Aki Flashcards
What is AKI
Abrupt disruption of kidney function including but not limited to acute renal failure
Which kidney is higher?
Left
Which peritoneal section are the kidneys
Retroperitoneal
Functions of the kidney
Acid base balance
Hormone regulation
Electrolyte balance
Blood pressure regulation
Toxin removal
Water balance
Where is both H+ and HC03- secreted in the kidney?
Proximal tubule
Where is H+ secreted in the kidney?
Proximal tubule and collecting ducts
What electrolyte determines ECF volumeV
Sodium
Perfusion of what allows the functioning of RAAS
Juxtaglomerular apparatus
How does the kidney regulate BP?
Volume of ECF (with sodium)
RAAS
What causes ADH secretion
Detection of increased plasma osmolality by hypothalamus
Where is ADH secreted from
Posterior pitusitarh gland
What toxins does the kidney remove?
Urea
Creatinine
Drug metabolites
How are toxins filtered by the kidney?
Glomerular filtration
Passive diffusion
Active transport
What can high urea cause
Uraemia encephalopathy
Uraemia pericarditis
What is the criteria for an AKI?
Rise in serum creatinine 26micromol/L or greater in 48 hours
50% greater rise in serum creatinine (more than 1.5x baseline) in last 7 days
Fall in urine output <0.5ml/kg/hour for > 6 hours - catheterised
What signs and symptoms should u suspect AKI in
N+V, diarrhoea, signs dehydration
Reduced urine output or colour change
Confusion, fatigue, drowsiness
What are methods of staging for AKI?
RIFLE criteria
KDIGO system
What is second stage AKI defined by?
100-199% creatinine rise from baseline in 7 days
Urine output <0.5ml in 12 hours
What criteria is 3rd stage AKI?
200% creatinine rise, 354 micro mil/L or more with acute rise
Urine output <0.3ml/kg/hr 24 hours, anuria for 12 hours
Risk factors for AKI
Diabetes
Emergency surgery
Intraperitoneal surgery
CKD if eGFR <60
Heart failure
Age over 65
Liver
Use nephrotoxic drugs
drugs need to stop in AKI
DAMN
Diuretics
ACEis/ARBs
Metformin
NSAIDs
Causes of loss of glomerular filtration rate (features of AKI)
Circulating volume overload
Hyperkalaemia
Acidosis
What reduces hydrostatic pressure in the glomerulus?
Hypotension
Renal artery stenosis
ACEi - efferent arteriole dilation
NSAIDs - afferent arteriole dilation
(NSAID +ACEi BAD)
What increases hydrostatic pressure in glomerulus
Urinary tract obstruction, hypertension
What do kidneys vitally control in the short term?
Maintenance of electrolyte homeostasis
Fluid homeostasos
Excretion of toxins
Regulation of acid base balance
Long term kidney functions
Hormone production
-> anaemia, renal bone disease
Pre-renal causes of AKI
Blood supple - hypovolaemia (haemorrhage), hypotension (sepsis, dehydration, shock)
Decreased circulating volume = cirrhosis, congestive HF
Medications - NSAIDs
Third space loss/intersitiial fluid loss
Narrowing of renal artery - thrombosis, stenosis
Hepatorenal syndrome
What is hepatorenal syndrome?
Rapid deterioration in kidney function in people with fulminant or fulminant hepatic failure. Caused due to back up in splanchic circulation, portal veins. Need liver transplant, otherwise manage with dialysis.
Investigations pre renal cause of AKI
Bloods, U+Es, LFTs, bone profile, CK, FBC, CRP
Dipstick analyisis
ECG
CXR
Urinary creatinine/serum creatinine
Urine osmolarity
Sediment
Renal doppler US
Fractional excretion of Na
Renal causes of AKI
Acute tubular necrosis
Acute intersistitial nephritis
Glomerular disease
Glomerulonephritis
Intratubular obstruction
Polycystic kidney disease
What is acute tubular necrosis?
Death of epithelial cells of renal tubules
Most common cause of AKI
Reversible - cells can regenerate. Week to a month recovery
Cuaes of acute tubular necrosis
Ischamia secondary to hypoperfusion
-shcok, sepsis, dehydration
Direct damage from toxins
-Gentomycin, radiology contrast dye, NSAIDs
What do you find on urinalysis in acute tubular necrosis?
