Pseudopregnancy (phantom pregnancy; false pregnancy; pseudocyesis) is a relatively common phenomenon in small dogs characterized by pregnancy behaviour, physical changes associated with pregnancy, but the absence of foetuses.
Pseudo pregnancy is a normal physiological process that occurs in female dogs, not usually associated with reproductive organ disorders. It is seen 45 - 60 days after a normal estrous (heat) period, as progesterone levels, which rise after ovulation, begin to fall. Decreasing progesterone leads to an increase of prolactin, responsible for most of the behaviors seen during a pseudopregnancy episode.
Histologically, during late metoestrous, endometrial epithelial surface cells frequently accumulate fat and thereby adopt a foamy morphology, giving the endometrial lining a characteristic foamy appearance during pseudopregnancy.
Clinical signs include mothering of toys, nesting, or even aggression. Mammary development and milk production are common.
Mastitis and vaginal hyperplasia are sometimes observed as a complication. Pseudopregnancy can also be acutely induced by spaying a dog near the end of estrus.
Diagnosis is based on the presence of typical clinical signs in metaoestrous non-pregnant bitches.
Treatment usually involves hysterectomy or allowing time for symptoms to abate by normal hormonal resolution.
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