A 64 year old diabetic with vasculopathy undergoes an attempted endovascular repair of an abdominal aortic aneurysm. However the procedure is abandoned because of technical difficulties and he undergoes a surgical repair. In the first 6 hours after the procedure, he is noted to be oliguric and a blood test reveals a creatinine of 0.24 mmol/L (pre op value 0.15 mmol/L).

a) List 5 likely causes of deterioration in renal function.

The patient is administered IV fluids overnight. Despite stable blood pressure overnight, the next morning he is noted to be still oliguric. The plasma biochemistry is as follows:

Sodium 137 mmol/L (135-145)
Potassium* 6.3 mmol/L (3.2-4.5)
Chloride* 106 mmol/L (100-110)
Bicarbonate* 18 mmol/L (22-33)
Urea* 15.0mmol/L (3.0-8.0)
Creatinine* 0.34 mmol/L (0.07-0.12)
Total calcium* 1.75 mmol/L (2.15-2.6)
Phosphate* 2.75 mmol/L (0.7-1.4)
Albumin 26 g/L (33-47)
Globulins 35 g/L (25-45)
Total bilirubin 20 μmol/L (4-20 μmol/L)
Conjugated bilirubin 4 μmol/L (1-4 μmol/L)
GGT 6 U/L (0-50)
ALP 100 U/L (40-110)
LDH* 3800 U/L (110-250)
AST* 2100 U/L (<40)
ALT 100 U/L (<40)

a) List 5 likely causes of deterioration in renal function.

b) What is the likely cause of this plasma biochemistry?

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College Answer

a) List 5 likely causes of deterioration in renal function.

1.  Hypovolemia
2.  Abdominal compartment syndrome
3.  Renal artery trauma
4.  Low output state from myocardial dysfunction from cross clamping and

5.  peri-op ischemia
6.  Use of contrast
7.   Post op bleeding
8.  Ischemic rhabdomyolysis
9.  Nephrotoxic drugs

b) What is the likely cause of this plasma biochemistry?

Rhabdomyolysis from lower limb ischemia

Discussion

a) List 5 likely causes of deterioration in renal function.

Why has this patient's creatinine doubled?

There could be various reasons.

One may divide the answer by pathophysiological criteria (pre-renal, renal and post-renal) or one may organise them by aetiology. The following structures are suggested:

Answer organised by pathophysiology:

  • Pre-renal
    • Hypovolemia due to blood loss
    • Hypotension due to distributive shock, eg. sepsis
    • Cardiac failure
    • Renal vascular damage
    • Abdominal compartment syndrome
  • Renal
    • ATN due to prolonged aortic cross-clamp time
    • Nephrotoxicity due to drugs, eg. gentamicin or metformin
    • Contrast-induced nephropathy
    • ATN due to rhabodomyolysis
  • Post-renal
    • Intraoperative ureteric or bladder injury
    • kinked or malpositioned IDC

Answer organised by aetiology:

  • Vascular and cardiac causes
    • Renal vascular damage
    • Abdominal compartment syndrome
    • ATN due to prolonged aortic cross-clamp time
    • Cardiac failure with low cardiac output
  • Infectious causes
    • Septic shock due to bacterial translocation from the gut during a period of ischaemia, or from ischaemic bowel due to atheromatous emboli
  • Drug-related causes
    • Nephrotoxicity due to drugs, eg. gentamicin or metformin
    • Contrast-induced nephropathy
  • Traumatic causes
    • Hypovolemia due to blood loss
    • Rhabdomyolysis

b) What is the likely cause of this plasma biochemistry?

Well, its clearly rhabdomyolysis (LDH and AST are enzymes which leak out of ischaemic muscle).

The question about rhabdomyolysis following AAA repair was truncated and reused as Question 6.2 in the second paper of 2012, where one might find a more detailed discussion of this complication.

References

References

Dattilo, Jeffery B., et al. "Clinical failures of endovascular abdominal aortic aneurysm repair: incidence, causes, and management." Journal of vascular surgery 35.6 (2002): 1137-1144.

Vanholder, Raymond, et al. "Rhabdomyolysis." Journal of the American Society of Nephrology 11.8 (2000): 1553-1561.

Bosch, Xavier, Esteban Poch, and Josep M. Grau. "Rhabdomyolysis and acute kidney injury." New England Journal of Medicine 361.1 (2009): 62-72.

Woodrow, G., A. M. Brownjohn, and J. H. Turney. "The clinical and biochemical features of acute renal failure due to rhabdomyolysis." Renal failure 17.4 (1995): 467-474.

Miller III, C. C., et al. "Serum myoglobin and renal morbidity and mortality following thoracic and thoraco-abdominal aortic repair: does rhabdomyolysis play a role?." European Journal of Vascular and Endovascular Surgery 37.4 (2009): 388-394

Safi, Hazim J., et al. "Predictive factors for acute renal failure in thoracic and thoracoabdominal aortic aneurysm surgery." Journal of vascular surgery 24.3 (1996): 338-345.