A previously healthy 24-year-old male has been admitted to your ICU with a pelvic fracture following a motor vehicle accident. He has been haemodynamically stable. The following results are obtained:

Parameter

Patient Value

Adult Normal Range

Sodium 

142 mmol/L

135 – 145

Potassium  

3.8 mmol/L

3.5 – 5.0

Chloride 

102 mmol/L

95 – 105

Bicarbonate 

22.0 mmol/L

22.0 – 26.0 

Glucose 

5.9 mmol/L

3.5 – 6.0

Urea 

41.0 mmol/L*

3.0 – 8.0

Creatinine  

520 μmol/L*

45 – 90 

Magnesium

0.81 mmol/L

0.75 – 0.95

Albumin 

42 g/L

35 – 50 

Protein 

63 g/L

60 – 80

Total bilirubin 

9 μmol/L

< 26

Aspartate aminotransferase (AST) 

21 U/L

< 35

Alanine aminotransferase (ALT)

15 U/L

< 35

Alkaline phosphatase (ALP)

34 U/L

30 – 110

γ-Glutamyl transferase (GGT)

21 U/L

< 40

Ionised calcium 

1.14 mmol/L

1.10 – 1.35

Calcium corrected 

2.40 mmol/L

2.12 – 2.62

Phosphate 

1.1 mmol/L

0.8 – 1.5

Creatinine Kinase 

180 U/L*

55 – 170 

         a) What is the likeliest diagnosis?                                                                             (20% marks)

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College answer

a) Ruptured bladder

Examiners Comments: 
 
Generally, these questions were answered well. Those candidates that failed, missed all or part of the question or misinterpreted what was being asked, reiterating how important it is to read the question and understand what is required before starting to answer. 

 

Discussion

The salient features of history are:

  • Pelvis fracture
  • Haemodynamic stability
  • Previous good health

The biochemical abnormalities are:

  • High creatinine
  • High urea

The relevant negative features are:

  • Normal acid-base balance
  • Normal phosphate

All of these (but mainly the apparent "renal failure" and otherwise normal patient story)  suggest bladder rupture due to pelvic injuries, a well-described bit of exotica from the Journal of Urological Oddities. One good article is Heyns & Rimington (1987) who reported on a series of 20 such patients. The best description of the biochemistry involved is offered by Wystrychowski (1996), who described "uroperitoneum" as resulting in a "reverse autodialysis " of urine. Other associated features are usually haematuria, "ascites", acidosis hyponatremia and a raised potassium, which in this case all appear to be normal. The scenario is in fact not completely realistic because all of the features of renal failure should be present; in human trauma victims and in experimental bovine models there is usually significant acidosis, which is usually a normal anion gap variety. For instance, in this case report from Pintar & Wilke (1998) the bicarbonate was 13 mmol/L and potassium was 7.5 mmol/L. 

References

Heyns, C. F., and P. D. Rimington. "Intraperitoneal rupture of the bladder causing the biochemical features of renal failure." British journal of urology 60.3 (1987): 217-222.

Sockett, D. C., et al. "Metabolic changes due to experimentally induced rupture of the bovine urinary bladder." The Cornell veterinarian 76.2 (1986): 198-212.

Kilari, S. K., et al. "Pseudo-renal failure due to intraperitoneal bladder rupture and silent subdural hematoma following a fall in an alcoholic." International urology and nephrology 39.3 (2007): 947-949.

Wystrychowski, A., M. Nowicki, and F. Kokot. "Hyponatraemic renal pseudofailure—don't forget the possibility of uroperitoneum." Nephrology Dialysis Transplantation 11.12 (1996): 2491-2492.

Pintar, Thomas J., and Russell A. Wilke. "Urinary ascites: spontaneous bladder rupture presenting as acute oliguric renal failure." The American journal of medicine 105.4 (1998): 347-349.