Imaging diagnosis of intrauterine fetal death in a cat with singleton pregnancy.

A 4-year-old intact 3.4 kg domestic mixed-breed queen presented with a 48-hour history of lethargy, polydipsia, inappetence, and sanguineous vaginal discharge. Abdominal palpation identified a firm, painful mid-abdominal mass. Hematology indicated a stress leukogram with granulocytosis and lymphopenia. Abdominal radiography demonstrated intracardiac gas accumulation and calvarial bone overriding, pathognomonic signs of intrauterine fetal death. Fetal biometry confirmed term gestation; pelvimetry established fetopelvic compatibility, excluding obstructive dystocia. Absence of pendulous soft tissue opacities along the thoracoabdominal mammary chains radiographically corroborated the clinical absence of mammary development, atypical at term. Abdominal ultrasonography revealed a heterogeneous echotexture with diffuse dirty acoustic shadowing and reverberation artifacts consistent with intrauterine and intrafetal emphysematous gas, alongside discrete clean acoustic shadowing artifacts attributable to hyperechoic mineralized skeletal foci of the macerated fetus. Additionally, a round, non-peristaltic structure presumed to represent the nongravid uterine horn was suggestive of concurrent purulent metritis. Laparotomy revealed no peritonitis or intra-abdominal adhesions. Ovariohysterectomy confirmed a single emphysematous fetus, weighing 176 g, with fetid serosanguinous exudate in the gravid horn and hemopurulent fluid in the contralateral horn. Recovery was uneventful; hematologic parameters normalized by week 4. Fetal overgrowth combined with attenuated cumulative cortisol production and insufficient myometrial mechanostimulation were proposed to have precluded luteolysis, causing primary uterine inertia and failure of parturition initiation. Absent mammary development corroborated luteolysis failure through sustained progesterone-mediated suppression of prolactin-driven lactogenesis. Cervical patency most likely facilitated ascending bacterial contamination, yielding emphysematous maceration rather than sterile mummification. In conclusion, multimodal diagnostic imaging is highly valuable in feline obstetrical emergencies, suggesting that singleton gestations represent a documented risk factor for dystocia that may justify rigorous monitoring as the patient approaches term.