CASE 58: THIRST AND FREQUENCY
History
A 63-year-old woman is referred to a nephrologist for investigation of polyuria. About 4
weeks ago she developed abrupt-onset extreme thirst and polyuria. She is getting up to
pass urine five times a night. Over the past 3 months she has felt generally unwell and
noted pain in her back. She has lost 3 kg in weight over this time. She also has a persist-
ent frontal headache associated with early morning nausea. The headache is worsened by
coughing or lying down. Eight years previously she had a left mastectomy and radiother-
apy for carcinoma of the breast. She is a retired civil servant who is a non-smoker and drinks
10 units of alcohol per week. She is on no medication.
Examination
She is thin and her muscles are wasted. Her pulse rate is 72/min, blood pressure
120/84 mmHg, jugular venous pressure is not raised, heart sounds are normal and she has
no peripheral oedema. Examination of her respiratory, abdominal and neurological sys-
tems is normal. Her fundi show papilloedema.
NormalHaemoglobin 12.2 g/dL 11.7–15.7 g/dL
Mean corpuscular volume (MCV) 85 fL 80–99 fL
White cell count 6.7% 109 /L 3.5–11.0% 109 /L
Platelets 312 % 109 /L 150–440% 109 /L
Sodium 142 mmol/L 135–145 mmol/L
Potassium 3.8 mmol/L 3.5–5.0 mmol/L
Bicarbonate 26 mmol/L 24–30 mmol/L
Urea 4.2 mmol/L 2.5–6.7 mmol/L
Creatinine 68 &mol/L 70–120&mol/L
Glucose 4.2 mmol/L 4.0–6.0 mmol/L
Albumin 38 g/L 35–50 g/L
Calcium 2.75 mmol/L 2.12–2.65 mmol/L
Phosphate 1.2 mmol/L 0.8–1.45 mmol/L
Bilirubin 12 mmol/L 3–17 mmol/L
Alanine transaminase 35 IU/L 5–35 IU/L
Alkaline phosphatase 690 IU/L 30–300 IU/LUrinalysis: no protein; no bloodINVESTIGATIONS
Questions
- What is the likely cause of her polyuria?
- How would you investigate and manage this patient?