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2013 Tech CE for the Upstate 2/10/2013 A case walks in the door… APPROACH TO POLYURIA / POLYDIPSIA Rob Presley, DVM, MS, DACIM (Int. Med) Upstate Veterinary Specialists TCTC Veterinary Technician Program February 10, 2013 Decision Time… • Causes of urinary accidents – – – – Polyuria Pollakiuria Behavioral Incontinence • Lower urinary disease • Neoplasia • strictures • “Doc, she’s peeing all over the trailer. I’m gone need you to FIXER!!!!” Pollakiuria • Increased frequency of urination – Small amounts of urine produced at a time – Often seen with stranguria • Straining to urinate Pollakiuria – Uroliths – Infection – Obstruction • 5 yr old FS Weimeraner Behavioral • You made someone angry!!! – More common in cats • Accidents typically occur 1-2 x day. • Often accidents occur in the same area – After going outside (dogs) 1 2013 Tech CE for the Upstate 2/10/2013 Behavioral Incontience • Accidental urination – Intermittent or continuous dribbling of urine • Very difficult to treat • Normal urine streams – Pets are unaware – Behavior drugs – Adults • Alprazolam • Amytriptylline • Fluoxetine • Spayed females • Often at rest – USMI – Puppies • Congenital defect – Ectopic ureters – Environmental enrichment • Litter box changes • Separation of pets Polyuria • Medical care – PPA – Estrogens • Surgical – Ectopic ureter – Collagen injections – Hydraulic occluders Polyuria • True increase in VOLUME of urine production • Normal urine output • So how do we determine this? • Urinary catheterization • Metabolic cage • Manual collection Polydipsia • Polyuria typically results in polydipsia – What goes in goes out… – 1-2mL / kg/ hour – 24-48 ml/kg/day Polydipsia • Is water intake easier to measure than urine output? • Unless 3rd spacing fluid – – – – Pleural effusion Ascites Peripheral edema Short term 2 2013 Tech CE for the Upstate 2/10/2013 Polydipsia • So how much water should a dog drink per day? Polydipsia • Maintenance – 40-60 ml/kg/day Polydipsia • Maintenance fluid rate? Now we have the basics… • Let’s go back to our dog • 4 yr old FS Weim – 50 kg • Polydipsic – > 100ml/kg/day • We’re suspicious this dog is truly PU/PD… • Normal urine production – 1-2 ml/kg/hr – 24-40 ml/kg/day Send dog home… • Have owners measure water intake – “A pint’s a pound the world around” • • • • 1 pint = 16 oz 1 pint = 2 cups 1 cup = 8 oz 1 oz = 30 mL • 1 cup = 240 mL Other option • Free catch urinalysis – Have owners bring sample from home • Specific gravity • Dipstick • Sediment exam – Infection – Casts – Crystals 3 2013 Tech CE for the Upstate 2/10/2013 Urinalysis • What is the normal specific gravity for a – dog? Urinalysis • Might be useful to determine if patient is PU/PD – If urine is concentrated.. • NOT PU/PD – Cat? • Evaluate: – Sediment » Lower urinary disease – Glucose » Diabetes mellitus » Renal glucosuria Urinalysis Urinalysis • Specific gravity • Pre-renal vs renal azotemia – Must use refractometer • Dipsticks worthless • Hypersthenuria – Specific gravity • >1.030 dog – >1.012 • Isosthenuria • >1.035 cat – 1.008-1.012 • Hyposthenuria – <1.008 How do the kidneys concentrate urine? Basics… • What are the main functions of the kidneys? – Excrete nitrogenous waste – Acid base management – Endocrine function • RAAS • Vitamin D activation – Blood pressure – Control fluid balance 4 2013 Tech CE for the Upstate 2/10/2013 Kidney structure Nephron • Functional unit of the kidney • Cortex – Glomerulus – Renal tubule – Outer layer • Medulla – Inner Layer • Pelvis Glomerulus • Kidneys receive 25% of cardiac output • Specially designed network of capillaries – Allows movement of fluid – Blocks movement of medium to high molecular weight products – Prevents protein loss Renal tubules • Segments – – – – – Proximal tubule Descending loop of Henle Ascending loop of Henle Distal tubule Collecting ducts Renal tubule • Function is to manipulate glomerular ultrafiltrate – Aka: dilute when you need it or concentrate when you need it Proximal convoluted tubule • Reabsorbs most particles – 100% of glucose – 80-85% of Na / Cl – Water soluble vitamins • Reabsorbs based on what’s available – i.e. not used for fine tuning – Overall reabsorbs approximately 75% of the glomerular filtrate 5 2013 Tech CE for the Upstate Loop of Henle • Functions as the “Wife” of the nephron • Most important component for urine concentration – Allows for high salt concentration in the inner medulla • Sets up concentrating ability of the kidney Collecting Duct • Under specific instruction… – Collecting duct becomes permeable to water • Pure water is drawn into the inner medulla • Leaves the salt and wastes in the lumen of the collecting duct 2/10/2013 Collecting Duct • “Husband” of the system – Loop of Henle set up high salt medulla – Without “being told” the tubule doesn’t do any work • Impermeable to water • i.e. what comes in, goes out – Urine is dilute Summary… • Loop of Henle – Does all the work – Allows for the urine to be concentrated • Collecting duct – Urine is concentrated – Becomes permeable to water • Concentrates the urine – Takes all the credit for the work – Like any husband… • HAS TO BE TOLD WHAT TO DO!!!! Antidiuretic hormone • Anatomy/physiology: – formed in hypothalamic nuclei – released from posterior pituitary • Released in response to: ADH effects • VS2 receptors – Cause insertion of aquaporins into principle cells