Assessment of renal function Flashcards
Define these: ESRF CKD ARF HD/HF CAPD AKI eGFR
End Stage Renal Failure Chronic Kidney Disease Acute Renal Failure Haemodialysis/haemofiltration Continous Ambulatory Peritoneal Dialysis Acute Kidney Injury Estimated Glomerular Filtration Rate
What hormones are released in the kidney?
Erythropoietin (blood oxygen), renin (plasma sodium levels), prostaglandins, 1a-vitD3 hydroxylation
What are some common symptoms of kidney disease? and why do they go unnoticed?
hypertension, urinary frequency or volume (normal people dont track this). All very non specific
Late stage often include; fatigue, nausea, vomiting, poor appetite, shortness of breath, fluid retention.
What are the main laboratory investigations used to test for kidney disease?
Imaging, histology and microscopy, immunology, biochemistry (urinalysis and other biomarkers)
What are some disadvantages to using imaging to investigate kidney condition?
expensive and the full damage cannot be assess + its extent
The functionality is not tested
BUT can detect masses e.g. cancer
What advantages does imaging have in assessing kidneys?
Looking at the size, symmetry and obstruction. You can also get a larger view of the connected organs and tissue - bladder, ureter and prostate glands
Name some immunology tests and what disease they investigate?
complement: low C4- systemic lupus erythematosus and cryoglobulinaemia
anti-glomerular basement membrane antibodies: goodpastures disease
cANCA: associated with vasculitis - wegeners disease
pANCA: associated with vasculitis
In what situation is a immunological approach to kidney assessment appropriate?
for specific diseases
What is a quick bedside snapshot of the kidney state/functionality?
urine dipstick - gives the operator a quick snapshot of what is going on and its non invasive, however it is not very specific.
Operator error, inter-operative variability, requires fresh urine
What are some quantitative markers of glomerular filtration?
creatinine, urea, proteinuria
What are some quantitative markers of tubular function? and what do they test?
pH (H+) (acid-base balance), urine volume/osmolality, phosphate, aminoaciduria, glycosuria, beta2-microglobulin
assessment of renal ability to ajust Na, K, H ions, water compoistion of filtrate & reabsorb small proteins, amino acids and glucose
What disease is associated with the improper absorption of phosphate, glucose and amino acids?
Fanconi syndrome
5 characteristics of ideal markers of kidney function.
Its freely filtered at the glomerulus
Not reabsorbed in the tubules
Its not secreted from the blood stream into the filtrate
Not metabolised and/or broken down in the kidney
It is not synthesised at any point in the kidney
Name the gold standard to assessing glomerular filtration, using an exogenous marker.
Inulin: metabolically inert sugar, provides good GFR
Disadvantages
Intravenously, expensive
How does an exogenous marker work and what do they test?
Introduced intravenously and provides a good GFR estimation using a urinalysis.
- measure how much is released over a time period (ml/min)
The marker should be freely filtered and metabolically inert
What are some common endogenous markers to assess glomerular filtration?
Urea: end product of nitrogenous metabolism
Creatinine: product of muscle metabolism, fairly constant rate of production
Cystatin C: small protein produced by all nucleated cells
Neutrophil Gelatinase Associated Lipocalin (NGAL): newer marker of AKI
Why can urea produce unreliable results?
It can give a false positive almost, where the levels do not match with the state of the person.
Urea levels can be skewed in people with high protein diets (high urea), GI bleeds (high urea), extremes of hydration states or low in liver disease. It is also passively reabsorbed in the renal tubules
Creatinine levels excreted can give false snapshots. True or false
True. The creatinine levels excreted will differ from person to person and is dependent on muscle mass, age, sex and ethnicity.
Therefore, creatinine can be confusing in the extremes - such as body builders or old elderly people
also affected by gender and race
Furthermore, the GFR has to fall by a substantial amount before the creatinine rises
What advantages does cystatin C have over urea and creatinine as a endogenous marker?
It is not affected by muscle mass, age, gender or race
In relation to serum creatinine how does a lowered GFR affect it?
The plasma/serum creatinine increases as there is a reduced creatinine clearance -
Creatinine clearance decreases
How is urine collected for a urinanalysis?
Day 1: 8am empty bladder
Commence 24h urine collection - All urine now passed until 8am next day must be collected into container
Day 2: 8am collect final urine output into container
Hand in urine sample with a blood sample
What variables are used in producing a eGFR?
Serum creatinine, age, sex, ethnicity
protein excretion should be >0.15g/24h. True or false
False, it should be <0.15g/24h.
Protein loss of >3g/24h result in nephrotic syndrome