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Nocturia

Definition1

Nocturia can be defined as the need to wake and pass urine at night (in contrast to Nocturnal Enuresis in Children, where urine is passed unintentionally during sleep). One episode of nocturia per night is considered within normal limits.

Most people can identify the number of times they wake to pass urine, and this is usually denoted as, for example, "nocturia x 3", meaning waking to pass urine three times per night.

The term nocturia as a symptom, is generally used to mean that the patient is waking to pass urine more frequently than normal, i.e. more than once per night. The rest of this article will use nocturia in this way.

Importance of nocturia as a symptom2

Nocturia is a common symptom in both men and women.3 It can be troublesome in itself, by disturbing sleep, and can have a significant impact on quality of sleep and quality of life.

Nocturia is a symptom, not a diagnosis. It is important to assess underlying causes, as some important conditions, such as diabetes, may present in this way.

Causes of nocturia

There are 3 ways in which nocturia can be caused: by problems of fluid balance; by neurological diseases affecting bladder control; or by disorders of the lower urinary tract. It is easy to overlook the first two categories while concentrating on the urinary tract.

Fluid balance causes of nocturia2

Polyuria (day and night) - defined as urine volume >40ml/kg/24 hours

Nocturnal polyuria - defined as normal 24 hour urine volume, with nocturnal volume > 35% total

  • Excessive evening fluid intake, including alcohol4
  • Diuretics (may depend on time of day taken)
  • Disruption of normal vasopressin (ADH) secretion - often due to age9
  • Nocturnal redistribution of fluid - cardiac failure; other causes of oedema, e.g. venous stasis
  • Sleep apnoea (unknown mechanism)10

Neurological causes of nocturia

The bladder is controlled via the brain, spinal cord tracts, sacral segments S2-4 and peripheral nerves. Therefore, many neurological conditions affect bladder function. Nocturia may be a symptom because:

  • The neurological problem may cause urinary frequency: this can occur in multiple sclerosis,11 and has been reported as an early feature of cervical cord compression12 and tethered spinal cord syndrome.13
  • The neurology may cause retention of urine, which either results in frequency and true nocturia, or leads to overflow incontinence, which may be misinterpreted as nocturia.

Doctors should be aware that:

  • If retention occurs in women or patients under 60, who are unlikely to have bladder obstruction, consider neurological causes.14
  • Important, urgent conditions to diagnose are:
    • Cord compression15 and cauda equina syndrome. The bladder innervation is easily damaged, and prompt referral/treatment can save bladder function.15
    • Tethered spinal cord syndrome (see below), though usually less acute, again needs early referral.13

Other common neurological disorders causing urinary symptoms are:

  • Multiple sclerosis11
  • Parkinson's disease16
  • Diabetic cystopathy17
  • Tethered spinal cord syndrome (as above): this is probably under-recognised.13 It has also been reported that spina bifida occulta is associated with lower urinary tract dysfunction, which may relate to tension on spinal cord or nerves.18

Lower urinary tract causes of nocturia2,19

This is a 'low nocturnal bladder capacity', and can be classified as due to:

  • Bladder outflow obstruction (where chronic retention in effect lowers any additional bladder capacity)
    • Prostatic disease
    • Urethral disease - this occurs in both men and women20
  • Bladder overactivity
  • Sensory urgency
  • Urinary tract infection
  • Inflammation, e.g. interstitial cystitis
  • Malignancy
  • Pregnancy
Assessment of nocturia in primary care

Nocturia in often ascribed to prostatic disease (in men), without due consideration of other causes.3,9 Other factors, or a combination, are just as likely to be the cause. The cause of nocturia can usually be determined by simple assessment using history, examination and a voiding diary, plus urodynamics if necessary.9

History

  • Clarify the patient's symptoms, and ask about other lower urinary tract symptoms (see box for details).
  • How are these symptoms affecting life and sleep?
  • Could this be a fluid balance problem?
    • Fluid intake pattern (including alcohol).
    • Excessive thirst suggests diabetes (mellitus or insipidus) or hypercalcaemia.
    • Are there any systemic illnesses which could be contributing, e.g. cardiac failure, obstructive sleep apnoea, oedema, chronic renal failure?
  • Are there any neurological or spinal symptoms: neck or back pain; limb weakness or sensory loss? Important symptoms and signs are:
    • Abnormal gait or spasticity suggest upper motor neurone lesions
    • Limb sensory loss or weakness: widespread or bilateral symptoms are worrying and suggestive of cord or cauda equina lesions (nerve root lesions usually cause more localised and unilateral symptoms).
    • Constipation can also occur as part of sphincter disturbance.
    • Saddle area sensory loss and sexual dysfunction ('numb bum') suggest cauda equina syndrome.
  • Medication: any contributing medicines, e.g. diuretics, excessive calcium supplementation or antacids,6 lithium?

Urinary symptoms defined1,3

  • Nocturia: waking up at night to pass urine
  • Daytime urinary frequency: is so variable that it is difficult to assess, but ask how it affects lifestyle.
  • Urinary incontinence or leakage: in men, a small urinary leakage at the end of the stream (also known as "post-micturition dribble") is so common that it does not constitute an abnormality. Many women leak a little urine on coughing. The most important question to follow a complaint of urinary incontinence is "What protection do you need to cope with the leakage?"
  • Obstructive symptoms (or 'voiding symptoms') are: hesitancy, poor stream, intermittent stream, terminal dribbling.
  • Irritative symptoms (or 'filling symptoms') are: urgency, burning on micturition, daytime frequency, nocturia, urge incontinence.

