The following venous blood results are from a 56-year-old patient presenting with abdominal pain.
Parameter |
Patient Value |
Adult Normal Range |
Sodium |
130 mmol/L* |
135 – 145 |
Potassium |
5.1 mmol/L* |
3.5 – 5.0 |
Chloride |
101 mmol/L |
95 – 105 |
Bicarbonate |
10 mmol/L* |
22 – 28 |
Creatinine |
305 mmol/L* |
50 – 100 |
Urea |
75.6 mmol/L* |
3.5 – 7.2 |
Glucose |
5.2 mmol/L |
3.5 – 6.0 |
Calcium corrected |
2.05 mmol/L* |
2.12 – 2.62 |
Ionized Calcium |
0.97 mmol/L* |
1.14 – 1.30 |
Phosphate |
3.97 mmol/L* |
0.73 – 1.37 |
Protein |
66 g/L |
61 – 83 |
Albumin |
29 g/L* |
35 – 50 |
Alkaline phosphatase |
220 U/L* |
30 – 110 |
g-Glutamyl transferase |
30 U/L |
< 40 |
Alanine transferase |
27 U/L |
< 35 |
Magnesium |
0.83 mmol/L |
0.75 – 0.95 |
Not available.
That's not a lot of history, and therefore for the candidates the real struggle would have been to fight the natural urge to spend a few minutes connecting these abnormalities into a single grand unifying diagnosis. Fortunately, one immediately presents itself.
So: the abnormalities are:
What could have caused all this, AND abdominal pain? The mind boggles. However, even the boggling mind would agree that the urea of 76 (!) is the most profoundly disturbed value here. Renal failure is also present, and any kind of renal failure could be to blame for the creatinine rise, but only one kind of renal failure can give rise to a urea/creatinine ratio so heavily skewed in favour of urea. The abdominal pain here, therefore, must clearly be the pain of a humongously overdistended (if not ruptured) bladder. This is obstructive uropathy. Marshall (1964) explained this phenomenon as the result of increased hydrostatic pressure in the tubule which slows tubular transport and increases the transport of urea out of the tubule lumen.
Thus:
Marshall, Sumner. "Urea-creatinine ratio in obstructive uropathy and renal hypertension." JAMA 190.8 (1964): 719-720.
Zamzami, Zuhirman. "Blood urea and creatinine levels in obstructive uropathy patients due to benign prostate hyperplasia after transurethral resection of the prostate." International Journal of Surgery and Medicine 5.1 (2019): 18-22.