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4th April 2024
A 79-year-old female presents to the GP complaining of marked thirst, drinking 3-4 litres of water daily, associated with polyuria.
A 79-year-old female presents to the GP complaining of marked thirst, drinking 3-4 litres of water daily, associated with polyuria. She wakes once nightly to pass urine. She denies any weight loss, weakness, or muscle cramps. She has recently begun taking senna twice daily but still strains to pass stool. She feels fatigued and struggles to climb the two flights of stairs to her flat. She reports poor sleep.
Initial investigations reveal the following:
| Result | Reference range | |
|---|---|---|
| Hb | 118 g/L | 115-160 g/L |
| MCV | 82 fl | 82-100 fl |
| WCC | 5.1 x 10⁹/L | 4.0-11.0 x 10⁹/L |
| Na | 137 mmol/L | 135-145 mmol/L |
| K | 4.1 mmol/L | 3.5-5.0 mmol/l |
| Cr | 89 umol/L | 55-120 umol/l |
| Urea | 6.1 mmol/L | 2.0-7 mmol/l |
| eGFR | 67 ml/min/1.73m² | >90 ml/min/1.73m² |
| AdjCa | 3.01 mmol/L | 2.1-2.6 mmol/L |
| Phosphate | 0.69 mmol/L | 0.8-1.4 mmol/L |
| PTH | 5.1 pmol/L | 0.9-5.4 pmol/L |
| HbA1c | 41 mmol/mol | <42 mmol/mol |
Her urine dipstick is negative for nitrites, leucocytes, ketones and protein. Urine electrolytes were also normal. What is the likely diagnosis?
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