Objective—To determine vasopressin (VP) secretory
capacity during osmotic stimulation and the response
to desmopressin treatment in dogs with pyometra
and control dogs.
Animals—6 dogs with pyometra before and after
ovariohysterectomy and 6 control dogs.
Procedure—Urine osmolality (Uosm) was measured
during 12 hours. Values measured on the first day
defined the basal Uosm pattern. On the second day,
dogs were given desmopressin to induce a desmopressin-stimulated Uosm pattern. On day 3, the VP
response to osmotic stimulation was examined.
Results—Median Uosm on day 1 was 340 mOsm/kg
(range, 104 to 1,273 mOsm/kg) and 807 mOsm/kg
(range, 362 to 1,688 mOsm/kg) in dogs with pyometra
before and after surgery, respectively, and 1,511
mOsm/kg (range, 830 to 1,674 mOsm/kg) in control
dogs. Median Uosm during desmopressin treatment
was 431 mOsm/kg (range, 168 to 1,491 mOsm/kg)
and 1,051 mOsm/kg (range, 489 to 1,051 mOsm/kg) in
dogs with pyometra before and after surgery, respectively,
and 1,563 mOsm/kg (range, 1,390 to 2,351) in
control dogs. In dogs with pyometra, threshold for VP
secretion was lower before surgery (median, 340
mOsm/kg; range, 331 to 366 mOsm/kg) than after
surgery (median, 358 mOsm/kg; range, 343 to 439
mOsm/kg) or in control dogs (median, 347 mOsm/kg;
range, 334 to 360 mOsm/kg). Highest maximum plasma
VP values were found in dogs with pyometra.
Conclusions and Clinical Relevance—Dogs with
pyometra had increased urine concentration in
response to desmopressin but not to the degree of
control dogs, whereas VP secretory ability was not
reduced. (Am J Vet Res 2004;65:404–408)