What is the diagnostic approach for nocturia (nocturnal urination)?

Diagnostic Approach to Nocturia

Nocturia diagnosis begins with a 72-hour bladder diary to quantify nocturnal voiding frequency and overnight urine volume, followed by systematic screening for underlying SCREeN conditions (Sleep, Cardiovascular, Renal, Endocrine, Neurological) through targeted history, physical examination, and laboratory investigations. 1

Definition and Initial Assessment

• Nocturia is defined by the International Continence Society as the number of times urine is passed during the main sleep period, where each void must be preceded and followed by sleep or the intention to sleep 1
• The diagnosis does not require determining the "reason for waking"—awakening for any reason followed by urination qualifies as nocturia 1
• Assess the impact on quality of life and daytime function to determine treatment thresholds 1

Essential Diagnostic Tool: 72-Hour Bladder Diary

• A 72-hour bladder diary is the cornerstone diagnostic tool, documenting nocturia severity and overnight urine volume patterns 2
• This helps identify nocturnal polyuria (defined as passing large volumes of urine during the main sleep period) versus other causes 1, 3

Comprehensive Medical History Review

Past Medical History - SCREeN Framework

Review for previously diagnosed conditions across five domains: 1

• Sleep disorders: obstructive sleep apnea, insomnia, restless legs syndrome/periodic limb movements, parasomnias 1
• Cardiovascular: hypertension, congestive heart failure 1
• Renal: chronic kidney disease 1
• Endocrine: diabetes mellitus, thyroid disorders (overactive or profoundly underactive), pregnancy/menopause, diabetes insipidus, testosterone deficiency 1
• Neurological: most neurological diseases are potentially relevant 1

Medication Review

Systematically review medications that may contribute to nocturia: 1, 2

• Diuretics, calcium channel blockers, lithium, NSAIDs 1, 2
• Drugs causing xerostomia (dry mouth leading to increased fluid intake): anxiolytics, antidepressants (especially tricyclics), antimuscarinics, antihistamines, decongestants, antiparkinsonians, pain medications, antipsychotics 1
• Alcohol and caffeine due to diuretic effects 1

Screening Questions for Undiagnosed SCREeN Conditions

Ask all patients the following nine screening questions: 1

1. "Do you have problems sleeping aside from needing to get up to urinate?" (Sleep) 1
2. "Have you been told that you gasp or stop breathing at night?" (Sleep) 1
3. "Do you wake up without feeling refreshed? Do you fall asleep in the day?" (Sleep) 1
4. "Do you experience ankle swelling?" (Cardiac, Renal) 1
5. "Do you get short of breath on walking for a certain distance?" (Cardiac, Renal) 1
6. "Do you get lightheaded on standing?" (Cardiac, Neurological) 1
7. "Have you noticed changes in your periods?" (Endocrine—for females of relevant age) 1
8. "Have you been feeling excessively thirsty?" (Endocrine) 1
9. "Do you have any problems controlling your legs? Do you experience slowness of movement? Have you noticed a tremor in your hands?" (Neurological) 1

Additional Sleep Disorder Questions (If Screening Positive)

If initial screening suggests sleep disorders, ask detailed follow-up questions: 1

• For obstructive sleep apnea: "Do you snore and sometimes wake up choking?" "Does your partner say that you stop breathing?" "Do you often wake with a headache?" 1
• For restless legs syndrome: "Does it vary over the day and is it worse later in the day/evening?" "Is it relieved by movement?" "Does it come back again a few minutes after you sit or lie back down?" 1

Physical Examination

Focus on three key examination findings: 1

• Reduced salivation (xerostomia) indicating potential autoimmune disease or medication effects 1
• Peripheral edema suggesting fluid retention (note that fluid retention can exist without manifest edema) 1
• Neurological signs: lower limb weakness, abnormal gait, speech disturbances, or tremor 1
• Blood pressure measurement (carefully conducted, including orthostatic measurements if indicated) 1, 2

Initial Laboratory Investigations

Obtain the following baseline tests for all patients: 1, 2

• Blood tests: electrolytes/renal function, thyroid function, calcium, HbA1c to identify renal or endocrine disease 1, 2
• Urine dipstick: albumin:creatinine ratio, hematuria, proteinuria (though only 80% sensitive) as potential indicators of chronic kidney disease 1, 2
• Blood pressure assessment 1, 2
• Pregnancy test where applicable 1

Supplementary Evaluations Based on Clinical Suspicion

Consider additional testing when specific conditions are suspected: 1, 2

For Sleep Disorders

• STOP-BANG questionnaire for obstructive sleep apnea 2
• Overnight oximetry with referral to respiratory or ENT sleep clinic 1
• Ferritin level for restless legs syndrome; supplementation if below 75 ng/ml 1

For Cardiovascular Disease

• Electrocardiogram 1
• Brain natriuretic peptide; echocardiogram if positive 1, 2

For Endocrine Disorders

• Morning urine osmolarity after overnight fluid avoidance (concentrations above 600 mosm/L rule out diabetes insipidus; indicated for patients urinating >2.5 L per 24 hours despite attempts to reduce fluid intake) 1
• Parathyroid hormone if hypercalcemia detected 1

For Neurological Disease

• Lying/standing blood pressure taken within 1st minute and at 3 minutes (fall of 20 mmHg systolic or 10 mmHg diastolic is diagnostic for orthostatic hypotension) 1

Clinical Review and Follow-Up

• Nocturia is commonly multifactorial, requiring evaluation of all possible causes 1
• Results of initial investigations typically require follow-up appointment review 1
• Some diagnoses (diabetes mellitus, chronic kidney disease) can be made in primary care or urology settings, while others (obstructive sleep apnea) require specialist confirmation 1
• Do not assume a link between a medical condition and nocturia without justification—establishing clinical connection requires evidence such as successful treatment of the condition leading to simultaneous reduction in nocturia 1

Critical Pitfalls to Avoid

• Failing to distinguish between nocturia caused by lower urinary tract dysfunction versus systemic medical conditions 2
• Not reviewing all medications, including over-the-counter drugs 2
• Overlooking sleep disorders as primary contributors 2
• Assuming nocturia is purely urological without screening for SCREeN conditions 1, 2
• Ignoring that nocturnal awakenings for reasons other than bladder fullness should not exclude patients from nocturia diagnosis and treatment 4