Renal disorders Flashcards
How much blood do the kidneys filter per day?
180L
How much urine do the kidneys create per day in the process of blood filtration?
~2L
What are the three functions of the kidneys?
- Filtration of blood and excretion of waste products
- Homeostasis (concentration of various substances in the blood)
- Endocrine (to maintain homeostasis)
List four metabolic wastes excreted by the kidneys and their sources
- Urea — metabolism of proteins
- Uric acids — metabolism of nucleic acids
- Creatinine — metabolism of muscle
- Bilirubin — breakdown of haemoglobin
How many nephrons are in each kidney?
~1 million
What is the function of the glomerulus?
High pressure filtration of water, salt, and other substances out of the blood
What is the glomerular filtration rate (GFR)? What is the normal rate?
How fast the glomeruli filter blood; normally 100-120mL/min
What tests can be used to estimate GFR?
- Creatinine level — it is proportional to GFR
- Inulin clearance (standard) — it is filtered but not secreted
What can skew a creatinine level test when trying to estimate GFR?
Muscular people have more creatinine
What is the maximal and minimal urine output?
Maximal: ~500mL/hour
Minimal: ~500mL/day
Which hormone is secreted from the adrenal gland to increase BP?
Aldosterone
Which hormone is secreted from the pituitary to increase BP?
Antiduiretic hormone (ADH/vasopressin)
What is the function of ADH?
Directs the distal tubules to retain more water in response to hydration state
What is acute kidney injury (previously called acute renal failure)?
Abrupt loss of kidney function within 7 days
List four causes of AKI
- Ischaemia
- Oxidising chemicals (e.g. paraquat)
- Obstruction
- Dehydration
What are the four sources of renal damage?
- Pre-renal (conditions above kidneys, e.g. CVD)
- Vascular
- Intrinsic (within kidneys)
- Obstructive (post-renal)
- Cardiorenal syndrome — linked system complications
Acute kidney can lead to what two life-threatening conditions?
- Metabolic acidosis — kidneys fail to remove H+ (acid)
- Hyperkalaemia — kidneys no longer regulate K+
AKI can lead to what two complications?
- Uraemia
- Altered fluid balance (HTN, oedema)
List the symptoms of AKI
- Urea and other nitrogen-containing substances in blood
- Fatigue
- Loss of appetite
- Headache
- N + V
- Hyperkalaemia
- Fluid imbalance
- Flank pain
What signs are used to dx AKI?
- Decrease in urine output OR large volumes of pale urine
- Blood tests: urea and creatinine
- Can take 24 hours before levels rise significantly
Describe the hospital rx for AKI
- Depends on underlying cause:
- Hypotensive — fluid, inotropes, vasoconstrictive drugs
- Hypertensive — diuretics
- Toxins — antidotes
- Obstruction — removal
- Kidney transplant/removal
What distinguishes diabetes insipidus from diabetes mellitus?
No glucose in urine
What triggers ADH release?
Hypotension
What two substances inhibit ADH release?
Caffeine and alcohol
What symptom is the result of too much ADH?
Oedema (fluid leaks out of capillaries and collects in the interstitium)
The hypothalamus and the pituitary comprise a ____ ____.
Neuroendocrine axis
What is the difference between central and peripheral diabetes insipidus?
Central — no ADH from the pituitary gland
Peripheral (AKA nephrogenic) — lack of specific aquaporins in the kidney; cannot respond to ADH
Similar to IDDM + NIDDM, like IDDM central cannot produce insulin and like NIDDM peripheral cannot respond to ADH
How do people with diabetes insipidus respond to a water deprivation test in comparision to healthy people?
- Healthy people
- ADH is released from the pituitary
- Concentrated urine, decreased urine volume
- Blood osmolarity is decreased, urine osmolarity is increased
- Diabetes insipidus
- No ADH from pituitary OR no ADH receptor in kidneys
- Constantly diluted urine, large urine volume
- Blood osmolarity is increased, urine osmolarity
How do you determine whether a pt’s diabetes insipidus is central or nephrogenic?
Give nasal spray of an ADH analogue and perform a water deprivation test. Central diabetes insipidus pts can respond to ADH and will concentrate urine. Peripheral diabetes insipidus pts cannot respond to ADH and there will be no effect.
What is used to rx central diabetes insipidus?
ADH nasal spray
What is used to rx peripheral diabetes insipidus?
Thiazide diuretics — they promote salt and water uptake in the proximal tubule
How many cases of diabetes insipidus are genetic?
<10%
What are the causes of central diabetes insipidus?
- Autoimmune — destruction of cells that produce ADH
- Tumour in pituitary
What are the causes of peripheral diabetes insipidus?
- Lithium toxicity
- Severe electrolyte disturbances
Accumulation of uric acid in joints are a sign of…
Long term renal issues.
List four of the most common causes of chronic kidney disease leading to chronic renal failure
- Diabetes mellitus
- Hypertension
- Glomerulonephritis
- Chronic obstruction
What is hydronephrosis, and what is it caused by?
Blockage in the ureter (the tube connecting the kidney to the bladder) caused by kidney stone or birth defect.
What are the symptoms of hydronephrosis?
- Pain
- Recurrent infections
- Sometimes asymptomatic
How is hydronephrosis dx?
Imaging, radionuclide scan to show how fluid moves in the kidneys
What is the rx for hydronephrosis?
Must be surgically altered/stone removed
What is nephrolithiasis?
Renal calculus — crystals comprised of calcium and uric acid
True or false: hydronephrosis can be bilateral or unilateral.
What is pyelonephritis?
Infection within the major calyx of the kidney
What are two severe outcomes of pyelonephritis?
Sepsis and AA amyloidosis
From which two places can pyelonephritis originate?
In the bladder or from renal obstruction
List four symptoms of pyelonephritis
- Fever
- Increased HR
- Flank pain
- Haematuria
How do hospitals test for pyelonephritis?
- Urine culture, antibiotic sensitivity test
- Ultrasound of kidneys (damage/obstruction requiring further testing)
What is indicative of hydronephrosis on a kidney ultrasound?
Pressurised voids (large dark spaces)
What may be easily missed in a CT scan with hydronephrosis?
Kidney enlargement
How does a radionuclide scan work?
Radionuclide is injected, the kidneys immediately begin to filter it and this is visualised using x-ray.
What is the rx for hydronephrosis caused by birth defect?
Pyeloplasty (reconstuction of renal pelvis)
What is the immediate danger resulting from release of cellular contents into circulation due to crush syndrome?
Dysrhythmias
Initial injury to kidney after crush syndrome is largely to due what?
Decreased circulating volume exacerbated by third spacing
What is the result of myoglobin release?
Myoglobin is nephrotoxic — it scavenges nitric oxide, causing vasoconstriction, and catalyses the generation of free radicals. The kidneys are highly sensitive to hypoxia and oxidative substances. Filtration of myoglobin causes obstructions because it precipitates with protein.
What is the most common long term complication post crush injury survival?
AKI
