1. Polyuria

2. Definition It’s the production of abnormal large urine output ( >2-3 Liters/day ). It must be differentiated from “urinary frequency” which is not necessarily associated with an increase in urine output. It often appears with polydipsia (Excessive thirst leading to increased fluid intake )

3. Polyuria results from any process that involves : Sustained increase in water intake (Polydipsia). Decreased ADH secretion (Central DI). Decreased peripheral ADH sensitivity (Nephrogenic DI). Solute diuresis.

4. Causes Most commonly, excessive fluid intake. Kidney can not concentrate urine; renal and extrarenal causes. Rarely, it’s a manifestation for “ Psychogenic Polydipsia “, whose patients may pass 12 L/day of urine. It’s a clinical disorder which is characterized by excessive water drinking due to the sensation of having a dry mouth.

5. Renal Causes Nephrogenic Diabetes Insipidus. Which is usually due to genetic mutation in the tubular ADH receptor. Chronic Tubular Interstitial Damage. Reflux Nephropathy. Analgesic Nephropathy. Drugs ( i.e. Lithium )

6. Extrarenal Causes Diuretic drugs. Hyperglycemia in Diabetes Mellitus. Decreased Antidiuretic Hormone (ADH) from the pituitary gland in cranial Diabetes Insipidus (DI). Decreased Aldosterone by the adrenal gland in Addison’s Disease.

7. History 1- Patient profile 2- Presenting complaint (polyuria) you should ask about Age of onset Rate of onset (example abrupt vs gradual ) Any recent clinical factors that may cause polyuria (eg, IV fluids, tube feedings, resolution of urinary obstruction, stroke, head trauma, surgery) you should ask about thirst. 3- Review of systems Seek symptoms suggesting possible causes, including dry eyes and dry mouth (Sjögren syndrome) and weight loss and night sweats (cancer).

8. 4- Past medical and surgical history You should ask about any conditions associated with polyuria, including diabetes mellitus, psychiatric disorders, sickle cell disease, sarcoidosis, amyloidosis, and hyperparathyroidism History of transurethral resection of prostate post obstructive diuresis History of neurosurgery central diabetes insipidus 5- Drug history If the patient took any drugs that cause polyuria like diuretics, lithium. 6- Family history Of polyuria and excessive water drinking should be noted, if there is anyone in the family have diabetes mellitus or diabetes insipidus. 7-Personal history Caffeine and alcohol consumption and high protein diet.

9. Physical Examination The general examination should note signs of obesity (as a risk factor for type 2 diabetes mellitus), dehydration or cachexia (weakness and wasting of the body due to severe chronic illness ) that may reflect an underlying cancer or eating disorder. The head and neck examination should note dry eyes or dry mouth (Sjögren syndrome). Skin examination should note the presence of any hyperpigmented or hypopigmented lesions, ulcers, or subcutaneous nodules that may suggest sarcoidosis. Comprehensive neurologic examination should note any focal deficits that suggest an underlying neurologic insult and assess mental status for indications of a thought disorder.

10. Diagnosis on examination Failure to thrive DM,DI Fever UTI Not oriented Schizophrenia Pallor Sickle cell anemia,CRF Edema Renal failure

11. Investigation 24 hour urine output More than 2.5 liters per day POLYURIA Further investigations

12. Urine Tests Urinalysis will help determine if there is glucose in the urine and thus may suggest DM Osmolality of the urine - Low urine osmolality 600 mosm/kg Less likely to be DI White blood cells count >5-10 UTI Water deprivation test if you suspected DI Specific gravity <1.005 DI

13. Blood Tests Urea,creatinine Serum electrolytes especially calcium (elevated level of calcium may cause polyuria like hyperparathyroidism ) Blood gas analysis Blood glucose Plasma osmolality High plasma osmolality >300 mosm/kg suggest DI

14. Other Tests Vasopressin response test To differentiate central DI from nephrogenic DI X-ray of the skull Ct scan for the brain if suspected pituitary diabetes insipidus Renal biopsy if suspected renal disease

15. Key Points Use of diuretics and uncontrolled diabetes mellitus are common causes of polyuria. In the absence of diabetes mellitus and diuretic use, the most common causes of chronic polyuria are primary polydipsia, central diabetes insipidus, and nephrogenic diabetes insipidus. Hypernatremia usually indicates central or nephrogenic diabetes insipidus. Hyponatremia is more characteristic of polydipsia. Abrupt onset of polyuria suggests central diabetes insipidus. A water deprivation test can help with diagnosis but should only be done with the patient under close supervision.