PU/PD Flashcards
Confirming pathological polydipsia
Dog over 100 mls and cat over 50 mls/ kg a day
Primary polydipsia
“Want to drink”
Lesions causing excessive water intake → polyuria
What causes primary polydipsia
Psychogenic causes (stress)**
Hyperadrenocorticism (behavioral, prominent sign)**
Hepatic encephalopathy
Hyperthyroidism**
Hypothalamic lesion affecting thirst receptors
Drug effect on thirst center (phenobarbitone)
Primary polyuria
“Need to drink”
Lesions causing excessive urine production → polydipsia
Structural renal disease
Extra-renal disease causing renal dysfunction
What are the 4 mechanisms of primary polyuria?
Primary renal: structural renal path.
Extra renal: reduced medullary hypertonicity, absent/ impaired ADH, osmotic diuresis
Primary structural renal disease (# 1 polyuria)
Chronic kidney disease***
Pyelonephritis
Nephrocalcinosis (vit. D calcification)
Bilateral neoplasia (lymphoma)
Reduced medullary tonicity causes (# 2 polyuria)
Hyponatraemia
↓ urea concentration
Endotoxemia
Hypercalcemia and hypokalemia
Hyponatremia
Hypoadrenocoticism (addisons)
Profound gut sodium loss
↓ urea concentration
ADH deficiency/ dysfunction
Liver disease
Endotoxemia
Disrupts the medullary osmotic gradient
Hypercalcemia and hypokalemia
Disrupts the Na-K pump in the ascending loop of Henle→ ↑ Na+ loss
What can cause absent/ reduced/ dysfunctional ADH (# 3 polyuria)
Diabetes insipudis**
Hyperadrenocorticism (cushings)
Hypercalcemia** and hypokalemia
Pyometra
Pyelonephritis (E. coli)
What does absent ADH cause?
↓ urea or water reabsorption
↓ urea concentration
Osmotic diuresis causes (# 4 polyuria)
Glucosuria from diabetes mellitus and renal tubular defect
Active molecules in tubules not allowing resorption
SG < 1.008
Actively diluted
Hyposthenuria
Hyposthenuria
Patient can’t have structural renal disease (CKD, nephrocalcinosis or bilateral neoplasia)
Can have pyelonephritis (disrupting medullary gradient and impaired ADH)
SG 1.008 -1.012
Urine neither diluted or concentrated
Isothenuria
SG > 1.012
Urine concentrated but to some degree
When is SG appropriate?
If <1.030 in dogs or 1.045 in cats in a dehydrated or azotemic patient
SG and primary polydipsia
If no other CS, blood unremarkable and patient bright and happy
NOT USED IF PATIENT UNWELL
