Urinary Frequency and Polyuria

Phone Call/Presentation Questions

• What is the main problem the patient complains of?
  • Polyuria = urine output >3L/day on review of the fluid balance chart
  • Frequency of urination = frequent passage of urine, whether larger or small volume
• Vital signs
• Is the patient catheterised
• What was the reason for admission

Instructions Over the Phone

• In a patient with mental state changes or who is sick:
  • Request for insertion of an IDC if one is not already in place
  • Ask for an IV trolley for the patient’s bedside to await your arrival
  • Check fingerprick BGL
  • Collect and send serum for FBC, UEC and LFTs
  • Collect a urine sample, perform bedside urinalysis and prepare sample to send for MCS and urinary electrolyte analysis
  • Commence volume replacement with initial bolus of 10-20mL/kg normal saline if the patient has signs of volume depletion

Prioritisation

• Immediate review if there are significant changes in vital signs, mental status or features of dehydration
• Otherwise a patient with polyuria, frequency or inctoninence need not to be seen urgently if the vital signs are stable

Common Cause (Corridor Thoughts)

• Polyuria
  • Diabetes mellitus (osmotic diuresis)
  • Diabetes insipidus
    • Either central DI or nephrogenic DI
    • DI is most commonly caused by head trauma, cerebral oedema, pituitary tumours or prescribed medication
  • Drugs
    • Diuretics, mannitol
    • Lithium toxicity, amphotericin B, demeclocycline
  • Renal disease
    • Diuretic phase of acute tubular necrosis
    • Post-obstructive diuresis
    • Salt-losing nephritis
    • Polycystic kidney disease (causes nephrogenic DI)
    • Hypercalcaemia (nephrogenic DI)
    • Hypokalaemia (nephrogenic DI)
    • Physiological diuresis following large volumes of PO or IV fluids during the resolution phase of major illness or during recovery from major surgery
    • Primary psychogenic polydipsia
• Increased frequency
  • Urinary tract infection
  • Partial bladder outlet obstruction
  • Bladder irritation
  • Large fluid intake
  • Psychological
• Incontinence
  • Urge incontinence
  • Stress incontinence
    • Usually in multiparous women
    • In men it occurs after prostate surgery
  • Overflow incontinence
    • Bladder obstructino such as BPH, urethral stricture, spinal cord disease, autonomic neuropathy, faecal impaction¹
  • Iatrogenic factors
    • Diuretics, sedatives, anticholinergics drugs, alpha-blockers, calcium channel blockers, ACE inhibitors
  • Environmental factors
    • Inaccessible call bell, poor mobility, obstacles to the bathroom

Assessment

End of Bed Assessment

• Most patients with polyuria, frequency or incontinence look well
• If the patient looks unwell, search for a previously unrecognised condition or look for a UTI in patients with frequency or incontinence

A to E Assessment

• Heart rate and blood pressure?
  • Look for signs of dehydration with intravascular volume depletion such as a resting tachycardia or hypotension (SBP <90mmHg)
  • Examine for postural changes if the HR and BP are normal at rest
    • A rise in HR >20 beats/min, a fall in SBP >20mmHg or any fall in DBP indicates hypovolaemia
• Does the patient have a fever?
  • May suggest a possible UTI

Immediate Management

• Attach continuous non-invasive ECG, BP and pulse oximeter monitoring to the patient
• Commence oxygen therapy to maintain oxygen saturation >94%
• Insert a large-bore (14-16G) peripheral cannula; send blood samples for FBC; UEC and calcium
  • Add blood cultures if suspicion of sepsis
• Dipstick the urine for sugar and ketones
  • Send an MSU for microscopy, culture and sensitivity as well as urinary sodium and osmolarity
• Commence fluid resuscitation to maintain normotension and normovolaemia
• Give a 20 mL/kg normal saline bolus for acute volume depletion
• Observe the effect of this fluid challenge on the BP
• A patient with significant polyuria will require further IV fluid to balance the urinary losses and maintain normotension
• Replace potassium according to UEC results
• Watch for complications, such as pulmonary oedema from excessive fluid resuscitation

