Clinical Exposures: Preovulatory stasis and dystocia in oviparous lizards


Clinical Exposures: Preovulatory stasis and dystocia in oviparous lizards

1. A dorsoventral radiograph of a bearded dragon with preovulatory stasis. Note the multiple rounded coalescing soft tissue opacities throughout the caudal half of the coelomic cavity, consistent with follicles.
A 2-year-old intact female bearded dragon (Pogona vitticeps) was presented to Tufts University's Cummings School of Veterinary Medicine for evaluation of weakness and anorexia of one day's duration. On initial presentation, the bearded dragon was lethargic, with a distended coelom and pale mucous membranes. The results of the initial blood work revealed severe anemia; the patient's packed cell volume was 6% (reference range = 24% to 36%).1 A dorsoventral radiograph revealed multiple rounded (about 1 cm in diameter), coalescing, soft tissue opacities throughout the caudal coelomic cavity (Figure 1). Preovulatory stasis was tentatively diagnosed. Coelomic ultrasonography was recommended to evaluate the abdominal opacities, but the owner declined further investigation.

The bearded dragon was hospitalized, an intraosseous catheter was placed in the left tibia, and fluid therapy was initiated. Reptile Ringer's solution (i.e. one part lactated Ringer's solution, two parts 2.5% dextrose/0.45% saline solution)1 was administered at a rate of 25 ml/kg/day. The lizard was placed in a heated, humidified cage with an ambient temperature of 85 F (29.5 C). The reptile became increasingly lethargic and weak over the next 12 hours. Because there was no improvement and the lizard's condition carried a poor prognosis, the owner elected euthanasia and a postmortem examination.

2. Postmortem examination of the coelomic cavity of a female bearded dragon with preovulatory stasis. The liver shows normal fatty change associated with vitellogenesis. Both ovaries contain numerous round, bright-yellow, nonshelled vitellogenic follicles. Part of the small and large intestines, both kidneys (K), and the fat bodies (FB) are also shown.
Necropsy revealed that the coelomic cavity contained about 10 ml of serosanguineous fluid. Each ovary contained about 30 enlarged (1-cm-diameter), round, bright-yellow vitellogenic follicles (Figure 2). The liver was diffusely pale-yellow, a typical physiologic finding in species that lay large numbers of eggs.

A histologic examination of the ovaries revealed that the follicles contained large amounts of bright eosinophilic proteinaceous yolk surrounded by several layers of flattened epithelial cells. Bone marrow, collected from the proximal aspects of the humerus and femur, was atrophic and composed mostly of sheets of intact adipocytes with rare hematopoietic cells, explaining the low hematocrit. The liver showed diffuse fatty change. The clinical history and gross and histologic findings were most consistent with a diagnosis of preovulatory stasis (follicular stasis). Marrow aplasia, which was seen in this lizard, is not a typical finding with this condition but may have been caused by estrogen toxicosis, as a result of the high estrogen concentrations associated with follicular growth. While estrogen-induced marrow aplasia has been well-documented in dogs and ferrets,2 this effect has not been reported in reptiles.