Chronic Kidney Disease Flashcards
Why is eGFR a better measure of renal function?
Large reductions in eGFR can occur with little increases in serum creatinine
What is a normal eGFR?
Above 90
How does eGFR change with age?
The number of functional nephrons an individual has reduces with age and so eGFR naturally declines with age
What might cause someone to have an abnormally raised creatinine but with normal renal function?
Creatinine is produced by muscle so body builders with a raised muscle mass will have higher serum creatinine levels
How can you investigate for proteinuria?
Urine dip
What test is very valuable in patients with CKD and is associated with a poor prognosis?
A:CR- Albumin to creatinine level
Albumin in the urine is a marker of declining renal function
What is the most common cause of CKD in the UK?
Diabetic nephropathy
How is CKD defined?
The presence of abnormal kidney structure or function for at least 3 months.
Note- eGFR naturally declines with age so there should be structural/functional changes (causing symptoms)
What two criteria are involved in the staging for CKD?
eGFR- Gives the G stage
A:CR- Gives the A stage
What are the eGFR values for G1?
What does this mean in real terms?
Greater than or equal to 90
This is normal or high eGFR
What are the eGFR values for G2?
What does this mean in real terms?
60-89
Mildly decreased eGFR
What are the eGFR values for G3a?
What does this mean in real terms?
45-59
Mildly to moderately decreased eGFR
What are the eGFR values for G3b?
What does this mean in real terms?
30-44
Moderately to severely decreased eGFR
What are the eGFR values for G4?
What does this mean in real terms?
15-29
Severely decreased eGFR
What are the eGFR values for G5?
What does this mean in real terms?
<15- This is end stage renal disease
What is the A:CR for A1?
0-3
What is the A:CR for A2?
3-30 (Microalbuminuria)
What is the A:CR for A3?
> 30 (Macroalbuminuria)
What measurement is associated with the greatest increased risk of CVD and so death?
Increasing A:CR
What are some causes of CKD?
Renal Artery stenosis (prolonged hypo-perfusion)
Diabetic nephropathy
IgA Nephropathy
Polycystic Kidney Disease
Vasculitic kidney disease
Prolonged exposure to nephrotoxic medications
Prolonged outflow obstruction- BPH, Tumour, Strictures, Fibrosis, Compression, Stones
Describe the pathological process involved in diabetic retinopathy?
Hyperglycaemia leads to glycosylation of the basement membrane proteins. This leads to mesangial expansion /thickening of the basement membrane (forms Kimmelsteil- Wilson Nodules). Mesangial expansion causes the slits between podocyte to widen and there is dysfunction at the glomerulus allowing proteins and other molecules to freely filter at the glomerulus
There is also hyaline arteriosclerosis which causes glomerular sclerosis, and when it occurs at the efferent arteriole causes the initial hyper-filtration stage
Summarise the changes that occur in diabetic retinopathy?
Hyperglycaemia leads to glycosylation of basement membrane proteins
Mesangial expansion (form Kimmelsteil- Wilson Nodules)
Filtration slits between podocytes widen causing dysfunction
Hyaline arteriosclerosis- leading to glomerular sclerosis
What screening test should be done at every diabetic check to investigate for diabetic nephropathy?
Urine dip for protein/albumin
Not every single case of proteinuria in diabetics will be due to diabetic nephropathy, what else might indicate it is likely to be due to diabetes?
No haematuria- if haematuria is present think nephritic
Presence of other microvascular complications (Retinopathy, neuropathy)
Long history of diabetes (>10 years)
Gradual deterioration over time
No obstructive symptoms
-Ve immunology work up (ANCA, ANA)
Are type 1 or type 2 diabetics more at risk for diabetic nephropathy?
Type 1- Longer exposure to hyperglycaemia
What histological features may be seen with diabetic nephropathy?
Kimmelsteil-Wilson Nodules- due to mesangial expansion
Abnormal glomerulus- glomerular sclerosis
Loss of open capillary loops
What type of nephropathy is seen within a couple of days of a mucosal infection in certain patients?
IgA nephropathy
Why might some patients develop proteinuria 1-2 days after the onset of a URTI or GI infection?
They have IgA nephropathy, with abnormal IgA
When is infection of the mucosal surfaces and so IgA levels are increased. IgG binds to this IgA to form circulating immune complexes which deposit in the kidneys causing damange leading to proteinuria
What type of hypersensitivity reaction is IgA nephropathy?
Type III- abnormal IgA that is bound by IgG as the body does not recognise them as self
What is the treatment for diabetic nephropathy?
Improved glycaemic control
Manage other risk factors- HTN (Target 130/90), Smoking
ACEi or ARB for HTN
Statins to reduce CVD risk
What features will be seen on a urine dip for IgA nephropathy?
Haematuria and proteinuria
What must be done for diagnosis of IgA nephropathy?
Renal biopsy under USS guidance
Looks for IgA deposits in the mesangium
Where does IgA deposition occur in IgA nephropathy?
In the mesangium- tissue that provides structural support to the capillaries of the glomerulus
What would you suspect if someone has a rash on their legs or buttocks and they have a renal biopsy suggestive of IgA nephropathy?
HSP- Henoch-Schonlein Purpura (HSP)
Also due to abnormal IgA that is not recognised as self and IgA binds to it to form circulating immune complexes. Causes systemic vasculitis due to wide spread deposition.
Both the renal and skin biopsy will show IgA deposition
What are some of the symptoms of HSP?
Purpuric rash typically affecting the shins and buttocks
Abdo pain
Nausea and vomiting
Arthritis (this is none erosive so not permanent)
What is the treatment for IgA nephropathy?
Immunosuppression- e.g. Steroids
Reduce other risk factors- ACEi/ARBs for HTN, Statins
Treat mucosal infection if required
If suspecting IgA nephropathy what investigations should be done?
Urine dip- Proteins/Albumin, Haematuria
Urine ACR
Renal biopsy
(And standard things, monitor renal function as large declines mean dialysis may be needed)
What kidney condition can cause CKD and has a very strong genetic component?
Polycystic kidney disease
What is the inheritance pattern of polycystic kidney disease?
Autosomal dominant- PKD1 gene
There is also a recessive type that is associated with later onset and less severe kidney disease
Why does polycystic kidney disease cause CKD?
Large cysts develop in the kidneys that disrupt the function of the nephron. There is compression of blood vessels which causes the kidneys to think they are in a low fluid state- this can drive HTN that is not responsive to normal therapy
Why might polycystic kidney disease cause hypertension?
Large cysts form which can compress blood vessels leading the kidneys to think they are in a low fluid state. Resulting RAAS activation increase sodium reabsorption and increases potassium excretion- driving fluid retention