Renal

Question 1

Define AKI.

Answer 1

An acute increase in serum creatinine level OR a decrease in urine output.
Technically:

• Increase in serum creatinine 1.5x baseline within 7 days
• Decrease in urine output to < 0.5mL/kg/hr for 6 hours

Question 2

What is your approach to treatment of AKI?

Answer 2

1. Determine likely mechanism of injury - treat underlying cause:
   - ? IV fluid resuscitation
   - ? relieve urinary tract obstruction - e.g. stent, nephrostomy tube etc.
   - ? discontinue causative medications
2. Prevent further injury
   - Discontinue all nephrotoxic drugs: NSAIDs, ACE-I, ARB
3. Correct any electrolyte abnormalities
   - Monitor: EUC at least daily
   - Limit sodium and K intake if necessary
   - RRT if necessary
4. Correct any fluid imbalance:
   - Monitor weight, fluid input and output
   - Fluid overload –> diuretic
   - Dehydration –> IV fluids
   - RRT if necessary
5. Correct any acid-base disturbance:
   - Monitor
   - RRT if necessary

Question 3

What are the complications of AKI?

Answer 3

IMMEDIATE
Fluid overload --> pulmonary oedema
Electrolytes --> hyperkalaemia
Metabolic acidosis
Uraemia --> 
Neurological: seizure, encephalopathy, decreased LOC --> coma
Haem: spontaneous bleeding

LONGER TERM
Progression to CKD
Requirement for long-term dialysis

Question 4

What are the features of nephrotic syndrome?

Answer 4

1. Proteinuria > 3.5g/24 hours (frothy urine)
2. Hypoalbuminemia
3. Oedema
4. Hyperlipidaemia

Question 5

What types of GN are associated with nephrotic syndrome?

What types of GN are associated with nephritic syndrome?

Answer 5

NEPHROTIC

• Minimal change disease
• Membranous
• Diabetic nephropathy
• FSGS
• SLE

NEPHRITIC

• IgA nephropathy
• Post-streptococcal GN
• Small vessel vasculitis: GPA, EGPA, microscopic polyangiitis
• Goodpasture syndrome
• SLE

Question 6

What are the features of nephritic syndrome?

Answer 6

1. Haematuria + RBC casts
2. Low level proteinuria < 3.5g/24 hours
3. Hypertension

Question 7

What is the best imaging test for a suspected renal stone?

Answer 7

NONCONTRAST

CT KUB

Question 8

What are the types of kidney stone?

Explain how they form including risk factors.

Answer 8

1. Calcium (>80% of all stones) - oxalate (80% of calcium stones) or phosphate (20% of calcium stones)
2. Struvite (10%) - typically in setting of UTI. Struvite is magnesium ammonium phosphate - urease producing organism (e.g. Klebsiella) –> splits urea producing ammonia –> increased concentration of ammonia and increased pH –> stone likely to form.
3. Uric acid (<10%) - assoc with gout
4. Cystine (2%) - from cystinuria (autosomal recessive disease of increase cysteine in urine)

Stones form when there are elevated urinary solutes (e.g. calcium) and decreased stone inhibitors (e.g. citrate) –> supersaturation of urine –> precipitation of solute –> stones.

RISK FACTORS:

• Past history - personal or family hx of stones
• Low fluid intake/ dehydration –> increased urine concentration
• Risk based on stone type:
• – increased urinary calcium (e.g. primary hyperparathyroidism)
• – gout
• – UTI
• – cystinuria

Question 9

How would you investigate a suspected kidney stone?

Expected findings?

Answer 9

Urinalysis - RBC + and WBC +. Nitrates also positive if UTI.
Urine MCS - RBC + and WBC + Bacteria and positive culture if superimposed UTI.
Crystals may be present

Bloods -
FBC, EUC, CRP, CMP, uric acid
EUC - creatinine may be raised if renal dysfunction secondary to stone/ obstruction

Imaging -
Non-contrast CT KUB is test of choice
May also use AXR for radio-opaque stones

Radio-opaque stones: calcium
Radio-lucent stones: uric acid, cystine
Variable: struvite - usually opaque but can be lucent

USS for pregnancy and paediatric patients

Stone analysis - stones are analysed after removal/ being passed — determine stone type.

To guide long-term management - 24 hour urine collection, ideally 6 weeks after stone passage/treatment.

Question 10

How would you treat a kidney stone?

Answer 10

Principles:

1. Analgesia
2. Hydration –> cannula + IV fluids
3. Treat stone

Conservative management for:

• Most stones pass spontaneously (especially if < 5mm)
• Provide analgesia + IV fluids as above
• Plus monitor - for development of infection, refractory pain or impaired kidney function.
• Alpha-1-antagonists can be trialled. Are effective in reducing the time taken for stones to pass.

If stones are unlikely to pass spontaneously (>10mm) or failure of conservative management – intervention performed. Possibilities are:

• Extracorporeal shock wave lithotripsy
• Uteroscopy
• Percutaneous nephrolithotomy

Urgent surgical intervention is needed for:

• Intractable severe pain and vomiting despite conservative management
• Superimposed UTI/ sepsis
• Obstruction from stone with anuria or AKI

4. Prevent recurrence
   - Increase water intake

If necessary, consider:

• Calcium stones –> thiazide
• Uric acid –> allopurinol