Nocturia
Differential Diagnosis
Common Diagnoses
- Age Related (in Part Caused by A Reduction in Bladder Capacity)
- Excess Fluid Intake at Bed Time (Especially Alcohol)
- Any Cause of Swollen Ankles (the Recumbent Posture Redistributes the Fluid Load At Night) – See ‘Swollen Ankles’
- Cystitis
- Luts in Men, Secondary to Benign Prostatic Enlargement
Occasional Diagnoses
- Overactive Bladder Syndrome
- Lower Urinary Tract Obstruction (other Than Prostate Problems)
- Any other Cause of Urinary Frequency (See ‘Frequency’)
- Diabetes Mellitus
- Any other Cause of Polyuria (See ‘Excessive Urination’)
- Sleep Apnoea (Causes Overproduction of Urine)
Rare Diagnoses
- Anxiety
- Drug Side Effect (Rare because Drugs Likely to Cause Diuresis Are Usually Taken in the Morning)
- Diabetes Insipidus
Ready Reckoner
Key distinguishing features of the most common diagnoses
| Age Related | Excess Fluid Intake | Swollen Ankles | Cystitis | LUTS | |
|---|---|---|---|---|---|
| Daytime Ankle Oedema | Possible | No | Yes | No | No |
| Daytime Frequency | Possible | No | No | Yes | Possible |
| Poor Urinary Flow | No | No | No | No | Yes |
| Long-Term Problem | Yes | Possible | Yes | No | Yes |
| Polyuria | No | Yes | Yes | No | No |
Possible Investigations
Likely:Urinalysis, MSU, urinary frequency volume chart.
Possible:Blood sugar/HbA1c, PSA.
Small Print:Cystoscopy, urodynamic studies, ultrasound, water deprivation test.
- Urinalysis: Protein, nitrites, leucocytes and possible haematuria in infection; glucose in diabetes; specific gravity very low in diabetes insipidus.
- MSU: To confirm infection and identify pathogen.
- Urinary frequency volume chart: To help distinguish nocturnal polyuria (increased urine production at night) from reduced bladder storage capacity.
- Blood sugar/HbA1c: To confirm diabetes mellitus.
- PSA: Pros and cons of this test may be discussed if assessment raises the possibility of prostate cancer.
- Specialist tests include: Cystoscopy and ultrasound (for lower urinary tract obstruction), urodynamic studies (for unstable bladder) and water deprivation test (for diabetes insipidus).
Top Tips
- In the elderly, the cause is often multifactorial.
- The effects: Such as disturbed sleep, a disrupted household, exhaustion and occasional incontinence – may be more important to the patient than the specific diagnosis.
- Swollen ankles: Of any aetiology – are frequently overlooked as an underlying cause
- Nocturia may just be a manifestation (albeit the most distressing) of polyuria or urinary frequency. Focus your approach on the underlying problem.
Red Flags
- Exclude diabetes – but remember that it is not the only cause of polyuria, nocturia and thirst.
- A habitual ‘nightcap’ may be the cause of nocturia – and may be a pointer to an underlying alcohol problem, especially in solitary elderly males.