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  2. Investigating polyuria
  3. Investigating polyuria
Practice Rational testing

Investigating polyuria

BMJ 2013; 347 doi: https://doi.org/10.1136/bmj.f6772 (Published 02 December 2013) Cite this as: BMJ 2013;347:f6772
  1. Adam D Jakes, academic foundation doctor1,
  2. Sunil Bhandari, consultant nephrologist/honorary clinical professor2
  1. 1Leeds Teaching Hospitals NHS Trust, Beckett Street, Leeds LS9 7TF, UK
  2. 2Renal Unit, Hull and East Yorkshire Hospitals NHS Trust and Hull York Medical School, Kingston upon Hull HU3 2JZ, UK
  1. Correspondence to: S Bhandari Sunil.bhandari{at}hey.nhs.uk
  • Accepted 3 October 2013

Polyuria represents a common presentation in primary care that can often be a diagnostic challenge requiring careful consideration. This article provides a structured, logical approach for investigating polyuria, highlights the importance and relevance of various tests, and advises on when to refer to a specialist

A 43 year old male teacher presented to his general practitioner with frequent urination and polydipsia for six weeks. He was passing large volumes of urine throughout the day and night, but he denied dysuria, hesitancy, or urgency. His fluid intake was approximately two litres a day and included two cups of tea. He had no relevant medical history; reported no weight loss, visual changes, or bowel disturbance; and took no drugs, including over the counter drugs or herbal remedies. There was no family history of diabetes or renal disease. Clinical examination was unremarkable, and his blood pressure was 138/84 mm Hg.

What is the next investigation?

Clinical history

A thorough clinical history is essential to distinguish between polyuria and urinary frequency (box 1). Urine volume can be difficult for patients to quantify, and use of fluid charts (measuring fluid input and output) may be helpful. The presence of urinary symptoms should be established, along with the timing of urination (nocturnal, throughout the day, or both). This may help clinicians to distinguish between possible causes by the relation to tubular disorders versus anatomical abnormalities, such as overactive bladder syndrome in which frequency and urgency of urination are present rather than polyuria or prostatic disease.

Box 1 Glossary of terms

  • Polyuria—The production of “abnormally” large volumes of urine (>3 L/day in adults)

  • Urinary frequency—The excessive need to urinate, which is not normal for the patient. The total volume of urine passed is within normal limits

  • Polydipsia—Excessive thirst as a symptom of disease or psychological disturbance (resulting consumption of >3 L/day)

  • Nocturia—The need to wake …

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