kidneys Flashcards
(46 cards)
1
Q
Functions of the kidney
A
- Elimination of waste: carbohydrate; Nitrogenous (urea, creatinine); sulphate and phosphate; water and acid regulation: fluids and electrolytes
- Endocrine: vitamin D deactivation; secretion of erythropoietin
- Blood pressure regulation: renin/ angiotensin and volume control
2
Q
acute kidney injury- facts
A
- 100,000 deaths a year in hospital are associated with acute kidney injury
- 30% could be prevented with the right care
- one in five people admitted to hospital as an emergency has acute kidney injury
3
Q
Acute kidney injury AKI or ARF
A
- Serious medical emergency that can develop very quickly (usually within 48 hours)
- Definition is varied
- Is not a single state disease with uniform aetiology
- Prognosis is not good if left untreated in a timely manner
- Hypovolaemia (shock) main cause-falling renal perfusion pressure. But also nephrotoxicity and acute glomeruli nephritis
4
Q
Definition of AKI
A
- A rising serum creatinine of 26 µmol/litre or greater within 48 hours -50% or greater rise in serum creatinine known or presumed to have occurred within the past seven days
- falling urine output to less than 0.5 mil/kg/hour >6 hrs in adults and >8 hrs in children and young people
- 25% or greater fall in e GFR in children and young people within the past seven days
5
Q
RIFLE criteria
A
Risk Injury Failure Loss End stage renal disease
6
Q
AKIN criteria
A
See BB slides for an illustration of the AKIN criteria
7
Q
Symptoms Of acute kidney injury
A
• Nausea and vomiting • Dehydration •Confusion • High Blood Pressure • Abdominal Pain • Slide Back out • Oedema
8
Q
Risk of developing acute kidney injury
A
- aged over 65
- patients with existing kidney problems e.g. CKD
- dehydrated patients who are unable to maintain their fluid intake independently
- urinary tract blockage
- sepsis
- medication : NSAIDs, ACEI, diuretics, antibiotics (gentamicin)
9
Q
Classification and cause of AKI
A
Pre-renal: reversible decreased perfusion through hypo-perfusion, via hypovoleamia or decreased CO, altered renal vascular regulation; 40-80%
- Intra renal (including acute tubular necrosis) : renal parachymal injury, tubular necrosis; 10-50%
- Post-renal: Urinary Tract obstruction, malignancies ; >10%
10
Q
Pre-renal causes acute kidney injury
A
Occurs before the kidneys blood vessels
Decreased effective extracellular volume
Example: hypovolaemia; decreased cardiac output; systemic dilation Altered renal vascular regulation
11
Q
intra renal
A
Cause within the kidney Caused by acute tubular necrosis
12
Q
post renal
A
This occurs after the kidneys: bladder, ureter, urethra Caused by obstruction of the urinary tract e.g.prostate hyperplasia, malignancies
13
Q
causes of acute tubular necrosis
A
- Hypoperfusion
- Radio contrast media (used to diagnose certain conditions)
- sepsis
- Rhabdomyolysis (breakdown of muscle from within the cell)
- Renal transplantation (immunosuppresants cause kindey toxicity)
- hepatorenal syndrome (End stage liver disease
- Nephrotoxins: NSAIDS, ahminoglycosides, immunosuppressant, chemotherapy, poisons
14
Q
Causes of AKI
A
- reduce fluid intake
- increased fluid loss
- urinary tract symptoms (post renal cause)
- recent drug ingestion
- sepsis
15
Q
Phases of recovery of acute tubular necrosis
A
- Oliguric phase: 10 to 30 days; glomerular and tubular dysfunction
- Polyuric phase: persisting tubular dysfunction
- Recovery phase: maybe prolonged-six months or sometimes longer
16
Q
Investigation of AKI
A
Full history- drug history
Clinical examination, including fluid balance assessment
Urinalysis- if it is conc urine it is pre renal cause; itra-renal or obstructive cause they will have isotonic urine; Obstructive uropathy the patient will have anuria (reduced urine productio) or crystal uria
Blood examination
Ultrasound scan renal tract is mandatory- this is to exclude obstruction and prepare patients for renal biopsy
17
Q
management of acute kidney injury
A
- Non-specific remedy
- Early aggressive intervention at the first sign of oliguria may prevent sustained oliguria-
- If due to shock-restoration of CVS function may involve transfusion, osmotic erratics or high dose of loop diuretics (furosemide 3mg/kg/6 hours)
- Otherwise careful management-fluid intake monitoring, may use plasma expanders, use of diuretics depends on a aetiology
18
Q
Chronic kidney disease
A
- One in 10 people live in CKD
- 6 million people in England
- Progressive loss of renal function over a period of months or years symptoms of worsening kidney function unspecific may include feeling generally unwell,
- Severity is in five stages: stage I is mildest causing few symptoms so stage V severe illness with poor life expectancy
- Stage 5 it is called established chronic kidney disease
- persistent fall in GFR (< 60 mil/Min/1.73 m²) for three months will be considered CKD
19
Q
