Canine Fetus with Presumed Encephalitis and Hydrocephalus: Qualiquantitative Ultrasonographic Evaluation of the Central Nervous System

Abstract

Background: Cerebral echobiometry involves the ultrasound evaluation of the brain by analyzing the appearance of cerebrospinal fluid and cranial structures, and measuring them, aiding in the investigation and monitoring of central nervous system disorders. Brain mass and volume indices (BMI and BVI) can be measured during the intrauterine period, providing valuable information for the early and accurate diagnosis of disorders such as ventriculomegaly. The study aimed to describe a case of presumed hydrocephalus and meningoencephalitis in a 5-week-old canine fetus, and to report the role of a quali-quantitative ultrasonographic approach to the detection and monitoring of this condition.

Case: A 1-year-and-9-month-old bitch Pinscher, weighing 1.59 kg, with a 31-day history of mating, was brought to the veterinary hospital with a dark, bloody vulvar discharge for one day. Ultrasound evaluation revealed the right uterine horn filled with anechogenic fluid and suspended echogenic spots, along with a viable fetus with a mean heart rate of 211 bpm, surrounded by an echogenic and irregular placenta. Gestational age was estimated at approximately 30 days, based on organogenesis. Subsequent ultrasonographic exams detected the fetus with an enlarged cranial vault and lateral ventricles distended with a hypoechoic content and suspended echogenic particles. Both BMI and BVI were lower than reference values (0.09 e 0.016, respectively), due to the increased area of the cranium (1.13 cm²) and its volume (0.863 cm³) and reduced brain mass area (0.05 cm² each hemisphere) and volume (0.006 cm³ and 0.008 cm³). The brain mass was irregular, hyperechoic, and retracted. On day 7 after presentation, the animal underwent an uneventful ovariohysterectomy. The right uterine horn revealed an amniotic sac containing an underdeveloped fetus with an enlarged, bulging skull. Fetus was exteriorized and euthanized due to the previous reported alterations, incompatible with life.

Discussion: The presumptive diagnosis of hydrocephalus was based on the progressive ventricular dilation and decreased brain mass (atrophy). These changes influenced the decrease in brain mass and volume indices observed in this study. The ​​BMI and BVI values were below normal, indicating underdevelopment of the fetal brain relative to cranial growth, and corroborating qualitative ultrasound findings of hyperechoic brain mass with an irregular appearance and ventricular dilation. Hyperechoic spots within the anechogenic cerebrospinal fluid (suggesting cellular debris) associated with cortical shrinkage (atrophy) and increased echogenicity of the brain parenchyma may suggest brain inflammation in dogs. However, the definitive diagnosis of meningoencephalitis typically relies on serological testing and cerebrospinal fluid analysis, with histopathological analysis (considered the gold standard). This case report highlighted the importance of qualitative and quantitative intrauterine ultrasound in the early diagnosis and monitoring of central nervous system abnormalities in the referred fetus. Brain echobiometry, through the assessment of brain mass and volume indices, provided an objective measure of cerebral development and the progression of structural alterations. Despite the lack of histopathological or serological confirmation, the detection of alteration in the echogenicity of the cerebral fluid pointed to an extra concern (meningoencephalitis) to be addressed along with the hydrocephalus. Therefore, this ultrasonographic approach can inform obstetric management by predicting the risk of dystocia, guiding the timing of surgical intervention during delivery, and supporting targeted postpartum care, ultimately contributing to a reduction in neonatal losses.

Keywords: dog, brain mass index, brain volume index, ventriculomegaly, ultrasonography.