Renal Flashcards
Day 4
Describe the kidneys
Sited at the back level with last thoracic and 12th lumbar vertebrae. Partially protected by 11th and 12th ribs. Rt kidney slightly lower then left. Adrenal gland sit on top of each kidneys. Embedded in fat and connective tissue.
What is the glomerulus ?
Sited at beginning of nephron.Where vascular filtration occurs. A positive pressure is created by efferent arteriole being narrower than the afferent. Filtration is dependent on positive pressure.
What does a drop in blood pressure cause for filtration pressure ?
Results in a loss. BP = CO x SVR so potential causes could relate to cardiac output through loss of circulating volume or poor cardiac function. Reduced BP detected in carotid sinus stimulates sympathetic nervous system which causes renin release from juxtaglomerular cells of the kidney. Kidneys release renin from stimulation of the juxtaglomerular cells or macula densa cells.
How is renin released into the bloodstream ?
Drop in BP. Renin released from kidney via juxtaglomerular and macula densa cells. Renin travels to the liver where angiotensinogen is converted into angiotensin I. Angiotensin I travels to lungs where it is affected by angiotensin converting enzyme and converts into angiotensin II. This leads to vasoconstriction and the release of anti diuretic hormone from posterior pituitary gland and release of aldosterone from adrenal glands.
What does aldosterone do ?
Regulates BP by ..
IncreasIng sodium retention in the blood stream and enhance excretion of potassium in urine. Promoting sodium reabosrption helps body to retain water, increasing blood volume.
Also when aldosterone levels rise kidneys reabsorb more water leading to elevated blood volume and BP, the aldosterone influences kidney water reabosprtion.
What does an anti diuretic hormone do ?
Causes increase in water reabsorption in the collecting duct of the nephron. Stimulates aquaporins (water channels)
Water is reabsorbed into circulatory system.
What is a nephron ?
Functional unit of the kidneys
What are the functions of the kidney ?
Dispose of waste - nitrogenous waste(urea) end product of protein breakdown, uric acid (results from nucleic acid), metabolism (creatinine)
Toxins, drugs, excess ions
Regulatory function - maintain homeostasis -
fluid and electrolyte balance, acid - base balance PH, production of renin to maintain BP, production of erythropoietin to stimulate RBC production, conversion of vit D to its active form.
Define AKI
Acute kidney injury is an abrupt decline in glomerular filtration with failure of the kidneys to excrete the waste products of metabolism & inability to maintain electrolyte & acid-base homeostasis. Potentially reversible.
What are the key issues associated with AKI ?
Rapid decline in kidney function, within hours or day - build up of nitrogenous waste in blood, alteration in fluid and electrolytes balance, decreased GFR.
What are the 3 causes of AKI ?
Prerenal, intrarenal / intrinsic, postrenal
Describe prerenal cause of AKI
Causes decrease in effective blood flow to kidneys and GFR (glomerular filtration rate). Caused by hypovolaemia, hypotension, stenosis, heart and liver failure
Describe intrarenal / intrinsic cause of AKI
Disease processes or damage directly to structure of kidney. Glomerular nephritis, interstitial nephritis, haemolytic uremic syndrome, Henoch Schoenlein purpura and some nephrotoxic medications can cause this
Describe postrenal causes of AKI
Downstream of the kidney, most often occurs as consequence of UT obstruction. Caused by blocked urinary catheter, benign prostatic hyperplasia, obstructive uropathy in children.
What are the common causes of AKI in children ?
Post cardiac surgery and stem cell transportation patients.
Hypoxia/ischemia and nephrotoxin induced AKI - causes in neonates and CYP.
How do you detect AKI ?
Rise in serum creatinine of 26 micromole/ Lor greater within 48 hours.
50% or greater rise in serum creatinine known or presumed to have occurred in past 7 days. fall in urine output 0.5ml/kg/hr for more than 6 hours adults, 8 hours children. 25% or greater fall in eGFR in CYP in past 7 days
How do you identify the cause of AKI ?
Urine dipstick (test for blood, protein, leucocytes, nitrates, glucose)
Referral to nephrology team with no cause of AKI and dipstick results of haematuria and proteinuria without UTI or catheter trauma.
Ultrasound.
What is chronic kidney disease ?
Irreversible, long term chronic condition.
Decline in kidney function, over many years. Failure of homeostasis occurs as disease progresses, increased risk of other conditions esp cardiovascular disease, mortality and morbidity.
What are the major causes of CKD ?
Hypertension and diabetes because they damage blood vessels. A good blood supply is essential for kidney function.
Glomerular disease polycystic kidney disease.
Which ethnicity is more likely to develop CKD ?
Black and Asian
What are the causes of AKI in CYP ?
Congenital disorders, renal dysplasia with reflux, obstructive uropathy, glomerular disease, congenital nephrotic syndrome, tubulo interstitial disease, renovascular disease polycystic kidney disease, metabolic, malignancy
What does the diagnosis of CKD require ?
Decline of kidney function for 3 months or more AND
Evidence of kidney damage (e.g. albuminuria or abnormal biopsy) OR
GFR <60 mL/min/1.73 m2
Urine, bloods, imagining, histology (biopsy), signs (oedema, hypertension)
What is the pathophysiology of CKD ?
Decline in nephron numbers - adaptive hyperfiltration at glomerulus leads to increased activation of renin angiotensin aldosterone system (increases BP) and increased glomerular permeability (albuminuria proteinuria).
Inflammation and fibrosis and glomerulus tubules. More nephron death = progression.
What is estimated eGFR ?
Key indicator of estimated renal function based on serum creatinine level, age, sex and race. Declines with age.
Normal - 100ml/min/1.73m2
Normal above 90 or above 60