Signs and symptoms of chronic kidney disease
A
CNS: confusion; seizures; coma
BLOOD: anaemia; platelet abnormalities
RENAL: polyuria; Na+, H2O retention, noturia
HORMONAL: infertility; loss of libido; impotence
BONE: osteomalacia; pain; osteosclerosis; hyperparathyroidism
CVS (RAAS malfunction): hypertension; HF; vascular disease; peripheral oedema
GI TRACT: nausea; vomiting; weight loss
PERIPHERAL NEUROPATHY
20
Q
Causes of CKD
A
- Diabetes- 16%
- Chronic Glomerulonephritis- 19%
- Pyelonephritis and obstructive uropathy-11%
- Polycystic Kidneys-10%
- Hypertension-6%
- Renovascular disease-3%
- Other-16%
- Unknown aetiology-16%
- Data not sent-3%
21
Q
Urine volumes by definition
A
OLIGURIA (Decreased urine output): in adults <500 ml/day
- may indicate CKD but may also indicate dehydration or urinary obstruction
- Anuria is below 50 ml/day
POLYURIA: in adults >2.5 L/day
- May cause diabetes (osmotic effect), high volume intake, diabetes insipidus
- May occur in early stage CKD
- Loss of urine concentrating capacity
22
Q
Renal clearance and GFR
A
- Direct measurements of clearance is difficult
- Clearance is used to measure renal function
- Equals the volume of blood from which a substance completely removed by filtration in one minute
- Clearance x [plasma] = [urine] x urine vol/min -Clearance = (Uc x Uv) / Pc
- If a substance were completely cleared and there is no tubular secretion of absorption then clearance = GFR
23
Q
Measurement of GFR
A
- Inulin: ideal but need to infuse and obtain steady plasma concentration: measure plasma conc and urea conc
- Creatinine: natural constituent from muscle
+Freely filterd but some tubular secretion
+Somewhat overestimates GFR
+Need 24 hour urine collection- difficult
-Various methods to estimate creatinine clearance and so GFR from single data point e.g. serum creatinine (oppsed to creatinine in urine)
24
Q
Cockroft-Gault equation
A
Derived from average population data 1976
Normal values for GFR fall with age- halve by age 75
-Most medicines that effect renal functions or are predominantly excreated through renal clearance use the cockroft-gault equation to adjust dose dependant on severity of kidney dysfunction (increased half life and so toxicity of drug)
25
MDRD formula
- Developed for use in CKD. No evidence of applicability in acute renal failure
- Underestimates GFR in healthy (\>60 ml/min)
eGFR=186x(serum creatinine (mcmol/L)-1.154x(age)-0.203xK1xK2
- K1= 0.724 if female
- K2= 1.212 if afro-American
26
chronic kidney disease epidemiology collaborated
- More accurate than MDRD
- Clinical labs should: use the CKD epidemiology collaboration (CKD-EPI) creatinine equation to estimate GFR creatinine, using creatinine assays with calibration traceable to standardized reference material
27
Plasma creatinine and GFR
- Plasma Cr inversely related to GFR
- Initially, relatively large falls in GFR causes small rises in PCr e.g. GFR 50% normal, PCr doubles to 200 mcg/L
- Serum Cr measurements are not reliable for measuring small changes in GFR
- Progression of disease best followed by reciprocal plot
- Serum Cr increases as renal function deteriorates
28
Progression of CKD
- Diminished renal reserve: GFR (120-90 ml/min), urine production UP(normal/mild polyuria)
- Renal impairment: GFR (90-60 Ml/min), UP (polyuria)
- early stage renal failure: GFR (60-30), UP (oliguria)
- Pre-end stage failure: GFR (30-15), UP (oliguria)
- End-stage renal failure:GFR \<15, UP (oliguria)
29
Plasma urea
- Normal \<8mmol/L. Some symptoms when 20-25 mmol/L and severe symptoms 50-60 mmol/L
- Uraemia is common in CKD but urea only one of the nitrogenous products affected
- Plasma urea still a general index of renal function
- Affected also by diet, liver function, muscle damage etc
30
Tubular function
- SPECIFIC GRAVITY: (1.01 to 1.02 normal adults)
- OSMOLARITY (normal adult 50-1400 mOsmol/L; random; 500-800 mOsmol/L 24 hours)
- Changes reflect concentration and can be used to indicate concentrating capacity e.g. water deprivation (lost in CKD)
- Also affected by fluid intake and ADH release (diabetes insipidus)
31
Fluid and electrolyte imbalance
- Maybe very slow onset- patients don't recognize urinary symptoms. Often mild polyuria early (loss of conc, capacity)
- Later stages inadequate renal function and Na+ and H20 retention. Maybe hypervolemia and oedema- including pulmonary. HF a possibility
- Late stage hyperkalemia and often acidosis- failure of K+ and H+ secretion
32
Potassium
- Generally Hyperkalaemia
- Levels over 7mmol/L are life-threatening
- Acidosis exacerbates hyperkalaemia because of movent of intracellular K+ out of the cell
- Major ECG changes as a result of hyperkalaemia
- If allowed to continue to rise will result in cardiac arrest
33
Cardiovascular effect
- Hypertension almost inevitable- number of causes: fluid retention, RA abnormalities
- Cardiomyopathy associated with Ca2+ and phosphate (PO4) imbalance
