It is not always what it seems: allantochorion cervical pole necrosis.

It describes a case of a pregnant mare that showed signs of possible abortion, and after complications and testing, the diagnosis revealed necrosis of the allantochorion at the cervical pole, linked to placental infarction and infection, highlighting the importance of histological examination for accurate diagnosis.

Case Summary

• A 286-day pregnant mare was referred due to signs suggesting impending abortion.
• Ultrasound showed a high normal combined thickness of the utero-placental unit (CTUP), decreased allantoic fluid (oligohydroallantois), and a living fetus.
• No vulvar discharge and negative cervical swab culture suggested no overt infection initially.

Clinical Events and Treatment

• The mare experienced a choke (esophageal obstruction), for which NSAIDs and antibiotics were administered.
• Following treatment, the mare developed systemic inflammatory response syndrome (SIRS), a serious systemic condition often related to infection or injury.
• Subsequently, the mare aborted the fetus.

Findings at Abortion

• The amniotic portion of the umbilical cord was found to be excessively long and twisted, which might impact blood flow.
• The chorionic side of the placenta displayed a brownish discoloration with roughened surface areas indicating tissue damage.
• Escherichia coli (E. coli) was isolated from fetal membranes, fetal fluids, and fetal tissues, pointing to an infectious process.

Histopathological Examination

• The chorial villi located at the cervical pole of the placenta showed degeneration and necrosis.
• Dystrophic calcification was also present, which is a sign of chronic tissue injury or infarction.
• These findings confirmed placental infarction and secondary placentitis (infection and inflammation of the placenta).

Diagnosis and Implications

• The final diagnosis was abortion due to placental infarction with secondary bacterial infection (placentitis).
• Cervical pole necrosis is a poorly understood condition of the allantochorion (the fetal membrane attached to the uterus near the cervix).
• This case underscores that gross clinical and ultrasonographic findings may not fully reveal the underlying pathology.
• A histological exam of the placenta and membranes is essential for definitive diagnosis in such cases of pregnancy loss in mares.

Clinical Significance

• Early ultrasonographic signs such as increased CTUP alone may be ambiguous and need further investigation.
• Despite the absence of initial vulvar discharge and negative cervical swab, severe placental pathology and infection were present.
• Management of pregnant mares with systemic illness and risk of abortion requires thorough diagnostic approaches.