Renal Flashcards
What is the main prostaglandin secreted by the kidneys?
Prostacyclin
What is the maximum possible concentration of urine?
1200 m.osmol/L
What percentage of glomeruli are superficial cortical glomeruli?
85%
What percentage of glomeruli are juxtamedullary glomeruli?
10%
Where do juxtamedullary glomeruli have their Bowman’s capsules?
In the cortex, near the junction with the medulla
How many afferent arterioles are there per nephron?
1
What percentage of cardiac output goes to the kidneys?
20%
Where is the macula densa?
At beginning of distal convoluted tubule
What do macula densa cells detect?
NaCl concentration
What do macula densa cells release to cause constriction of the afferent arteriole?
Adenosine
Where does creatinine come from?
Turnover of muscle cells and protein degradation
What percentage of renal plasma flow is filtered by the glomerulus?
20%
What is the hydrostatic pressure in the glomerular capillary?
50mmHg
What is the net filtration pressure across the glomerulus?
10mmHg
What happens to GFR when afferent arteriole constricts?
Decreases
What happens to GFR when efferent arteriole constricts?
Increases
What does angiotensin II do?
Constriction of efferent arteriole to cause increase in GFR
What happens to GFR when MAP increases from 80 to 180?
Nothing
Where does autoregulation in the kidney occur?
Afferent arteriole
Which cells of the kidney release renin?
Granular cells
Where are granular cells in the kidney?
In the wall of the afferent arteriole where it enters the glomerulus
What does renin do?
Catalyses angiotensinogen –> angiotensin 1
What causes granular cells to release renin?
Decreased NaCl, sympathetic drive and pressure.
The clearance of substance X is…..
The volume of plasma cleared of X per time
What do we call infection of the bladder and lower UT?
Cystitis
What do we call infection of kidney and renal pelvis?
Pyelonephritis
How far along the urinary tract should be sterile?
Everything above bladder sphincter
What’s the most common pathogen in UTI?
E. coli
How do must bacteria get into the urinary tract to cause infection?
Ascend up the urethra
What is the major innate immune mechanism in the urinary tract?
Constant flushing effects of urine and regular emptying of bladder
What is the most important thing to remember when taking a urine sample from a catheter bag?
Never collect it from the bag itself; collect freshly passed urine from the catheter itself
Why must a urinalysis be performed promptly?
More time would allow the bacteria to replicate and quantitative analysis is important in urine samples
What do we call pus in the urine?
Pyuria
What is sterile pyuria?
Pus in urine, but without bacterial growth
What antibiotics should be used for a UTI?
Cephalexin OR co-amoxyclav OR trimethoprim
What antibiotics should be used for pyelonephritis?
Cephalexin OR co-amoxyclav OR trimethoprim
What is the definition of recurrent UTI in women?
>2 UTIs in 6 months
What percentage of water is reabsorbed by the kidneys after it has been filtered?
99%
Where is water reabsorption in the kidney regulated?
Collecting ducts
Where is calcium mainly reabsorbed in the nephron?
Proximal convoluted tubule
What percentage of creatinine is reabsorbed in the kidney?
None
How is Na reabsorbed in the thick ascending limb of the nephron?
Na/K/2Cl co-trasnporter
What percentage of nephrons are juxta-medullary?
15%
What size are the fenestrations in glomerular capillaries?
70-100nm
What size are the podocyte interdigitating slits in the glomerulus?
3-5nm
What type of epithelium lines the proximal convoluted tubule?
Simple cuboidal
What type of epithelium lines the thin descending loop of Henle?
Simple squamous
What type of epithelium lines the ureters?
Transitional epithelium
Which substance is responsible for constriciton of the efferent arteriole in the kidney?
Angiotensin II
Where is reasborption greatest along the nephron?
Proximal convoluted tubule
What is the most important solute to be reabsorbed in the nephron?
Sodium
What measure is the most important for defining renal failure in clinical practice?
GFR
Urine output of less than 500ml per day indicates what?
Renal failure
Define acute renal failure
A sudden fall in GFR over hours to days
When does kidney function begin to decline?
40 years of age
What is the most accurate measure of daily fluid balance?
Daily weight measurement
What is the most common cause of acute renal failure?
Acute tubular necrosis
Define oliguria
In which 2 ways can the kidney regulate HCO3- levels?
Can reabsorb HCO3- in PCT. Can synthesise HCO3- in DCT
What is a normal pH in the body?
7.35-7.45
How do you calculate the anion gap?
Na + K - Cl - HCO3
What makes up most of the unmeasured ions in the anion gap?
Albumin
Name 3 types of acidosis with a large anion gap
Renal failure. Diabetic ketoacidosis. Lactic acidosis
What is a normal HCO3- level?
21-28 mmol/L
What happens to bicarbonate levels in metabolic alkalosis?
Increased
What happens to bicarbonate levels in metabolic acidosis?
Decreased
What happens to bicarbonate levels in respiratory alkalosis?
Decreased
What happens to bicarbonate levels in respiratory acidosis?
Increased
What effect does metabolic acidosis have on potassium levels?
K+ levels increase in metabolic acidosis
Define Grave’s disease
Type II hypersensitivity in which host generates Ig to TSH receptor on thyroid gland, which stimulates thyroid hormone release. Leads to hyperthyroidism.
Define myasthenia gravis
Type II hypersensitivity in which host generates Ig to muscle nicotinic ACh receptors. When bound, this stops ACh from activating muslce, leading to weakness.
Define vasculitis
Type III hypersensitivity in which immune complexes are deposited in vessel walls
What are the 4 features of nephrotic syndrome?
Proteinuria. Hypoalbuminaemia. Oedema. Hyperlipidaemia
Which part of the nephron is impaired with proteinuria?
Glomerular filter
Define glomerulonephritis
Injury to the glomerulus that is almost always immune mediated
What is focal vs diffuse glomerulonephritis?
Every glomerulus is abnormal vs no all
What is segmental vs global glomerulonephritis?
All or most part of each glomerulus is involved with not
What is the leading cause of end stage renal failure in Australia?
Diabetic nephropathy
What is suggested by cresents in the urinary space outside the glomerular tuft?
Severe acute injury to the glomerulus
What is the “triple whammy”?
Combination of ACE inhibitor, diuretic and NSAID
How do NSAIDs impair renal function?
By interfering with vasodilation from PGI2
What is the mechanism of action of potassium-sparing diuretics?
Block Na transporter in collecting tubules and ducts
Plus or minus:
Inhibit synthesis of Na/K cotransporter in collecting tubules and ducts