Muddy brown cast
What is acute interstitial nephiritis and what causes it?
Inflammation of nephrons - hypersensitivity reaction atypical
-Autoimmune
-Drugs - NSAIDs, penicillin
Infection - TB, pneumonia
Sarcoidosis
What often presents alongside acute interstiial nephritis if caused by NSAIDs?
Nephrotic syndrome
Nephrotic vs nephritic syndromes
Both glomeruklar diseases
Nephrotic is a loss of protein -> hypoalbuniaemia -> oedema
Nephritic - lose blood, cause HPTN
https://geekymedics.com/nephrotic-vs-nephritic-syndrome/
What is goopasteurs syndrome?
Rare autoimmune disease where antibodies attack basement membrane in kidney andlungs leading to haemoptysis, glomerulonephritis and acute renal failure.
anti-GBM antibody
https://rarediseases.info.nih.gov/diseases/2551/goodpasture-syndrome/
Glomerular diseases causes of AKI
Nephrotic and nephritic syndrome
Good pastuers syndrome
Systemic autoimmune eg IgA vasculitis, granulomatosis with polyangitis
Inflammation of glomeruli and small blood vessels
What is intratubular obstruction?
Increase tubular pressure by increasing eGFR
Large protein deposits eg rhabdomyolysis and myeloma cuase blockage
Investigations renal causes of AKI
History and exam
Bloods
Urinalysis
US
Nephrology for biopsy
Post renal causes of AKI
Urinary retnetion - obstruction
Renal calculus
Pyelonephrosis
Pelvic mass
Enlarged prostate
Carcinomas
Blood clot in ureter - catheter trauma, cancer
Stricture
Neurogenic bladder - ketamine
Investigations post renal causes
CT no contrast
CTKUB for renal calculi = gold standard.
What does dilatation of the ureters on CT suggest?
Hydronephrosis
What calculi will not show up on CT?
Uric acid - not radioopaque
What presentation suggests an AKI?
N+V or diarrhoea, evidence of dehydration
Reduced urine output or change colour
Confusion, fatigue, drowsiness
How do you stage an AKI?
RIFLE criteria
KDIGO system
AKIN
RIFLE staging
RISK - 1.5 x creatinine / GFR decrease >25% / <0.5ml x 6 hrs
INJURY- 2 x creatinine / >50% decline GFR, <0.5ml/kg/hr urine in 12hrs
FAILURE -
3x SCR or >75% decreased GFR or if baseline SCR >353.6umol/L or increased by >44.2
<0.3mol/kg/hr, 24 hrs or anuria x 12hrs
Persistent ARF =
Loss of kidney function
Complete loss >4 weeks
End stage kidney disease >3 months
Risks for AKI
Emergency surgery
INtraperitoneal surgery
CKD ie eGFR < 60
Diabetic
HF
>65
liver
Nephrotoxic drug use
What to look for in bloods AKI
- Anaemia
- Biochem
- Increase UR + Cr
- Increased potassium, phosphate
- Decrease Ca, HC03, albumin
- ABGs go deeper - anion gal = sodium -(chloride and HC03-)
- Normal = 4-13
- Higher anion gap >12
Management on AKI
Stop offending drugs - DAMN
IV fluids
Improve renal perfusion
Treat precipitants
Monitor U+Es and fluid balance closely
Indications fro renal replacement therapy
AEIOU
Acidosis
Electrolytes - refractory hyperkalaemia
Intoxication
Overload - pulm oedema
Uraemia - encephalopathy, pericarditis
What can use to monitor kidney function
eGFR
CrCl 0 estimation of eGFR, slightly higher than true value, some creatinine secreted in porximal tubule adds to calue
DAMN drugs
Diuretics - exacerbate dehydration and hypopefusion
ACEis/ARBs → vasodilation efferent arteriole, hypoperfusion, aspirin (aminoglycosides - gentomycin)
Metformin → lactic acidosis, methotrexate
NSAIDs → prostaglandin vasodilation reduced, renal hypopeefysion
Other offending drugs
Statins, CCBs,
Summary of causes of acute kidney injury
Pre-renal (most common) — due to reduced perfusion of the kidneys and leading to a decreased glomerular filtration rate (GFR).
