Clinical Exposures: Preovulatory stasis and dystocia in oviparous lizards - Veterinary Medicine
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Clinical Exposures: Preovulatory stasis and dystocia in oviparous lizards

Diagnosis

Diagnosing preovulatory stasis or dystocia can be problematic because it can be difficult to differentiate between true reproductive system pathology and the normal phases of egg development. The presence of eggs in the coelom can be easily detected by ultrasonography, which allows the distinction between shelled eggs and preovulatory follicles. (Shelled eggs are oblong rather than rounded and are arranged in a line rather than in clusters. Shelled eggs have a hypoechoic center and a hyperechoic perimeter [shell].7 ) Radiography can be useful in determining egg positioning, but it can be difficult to detect nonshelled eggs, and if visible, it may not be possible to determine if the eggs have well-developed shells. Lizard eggs may be detected by abdominal palpation by experienced practitioners, but it is best to confirm their presence by abdominal radiography or ultrasonography because other masses could be mistaken for eggs.

After confirming the presence of eggs, the next step is to determine whether the animal is undergoing the normal physiologic order of events that will lead to egg deposition or if it is experiencing preovulatory stasis or dystocia. Obtaining a good history, observing clinical signs, and performing supplemental diagnostic tests are fundamental to an accurate diagnosis. An extremely swollen abdomen is common in normal, gravid female lizards, and some females will not eat for several weeks before laying eggs. However, a normal, gravid female is active and alert. Acute onset of lethargy or unresponsiveness, tremors, weight loss, or a dull skin color are important abnormalities.8 Carefully question the owner about all husbandry practices to detect possible husbandry-related problems.

If the reptile has already passed several eggs and additional eggs remain in the coelomic cavity, dystocia is most likely, especially if the animal is depressed and reluctant to move. If the animal has not passed any eggs and is depressed and abdominal palpation and radiography or ultrasonography confirm that nonshelled eggs are in the coelom, preovulatory stasis is most likely. In some cases, it can be difficult to discern between a nonshelled and a shelled egg, so dystocia should remain on the list of differential diagnoses.

Treatment


4. Surgical removal of the ovaries with multiple follicles. Shelled eggs are present within the oviduct. The shelled eggs were also removed but not the oviduct. (Image courtesy of Paolo Selleri, Dr. med. Vet., Centro Veterinario Specialistico, Rome Italy.)
Ovariectomy is the treatment for preovulatory follicular stasis (Figure 4).6 In rare species, follicle removal can be attempted but only by surgeons with experience performing this procedure. If follicles fail to ovulate and are not reabsorbed or surgically removed, they may coalesce, forming a large friable yolk mass. If this mass ruptures, it can result in severe inflammation and possible death. In this case, the owner declined surgery because of the lizard's poor prognosis.

With dystocia, if the animal is not severely debilitated, medical therapy and physical massage to assist in egg passage can be attempted.3 However, physical massage is not recommended in lizards, especially for inexperienced veterinarians. The eggs may rupture and cause serious pathology (such as egg yolk coelomitis). Administering calcium gluconate, subcutaneous fluids, and oxytocin and providing a warm and humid environment may help the reptile pass the shelled eggs. However, it is important to first rule out preovulatory stasis since medical therapy with calcium and oxytocin will be ineffective if the lizard has this condition. Surgery (to remove the shelled eggs and the ovaries) may be necessary if medical therapy fails. If surgery is required, it is advantageous to first stabilize the animal. A complete blood count and serum chemistry profile are important in ruling out infection or organ failure.

CONCLUSION

The reproductive diseases discussed above are common in captive female reptiles, but obtaining an accurate diagnosis and resolving the problem can be difficult for practitioners with little experience in reptile medicine. Prevention remains the best approach, so properly educating reptile owners is essential. Elective ovariectomy of lizards and chelonians should be considered but is best performed by exotic-animal specialists.

This case report was provided by Raffaele Melidone, Dr. med. vet.; Joyce S. Knoll, VMD, PhD, DACVP; and Nicola Parry, BSc, MSc, BVSc, DACVP, Department of Biomedical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536.

REFERENCES

1. Campbell TW. Clinical chemistry of reptiles. In: Thrall MA, Baker DC, Campbell TW, et al. eds. Veterinary hematology and clinical chemistry. Philadephia, Pa: Lippincott Williams & Wilkins, 2004;493-498.

2. Hart JE. Endocrine pathology of estrogens: species differences. Pharmacol Ther 1990;47(2):203-218.

3. DeNardo D. Dystocias. In: Reptile medicine and surgery. 2nd ed. St. Louis, Mo: Elsevier Saunders, 2006;787-792.

4. DeNardo D. Reproductive biology. In: Reptile medicine and surgery. 2nd ed. St. Louis, Mo: Elsevier Saunders, 2006;376-390.

5. Diethelm G. Reptiles. In: Exotic animal formulary. 3rd ed. St. Louis, Mo: Elsevier Saunders, 2005;53-131.

6. Mader DR, Bennett A, et al. Surgery. In: Reptile medicine and surgery. 2nd ed. St. Louis, Mo: Elsevier Saunders, 2006;594.

7. Stetter MD. Ultrasonography. In: Reptile medicine and surgery. 2nd ed. St. Louis, Mo: Elsevier Saunders, 2006;665-674.

8. Wissman MA. When to intervene in reptile parturition. Veterinary Practice News http://www.veterinarypracticenews.com/vet-dept/avian-exotic-dept/reptile-breeding.aspx. Accessed October 20, 2008.


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Source: VETERINARY MEDICINE,
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