Examination

  • Percuss abdomen for enlarged bladder
  • Leg oedema present?
  • Urine dipstick will screen for, but not exclude, diabetes mellitus, infection, haematuria and proteinuria
  • Other relevant examination, depending on suspected cause:
    • cardiovascular
    • neurological - especially important if there is urinary retention where obstructive causes are unlikely, i.e. in women and the under-60s
    • rectal examination (men) to assess prostate; pelvic examination (women)

Investigations in primary care1

  • Voiding diary by the patient: an example is given below.
  • Blood tests: renal function, electrolytes, glucose and calcium.
  • Midstream urine culture and microscopy.
  • Urodynamics: GPs may have direct access to these clinics, which assess urinary flow rate and residual volume. Some clinics perform additional measurements, such as bladder capacity by ultrasound, bladder pressures using a urethral catheter, or fluoroscopic pressure and flow measurement.

Input/output fluid chart (or 'voiding diary')1

Name and date
Time Volume of fluid taken Time Volume of urine passed
       
       
       
Further management

Urgent problems which will need same day referral are:

  • Metabolic problems, e.g. diabetes mellitus if ketotic, dehydrated or severe hyperglycaemia; hypercalcaemia; significant renal failure, electrolyte disturbance or lithium toxicity
  • Neurological problems: suspected cord compression or cauda equina syndrome
  • Urological problems: acute retention, chronic retention with renal impairment

Other problems, after initial assessment and investigations, can be classified according to the type of cause above, and then managed accordingly. Note that several conditions may coexist, all contributing to nocturia, e.g. cardiac impairment, diabetes mellitus and prostatic hypertrophy.


Document references
  1. Whitfield HN; ABC of urology: Urological evaluation. BMJ. 2006 Aug 26;333(7565):432-5.
  2. Marinkovic SP, Gillen LM, Stanton SL; Managing nocturia. BMJ. 2004 May 1;328(7447):1063-6.
  3. Abrams P; New words for old: lower urinary tract symptoms for "prostatism". BMJ. 1994 Apr 9;308(6934):929-30.
  4. Paton A; Alcohol in the body. BMJ. 2005 Jan 8;330(7482):85-7.
  5. Waise A, Fisken RA; Unsuspected nephrogenic diabetes insipidus. BMJ. 2001 Jul 14;323(7304):96-7.
  6. Kaklamanos M, Perros P; Milk alkali syndrome without the milk. BMJ. 2007 Aug 25;335(7616):397-8.
  7. Hilton R; Acute renal failure. BMJ. 2006 Oct 14;333(7572):786-90.
  8. Reynard J; Fluid balance therapy of nocturia in women. Int Urogynecol J Pelvic Floor Dysfunct. 1999;10(1):43-8. [abstract]
  9. Baxby K; Prostatic symptoms. Essential simple investigations were not mentioned. BMJ. 2001 Sep 29;323(7315):750; author reply 751.
  10. Kramer NR, Bonitati AE, Millman RP; Enuresis and obstructive sleep apnea in adults. Chest. 1998 Aug;114(2):634-7. [abstract]
  11. Larner AJ, Farmer SF; Recent Advances. Neurology. BMJ. 1999 Aug 7;319(7206):362-6.
  12. Bentley PI, Grigor CJ, McNally JD, et al; Lesson of the week: Degenerative cervical disc disease causing cord compression in adults under 50. BMJ. 2001 Feb 17;322(7283):414-5.
  13. Payne J; Tethered spinal cord syndrome. BMJ. 2007 Jul 7;335(7609):42-3.
  14. Emberton M, Anson K; Acute urinary retention in men: an age old problem. BMJ. 1999 Apr 3;318(7188):921-5.
  15. Husband DJ; Malignant spinal cord compression: prospective study of delays in referral and treatment. BMJ. 1998 Jul 4;317(7150):18-21. [abstract]
  16. Clarke CE; Parkinson's disease. BMJ. 2007 Sep 1;335(7617):441-5.
  17. Olapade-Olaopa EO, Morley RN, Carter CJ, et al; Diabetic cystopathy presenting as primary acute urinary retention in a previously undiagnosed young male diabetic patient. J Diabetes Complications. 1997 Nov-Dec;11(6):350-1. [abstract]
  18. Fidas A, MacDonald HL, Elton RA, et al; Neurological defects of the voiding reflex arcs in chronic urinary retention and their relation to spina bifida occulta. Br J Urol. 1989 Jan;63(1):16-20. [abstract]
  19. Walker R; Managing nocturia: article is removed from clinical practice. BMJ. 2004 Jun 12;328(7453):1438; author reply 1438.
  20. Klijer R, Bar K, Bialek W; Bladder outlet obstruction in women: difficulties in the diagnosis. Urol Int. 2004;73(1):6-10. [abstract]
Acknowledgements EMIS is grateful to Dr N Hartree for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2007.
DocID: 510
Document Version: 1
DocRef: bgp25202
Last Updated: 1 Nov 2007
Review Date: 31 Oct 2009






















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