First, we have a study on the effects of intra-abdominal pressure (IAP) on the pneumoperitoneal volume, or the laparoscopic working space. If you are not familiar with the terminology, working space means the volume of abdominal space created by insufflation. The goal is to maximize this while minimizing negative side-effects. Now, onto the study.

Six female rabbits were used for the study, and were randomly allocated sequences of 3 IAPs (4, 8, and 12 mmHg) in a crossover study. After being anesthetized, each rabbit has a subumbilical cannulae were placed, followed by CT scans (dorsal, left lateral oblique, and right lateral oblique recumbencies) to obtain baseline measurements. Each IAP was achieved with CO2 insufflation and maintained for ≥ 15 minutes, and then the abdomen was desufflated for 5 minutes between the different IAPs.

Their results showed that the mean working space volume at an IAP of 8 mmHg was significantly greater than that at 4 mmHg, and was significantly greater at 12 mmHg than that at 8 mmHg. However, adverse effects such as increased PETCO2, tachycardia, and GI stasis were seen. With 8 and 12 mmHg, all rabbits had increased PETCO2 and required higher ventilation rates. The rabbits’ position did not affect working space volume.

The take home message is: there is a nonlinear increase in working space volume with higher IAP in rabbits. The reported adverse effects may be higher at higher IAPs. Depending on the type of procedure and visual access requirements, IAPs > 8 mmHg may not provide a clinically important benefit for laparoscopy in rabbits.

Second, we have a retrospective study on the clinical characteristics and response to treatment of cutaneous squamous cell carcinomas (SCC). SCC is the most common neoplasm in many species, locally invasive, and prone to recurrence. This study compiled 39 cases of spontaneous SCC in order to better characterize the typical presentation, prognosis, and therapeutic response of this neoplasm in pet rabbits. Sixteen of the cases were also sent in for PCR for detection of papillomavirus.

Their results showed that SCC was identified in rabbits between 2 and 10 years of age, with a median age of 7 years. The most common sites were ears and feet, and lighter colored rabbits may be predisposed to developing SCC. Aggressive surgical resection provided the most successful therapeutic option and proved curative in 12 of 23 rabbits. Only one SCC tested positive for papillomavirus, and was located in the oral cavity.

The take home message is: there is a low prevalence of SCC in pet rabbits, and there is site predilection for feet and ears. There is good prognosis with complete surgical resection, and likely a minimal role of papillomavirus in SCC development in rabbits.

Lastly, we have a retrospective study that aimed to determine the clinical behavior of spontaneous intranasal tumours. While respiratory diseases are very common in rabbits, nasal cavity neoplasia is rare. The study compiled data of seven pet rabbits diagnosed with intranasal tumors. 

The most common clinical signs were nasal snoring when breathing, nasal discharge, and subsequent dyspnea and anorexia. Six different histopathological types of tumors were diagnosed: intranasal adenocarcinoma, SCC, osteosarcoma, carcinoid tumor, osteoma, and lymphoma. The patients were all older than 5 years, and no apparent sex predisposition was found.

Skull radiography only revealed the abnormalities in three of seven cases; however, on CT, the masses were more clearly identified in all cases. All tumors were resected through rhinostomy, and four cases received radiotherapy after surgery (adenocarcinomas, carcinoid tumor, and SCC). In the six cases with a known outcome, the survival time after surgery was more than 13 months!

The take home message is: the clinical signs are similar to those seen for non-neoplastic nasal diseases (e.g., infections), so it’s important to keep neoplasia as a (rare) differential for middle-aged rabbits. CT clearly delineated space-occupying masses in all cases, unlike radiographs. Surgical therapy and radiation, when needed, lead to clinical improvement and prolonged survival time.