- Cardiac failure- volume overload, oedema, hypertension, anemia
- Overall CVS events account for over half the deaths in CKD
34
Anaemia
- Bone marrow hypoplasia (wont produce RBC) due to reduced or no erythropoietin
- Haemoglobin levels fall:\<8d/dl Rf 12-18 g/dl
- Fe and or folate deficiencies exacerbates the above- Poor dietary uptake and losses e.g. bleeding from the GI tract
- Aggravates effects on heart and major effect on quality of life
35
Calcium and phosphate
- Kidney essential for final stage activation of Vit D
- Lack of Vit D causes reduction GI Ca2+ absorption and renal reabsorption
- Hypocalcaemia stimulates PTH release- increased bone resorption. osteomalacia--\> renal rickets
- Poor phosphate excretion leads to solubility product for Ca and PO4 to be exceeded. Ectopic calcification
- This can be treated by restricting phosphate in the diet however this is hard because it is in alot of food stuff, phosphate binders can be used to absorb them
- AlOH used to be used as a phosphate binder but patients used to absorb and not eliminate Al so would get neurological side effects including dementia
36
Management of CKD
- BP control: ARBs, ACEI this is used bevause they reduce protein uria and progression of CKD
- Anaemia management
- Oral bicarbonate supplement for management of metabolic acidosis
- Encourage those with CKD to exercise, achieve a healthy weight and stop smoking
- Offer dietary advice about K+, PO4, calorie and salt intake, but patient needs dietary assessment to prevent malnutrition
- Low protein diets are no longer offered
37
Drug use in renal impairment
- Avoid drugs that are likely to cause further damage
- Many drugs are excreted by the kidneys
- Some drugs may need to be excreted in order to work
- ADRs are more likely with many drugs
38
Drug use in renal impairment
PATIENT FACTORS: degree of renal impairment; stable, improving or deteriorating; concomitant medication/disease
DRUG FACTORS: is the drug essential; How quickly is needed; what proportion is renally cleared; is the drug nephrotoxic; does the drug have a narrow therapeutic index; measure safety/efficacy parameter; our ADRs more likely in renal impairment; mechanism of action; half life
39
Renal replacement therapy
- Towards end-stage CKD-how shall require an organ transplant
- there is a waiting list
- the best option for most CKD patients
- 2929 Kidney Transplants Took Pl; aprox one third were live donors
- major limiting factor is donors-UK one of the worst in Europe for diners
40
Dialysis
**Peritoneal**: up to 25 L of sterile fluid into the peritoneal cavity under gravity. The exchange between peritoneal capillaries and fluid. drain out under gravity
**H****aemodialysis-**artificial kidney with large area exchange membrane. Arterial blood pumped by peristaltic pump countercurrent flow of dialysis fluid
**continuous venovenous haemofiltration-** short-term treatment using ICU patients with acute or chronic renal failure. Blood is passed through hemofilter
-Dialysis fluid is adjusted to the individual- low in ions to be removed and high in those to be added to patient plasma
41
42
Erythropoietins
- Recombinant human erythropoietins
- Epoetin alpha, beta, theta and zeta and darbepoetin (hydroxylated derivative with longer half life)
- Can be used in CKD
- MRHA warning on use in cancer- increase in mortality- 2008
- Revised NICE guidelines- erythropoiesis stimulating agents are recommednend, within their MA as options for treating anaemia in people with cancer who are having chemotherapy
43
Dialysis
- This is taking toxins out of the blood
- The blood passes through a semi permeable membrane that lets low MW compounds through
- This is via difusion which is dependant on conc gradients as well as movement of dialysis pores of membrane so small moleucles are cleared better
- This can be done with pressure changes
- The movement of substances can be done by convection- small molecules move with ultrafilrate
44
Peritoneal dialysis
- Rarely used but is used when Haemodialysis
- A catheter is then placed into the peritoneal cavity
- 1-2L of dialysis fluidis then placed into the abdomen and left for around 30 minutes then drained into bag
- This can be carried out up to 20 times a day
- This is keep and simple and doesn't need specialist kidney untis or staff
- However this can take a long time and be tiring for the patient; Cause infection of peritoneum as well as protein loss
45
Haemodialysis
- A dialysis line is used, this is placed in a vein and an artery
- This can be intermittent of continuous
- This is expensive bevcause it has to be in a renal unit as well as specialist staff (this can be inconvient, travel)
46
Continuous venvenous haemofiltration
- Blood is passed through a haemofilter
- For each case the dialysis fluid is adjusted dependant on electrolyte and needs for the specific patient
