Renal

Question 1

Definition of AKI

Answer 1

Any of:
- Increase in creatinine by >26.5mmol/L within 48hr
- Increase in creatinine to ≥1.5x baseline which is presumed to have occurred within the last 7 days
- Urine volume <0.5ml/kg/h for ≥6 hours

Question 2

Acute Tubular Necrosis

Answer 2

Ischaemic ATN essentially an extension of pre-renal AKI

Toxic ATN causes:
- Endotoxins: Myoglobin, Casts from MM, SLE
- Exotoxins: Aminoglycosides, IV contrast, chemo,

Oliguria = key predictor of need for RRT

Question 3

Acute Interstitial Nephritis

Answer 3

Drugs: beta lactams, PPI, NSAIDs, Immunotherapy
Immune Mediated: Sjogren’s, Sarcoidosis, IgG4 Disease

Diffuse cellular infiltrate on biopsy

Question 4

Urine Testing and Rhabdomyolysis

Answer 4

Positive dipstick for haematuria with absence of blood on microscopy is indicative of presence of myoglobin

Question 5

Urine Casts

Answer 5

Hyaline: exercise, dehydration
Renal Tubular Epithelial Cells: suggests ATN
Granular: suggests ATN (appears muddy brown)
White Cell: Rarely isolated, suggests AIN
Dysmorphic Red Cells/RBC Casts: GN

Question 6

Ultrasound features suggesting chronicity of kidney injury

Answer 6

Reduced kidney size
Reduced cortical thickness
Reduced echogenicity

Question 7

Fluid Management in AKI

Answer 7

Restrictive fluid approach:
- Increased AKI in abdominal surgery
- No difference in ARDS or Cardiothoracic surgery

Fluid overload is associated with higher mortality

Modest benefit of crystalloid over normal saline for renal outcomes, similar for albumin

Question 8

Renal Replacement Therapy in AKI

Answer 8

No different in mortality between early and late initiation
Delaying RRT can avoid RRT in 29% of patients

Question 9

Urine Sodium in AKI

Answer 9

Urine Sodium and FENa used to distinguish Pre-Renal and ATN
Urine sodium >40 - ATN
FENa: >1% = ATN

FENa not confounded by volume state
These tests only indicated in oliguric AKI without diuretic use, CKD, obstructive cause, GN

Question 10

Type 1 Renal Tubular Acidosis

Answer 10

• Hypokalaemic distal renal tubular acidosis
• Decreased distal tubule hydrogen ion secretion
• High urine pH
• Low urine pH → low urinary citrate → calcium phosphate stone formation
• Causes: Inherited, SLE, Sjogren’s, Drugs
• Management: Potassium citrate
• Can cause Osteomalacia and Rickets

Question 11

Type 2 Renal Tubular Acidosis

Answer 11

• Proximal RTA
• Impaired bicarb reabsorption in proximal tubules → renal bicarb loss
• Causes: Fanconi Syndrome
• Low urine pH, raised urine glucose, protein, phosphate
• Mild hypokalaemia
• 1,25-Colecalciferol deficiency → hypocalcaemia and osteomalacia
• Treat cause as bicarb doesn’t work well

Question 12

Type 4 Renal Tubular Acidosis

Answer 12

• Hyperkalaemic distal RTA
• Causes: Addison’s, other hypoaldosteronaemic states
• Potassium not secreted, ammonia not produced
• Management of hyperkalaemia corrects acidosis as it allows increased ammonia production

Question 13

Fanconi Syndrome

Answer 13

Proximal tubular malfunction

Leads to loss of: amino acids, glucose, phosphate, bicarbonate

Causes: congenital, idiopathic, Wilson disease, Heavy metals, Gentamicin, Myeloma, Amyloid, Sjogren

Manage cause and replace losses to treat