Dystocia in a rabbit (Oryctolagus cuniculus)

A 4-year-old female dwarf lop rabbit was presented with dystocia after mis-mating. Abdominal palpation, vaginal examination, and radiography confirmed that the doe was carrying 3 kits. Treatment for the dystocia consisted of gentle manual extraction of the fetuses and fetal membranes, and administration of oxytocin and calcium borogluconate.     

Evaluation of alfaxalone total intravenous anesthesia in rabbits (Oryctolagus cuniculus) premedicated with dexmedetomidine or dexmedetomidine and buprenorphine

ObjectiveTo evaluate alfaxalone for total intravenous anesthesia (TIVA) in rabbits premedicated with dexmedetomidine or dexmedetomidine and buprenorphine.Study designCrossover study (part 1) with observational study (part 2).AnimalsA total of eight New Zealand White rabbits (Oryctolagus cuniculus), four female and four male, aged 12–16 weeks and weighing 2.8–3.5 kg in part 1. Separately, four additional rabbits in part 2.MethodsCrossover study design with eight rabbits per treatment. Rabbits were administered treatment D, dexmedetomidine (0.2 mg kg^–1), or treatment DB, dexmedetomidine (0.1 mg kg^–1) and buprenorphine (0.05 mg kg^–1) intramuscularly. Anesthesia was induced with alfaxalone intravenously until a supraglottic airway device was placed to deliver 100% oxygen. Anesthesia was maintained with alfaxalone (TIVA). Infusion rates were adjusted to achieve an absent pedal withdrawal reflex. Heart rate, respiratory rate, noninvasive blood pressure, end-tidal carbon dioxide partial pressure and peripheral hemoglobin oxygen saturation (SpO₂) were recorded every 5 minutes. Subsequently, four rabbits underwent ovariohysterectomy using treatment DB and alfaxalone TIVA.ResultsThe mean ± standard deviation alfaxalone infusion rate was 9.6 ± 2.6 and 4.5 ± 1.3 mg kg^–1 hour^–1 for treatments D and DB, respectively. In both treatments, blood pressure remained within acceptable range and SpO₂ was > 95%. Postinduction apnea and respiratory depression were observed in both treatments and managed with manual positive pressure ventilation. Four separate rabbits underwent successful ovariohysterectomy with treatment DB and alfaxalone TIVA. One rabbit required supplementation with inhalant anesthesia; three rabbits were successfully maintained using alfaxalone TIVA alone.Conclusions and clinical relevancePremedication with dexmedetomidine–buprenorphine combined with alfaxalone TIVA may be a viable alternative for performing abdominal surgery in the rabbit. The use of supplemental oxygen and ability to provide respiratory support are advised.     

Spontaneous osteosarcoma in a rabbit ( Oryctolagus cuniculus)

A 6-year-old male cross-breed rabbit ( Oryctolagus cuniculus) was presented with lameness and severe swelling from the right shoulder to brachium. On 16-detector helical computed tomography images of the amputated right forelimb after being fixed in formalin, evident proliferative and destructive lesions of bone were observed. On histologic examination, the tumor was composed of proliferating neoplastic cells that resembled histiocytes, with abundant osteoid production. A large number of multinucleated giant cells were found throughout. This case was diagnosed as osteosarcoma by clinical, radiographic, and histologic findings. This is a rare case report of osteosarcoma in a rabbit consistent with canine predilection sites.     

Spontaneous deciduosarcoma in a domestic rabbit (Oryctolagus cuniculus)

Deciduosarcoma is a rare, hormonally dependent neoplasm with features of malignancy, previously reported only in rabbits enrolled in chronic toxicology studies involving estrogens with or without progestins. An exploratory laparotomy was performed on a 6-year-old pet Dutch dwarf rabbit following palpation of a 6-cm-diameter abdominal mass. Grossly, the mass was fleshy and nodular, adhered to but not appearing to originate from the small intestine, with a smaller mass of similar appearance involving the uterus, and an effaced mesenteric lymph node. Histologically, the mass was characterized by spindloid cells and large epithelioid cells with abundant pale eosinophilic vacuolated cytoplasm and an infiltrative pattern of growth. Giant cells with large, bizarre, hyperchromatic nuclei were common. Cells were positive by immunohistochemistry for vimentin and progesterone and estrogen receptors and negative for pancytokeratin (AE1/AE3), cytokeratin 18, desmin, alpha-smooth muscle actin (SMA), and CD10. Based on histologic and immunohistochemical findings, a diagnosis of deciduosarcoma was made.     