of renal collecting ducts – CNS osmoreceptors • 2% increase in ECF osmolality – Maxed out by 5% dehydration – Baroreceptors • 10% decrease in circulating volume) – Angiotensin II 6 2013 Tech CE for the Upstate 2/10/2013 ADH effects ADH effects Back to our case… Back to our case… • We believe she truly is PU/PD – To be polyuric • Urine must be dilute • i.e. effects of ADH are blocked Primary polydipsia • Drinks excessively – Leads to increased urine output • Psychogenic – Typically young, active dogs – Competitive • Liver disease? • What are the potential causes of PU/PD?? – In other words, what can keep the kidneys from concentrating urine? Primary polyuria • Diabetes Insipidus – Central – Nephrogenic • Renal Failure • Hyperadrenocorticis m • Hypoadrenocorticis m • Hyperthyroidism • Diabetes Mellitus • Hepatic Insufficiency • Hypercalcemia • Hypokalemia • Post obstructive diuresis • Normoglycemic glucosuria • Pyometra 7 2013 Tech CE for the Upstate 2/10/2013 Primary Polyuria • Hypothyroidism? Primary Polyuria • Urinary tract infection – Once again NO!!!!! – Causes pollakiuria – Only exception is renal failure secondary to pyelonephritis How do we get a diagnosis? • Diabetes Insipidus • Establish PU/PD exists – Measure water intake – Measure urine specific gravity • Get a good history – Medications • Including topicals – Other medical issues • Polyuria / dysuria / incontinence • Physical examination Diagnosis • Is urine hitting the ground? Diagnosis • Diabetes Insipidus – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra Diagnosis • Is urine hitting the ground? • Diabetes Insipidus – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra 8 2013 Tech CE for the Upstate 2/10/2013 Diagnosis • Is urine hitting the ground? • Routine labwork – – – – Complete Blood Count Serum Chemistries Urinalysis Urine culture • Diabetes Insipidus – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra Diagnosis • Is urine hitting the ground? • Routine labwork – – – – Complete Blood Count Serum Chemistries Urinalysis Urine culture Diagnosis • Is urine hitting the ground? • Routine labwork – – – – Complete Blood Count Serum Chemistries Urinalysis Urine culture • ACTH stimulation test • Diabetes Insipidus – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra • Routine labwork – – – – Complete Blood Count Serum Chemistries Urinalysis Urine culture • ACTH stimulation test • Total T4 (cats) • Diabetes Insipidus – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra Diagnosis • Is urine hitting the ground? • Routine labwork – – – – Complete Blood Count Serum Chemistries Urinalysis Urine culture • ACTH stimulation test Diagnosis • Is urine hitting the ground? • Diabetes Insipidus • Diabetes Insipidus – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra Diagnosis • Is urine hitting the ground? • Routine labwork – – – – Complete Blood Count Serum Chemistries Urinalysis Urine culture • ACTH stimulation test • Total T4 (cats) • Diabetes Insipidus – Central – Nephrogenic • • • • • • • • • • • Renal Failure Hyperadrenocorticism Hypoadrenocorticism Hyperthyroidism Diabetes Mellitus Hepatic Insufficiency Hypercalcemia Hypokalemia Post obstructive diuresis Normoglycemic glucosuria Pyometra 9 2013 Tech CE for the Upstate 2/10/2013 What’s left??? Available tests • Diabetes insipidus • DDAVP response test • Water deprivation test – Central DI – Nephrogenic DI – DO THESE TESTS LAST!!! • Psychogenic water drinker – Distinguish • Psychogenic polydipsia • Central DI • Primary nephrogenic DI Modified water deprivation test – Basics Modified water deprivation test • Absolute endpoints • Measure water consumption prior to test – Slowly begin limiting water over 1-2 weeks » Trying to correct medullary washout in kidneys • Make sure an absolute endpoint is reached • If hasn’t concentrated at endpoint, give dose of ADH – Azotemia (ABSOLUTE contraindication) – Plasma osmolality > 320 mOsm/kg – Urine specific gravity • >1.030 (dogs) • >1.035 (cats) – Loss of 5% body weight Modified water deprivation test Interpretation Disorder Initial 5% dehyd Post-ADH Complete CDI Partial CDI <1.006 <1.006 >1.018 <1.006 NDI <1.006 1.0081.020 <1.006 10-50% increase <1.006 1° polydipsia 1.0021.020 >1.030 NA • Most clinicians strongly recommend AGAINST performing this test – Can be very dangerous even if monitored very closely 10 2013 Tech CE for the Upstate DDAVP Response Test • Better option to modified water deprivation test • Protocol: – measure water intake 2-3 d – catch urine at same time each day – treat with DDAVP for 5-7 d – monitor water intake and urine on d 5-7 2/10/2013 DDAVP Response Test • Interpretation: – Central DI • dramatic reduction in water intake and/or increase in urine concentration (>50%) – Nephrogenic DI • No response Diabetes insipidus DDAVP response test • Must monitor electrolytes – If psychogenic • May become hyponatremic – Fluid overloaded – Continued water consumption despite FORCED urine concentration • Signalment – Central DI • dogs – no sex, age or breed predilection – most < 2 or > 6 yrs • cats - too few cases to say. – Nephrogenic DI • dogs - too few cases to say; young dogs? • cats - not reported Treatment of pu/pd Questions??? • Treat underlying disease • Unless psychogenic polydipsia, do NOT restrict water intake • Central DI: – replace ADH (DDAVP, Desmopressin®) – chlorpropamide (Diabenese®) • Nephrogenic DI: thiazide diuretics 11