Chronic Kidney Disease Flashcards
What is the acronym for the functions of the kidney?
A - acid base balance
W - water removal
E - erythropoiesis
T - toxin removal
B - blood pressure control
E - electrolyte balance
D - vitamin D activation
How is the kidney involved in acid base balance?
It reabsorbs and produces bicarbonate
How is the kidney involved in water removal?
It produces urine
How is the kidney involved in erythropoiesis?
The kidney produces erythropoietin in the peritubular interstitial fibroblasts
This stimulates RBC production in bone marrow
How is the kidney involved in blood pressure control?
It is involved in the renin-angiotensin-aldosterone system
Renin is activated when blood pressure is low
This leads to Na+ and water retention that increases BP
What electrolytes are involved in electrolyte balance in the kidney?
sodium
potassium
chloride
magnesium
glucose
phosphate
bicarbonate
How is the kidney involved in Vitamin D activation?
It produces calcitriol
This promotes Ca2+ absorption in the gut and renal reabsorption of phosphate
What is involved in glomerular filtration?
The movement of substances from the blood within the glomerulus into the capsular space
What is involved in tubular reabsorption?
The movement of substances from the tubular fluid back into the blood
What is involved in tubular secretion?
The movement of substances from the blood into the tubular fluid
What is the main function of the glomerulus?
It filters small solutes from the blood
What is the main function of the Bowman’s capsule?
It collects what is filtered through the glomerulus
What is the main function of the proximal convoluted tubule?
- reabsorbs 65% of filtrate volume
(nutrients, ions and water)
- secretes toxins
(ammonia, creatinine, some drugs)
- adjusts filtrate pH
What is the main function of the descending limb of the loop of Henlé?
Water reabsorption through aquaporins
This increases osmolarity
What is the main function of the ascending limb of the loop of Henle?
- It reabsorbs Na and Cl
This reduces osmolarity
- Urea is secreted
What is the function of the distal convoluted tubule?
Aldosterone leads to reabsorption of Na+ (and Cl-) and secretion of K+
PTH causes Ca2+ reabsorption
It also reabsorbs bicarbonate and water and synthesises bicarbonate
What is the function of the collecting duct?
ADH leads to water reabsorption
It reabsorbs and secretes various ions to maintain blood pH
What does glomerular filtration rate refer to?
The ultrafiltrate of plasma which crosses the glomerular barrier into the urinary space
What is GFR equivalent to?
What is it used to measure?
It is equal to the total filtration rates of all functioning nephrons
It is a surrogate for the amount of functioning renal tissue
What is normal GFR?
90 mL/min/1.73 m^2 or higher
It cannot be measured directly and is adjusted for body surface area
What are the 2 different calculations that can be used to estimate GFR?
- CKD-EPI
2. MDRD
What is CKD-EPI based on?
When can it not be used?
It uses serum creatinine, sex, age and race
It cannot be used for children, pregnant women, elderly and some ethnic groups
What is the problem with MDRD calculations?
They underestimate GFR
CKD-EPI is a better predictor of risk
What must be taken into account when using formulae based on serum creatinine?
- higher average muscle mass in African patients means higher creatinine generation rate
- men have a greater muscle mass than women
- younger people have a greater muscle mass
What is chronic kidney disease?
How is it defined?
It describes abnormalities of kidney function or structure
eGFR of less than 60 ml/min/1.73m2 must be present on at least 2 occasions 90 days apart
How many stages of chronic kidney disease are there?
What are the GFR rates for each stage?
- mild reduction - eGFR 60 - 89
- mild to moderate reduction - eGFR 45-59
- moderate-severe reduction - eGFR 30-44
- severe reduction - eGFR 15-29
- kidney failure - eGFR < 15
What is normal eGFR?
> 90
What is CKD related to in terms of increasing risk of other conditions?
- cardiovascular disease
- acute kidney injury
- falls and frailty
- mortality
It can progress to end-stage renal failure
What ethnic minorities are more affected by CKD?
South Asians and black people
There are genetic factors
If someone has a eGFR of >60 ml/min, do they have CKD?
NO!!
They only have CKD is there are other signs of kidney damage as well
What is the aetiology of CKD?
- raised intraglomerular pressure
- glomerulosclerosis
- tubulointerstitial fibrosis
- loss of renal cortex
- shrunken kidneys
What is glomerulosclerosis?
Expansion of glomerular mesangium and deposition of extracellular matrix
What is tubulointerstitial fibrosis?
Tubular atrophy, interstitial inflammatory cell infilitrate and deposition of EC matrix in the interstitium
What conditions may people have that warrant a test for CKD?
- diabetes
- hypertension
- acute kidney injury
- CVD
- detection of haematuria or proteinuria
- chronic nephrotoxin use
- family history of stage 5 kidney disease
If someone has CKD risk factors, what tests are carried out on them?
- bloods and eGFR
- urinalysis to look for blood/protein
- blood pressure
What signs are seen in an unhealthy kidney?