Intrinsic renal — structural damage to the kidney, eg tubules, glomeruli, interstitium, and intrarenal blood vessels. damaging renal cells
Post-renal — acute obstruction of urine flow resulting in increased intratubular pressure and decreased GFR
Groups at higher risk of AKI
> 65
Prev AKI
CKD
Symptoms or history urological obstruction - at risk conditions
HF, liver disease, DM
Sepsis., Hypovolaemia.
Oliguria
Cancer and cancer therapy
Immunocompromise
Toxins
In last week:
Nephrotoxic drug - (NSAIDs), (ACE) inhibitors, (ARBs), and diuretics.
Exposure to iodinated contrast agents
Complications of AKI
Hyperkalaemia
Electolyte imbalances - hyperphosphatemia, magnesaemia, hypnatremia, calcemia
Metabolic acidosis
Volume overload - peripheral and pumonary oedema
Uraemia
CKD and end stage renal disease
Predictors for CKD after AKI
older age, lower baseline eGFR, higher baseline albuminuria, and higher stages of AKI
Symtpoms of uraemia and how treat
Confusion, lethargy, altered LOC
Dialysis
Presentation of metabolic acidosis
altered LOC, circulatory collapse, hyperventialtion
Hyperkalaemia presentation
Asymptomatic until severe
Muscle weakness, paralysus, cardiac arrhytmias, cardiac arrest
When there is an illness with no clear acute componenet, which features would make you suspect an AKI?
Chronic kidney disease (stage 3B, 4, or 5), or urological disease.
New onset or significant worsening of urological symptoms.
Symptoms or signs of multi-system disease - kidneys and other organ systems
Symptoms of complications of AKI
What test can flag AKIs early?
AKI warning stage test result from electronic detection systems in a lab
3 stages measuring creatinine levels
Determines how quickly admit/patient is monitored how often
What to do if no creatinine prev abailvabe
Repeat within 48-72 hours and compare
What to consider in people who take trimethoprin?
False positives for serum creatinine - increases but does not affect eGDR
Volume status assessment
Fluid intake and losses.
Peripheral perfusion (capillary refill time).
Heart rate/blood pressure (and any postural changes).
Jugular venous pressure.
Moistness of mucous membranes, skin turgor.
Changes in urination pattern.
For peripheral oedema and pulmonary crackles
Questions to ask about possible underlying causes
Current symptoms, if the person is unwell
underlying obstructive cause
History of CVSD increasing the risk of impaired renal perfusion.
Symptoms of an underlying inflammatory process
Drug history
Possibility of rhabdomyolysis
What does a negative urinalysis but AKI symptoms indicate?
Pre renal cause
Symptoms of urinary obstruction
(for example lower urinary tract symptoms, bloating from a pelvic mass, renal colic).
Symptoms of underlying inflammatory process
(for example vasculitic rash, arthralgia, epistaxis, or haemoptysis).
Causes of rhabdomyolysis
skeletal muscle injury, muscle overexertion, crush injury, prolonged immobility.
Why are patients with neuroglogical deficits more likely to get an AKI?
fLUID INTAKE more difficult to regulate themselves or regulated by a carer
WHat is oliguria
(urine output less than 0.5mL/kg/hour).
