Prolonged Proestrus in a Young Spitz: A Case-Based Approach to Diagnosis and Management

Article

Prolonged Proestrus in Dogs Canine Reproductive Disorders Estrous Cycle Abnormalities Vaginal Cytology in Dogs Vaginal Cytology in Dogs Infertility in Bitches Prolonged Vaginal Bleeding in Dogs Canine Estrous Cycle Management Ovarian Dysfunction in Dogs Reproductive Endocrinology in Dogs

Prolonged Proestrus in a Young Spitz: A Case-Based Approach to Diagnosis and Management

Reproductive cycle abnormalities are a common cause of infertility in bitches, yet some conditions can be easily overlooked during routine clinical examinations. One such disorder is prolonged proestrus, a condition characterized by an extended proestrous phase lasting three weeks or longer without progression to estrus and ovulation¹. Early recognition is essential to prevent prolonged reproductive dysfunction and guide appropriate treatment.

Understanding Prolonged Proestrus

The normal canine estrous cycle consists of proestrus, estrus, diestrus, and anestrus. In prolonged proestrus, the bitch exhibits persistent signs of heat, including vulvar swelling and vaginal bleeding, but fails to transition into estrus due to inadequate estrogen stimulation. As a result, ovulation does not occur, potentially leading to infertility if the condition remains undiagnosed.

Other reproductive cycle abnormalities seen in bitches include prolonged estrus, split estrus, anovulatory cycles, shortened or prolonged interestrous intervals, and anestrus. Many of these disorders arise from abnormal ovarian function and can significantly impact breeding outcomes¹.

The Case Presentation

A one-year-old Spitz was presented to the Teaching Veterinary Clinical Complex (TVCC), Durg, with a history of vaginal bleeding that had persisted for approximately 20–25 days².

Clinical examination revealed that all vital parameters were within normal limits. However, the vulvar lips were markedly swollen, suggesting that the bitch was in the proestrous phase of the reproductive cycle. Vaginal examination confirmed the presence of hemorrhagic discharge, but no masses or abnormal growths were detected².

The prolonged duration of bleeding raised concerns about an abnormal estrous cycle, prompting further reproductive evaluation.

Diagnostic Work-Up

Vaginal cytology was performed to assess the stage of the estrous cycle. Smears were stained using the Giemsa staining technique and examined microscopically.

Cytological evaluation revealed²:

Approximately 40–50% superficial epithelial cells

Large numbers of red blood cells (RBCs)

The persistence of vaginal bleeding along with the cytological findings supported a diagnosis of prolonged proestrus.

Previous reports have indicated that prolonged hemorrhagic vaginal discharge, combined with elevated percentages of cornified cells and low serum progesterone concentrations (<2 ng/mL), is suggestive of prolonged proestrus².

Therapeutic Intervention

The bitch was treated with human chorionic gonadotropin (hCG) at a dose of 500 IU administered intramuscularly at two-day intervals.

The objective of treatment was to stimulate ovarian activity and facilitate progression of the reproductive cycle.

Outcome

Clinical improvement was observed following therapy. Vaginal bleeding gradually diminished, and the estrous episode resolved completely within approximately 15 days.

Follow-up vaginal cytology demonstrated a marked change in cellular composition:

Absence of RBCs

Predominance of intermediate cells

Presence of a few parabasal cells

These findings indicated successful resolution of the prolonged proestrous state and return toward normal reproductive cyclicity.

Clinical Takeaways for Practitioners

Cases of prolonged vaginal bleeding are not always indicative of reproductive tract pathology. When a bitch presents with an extended proestrous phase, veterinarians should consider reproductive cycle abnormalities as part of the differential diagnosis.

Vaginal cytology remains a valuable and cost-effective diagnostic tool for determining cycle stage and monitoring treatment response. In selected cases, hormonal therapy using gonadotropins such as hCG may help restore normal ovarian function and facilitate cycle progression.

Most importantly, accurate diagnosis is the cornerstone of successful management. A systematic approach combining clinical examination, reproductive history, and vaginal cytology can help clinicians distinguish prolonged proestrus from other reproductive disorders and improve reproductive outcomes in breeding animals.

References

Concannon PW, Castracane VD, Temple M, Montanez A. Endocrine control of ovarian function in dogs and other carnivores. Animal Reproduction (AR). 2018 Jul 26;6(1):172-93. https://www.animal-reproduction.org/article/5b5a606ef7783717068b4766/pdf/animreprod-6-1-172.pdf