Extraskeletal fibroblastic osteosarcoma in a rabbit (Oryctolagus cuniculus)

A seven-year-old rabbit was presented with a non-painful mass in the right upper lip. Tissue samples from the mass at three different stages of the disease process were diagnosed sequentially as an osteogenic sarcoma, a fibroblastic tumour with rudimentary osteoid formation and, lastly, a fibrosarcoma. No bone involvement or metastatic disease was found. The final diagnosis was of an extraskeletal fibroblastic osteosarcoma, which is, to the authors' knowledge, the first reported such case in a domestic rabbit. Without the first two tissue samples, an incorrect diagnosis would have been reached; therefore, this disease may be underrepresented in the literature.     

Ossifying fibroma in a miniature rex rabbit (Oryctolagus cuniculus)

In humans and animals, ossifying fibroma is a benign neoplasm that most frequently affects the mandible, often resulting in cosmetic deformities and malocclusion. It is considered rare in animals and most frequently affects young horses. A surgical biopsy of a solitary mass located beneath the gingiva in the right maxillary region, which had overgrown teeth and expanded the adjacent hard palate from a 6-year-old miniature Rex rabbit was submitted for light microscopic examination. The submitted incisional biopsy specimen was pale pink, firm, and nodular. Histopathologically, the neoplasm was composed of fibroblastic cells separated by abundant collagen. The neoplastic cells were interwoven with osteoblasts surrounding islands of mineralized, bony matrix containing few, widely spaced, often empty, lacunae. Minimal inflammation was present. Based on the histopathologic features, the tumor was diagnosed as an ossifying fibroma. To our knowledge, this is the first report of an ossifying fibroma in a rabbit.     

Pharmacokinetics of ketamine following a short intravenous infusion to isoflurane-anesthetized New Zealand White rabbits (Oryctolagus cuniculus)

ObjectiveTo describe the pharmacokinetics of ketamine following a short intravenous (IV) infusion to isoflurane-anesthetized rabbits.Study designProspective experimental study.AnimalsA total of six adult healthy female New Zealand White rabbits.MethodsAnesthesia was induced with isoflurane in oxygen. Following determination of isoflurane minimum alveolar concentration (MAC), the isoflurane concentration was reduced to 0.75 MAC and ketamine hydrochloride (5 mg kg^–1) was administered IV over 5 minutes. Blood samples were collected before and at 2, 5, 6, 7, 8, 9, 13, 17, 21, 35, 65, 125, 215 and 305 minutes after initiating the ketamine infusion. Samples were processed immediately and the plasma separated and stored at –80 °C until analyzed for ketamine and norketamine concentrations using liquid chromatography–mass spectrometry. Compartment models were fitted to the concentration–time data for ketamine and for ketamine plus norketamine using nonlinear mixed-effects (population) modeling.ResultsA three- and five-compartment model best fitted the plasma concentration–time data for ketamine and for ketamine plus norketamine, respectively. For the ketamine only model, the volume of distribution at steady state (Vss) was 3217 mL kg^–1, metabolic clearance was 88 mL minute^–1 kg^–1 and the terminal half-life was 59 minutes. For the model including both ketamine and norketamine, Vss were 3224 and 2073 mL kg^–1, total metabolic clearance was 107 and 52 mL minute^–1 kg^–1 and terminal half-lives were 52 and 55 minutes for the parent drug and its metabolite, respectively.Conclusions and clinical relevanceThis study characterized the pharmacokinetics of ketamine and norketamine in isoflurane-anesthetized New Zealand White rabbits following short IV infusion. The results obtained herein will be useful to determine ketamine infusion regimens in isoflurane-anesthetized rabbits.     

Solitary biliary hamartoma with cholelithiasis in a domestic rabbit (Oryctolagus cuniculus)

Hamartomas of the liver and biliary system are extremely rare entities in both animals and humans. Biliary hamartomas in humans are usually multiple and constitute the von Meyenburg complexes. This report describes the presence of a large solitary mass arising from the edge of the right medial liver lobe of a domestic rabbit. Histologically, the mass was composed of an extensive network of large varying sized cystic structures lined by simple cuboidal to columnar epithelium within an abundant fibrous stroma. Within many of the cyst lumina were varying sized, pale white to greenish hard concretions identified as choleliths and were analyzed and found to be composed of calcium carbonate. This is the first known report of biliary hamartoma with cholelithiasis in rabbits.     

Fungiform papillae of the tongue in the rabbit (Oryctolagus cuniculus)

Examinations were conducted on four tongues of adult rabbits (Oryctolagus cuniculus). On the basis of observations in a scanning electron microscope (SEM) it was found that fungiform papillae in the rabbit are located on the dorsal surface of the apex and body of the tongue, in the front of the torus of the tongue and on the margins of the tongue. Moreover, fungiform papillae are located laterally in relation to the torus of the tongue and are arranged linearly. Fungiform papillae are distributed among filiform papillae and are separated from them by the interpapillary epithelium. The connective tissue core of fungiform papillae is formed from the body, narrow at the base and wider at the apex and 10-17 crest-like folds arranged around them. On the dorsal surface of the connective tissue core of fungiform papillae there are impressions of taste buds and occasionally traces of lymphatic nodules.     

