renal Flashcards
eGFR is a blood test result which gives the clinician an estimate of renal function.
What is the eGFR in a healthy adult?
eGFR is 90+
Renal failure can occur due to disease in a variety of sites within the renal system.
B. Describe what is meant by each of the terms below and give an example of a cause of each:
(4 marks)
PRE-Renal Definition:
Example cause:
POST-Renal Definition:
Example cause :
PRE-RENAL = DECREASED RENAL BLOOD FLOW = drop in GFR
example: blood loss, dehydration, burns, NSAIDs
POST-RENAL = a process downstream of the kidney prevents drainage of urine (URINARY TRACT OBSTRUCTION)
example: renal/ureteral calculi, tumors, blood clots, or any urethral obstruction.
Glomerular function is dependent on the perfusion pressure in the glomerulus remaining constant.
C. Explain how this is achieved (2 marks)
auto regulation = kidneys can regulate their own blood flow by adjusting the diameter of the afferent arteriole
renin-angiotensin-aldosterone system = when the blood pressure drops, the kidneys release the hormone renin, which leads to the production of angiotensin II. This hormone constricts the blood vessels, increasing the blood pressure and maintaining a constant perfusion pressure in the glomerulus.
tubuloglomerular feedback: The tubuloglomerular feedback mechanism involves the detection of changes in the flow rate of fluid through the renal tubules. If the flow rate increases, the afferent arteriole constricts to reduce the flow rate and maintain a constant perfusion pressure in the glomerulus.
Explain how NSAID medicines interfere with this process (2 marks)
ANSWER HERE:
inhibit glomerular blood flow
cause interstitial nephritis (the spaces between tubules inside the kidney become inflamed = reduces the kidneys’ ability to filter properly)
When there is glomerular disease, protein can escape into the urine and result in hypoalbuminaemia
E. Give TWO physiologic consequences of this protein loss to the patient (2 marks)
oedema = legs and ankles
impaired immunity and risk of infections as albumin is a carrier protein in the blood
renal dialysis can be an option for a patient with end stage renal disease.
Explain the process by which haemodialysis corrects the biochemical irregularities
(4 marks)
patient’s BLOOD IS REMOVED into the hemodialysis machine.
Filtration: The blood passes through a semipermeable membrane within the hemodialysis machine. This membrane acts as an artificial kidney, allowing waste products such as urea, creatinine, and excess electrolytes to diffuse from the patient’s blood into the dialysis fluid.
Dialysis fluid: The dialysis fluid contains a specific balance of electrolytes, which is designed to match the normal balance found in healthy blood. This fluid helps to REMOVE EXCESS ELECTROLYTES from the patient’s blood, while also restoring the NORMAL electrolyte balance.
Blood return: Once the blood has been filtered and corrected, it is RETURNED to the patient’s bloodstream through a separate needle or catheter.
acute kidney failure cause and symptoms
rapid loss of renal function
no urine produced = volume overload
ankle or sacral oedema, polyuria (increased urination)
hyperkalaemia (high potassium = no action potentials = cardiac arrest)
acidosis
urea in blood
chronic kidney failure causes and symptoms
Glomerulonephritis = glomerulus doesn’t filtrate properly = blood and proteins in urine
Polycystic kidney disease = cysts present on kidney parenchyma
Secondary causes include diabetes, hypertension, drugs, vasculitis and renal artery/aorta disease.
tests for kidney failure
serum urea and creatinine
eGFR - estimated glomerular filtration rate
24 h urine collection
treatment for chronic kidney failure
aim to reduce the rate of decline of the kidneys =
by eliminating nephrotoxic drugs such as cyclosporin. Also hypertension, diabetes and vasculitic disease
must be controlled
correcting the fluid intake and restricting salt, potassium and protein intake. Also any deficiencies due to
kidney malfunction must be addressed such as replacing erythropoietin to correct anaemia and replacing
Vitamin D for calcium deficiencies
pre-renal failure
hypo perfusion of the kidneys
not enough oxygen
can occur in either hypovolaemic shock or due to renal artery/aorta disease as atherosclerosis may occlude the vessels.
dental relevance in kidney failure
All drugs must therefore be checked with the renal physician and MUST AVOID NSAIDs and some tetracyclines (antibiotics)
In children the growth rate may also be disturbed which leads to late tooth eruption.
There may also be secondary effects of anaemia with oral ulcerations and dysaesthesia with white patches
named uraemic stomatitis. Opportunistic infections may also be present post-operative and also the patients
may have a dry mouth with taste disturbance due to fluid restriction and electrolyte imbalance.
Patients may also have platelet dysfunction leading to bleeding tendencies.
Also in Renal osteodystrophy the lamina dura is lost and this should be surrounding the healthy periodontium. It may also lead to bony radiolucencies as hyperparathyroidism will increase the activities of osteoclasts.
Renin-angiotensin system & definitions
is a hormone system that regulates blood pressure and water balance.
when blood volume is LOW, juxtaglomerular cells in the kidneys SECRETE RENIN
Renin converts angiotensinogen from liver to angiotensin I
Angiotensin I TO angiotensin II by the enzyme angiotensin converting enzyme ACE found in the lungs.
Angiotensin II is a potent VASOCONSTRICTOR, resulting in increased blood pressure.
also stimulates the secretion of the ALDOSTERONE from the adrenal cortex = causes the tubules of the kidneys to INCREASE THE REABSORPTION OF SODIUM AND WATER
this increases the VOLUME OF FLUID in the body, which also INCREASES BP.