Selective History and Chart Review

• Polyuria
  • Ask about associated symptoms such as polydipsia in diabetes mellitus, DI, hypercalcaemia or compulsive water drinking (primary, psychogenic polydipsia)
  • Review the medication chart for causative medications:
    • Lithium, amphotericin B and demeclocycline
    • Diuretics
  • Check for recent laboratory results
    • Blood glucose and bicarbonate (diabetes mellitus)
    • Hypokalaemia and hypercalcaemia
• Frequency
  • Ask about associated symptoms:
    • Fever, dysuria, haematuria and bad-smelling urine suggesting UTI
  • Poor stream, hesitance, terminal dribbling and nocturia ⇒ prostatism
• Incontinence
  • Ask them when the incontinence occurs to figure out what type of incontinence it is

Examination

Examination	Notes
Vitals	Repeat now; look for signs of tachycardia or postural BP changes ⇒ hypovolaemia
Mental status	Altered mental status ⇒ decreased cerebral perfusion, sepsis, intracranial pathology
HEENT	Dry mucous membranes and flat neck veins ⇒ dehydration
	Visual field abnormality ⇒ pituitary tumour
	Papilloedema ⇒ increased intracranial pressure
Resp	Kussmaul’s breathing (deep sighing respirations from metabolic in DKA or uraemia)
	Ketotic breath ⇒ DKA
Abdo	Enlarged palpable bladder ⇒ bladder outlet obstruction with overflow incontinence, neurogenic bladder
	Suprapubic tenderness ⇒ UTI, cystitis
Rectal	Enlarged prostate or pelvic mass ⇒ bladder outlet obstruction
Neuro	Focal neurological signs
	Perform a complete neurological examination, particularly for altered perineal sensation, abnormal anal tone or bilateral leg weakness suggesting a neurogenic bladder
Skin	Perineal skin breakdown ⇒ complication of repeated incontinence and a source of infection

Investigations

• Send blood for UEC
• Serum glucose or fingerprick blood glucose testing
• Urinalysis:
  • Urine sodium

    • 40mmol/L ⇒ acute tubular necrosis

    • <40mmol/L ⇒ pre-renal failure and dehydration
    • <10mmol/L ⇒ diabetes insipidus
  • Specific gravity
    • Very low (SG <1.010) ⇒ diabetes insipidus
    • High (SG >1.020) ⇒ dehydration
  • RBCs ⇒ UTI or kidney stones
  • Abnormal RBCs >70% dysmorphic (glomerular disease)
  • Glucose or ketones

Specific Management

• Polyuria
  • Once intravascular volume has been restored, ensure adequate continuing replacement fluid (usually IV) estimated by urine output, insensible loss (400-800 mL/day) and other losses such as NG suction, vomiting and diarrhoea
  • Start strict fluid balance chart with daily weight
  • Review serum and urine result
    • Replace potassium as required and manage hypercalcaemia
    • Manage serum hyperglycaemia
  • Cease all non-essential medications that may have caused nephrogenic DI; check no diuretic is being given in the evenings
• Frequency
  • Commence trimethoprim 300mg PO once daily or cephalexin 500mg PO QID for uncomplicated cystitis
  • Catheterise the bladder for suspected partial bladder outlet obstruction
  • Other causes of frequency, such as bladder irritation by stones or tumours consult seniors for advice
• Incontinence
  • Check for UTI, hypergylcaemia, hypokalaemia and hypercalcaemia if there is also polyuria, as these may present an incontinence in an elderly or bedridden patient
  • Arrange specialist consult for neurogenic bladder
    • Urgent consult if cauda equina compression is suspected
  • Differentiate overflow caused by bladder outlet obstruction from impaired detrusor contraction (e.g. LMN bladder)
  • Urge incontinence is most common cause of incontinence in elderly population
    • Ensure that there are no physical barriers preventing the patient from reaching the bathroom or commode and check that there is easy access to the call bell
    • Arrange occupational therapy to address medical disabilities in the morning
  • Consider temporary IDC or condom catheter to allow skin healing in patients with perineal skin breakdown

Footnotes

Footnotes

1. On call says to always do a PR examination ↩