforward
- times urine collection for creatinine measurement
- blood sample taken within measurement period
What are some problems with creatinine clearance?
- practical problems of accurate urine collection and volume measurement
- interference in creatinine measurement
Describe Serum Creatinine Concentration
- simple test to assess glomerular function
- useful in monitoring changes in CKD
What are some limitations of Serum Creatinine Conc?
- conc. depends on balance between input & output
- production determined by muscle mass - related to age,sex,weight
- reference limits can be misleading
Describe Cockroft & Gault
- uses serum creatinine & weight to predict creatine clearance
- unreliable if patients is obese
What are advantages of eGFR ?
- doesn’t require any infusion
- easy to measure
- lab computer automatically
- doesn’t require urine collection
