AKI + CKD Flashcards
Acute kidney injury definition
and
KDIGO guidelines
Abrupt and sustained decrease in kidney function.
- Rise in serum creatinine >26 micromol/L within 48 hours OR
- Rise in serum creatinine >1.5x baseline (before AKI) within 7 days OR
- Urine output <0.5ml/kg/h for >6 consecutive hours
Pathophysiology of pre-renal AKI
-
Decreased blood flow to glomerulus due to:
- Volume loss
- Reduced cardiac output
- Systemic vasodilation
- Renal vasclature
-
Decreased blood filtration leading to:
- Reduced urine output
- Raised urea (increases more than creatinine)
- Raised creatinine
Symptoms of AKI
- Oligouria / anuria
- Confusion
- Nausea
- Shortness of breath
Signs of AKI
- Peripheral oedema
- Chest crackles (pulmonary oedema)
- Raised JVP
- Haematuria
- Proteinuria
Which medications need to be stopped in AKI?
- ACE inhibitor; angiotensin receptor blocker: dilates efferent arteriole
- Diuretics: reduce flow through tubular capillaries
- NSAIDs: constricts afferent arteriole
Managment of AKI pre-renal AKI
- IV fluid bolus: treat hypovolaemia with 250-500ml boluses of crystalloid
- Maintainance fluids
- Serial VBGs: monitor lactate for tissue hypoperfusion
Renal causes of AKI
- Glomerular
- Glomerulonephritis conditions
- IgA nephropathy
- SLE
- Amyloidosis
- May present as acute kidney injury, more commonly will present with nephrotic or nephitic syndrome
- Glomerulonephritis conditions
- Interstitium
- Acute interstitial nephritis
- Neutrophils/eosinophils infiltrate the interstitium of the kidney
- NSAIDs
- Penicillin
- Diuretics
- Acicloir
- May present as AKI, more commonly will present with: rash, joint pain, eosinophils
- Acute interstitial nephritis
- Tubular
-
Acute tubular necrosis
- Ischaemia
- Rhabdomyolysis (eg myoglobin)
- Aminoglycoside antibiotics (eg amikacin, gentamicin)
- Lead
- Ethylene glycol (anti-freeze)
- Aciclovir
- Good prognoisis as tubular cells continually replace within 1-3 weeks
-
Acute tubular necrosis
- Renal vascular supply
- Not to be confused with glomerular blood supply (for ultrafiltration)
What does muddy brown casts in urine indicate?
Tubular necrosis
Investigations in AKI
- Bloods
- Serum urea : creatinine ratio
- WCC
- CRP
- Cultures
- VBG
- Urine
- Dipstick
- MC&S
- Sodium
- Imaging
- Renal US
- Bladder scan
- CT KUB (non-contrast)
- Special tests
- Renal biopsy
Urea : creatinine ration interpretation
Urea : creatinine ratio
- > 100:1 = pre-renal
- <40:1 = renal
- 40-100 = normal/post renal
Distinguishing features of renal AKI
- Unresponsive to fluids or catheterisation
- Complex medical history
- Nephrotoxic agent use
- Low urea : creatinine ratio
- High urine sodium
Causes of post renal AKI
- General:
- Urinary tract infection
- Kidney stone
- Malignancy
- Strictures
- Specific
- Enlarge prostate. (BPH)
- Phimosis
- Occluded in dwelling catheter
- Pharmacological
- Anti-cholinergics
- alpha-adrenergic agonists
- Calcium channel blockers
Managment of post-renal AKI
- First line
- Flush catheter OR replace catheter OR insert new catheter
- Stop medications eg amitrptyline
- UTI
- Empirical antibiotics whilst awaiting sensitivities
- Ureteric stones
- <5mm: wait to pass
- 5-10mm: tamsulosin or nifedipine; lithotripsy; uteroscopy
- >5mm: ureteroscopy; lithotripsy
- Malignancy
- surgery and/or chemotherapy
Complications of AKI
- Metabolic acidosis
- Hyperkalaemia
- Oedema (due to loss of normal glomerular filtration leading to fluid accumulation)
- Encephalopathy (secondary to uraemia)
- Pericarditis (secondary to uraemia)
Criteria for CKD
GFR <60 on at least 2 occasions separated by a period of at least 90 days
Most common causes of CKD
Diabetes and hypertension
Symptoms of CKD
- Lethargy
- Pruritus
- Nausea
- Anorexia
- Swollen ankles
Signs of CKD
- Hypertension
- Fluid overload
- Proteinuria (frothy urine)
- Uraemia sallow: a yellow or pale brown colour to the skin
- Evidence of underlying cause: eg butterfly rash in lupus
Investigations in CKD
- Urine dip: screen for proteinuria and haematuria
- Urine albumin : creatinine ratio: a ratio of >3mg/mmol is clinically significant proteinuria
- U&Es: serum creatinine can be used to calculate eGFR
- FBC: normocytic normochromic anaemia
- Bone profile and PTH: patients are at risk of hypocalcaemia, hypophosphateaemia, and secondary or tertiary hyperparathyroidism
- Renal ultrasound
What lifestyle advice would you give to a patient with CKD?
- Smoking cessation, exercise, drinking alcohol in moderation
- Avoid nephrotoxic medications eg NSAIDs
- Dietary advice: low salt and potassium diets, with fluid restriction if there is evidence of overload
Managment of anaemia in CKD
- Target Hb: 100-120 g/dl
- Iron replacement: commence iron replacement, either orally or intravenously, prior to commencing ESAs; particularly important in patients on haemodialysis
- Erythropoiesis stimulating agents: eg erythropoietin (EPO)
When is renal replacement therapy initiated?
- Typically performed when eGFR is in single digits (CHD stage 5) or there are signs or uraemia
- Dialysis is usually commenced first, followed by renal transplantation if the patient is eligible
Complications of CKD
Cardiovascular
Musculoskeletal
Endocrine
Haematological
Metabolic
- Cardiovascular
- Cardiovascular disease is the leading cause of death in CKD
- Heart failure: due to fluid overload
- Musculoskeletal
- CKD metabolic bone disease
- Endocrine
- Secondary hyperparathyroidism
- Tertiary hyperparathyroidism occurs after a prolonged period of secondary hyperparathyroidism
- Haematological
- Anaemia: usually normocytic and normochromic and is multi factorial; predominantly due to low EPO, but also reduced erythrpoiesis due to uraemia, reduced iron absorption and anorexia due to uraemia
- Metabolic
- Uraemia
- Hyperkalaemia
- Metabolic acidosis
CKD-metabolic bone disease expected laboratory results
Serum calcium
Serum phosphate
Serum vitamin D
Serum PTH
Alkaline phosphatase (ALP)
- Serum calcium: reduced
- Serum phosphate: increased
- Serum vitamin D: reduced
- Serum PTH: increased
- Alkaline phosphatase (ALP): increased
Staging of CKD
G1: >90ml/min, with some sign of kidney damage on other tests
G2: 60-89ml/min
G3a: 45-59ml/min
G3b: 30-44ml/min
G4: 15-29ml/min
G5: <15ml/min