Solution to last week’s patient

To remind you:

Exam reveals a markedly volume contracted 61 year old woman.

Her serum albumin was 4.8. Her urine creatinine was 330 with a urine sodium of 14. Her PTH level was 138.

Resolution

This patient had remarkable volume contraction. She had both an increased anion gap acidosis as well as a metabolic alkalosis.

1. Anion gap = 33, defining an increased anion gap acidosis.

2. Using the delta gap process, we subtract her expected gap (14 in this patient with an albumin of 4.8) from her measured gap. The difference is 19. If we add 19 to her observed bicarbonate of 14, we obtain her adjusted bicarbonate of 33. This suggests that she first developed a metabolic alkalosis (probably from volume contraction.)

Note that her respiratory compensation is perfect using Winter’s equation.

3. We measured ketones and lactic acid – both were normal. Her phosphate was 13.3!

Thus, we have a woman who developed severe volume contraction, prerenal azotemia, then hyperphosphatemia with subsequent metabolic alkalosis and increased anion gap acidosis.

This represents a very unusual cause of increased anion gap acidosis.