COmplications of UTI
Hyperkalaemia + other electrolyte disturbances
Pulmonary oedema
Metabolic acidosis
Uraemic pericarditis, encephalopathy
electrolyte disturbances caused by AKI
Hyperkalaemia
Hyperphosphatemia
Hypermagenesiumia
Hyponatremia
Hypocalcemia
Pre renal causes AKI
Hypovolaemia
Decreased cardiac output
Drugs that reduce BP
Renal causes AKI
Drugs
Vascular
Glomerular - nephritits, good pasteur
Tubular - ischaemia, meyloma, contrast agent
Interstitiatl - interstitial nephritis eg ascending UTI
Obstructions that can cause AKI
Renal stones, pyelonephrosis, blocked cathertet, pelvic mass, enlarged prostate, cervical carcinoma, ,retroperitoneal fibrosis
Urine investgiatones - bedside AKI
Dipstick
Microscopy, culture and sensitivity
Electrolytes abd somolalilty
What test for on dipstick for AKI
Blood
Protein
Leucocytes
Nitrities
Glucose
Detects glomerulonephritis, acute pyelonephritis and intersitital nephritits
Bloods in AKI
FBC
U+Es
LFTs
Creatinine kinase
Immunology
CRP/ESR
Virology
ABG
Blood culture - sepsis
What can increased eosinophils suggest in AKI>
Acute intertitial nephritis, cholesterol embolisation and vasculitis
What suggests thrombocytic microangiopathy in bloods
Decreased platelets
Haemolytic anaemia
Why chcek for creatinine kinase in AKI
Rhabdomyolysis
Immunology tests in SLE
ANA, anti-DsDNA, decreased C3, C4
What condition suggests ANCA
Granulomatosis with polyangitis
Imaging for AKI adn why
CXR - rule out oedema
US KUB - urinary retention
Doppler US - assess renal artery
MRA - renal vascular occlusion
Presentation of AKI
Nausea, vomitting, dehydration, confusion, oliguria or anuria
AKI warning stage 1
Creatinine >1.5 x baseline OR >26mol<48 hrs
AKI warning stage 2
Current creatinine >2 x baseline level
AKI warning stage 3
Current creatinine >3 x baseline
OR 1.5 x baseline and >354 umol/L
What is azotemia
High levels of nitrogenous compounds in the blood
Neurogenic causes of postrenal AKI
DM
MS
Spinal cord compression
Cauda equina
Anticholinergics
Sympathomimetic drugs
Clinical signs of AKI
Oliguria, anuria
Hypovolaeia signs
Volume overload - HPTN, pulmonary/peripheral oedema
Uraemia - encephalopathy, ecchymosis (platelet dysfunction)
Post renal obstrucution - tender/palpable bladder
Bedside investigations AKI
Urine dipstick
Urine micoscopy
Urine osmolality and electrolytes
ECG
Urine studies
Urinalysis
Urinary PCR or nephritic screen
Urine volume/output
Microscopy and sediment - cast, crystals
Urine osmolarity and specific gravity
Urine eosiniphil count - AIN evaluation
Bloods in AKI
FBC - Hb, platelets, WCC
U+Es - Creatnine, urea, potassium, sodium
ABG/VBG
For intrinsic:
CK
Vasculitis screen - ANCA, ANA
Clotting
Blood film
Complement
Immunoglobulins
Serum electrophroesus
Virology (hep B/C)
Imaging for AKI
US - key fo robstructive pathology
non contrast CT for urinary stones
CXR
Renal dopplers
MR angiography
CT urogram
Indications for renal biopsy
Intra renal AKI cause or sus rapid progressive glomerulonephritis -
Unexplained renal impairment
- Unexplained glomerular haematuria
- Renal masses - urology
- Renal transplant
- Rejection
- Dysfunction
- Connective tissue diseases
- Treatment monitoring/research
General management AKI
Withdrawal nephrotoxic meds (DAMN) + adjust renally cleared drug doses
Fluid resus + monitoring
Catheterise to monitor output
Evidence of spesis
Daily U+Es
Treat causes and complications
What to do in pulmonary oedema patients with AKI
Can give diuretics - weigh up benefits and risks
What is considered in AIN or RPGN to slow progression
Immunosupression
Indications for renal replacement therapy
A - acid 0- Metabolic acidosis <7.15 or worsening
E - electrolytes - Refractory electrolyte abnormalities - hyperkalemia >6.5
I - intoxication - Presence of dialysable toxins
O - Overload - Refractory fluid overload
U -Uraemia - End organ uraemic complications - pericarditis, encephalopathy
What substances are dialysable in intoxication
Methanol, ethylene glycol, lithium, ASA
Any severe posisonning or drug overdose suitable
Types of continious renal replacement therapy
Cont. venovenous haemodialysis - CVVHD
Cont, venovenous haemofiltration - CVVHF
Cont venovenous haemodiafiltration - CVVHDF
Complications AKI
Fluid overload
Electrolyte derangement
Metabolic acidosis
End organ complications
CKD
End stage renal disease
Treatment for rhabdomyolysis
IV fluids - 0.9% sodium chloride at 10-15ml/kg/hr to achieve urine (>100ml/hr),adding f sodium bicarbonate 1.4% to maintain urinary pH> 6.51.
AND regularly monitor CK and U+Es
