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41 Cards in this Set
- Front
- Back
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What is the normal specific gravity of feline urine? canine?
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Cat > 1.035
Dog > 1.030 |
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True or false. A urine specific gravity > 1.025 is not consistent with polyuria and polydipsia.
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True
-indicates active concentration is occurring except syndrome of inappropriate ADH secretion |
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What is the definition of polyuria?
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> 50 mL/ kg /day
Normal: 20-45 mL/kg/day |
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What is the definition of polydipsia?
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> 100 mL/kg/day of water intake
-normal: 20-70 mL/kg/day |
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What is the physiology of water metabolism?
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Hypothalamus--< pituitary releases ADH--> angiotensin II (hyperosmolality,decreased atrial receptor firing, sympathetic stimulation) --> vasoconstriction & increased renal fluid absorption--> increased arterial pressure & increased blood volume
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What is the action of ADH?
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Acts on collecting tubules of nephron resulting in release of aquaporin-2 which allows water to flow from filtrate to the hyperosmolar region of renal medulla
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What is the hyperosmolar region of the renal medulla?
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A gradient of urea occurs throughout the medulla, if not present then even if have ADH and opening up aquaporins urine can't be concentrated bc no osmotic pull for water to be removed
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What are 3 causes of primary polyuria?
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1) Osmotic diuresis
2) ADH deficiency -central diabetes insipidus 3) Inability to respond to ADH -nephrogenic diabetes insipidus |
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What is the only cause of primary polydipsia?
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Psychogenic polydipsia
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What 3 molecules can cause osmotic diuresis?
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1) Glucose-diabetes mellidus
2) Urea: renal insufficiency 3) Amino acids/proteins -Fanconi syndrome -Glomerulonephritis |
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What is Fanconi syndrome?
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Glucosuria and amino acids in urine seen in the absence of hypoglycemia
-in basenjis |
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What is Fanconi-like syndrome?
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Caused by the chicken jerky treats made in china where lose AAs in urine and some glucose loss
-acute onset -so if not a basenji think fanconi-like syndrome |
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What is the most common cause of central diabetes insipidus?
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Idiopathic
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What is central diabetes insipidus? What can cause it?
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Failure of synthesis/ release of preproADH or AD itself
-Rare- trauma, neoplasia, CNS inflammation or idiopathic |
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What is nephrogenic diabetes insipidus? What 2 types of disorders can cause it?
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Congenital lack of ADH receptors (rare)
1) Distal tubule defects 2) Metabolic disorders |
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What are 3 causes of distal tubule defects that can result in nephrogenic diabetes insipidus?
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1) Gram negative endotoxin (pyometron)
2) Pyelonephritis 3) Chronic kidney disease |
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What are 5 metabolic disorders that result in nephrogenic diabetes insipidus?
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1) Hypokalemia
-pumps don't work as well 2) Hypercalcemia -Ca interferes w/ ADH interaction w/ receptor 3) Hyperadrenocorticism 4) Hyperthyroidism -increased GFR so transtubular flow is too high for concentration to keep up 5) Hypoadrenocorticism |
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What is psychogenic polydipsia?
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Compulsive drinking
-polyuria is secondary |
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Psychogenic polydipsia is ____/___ related in many cases resulting in renal medullary washout.
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Behavioral/ stress
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It is important to differentiate polyuria from ____ & _____.
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Dysuria and pollakiuria
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What is really important to confirm polydipsia?
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Quantify the water intake
-Don't restrict water access |
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The specific gravity in patients with PU/PD usually have <______.
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1.025
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What is the definition of isosthenuric?
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1.008-1.012
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What are 3 causes of isosthenuria?
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1) Renal insufficiency
2) Partial central diabetes insipidus 3) Nephrogenic diabetes insipidus |
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What are 2 components to performing urinalysis?
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Specific gravity
Dipstick: glucose, protein |
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What are 4 things to examine on the clinical chemistry when dealing with an animal with polyuria/ polydipsia?
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1) Renal parameteres
-BUn, creatinine, K+ 2) Glu 3) Electrolytes -hypoadrenocrticism, hypercalcemia 4) Liver enzyme activities -Alk phos elevated? Cushings 5) Total T4 in adult/ older cats |
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If there's glucose in the urine but not the plasma, what does that make you worry about?
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Fanconi syndrome
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What's the purpose of performing an abdominal ultrasound in an animal with PU/ PD?
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Assess renal architecture (but form does not indicate function), hepatic parenchyma, adrenal size
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What is your next step in an animal with hypercalcemia and PU/ PD?
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*Lymphoma or primary hyperparathyroidism -start looking for tumors
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What is the plasma osmolality like in an animal with central diabetes insipidus or nephrogenic diabetes insipidus?
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High
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What is the plasma osmolality in patients with psychogenic polydipsia?
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Low
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what is the etiology of polyuria in CDI or NDI? Psychogenic polydipsia?
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CDI, NDI; primary, unable to concentrate
Psychogenic polydipsia: secondary to increased water intake |
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When is the acute water deprivation test used?
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Don't do it!
Lethally dangerous, potential for severe dehydration and hyperosmolality -very bad idea |
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What are the 2 goals of the modified water deprivation test?
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1) Assess release of ADH in response to dehydration
2) Assess kidney's response to ADH -endogenous/ exogenous -DDAVP (desmopressin acetate) |
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What can the modified water deprivation test distinguish as a cause of PU/PD?
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CDI
Primarily NDI Psychogenic polydipsia -*All other DDX must be ruled out already!!!! RARLY indicated |
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what are 2 contraindications to using the modified water deprivation test?
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1) Clinically dehydrated
2) Plasma osmolality > 320 mOsm/kg |
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What is phase I of the modified water deprivation test?
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Restore renal medullary gradient
-graduated reduction in water available over several days, restores medullary hyperosmolality |
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What is phase II of the modified water deprivation test?
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Dehydrate animal (over ~8 hours)
-Monitor urine concentration, BW |
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What does it mean if an animal is able to concentrate its urine in phase II of the water deprivation test?
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Psychogenic polydipsia
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What is phase III of the modified water deprivation test?
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Exogenous administration of ADH
-determines if kidneys can respond |
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What does it mean if there's no response to phase III of the water deprivation test?
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Nephrogenic Diabetes insipidus
-if not response CDI |