- fluid overload
- elevated wastes - urea, creatinine, K+
- changes in hormone levels controlling BP, RBC production and calcium uptake
When do the symptoms of CKD tend to present?
It is generally asymptomatic in stages 1-3
What are the visible clinical manifestations of CKD?
- vomiting
- reduced urinary output
- loss of lean body mass/muscle weakness
- skin pigmentation
- bleeding/bruising
- loss of appetite, nausea, metallic taste
What are the non-visible clinical manifestations of CKD?
- salt and water retention
- aches and pains
- lethargy, impaired immune function
- sleep disturbance
What is uraemia?
This is the accumulation of toxins
It involves a raised level in the blood of urea and other nitrogenous waste compounds
What are the symptoms of uraemia?
- pericarditis
- encephalopathy (impaired cognition, confusion, coma, seizures)
- uraemic frost (urea and urate deposits on the skin)
What further investigations are performed to look for the underlying cause of CKD?
- bloods
- renal biopsy
- imaging
What further investigations are performed to look for the complications of CKD?
- blood count for anaemia
- Ca2+, phos, ALP, vit D for renal bone disease
- bicarbonate for metabolic acidosis
What further investigations are performed to look for the end-organ damage relating to complications of CKD?
ECG and echocardiogram
What further investigations are performed to look for the CV risk?
Lipid profile
When should a renal ultrasound scan be performed?
- accelerated progression of CKD
- visible or persistent invisible haematuria
- symptoms of urinary tract obstruction
- polycystic kidney disease and over 20
What are the non-modifiable factors influencing CKD progression?
- underlying cause of kidney disease
2. race
What are examples of modifiable factors influencing CKD progression?
- dyslipidaemia
- exposure to nephrotoxic agents
- metabolic acidosis
- anaemia
- smoking
- glycaemic control (diabetics)
- blood pressure
- level of proteinuria
What is the blood pressure aim for someone with CKD and ACR < 70?
Target BP < 140/90
What is the blood pressure aim for someone with CKD, DM and ACR >70?
Target BP < 130/80
When are ACEi or ARBs the first choice of treatment for high blood pressure in CKD?
Diabetic patients with hypertension or microalbuminuria
Hypertensive patients with ACR >/= 30 mg/mmol
All patients with ACR >/= 70 mg/mmol
What treatment is given for proteinuria?
ACE inhibitors or ARBs
What is the treatment for dyslipidemia?
Statins are given to patients over 50
They are given to patients <50 with risk factors for stroke, DM or CVD
What is hyperphosphataemia?
An electrolyte disorder in which there is an elevated level of phosphate in the blood
What is the risk of calcium phosphate deposition in hyperphosphataemia?
It can potentially lead to interstitial fibrosis and tubular atrophy
What is metabolic acidosis?
What may it result in?
Increased acid secretion as the number of functioning nephrons decline
It may result in complement activation and interstitial damage
Why are sodium bicarbonate supplements given in metabolic acidosis?
- to buffer the acid
- to prevent osteopenia
- to prevent muscle wasting
What type of anaemia is present in CKD and why?
Normocytic anaemia
It is due to an erythropoietin deficiency
What treatments are given for anaemia as a result of CKD?
- erythropoiesis stimulating agents
2. iron supplements
What are the 6 main complications of CKD?
- anaemia
- CKD mineral bone disorder
- cardiovascular disease
- volume overload
- hyperkalaemia
- malnutrition
What is the underlying cause of CKD-MBD?
Hyperphosphataemia leading from reduced renal clearance
What are the other contributing factors to CKD-MBD?
- reduced renal hydroxylation of 25-hydroxyvitamin D
- reduced calcium
- secondary hyperparathyroidism
What are the treatments for CKD-MBD?
- dietary restricition of phosphate and phosphate binders
- 1a-hydroxylated analogues
- calcimimetics
- vitamin D replacement
- parathyroidectomy
What is the role of 1a-hydroxylated analogues?
e.g. calcitriol
They suppress PTH and control secondary hyperparathyroidism
What are the treatments for cardiovascular disease in CKD?
- statins
- antiplatelets
- antihypertensives
What are the treatments for volume overload?
- fluid and salt restriction
- diuretics
- renal replacement therapy
What must the ACR be for a patient to be referred for further treatment?
- stage 4/5 CKD
- ACR > 70 mg/mmol (not due to diabetes)
- ACR > 30 mg/mmol plus haematuria
What must the GFR decrease be for someone to be referred for further treatment?
- sustained decrease in GFR of >25% and a change in GFR category within 12 months
- sustained decrease in GFR of > 15 ml/min/1.73m2 per year
What are the other factors that cause someone to be referred for further treatment?
- raised BP despite 4 or more antihypertensives at therapeutic dose
- known or suspected rare or genetic causes of CKD
What is involved in advanced CKD?
- transplantation
- haemodialysis
- peritoneal dialysis
- conservative management
What are the indications for renal replacement therapy?
- uraemia
- severe metabolic acidosis
- hyperkalaemia
- fluid overload