Effect of romifidine on gastrointestinal motility, assessed by transrectal ultrasonography.

A technique of transrectal ultrasonography was developed to investigate the effects of romifidine 80 and 120 microg/kg bwt on intestinal motility in the horse. Motility of the small intestine, caecum and left ventral colon were assessed following injection of romifidine and a saline control, using a blinded, cross-over study design in 6 horses. Measurements were taken at 15, 30, 60, 120, 180 and 240 min after drug administration. There was a slight nonsignificant decrease in motility in the control group over the 4 h study period. Both doses of romifidine produced a marked decrease in gastrointestinal motility and were associated with the presence of reduced (nonpropulsive) contractions. Transrectal ultrasonography proved suitable for monitoring changes in the type and frequency of intestinal motility in the horse.     

Intra-abdominal torsion of a neoplastic testicle in a rabbit (Oryctolagus cuniculus) with cryptorchidism

Background: Testicular torsion is a relatively common complication of cryptorchidism in domestic mammals but is currently unreported in rabbits. Case presentation: A 7-year-old Dutch rabbit was examined for sudden anorexia and lethargy. The rabbit was previously diagnosed with unilateral cryptorchidism 5 years earlier; however, the owner declined surgical treatment at that time. Transabdominal ultrasonography showed a structure consistent with an enlarged testis, with decreased echogenicity, and absent blood flow upon color Doppler ultrasonography. After induction of general anesthesia and during preparation for surgery, the patient had an episode of cardiac arrest. After successful resuscitation, bilateral cryptorchidectomy continued as planned. A ventral midline laparotomy was performed and confirmed presence of an enlarged, dark red left testicle torsed on its spermatic cord. The contralateral testicle was atrophic. Both testicles were removed after standard hemostasis. Recovery was uncomplicated. Histopathologic examination revealed a diagnosis of Sertoli cell tumor and extensive hemorrhage and necrosis in the torsed testicle. Conclusions and Clinical Relevance: Based on literature search, this is the first reported case of intra-abdominal torsion of a neoplastic testicle in a cryptorchid rabbit. Early elective cryptorchidectomy before the potential development of life-threating complications may be beneficial in rabbits as in other species.     

Osteosarcoma with multiple metastases and subcutaneous involvement in a rabbit (Oryctolagus cuniculus)

BACKGROUND: Osteogenic sarcomas are rare in rabbits, but cases involving the mandible, ribs, frontal bones, and tibia have been reported. OBJECTIVE: The purpose of this study was to describe the clinical and pathologic findings in a rabbit with osteosarcoma and multiple metastases with subcutaneous involvement. METHODS: A 1-year-old female Polish rabbit was evaluated for dysorexia, lameness, gait difficulties with the hind limbs, and the presence of 2 subcutaneous nodules, on the left thigh and in the dorsal region. A hard swelling was also present at the base of the tail. Radiographic findings revealed multiple abnormalities in several bones, which were more severe in the sacrococcygeal region and femur. Several areas of calcification involving the thorax and abdomen as well as skeletal muscles, also were noted. The thigh nodule was surgically removed, and cytologic and histologic evaluations were performed. Following the rabbit's death, postmortem radiographs were taken and necropsy was performed. Samples of tissues and organs, involved bone segments, and other subcutaneous nodules were collected and examined by cytology and histology. RESULTS: Both the subcutaneous nodules and the majority of tissues and organs contained neoplastic cells whose appearance was consistent with osteogenic sarcoma. CONCLUSION: Clinical, radiologic, and pathologic data supported a diagnosis of osteosarcoma with multiple metastases and subcutaneous involvement.     

Renal embryonal nephroma exhibiting malignant features in a Dutch rabbit (Oryctolagus cuniculus)

BackgroundBenign embryonal nephromas have been documented in rabbits. However, only one case of nephroblastoma with concurrent metastasis (pulmonary), a postmortem incidental finding, has been published.Case presentationA 3-year-old neutered male Dutch rabbit (Oryctolagus cuniculus) was referred for assessment of a firm mass located in the mid-dorsal abdomen. Abdominal ultrasonography confirmed a large soft tissue mass of suspected renal origin. A left-sided nephrectomy was performed via a ventral midline approach. Multiple white macular lesions, hyperemia, and petechiae were observed in the mesenteric fat surrounding the spleen. Histopathological examination of the abnormal kidney and the mesenteric fat revealed microscopic findings consistent with an embryonal nephroma exhibiting distinct features of malignancy. At 6- and 12-month postsurgery, ultrasonographic evidence of tumor recurrence was not observed.Conclusion and case relevanceThis is the first report of successful treatment of an embryonal nephroma showing malignant behavior and metastasis to the surrounding adipose tissue with a minimum postoperative survival time of 12 months and no ultrasonographic evidence of local recurrence.