Renal dysfunction Flashcards
what is creatinine
- waste product derived from muscle metabolism in the body
- present in bloodstream
- excreted in urine
define acute kidney injury (AKI)
defined as any of the following:
- increase in creatinine by >0.3mg/dl within 48h OR
- increase in creatinine to >1.5x baseline, which is known or presumed to have occured within prior 7 days OR
- urine vol <0.5ml/kg/h for 6 hours
types of AKI
- non-oliguric AKI -> AKI with urine output > 400ml/day
- oliguria -> <400ml/day
- anuria -> 100ml/day
what are the criteria of stage 1 AKI
1.5-1.9x baseline SCr OR
>0.3mg/dl increase in SCr
<0.5ml/kg/h urine output for 6-12h
what are the criteria of stage 2 AKI
2-2.9x baseline SCr
<0.5ml/kg/h urine output for >12h
what are the criteria of stage 3 AKI
3x baseline SCr OR
>4.0mg/dl increase in SCr OR
initiation for RRT OR
decrease in eGFR to <35ml/min per 1.73m^2
<0.3ml/kg/h for >24h OR
anuria for >12h
define chronic kidney disease
abnormalities of kidney structure OR renal function present for more than 3months with implications for health: (either of the following) - albuminuria - urine sediment abnormalities - electrolyte and other abnormalities due to tubular disorders - abnormalities detected by histology - history of kidney transplant - GFR <60ml/min/1.73m^2
possible causes of AKI
pre-renal
- inadequate perfusion -> not enough blood at sufficient pressure to allow filtering
renal
- cellular damage/intrinsic -> damage to the cells that make filtering mechanism possible
post-renal
- obstruction -> urine unable to drain adequately resulting in system “back up”
possible renal causes of AKI
small vessel disease
- inflammation (vasculitis)
glomerular disease
- inflammation (glomerulonephritis)
acute tubular necrosis
- toxins
- ischaemia
acute interstitial nephritis
intratubular obstruction
explain what pre-renal AKI will result in
due to the lack of blood flow to the kidneys, it will result in ischemia, which will result in endothelial injury. this activates vasoconstrictors and impair vasodilation, and increase leukocyte adhesion which leads to inflammation (inflammation = endothelial injury)
vasoconstriction + leukocyte adhesion will lead to capillary obstruction and continued ischemia eventually.
ischemia will lead to tubular injury, followed by desquamation of cells and then tubular obstruction.
explain what post-renal AKI will result in
system back up will cause build up in waste, ureteric and tubular pressure which compromises urinary blood flow and decrease in glomerular filtration, affecting function of kidney
what is radiation nephropathy
renal injury and loss of function caused by ionising radiation
damage to renal blood vessels resulting in ischemic insult to the kidneys
patients who develop acute radiation nephritis can progress to chronic kidney disease and subsequently end stage renal failure
explain the pathophysiology of radiation therapy on kidney function
ionising radiation of sufficient energy disrupts chemical bonds and knocks electrons out of atoms,
this generates oxygen radicals that cause prompt DNA injury within ms of irradiation
this can cause death of cancer cells and/or injury to irradiated normal tissues
explain the radionuclide therapy on kidney function
radioisotope protein conjugate filtered at glomeruli and reabsorbed by tubular epithelium. this acts as a radioemitter when it is lodged in the kidney and result in injury to renal tissue
what is the accepted threshold dose of photon irradiation for radiation nephropathy
exposure of both kidneys to a total dose of 23Gy, fractionated in 20 doses over 4 weeks
renal failure from radiation nephropathy will not occur if only one kidney is irradiated with a threshold or higher dose though radiation injury will occur in that kidney
explain what will CKD result in
systemic hypertension -> elevated intraglomerular pressure -> progressive glomerular and tubulointerstitial damage -> proteinuria
damage -> loss of nephrons -> afferent arteriole dilation and activation RAAS (to increase systemic hypertension) -> efferent arteriole constriction -> elevate intraglomerular pressure
function of kidney
regulation of RBC production
regulation of BP
regulation of bone-mineral-metabolism
influence on blood pH acid-base-metabolism
excretion of metabolic waste products and water
complications of renal failure
A- anemia; acidosis
B- blood pressure (hypertension); bone (mineral bone)
C- cardiovascular complications; constitutional
D- diet (nutrition)
E- electrolytes (hyperkalaemia)
F- fluid overload
explain anemia in CKD patients
RBC have decreased lifespan (to 60-90 days)
reduced synthesis of erythropoietin hormone responsible for bone marrow stimulation for RBC production
uraemic toxins induced platelet dysfuntion and increases bleeding tendencies
explain metabolic acidosis in CKD patients
kidneys are unable to produce enough ammonia in the PCT to excrete the endogenous acid (H+) into the urine in the form of ammonium
aggravates bone disease, protein/muscle wasting, CKD progression and mortality
what is the constitutional symptom present in CKD
itch related to uremic toxic accumulation
hyperkalaemia vs hyperphosphataemia vs hypocalcaemia
hyperkalaemia: reduced excretion of potassium from the kidneys
hyperphosphataemia: reduced excretion of phosphate from the kidneys
hypocalcaemia:
- decreased intestinal calcium absorption due to low vitamin D (calcitriol) levels
- increased calcium-phosphate binding caused by elevated serum phosphate levels
benefits and risk of renal transplant
benefits:
- improved patient survival
- correction of metabolic abnormalities
- avoidance of complications related to dialysis access and treatment
- improved quality of life
- reduced healthcare cost
risks:
- surgical risks
- rejection
- cancer
- infections
- cardiovascular disease
- transplant failure
- aggravation of pre-existing comorbidities
- toxicities of drugs
classification of deceased donor
standard criteria donor (SCD)
expanded criteria donor (ECD)
- > 60 years old
- 50-59 years of age with any 2 criteria: terminal Cr >1.5mg/dl; death due to CVA; hypertension
- diabetes mellitus of any age
donor after cardiac death (DCD)