Week 10 Flashcards
What is AKI
Abrupt decline in renal function (GFR)
Criteria for AKI
Serum creatinine increases by >1.5x baseline
Urine output <0.5ml/kg/hour for 6 hours
Classification of AKI
Pre renal
Intrinsic
Post renal
Broad causes of pre renal failure
Low effective circulating volume
Impaired renal auto regulation
What can cause low ECV
Hypovolaemia - blood or fluid loss (D&V
Cardiac failure - LV dysfunction, cardiac tamponade, valve disease
Systemic vasodilation - sepsis, anaphylaxis, cirrhosis
What can cause impaired renal auto regulation
Afferent vasoconstriction - sepsis, NSAIDs, hypercalcaemia
Efferent vasodilation - ACEi, AT2 receptor antagonists
Treatment and outcome of pre renal failure
Aldosterone and ADH are released to restore blood flow
Responds well to fluid resuscitation
Will progress to ATN without treatment
Causes of intrinsic renal failure
Renal artery/vein occlusion Acute glomerulonephritis Acute tubular necrosis Acute tubular interstitial nephritis Intra renal obstruction Intra renal vascular disease
Describe acute tubular interstitial nephritis
Inflammation of intersticium
Due to:
Infection - acute pyelonephritis
Toxin - antibiotics, PPIs, NSAIDs
Do you give fluid resuscitation for ATN
No
Risks volume overload
Causes of ATN
Ischaemia - usually secondary to pre renal failure
Nephrotoxins
Sepsis
What is most affected in ATN and why
S3 segment
High metabolic acid and has a nearly hypoxic supply with normal perfusion
Difference between pre renal failure and ATN
Urine Na is low in pre renal and high in ATN
Endogenous nephrotoxins
Urate
Billirubin
Myoglobin (rhabdomyolosis)
Exogenous nephrotoxins
Loop diuretics Aminoglycosides ACE inhibitors Endotoxins XR contrast NSAIDs Weedkiller Antifreeze
What must occur for post renal failure to occur
Obstruction blocking both kidneys or a single functioning kidney
Causes of post renal failure
Lumen - stones, tumour, blood clot, papillary necrosis
Wall - neurogenic bladder, megaureter, pelivureteric neuromuscular dysfunction, bilateral Ureteric stricture
Pressure from outside - BPH, tumour, abdominal aneurysm, ligation of ureter
What does post renal failure cause
Hydronephrosis
Investigations for AKI
Urea
Creatinine
K, Na, Ca and PO4
(In serum and urine)
Investigations for pre renal AKI
Look for shock and vascular disease
Investigations for intrinsic AKI
Nephrotoxins
Parenchymal disease
Multi system diseases e.g UTI
Investigations for post renal AKI
Anuria
Prostatism
Signs of depleted volume
Cool peripheries Tachycardia Low BP Low JVP Low skin turgor Dry axillae Sunken eyes
Signs of volume overload
Gallop rhythm
High BP
Raised JVP
Pulmonary, ankle and sacral oedema
Signs of urinary tract obstruction
Anuria Loin or suprapubic pain History of renal stones Previous pelvic or abdominal surgery Palpable bladder or kidney Prostatism
Urine investigations for AKI
Urine dipstick - proteins and blood = intrinsic Microscopy: Normal = pre renal RBC casts = glomerulonephritis Muddy brown granular casts = ATN
Imaging for AKI
Ultrasound within 24 hours if unknown cause or suspected post renal AKI
Biopsy if pre and post renal have been ruled out
CXR to look for fluid overload or infection
Antibody detection in intrinsic AKI
Antinuclear antibody - SLE
Anti neutrophil cytoplasmic antibody - vasculitis
Collagen IV glomerular BM antibody - Good pastures syndrome
Treatment of AKI
Volume overload - restrict dietary Na and water
Hyperkalaemia - calcium gluconate, insulin, glucose
Acidosis - NaHCO3
Nutrition
Remove nephrotoxins (might need dialysis or chelation)
Dialysis if no improvement
First line investigation in asymptomatic glomerular disease picked up by urine dipstick (protein and bloods)
Flexible cystoscopy
Appearance of macroscopic haematuria with glomerular disease
Brown
Episodic
Reasons for brown urine
Glomerular disease
Haemoglobinuria
Myoglobinuria
Consumption of food dyes
Commonest cause if macroscopic haematuria
IgA nephropathy
