Abstract
Background:
Estradiol benzoate (EB) has been used in small-animal practice for lactation suppression in postpartum bitches; however, evidence regarding its safety is limited, and severe adverse events have been insufficiently documented. This report describes the case of a postpartum dog that developed extensive mammary tissue destruction and marked liver enzyme elevation shortly after EB administration.

Case Description:
A four‑year‑old, 4.3‑kg female Teddy dog presented with fever, depression, and severe mammary ulceration seven days postpartum. The dog received 0.5 mg/kg estradiol EB intramuscularly on postpartum day three to suppress excessive lactation. Marked mammary swelling occurred within 12 hours, followed by skin necrosis, ulceration, and fever within 24 hours. Physical examination revealed a 10 × 8-cm full‑thickness mammary wound with exposed parenchyma, necrotic debris, purulent discharge, malodor, and bilateral inguinal lymphadenopathy. Hematology revealed leukocytosis, neutrophilia, monocytosis, and mild thrombocytopenia, with elevated C‑reactive protein. Serum biochemistry revealed severely increased alanine aminotransferase (ALT) and alkaline phosphatase (ALP) levels, consistent with suspected drug-associated acute hepatocellular injury and cholestasis. Staged treatment initially included systemic stabilization and hepatoprotective therapy. Following improved liver enzymes, surgical debridement was performed under general anesthesia, combined with ovariohysterectomy. An incidental uterine nodular lesion was excised en bloc. Post-operative ceftriaxone sodium and wound care were administered. The dog recovered uneventfully with no recurrence of mammary engorgement during follow‑up.

Conclusion:
In a postpartum dog, this case suggests a temporal association between EB administration for lactation suppression and severe adverse outcomes, including extensive mammary tissue injury and acute liver enzyme elevation. This study also highlights the clinical value of a staged treatment strategy in which systemic stabilization precedes definitive surgical intervention. Conservative approaches should be considered first for lactation management, and individualized risk assessment and close clinical monitoring are advisable when pharmacologic suppression is contemplated.

Key words: Dog; Drug-associated liver injury; Estradiol benzoate; Lactation suppression; Postpartum complication.