Polyuria resident survival guide

Polyuria Resident Survival Guide Microchapters
Overview
Causes
Diagnosis
Treatment
Do's

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Zaida Obeidat, M.D.

Synonyms and keywords: Approach to polyuria, Approach to dilute urine, Polyuria management, Polyuria work-up

Overview

• Polyuria is defined as urine output more than 2 L/24 hours, or 30 ml/kg/24 hours. There are 3 pathophysiologic causes of polyuria: increased thirst (idiopathic, psychogenic polydepsia, hypothalamic disease, and medications), central diabetes insipidus (DI) (decreased secretion of arginine vasopressin (AVP)), and nephrogenic diabetes insipidus (DI) (renal resistance to AVP).

Causes

Life Threatening Causes

• Life-threatening causes include conditions that may result in death or permanent disability within 24 hours if left untreated.
• Polyuria does not have life-threatening causes.

Common causes

• The most common causes of polyuria are:
  • Pregnancy
  • Psychogenic polydipsia
  • Central diabetes insipidus (CDI)
  • Nephrogenic diabetes insipidus (NDI)
  • Diabetes mellitus (DM)
  • Chronic kidney disease (CKD)
  • Urinary tract infection (UTI)
  • Interstitial cystitis
  • Nephrolithiasis
  • Primary hyperparathyroidism
  • Familial hypocalciuric hypercalcemia
  • Hypercalcemia
  • Hypokalemia
  • Sickle cell disease (SCD)
  • Stroke or neurological diseases
  • Benign prostatic hyperplasia (BPH)
  • Stress incontinence
  • Medications:
    • Lithium
    • diuretics
  • Overactive bladder
  • Drinking alcohol or caffeine

Approach to Polyuria

Shown below is an algorithm summarizing the approach to polyuria.
Abbreviations: DI: Diabetes insipidus;

Hypotonic Polyuria

Suspected hypotonic polyuria

Confirm presence of polyuria >50ml/kg/24hrs or >3-4L/day

Polyuria confirmed

No polyuria/ or >800 mOsm/kg

Measure urine osmolality

Diabetes insipidus(DI)/Primary polydipsia ruled out

<800 mOsm/kg

Hypotonic polyuria confirmed

Measure serum Sodium and plasma osmolality

Low normal or low serum Sodium <150 mmol/L, plasma osmolality <280 mOsm/kg

Normal serum Sodium/plasma osmolality

High serum Sodium >146 mmol/L, plasma osmolality >300 mOsm/kg

Primary polydipsia

Indeterminate diagnosis

Central or Nephrogenic DI

Water deprivation test

Baseline plasma copeptin

Hypertonic saline infusion test

Urine Osm >800 mOsm/kg

Urine Osm <300 mOsm/kg

Urine Osm 300-800 mOsm/kg

Plasma coprptin >4.9pmol/L

Plasma coprptin <4.9pmol/L

Mild primary polyuria

Desmopressin administration

>21pmol/L

<2.6pmol/L

>2.6pmol/L

Urine Osmolality: 300-800 mOsm/Kg and <50% increase

Nephrogenic DI(partial or complete)

Complete Central DI

Therapeutic trial with desmopressin

Primary polydipsia

Partial Nephrogenic DI

Partial Central DI

Initial urine osmolality: 30 mOsm/kg and >50% increase after desmopressin:

Urine osmolality <300 mOsm/kg or <50% increase

Complete Central DI

Complete Nephrogenic DI

Polyuria

Shown below algorithm for the diagnostic approach to polyuria based on the American Journal of Kidney Diseases.

Polyuria (Urine Output > 3L/d)

Urine Osmolality

Uosm <100mOsm/kg (Water Diuresis) *Psychogenic Polydipsia *DI (central and nephrogenic)

Uosm =100-300mOsm (Mixed Polyuria) *Partial DI(central and Nephrogenic) *Simultaneous water and solute intake *CKD

Uosm >300mOsm/kg (Solute Diuresis) *Hyperglycemia *Azotemia *High solute intake intravenous fluids enteral and parenteral nutrition Exogenous supplements

Water Deprivation Test

24-Hour Urine Collection (estimation of osmoles) *Urine sodium *Urine potassium *Urine glucose *Urine urea nitrogen *Other osmoles

Treatment

The management of polyuria depends on the underlying cause. Click on each disease shown below to see detailed management for every cause of polyuria.

• Psychogenic polydipsia
• Diabetes insipidus
• Nephrogenic diabetes insipidus
• Diabetes mellitus type 1
• Diabetes mellitus type 2

Do's

• Recommend diet modification, like avoiding any food that irritates the bladder including caffeine, alcohol, carbonated drinks, tomato-based products, chocolate, artificial sweeteners, and spicy foods.
• Monitor fluid food intake, drink enough to prevent constipation and over-concentration of urine, and avoid drinking just before bedtime.
• Recommend Kegel exercises to strengthen the muscles around the bladder and urethra.