Lecture 6.5 Renal Disorders Flashcards
What are the two types of kidney failure?
Acute and Chronic
What separates acute from chronic kidney failure?
Chronic is irreversible damage and is progressive. It involves loss of function of nephrons.
Acute is abrupt but reversible. (sometimes)
What are the 3 kinds of acute renal failure?
Prerenal acute renal failure
Intrarenal acute renal failure
Postrenal acute renal failure
Define prerenal acute renal failure
Decreased blood supply to kidneys.
Causes:
Diminished blood volume
Severe hemorrhage
Define intrarenal acute renal failure
Abnormalities originating from within the kidney.
Causes:
Abnormal blood vessels
Abnormal glomeruli
Abnormal tubules
Define postrenal acute renal failure
Obstruction of the urinary collecting system. Anywhere from calyces to the ureter outflow.
Causes:
Kidney stones
What generally occurs in prerenal acute renal failure?
Decreased GFR
Decreased Urine output of water/solutes
Results in oliguria and can progress to anuria.
Note:
This simultaneously means water and solutes are building up in the body.
What are the main causes of prerenal acute renal failure?
Intravascular volume depletion (Hemorrhage, diarrhea/vomiting, burns)
Cardiac failure (MI, Valvular damage)
Peripheral vasodilation & resultant hypotension (anaphylactic shock, anesthesia, sepsis, primary renal hemodynamic abnormalities, renal artery stenosis, embolism, or thrombosis)
At what point does prerenal acute renal failure become irreversible?
When renal blood flow drops under 20-25%.
How do the kidneys compensate during decreased renal blood flow?
Decreased renal blood flow decreases GFR.
lower GFR = lower filtered sodium
Lower filtered sodium = less reabsorption of sodium (saving energy)
This means O2 requirements decrease, but the tubular epithelial cells can only survive in a hypoxic environment for so long.
What are the 3 categories of intrarenal acute renal failure?
- Conditions that injure the glomerular capillaries/small renal vessels.
- Conditions that damage the renal tubular epithelium.
- Conditions that damage the renal interstitium.
What are the primary causes of intrarenal acute renal failure?
Small vessel/glomerular injury
Tubular epithelial injury (Tubular necrosis)
Renal interstitial injury
What are the types of small vessel/glomerular injury diseases?
Vasculitis
Cholesterol emboli
Malignant hypertension
Acute glomerulonephritis
What is the common cause of glomerulonephritis?
Group A beta-hemolytic Strep
S. pyogenes is the most common.
What is the exact pathophys that causes glomerulonephritis? (Possible exam Q?)
The antibodies and antigens that react to S. pyogenes form a complex that gets stuck in basement membrane.
This causes the available membrane openings to become permeable to proteins and RBC, moving it into your filtrate.
Note:
The infection can occur elsewhere in the body 1-3 weeks prior, but the leftover antibodies and antigens are the issue. This makes it a type 3 hypersensitivity reaction, immune complex-mediated!
What are the two causes of tubular necrosis?
Renal failure, which is due to hypoxemia or poisons/toxins/meds killing the tubular epithelial cells.
Severe renal ischemia, which is due to shock. The dying tubular cells slough off and cover nephrons as they die.
What happens if only one kidney is blocked in postrenal acute renal failure?
Other kidney can usually maintain normal levels for a few hours, but if it is chronic, it can become irreversible.
What are the common causes of postrenal acute renal failure?
Blood clots/kidney stones in the ureters/renal pelvis.
Bladder obstruction (prostate in males is common)
Obstruction of the urethra.
What happens physiologically in postrenal acute renal failure?
Everything backs up.
Edema, HTN (Can’t excrete water)
Hyperkalemia (Can’t excrete K+)
Metabolic acidosis (Can’t excrete H+)
What are the nephrotoxic injuries that cause intrarenal acute renal failure?
Drugs
Contrast dye
Crush injury
At what nephron percentage do we start to see clinical symptoms?
under 70-75%.
What are the causes of chronic renal failure?
Metabolic disorders (DM, obesity, amyloidosis)
HTN
Renal vascular disorders
Immunologic disorders
Infections
Primary tubular disorders
Urinary tract obstructions
Congenital disorders
What is the final stage of chronic renal failure?
End-stage renal disease, AKA ESRD.
What are the two common treatments for ESRD?
ACEI
ARBs (which block AT1 receptors.)
Describe the cycle of ESRD.
Primary kidney disease causes decreased nephron number.
From there, the remaining nephrons have to hypertrophy and dilate to make up. The arterial pressure also increases.
All of this causes increased glomerular filtration/pressure.
This leads to glomerular sclerosis which eventually leads to more nephrons dying, and the cycle repeats.
What are the top 5 causes of ESRD?
DM (45%)
HTN (27%)
Glomerulonephritis (8%)
Polycystic kidney disease (2%)
Idiopathic/Other (18%)
Note:
Top two are commonly linked with obesity.
Renal vasculature injury can also lead to ESRD. What are the 4 causes that can do injury?
Atherosclerosis of the renal arteries
Fibromuscular hyperplasia of the large arteries
Nephrosclerosis (irreversible) of the smaller arteries
Benign nephrosclerosis
What is benign nephrosclerosis?
Most common form of kidney disease that is see in 70% of postmortem exams for patients > 60 yo.
It is characterized by lesions in the interlobular arteries and afferent arterioles.
What two conditions are concurrent with benign nephrosclerosis and worsen it?
HTN and DM greatly increase frequency and severity.
What is it called when lesions are in the glomeruli?
Glomerulosclerosis.
What are the two causes of glomerulonephritis?
Primary diseases (infection)
Lupus!!!
How does glomerulonephritis lead to ESRD?
Inflammation and damage to the capillaries.
The immune complexes precipitate and inflame the membranes, causing it to get thicker and invaded by fibrous tissue.
What is pyelonephritis?
Damage to the interstitium by bacterial infections.
Caused when bacteria in the fecal matter contaminates the urinary tract.
What happens as pyelonephritis progresses?
Cystitis occurs as the bladder gets inflamed next. It will progress higher to the renal pelvis and medulla eventually.
What is nephrotic syndrome?
Excretion of protein in the urine due to increased glomerular permeability. This causes a large loss of plasma protein in the urine.
Note:
Endothelium of the glomerulus normally repels proteins.
What are the causes of nephrotic syndrome?
Chronic glomerulonephritis
Amyloidosis
Minimal change nephrotic syndrome
What is minimal change nephrotic syndrome?
Loss of the negative charge of the membrane, but no major abnormalities.
It commonly occurs in children 2-6 and results in a low colloid osmotic pressure in the plasma, leading to severe edema.
Note:
Lack of colloid osmotic plasma pressure means fluid leaks out of the plasma.
