Kidney Patho Flashcards
Definition
Acute Kidney Injury (AKI)
Acute onset (hours to days)
3 types
1. pre-renal
2. intra-renal
3. post-renal
Increase in serum creatinine
Decrease urinary output
OR
BOTH
Definition
Oligouria
urinary output < / = 30cc/hour
Definition
Azotemia
Increased serum creatinine
Increase serum blood urea nitrogen (BUN)
BUN:Cr ratio > 20:1
*inability kidney to filter waste products (nitrogenous waste)
Definition
Uremia
Systemic signs and symptoms resulting from loss of kidney function (inability filter waste)
3 categories of acute kidney injury
- pre-renal
- before the kidney
- blood volume
- cardiac output
- obstruction blood flow - intra-renal
- inside the kidney - post-renal
- after the kidney
- obstruction of urine flow
Pre-renal AKI
Definition
Trigger –> decrease renal blood flow –> decrease glomerular perfusion, filtration
Triggers include
1. obstruction
2. decrease blood volume - hemorrhage, dehydration, third spacing
3. decrease cardiac output
4. decrease renal blood flow
Urinalysis and serum indicators
Pre-renal AKI
Decrease renal blood flow sensed by juxtaglomerular cells
Release renin and activation RAAS compensation
Reabsorption sodium, water, urea
- BUN:Cr > 20:1
Oliguria (< 30ml/hour)
High urine osmolality > 500mOsm/kg
- aldosterone promotes water reabsorption
Decreased excreted sodium
- FEna = Na excreted / Na filtered < 1%
Decrease glomerular filtration
increase creatinine, increase BUN
Most common cause of pre-renal AKI
sepsis
Compensatory systems
Decreased renal blood flow
- SNS
- NE and E released
- vasoconstriction - HPA axis
- Cortisol release
- vasoconstriction - ADH
- anti-diuretic hormone release
- reabsorption water - RAAS pathway
- vasoconstriction
- retention sodium and water
- reabsorption urea
Drugs that potentiate pre-renal AKI
Vasoactive medications
- dopamine
- ACE inhibitors
- ARBs
NSAIDS & Radioactive contrast dyes
- decrease blood flow to kidney
Definition
Intra-renal AKI
INtra-renal AKI
- intrinsic
- direct damage to the renal parenchyma
- results in nephron dysfunction
Causes of Intra-renal AKI
- Glomerulus: Glomerulonephritis
- Tubules: acute tubular necrosis
- Vasculature: infarct, thrombosis (pre-renal progresses to intra-renal)
- interstitial disease: infection, tumors (acute nephritis)
Most common cause of intra-renal AKI
Acute tubular necrosis (ATN)
Glomerulonephritis
Definition
Injury to the glomerulus
Leads to inflammation of the glomerular capillaries and destruction of the glomerular membrane
Acute or chronic
Nephrotic Syndrome
Definition
Results from injury to the glomerulus
Unable to prevent filtration of proteins
Results in >/= 3.5g / day of protein in urine
Pathophysiology
Acute Tubular Necrosis
- Injury: nephrotoxins
- Ischemia
Nephrotoxins
- direct damage to tubular epithelial cells
Ischemia
- Lack of blood supply
Tubular epithelial cell dysfunction
- Cannot reabsorb
- High urine sodium (> 30mmol/L)
- High FEna (Na excreted / Na filtered) > 1 %
- Low urine osmolality (<400mOsM/L)
- Low urine specific gravity (1.010-1.012)
- Low BUN:Cr ratio < 15:1 - Cannot secrete
- hyperkalemia
- metabolic acidosis (cannot secrete H+ ions) - Increase Tubular pressure = decrease GFR
- necrotic cells slough off
- plug the tubule
- formation brown casts in urine
- tubule opposes filtration pressure in artery
- decrease GFR
- increase serum creatinine, increase serum urea (azotemia)
- decrease urinary output (oliguria)
Factors required for reversible intra-renal AKI
- ischemia is not prolonged
- basement membrane is present
- tubular epithelial cells regenerate
Definition
Post-Renal AKI
Obstruction of urinary flow
Backs up into the renal pelvis
increase intra-tubular pressure
Decreases filtration
Causes of Post-Renal AKI
tumour
stones
trauma
strictures
prostate
neurogenic bladder
*< 5% of AKI
4 stages to the clinical course of AKI
- Initiation (onset)
- oligouria
- increase Cr
- increase BUN
-*reversible before damage at this stage - Extension
- ischemia
- inflammation - maintenance phase (oliguric phase)
- initiation event resolved
- injury established by extension phase (ischemia, inflammation)
- 10-14 days (healing inflammation)
- longer duration is poor prognosis - recovery phase (polyuria)
- most recovery within 3 weeks, can take up to 1 year for full recovery of function
Clinical Signs and Symptoms
Oliguric phase (maintenance phase) AKI
Oligouria
- decrease U/O
- normal SG (cannot reabsorb water)
- high urine sodium (cannot reabsorb sodium)
- low urine osmolality (cannot reabsorb water)
- BUN:Cr < 15:1
- FEna > 1%
Urinalysis
- RBC, protein (damage glomerular membrane)
- brown casts (tubular necrosis)
- WBC (inflammation)
FVO
- decrease GF = fluid retention
- edema, hypertension, heart failure
- pulmonary edema, crackles
- bounding pulses, jugular venous distention
metabolic acidosis
- tubules cannot excrete H+
- tubules cannot reabsorb HCO3-
- decrease pH
hyponatremia
- tubules cannot reabsorb sodium
- sodium excrete in urine
- hyponatremia serum
hyperkalemia
- tubules cannot excrete potassium
- hyperkalemia in serum
- cardiac dyrhythmias
hypocalcemia, hyperphosphatemia
- kidney cannot activate vitamin D
- cannot absorb calcium in GI
- PTH released increase bone reabsorption - increase phosphate in blood
Azotemia and neurological symptoms
- increase waste, creatinine, BUN
- fatigue, stupor, coma, confusion
Clinical Signs and Symptoms
Recovery (polyuric) phase
Kidney able to excrete waste (unable to concentrate urine)
result is polyuria > / = 3-5 L / day urine
Recovery function 1-3 weeks , up to 1 year
Risk in Recovery phase
dehydration
hypovolemia
electrolyte imbalances
Management of AKI
Hospital admission
- electrolytes
- monitor and manage sodium, potassium, calcium, phosphate - fluid
- monitor fluid volume overload / dehydration
- replacement / diuretics / dialysis - blood pressure and cardiac output = kidney perfusion
- dietary changes
- fluid volume restrictions
- sodium or potassium restrictions or supplements
- increase protein - dialysis
- acidosis, FVO, hyperkalemia - medication renal dose adjustments
Prevention of AKI
Renal dose adjustments for medications and age
Fluid to wash out nephrotoxic medications
Maintaining renal perfusion
- treating infections (sepsis)
- hydration and prevention dehydration
- monitoring fluids post operatively, trauma, burns
- maintaining healthy blood pressure and cardiac output
- maintaining normoglycemia
- maintaining healthy liver
Immediate treatment of urinary obstructions
- BPH, tumours, stones
Definition
Chronic Kidney Disease
Also known as
- renal insufficiency
- chronic renal failure
chronic, irreversible loss of kidney function
- nephron destruction
change in structure or function present for > 3 months
Classification
Chronic Kidney disease
- GFR
- Albuminuria
GFR
Stage 1, normal, > 90ml/min
stage 2, mild, 60-89ml/min
stage 3, moderate, 30-59ml/min
stage 4, severe, 15-29ml/min
stage 5, end stage renal disease < 15ml/min
albuminuria
stage 1, mild, < 3mg/mmol
stage 2, moderate, 3-30mg/mmol
stage 3, severe, > 30mg/mmol
Definition
Glomerular filtration rate
Amount of blood filtered in mL per minute by the glomerular membrane = number functioning nephrons = kidney function
Factors that affect GFR
Age
sex
height
weight
*serum creatinine
Over-estimation GFR
kidney actively secretes creatinine in addition to creatinine that is filtered at the glomerulus
Clinical ways to assess albuminuria
Urinalysis
- albumin
- creatinine
24 hour urinalysis
- albumin
- creatinine
POCT
- albumin dipstick
Who should be screened for CKD?
Anyone who has risk factors for CKD
- smoking
- diabetes
- hypertension
- hyperglycaemia
- physically inactive
Screen
1. GFR
2. albuminuria
earlier diagnosis = slow progression
Nephropathy secondary to Diabetes Mellitus
Pathophysiology
Clinical signs
- Hyperglycemia
- Inflammation -> scaring -> dysfunction glomerular filtration membrane/tubular dysfunction
hyperglycaemia –> oxidative radicals –> microvascular damage, glomerular filtration membrane damage, epithelial cell damage
glucose -> free radicals -> inflammation -> scaring/fibrosis -> decreased filtration, decreased tubular reabsorption, proteinuria, waste/FVO
Nephropathy secondary to hypertension
- HTN
- renal artery stenosis
- ischemia -> inflammation -> scarring/dysfunction (glomerular filtration membrane, tubular epithelium)
Hypertension –> microvascular damage –> renal artery stenosis –> decreased renal blood flow –> ischemia –> inflammation –> scarring/fibrosis –> damage and reduce glomerular filtration –> ischemia tubular epithelium –> dysfunction