You don't need to be signed in to read BMJ Blogs, but you can register here to receive updates about other BMJ products and services via our site.

Veterinary Record Case Reports

A new differential for canine pneumothorax

6 Dec, 16 | by gmills

By Cameron Knight

An article recently published in Veterinary Record Case Reports describes a case of fatal pneumothorax in a dog secondary to malformation of a single lung lobe. Within the published literature, most canine cases with a similar presentation are diagnosed as congenital lobar emphysema (CLE). However, in this particular dog, CLE was ruled out by a panel of veterinary and human paediatric pathologists. Histological lesions closely resembled congenital pulmonary airway malformation (CPAM), a disease that is well recognised in children, but that has never been reported previously in any veterinary species. This report proposes that CPAM be considered in the differential diagnosis for canine spontaneous pneumothorax, and clarifies the distinction between CLE and CPAM.

The case describes an eight-month-old female boxer dog with progressive respiratory distress and no previous history of disease, trauma or toxin exposure. Pneumothorax was diagnosed and repeat thoracentesis and oxygen supplementation were performed for three days. CT confirmed bilateral pneumothorax and showed variably sized bullae in the right middle lung lobe, leading to a presumptive diagnosis of CLE.

During anaesthetic induction for lung lobectomy, the dog developed cardiopulmonary arrest and died. A postmortem examination was performed, which confirmed severe bilateral pneumothorax with atelectasis of all lung lobes, and revealed a small, pale and flaccid right middle lobe with several ruptured bullae (Fig 1). The primary bronchus supplying this lobe was flattened, with a slit-like, rather than circular lumen. In addition, the right subclavian artery had an aberrant origin from the left subclavian artery, rather than from the brachiocephalic trunk.

Fig 1: Right lung of a dog that died from spontaneous pneumothorax. (A) The right pleural cavity, with the cranial (RCr), middle (RMd) and caudal (RCd) lobes of the right lung labelled. The caudal lobe has been reflected dorsally to better expose the middle lobe. All lobes are severely atelectatic. In addition, the middle lobe is pale and flaccid. (B) The right middle lung lobe at higher magnification. Several collapsed bullae (yellow arrowheads) are present along its ventral and ventrocaudal margins

Histological sections of the right middle lobe were difficult to recognise as lung tissue. They consisted predominantly of thick fibrovascular trabecular networks outlining collapsed, empty cavities lined by a simple cuboidal to simple squamous epithelium. All other lung lobes in the dog had normal histological architecture.

A diagnosis of CLE was ruled out histologically. CLE requires overinflated alveoli or hyperplastic alveoli, whereas the affected lobe in this dog lacked alveoli. Instead, after consultation with seven human paediatric pathologists, a diagnosis of CPAM-like disease was reached. The term CPAM refers to a spectrum of human airway malformations characterised by abnormal development of various portions of the tracheobronchial tree. CPAMs are well recognised and relatively common in people, and are characterised by multiple irregular pulmonary cystic structures lined by varying types of epithelium. The distinction between CLE and CPAM in humans is not merely academic. Importantly, CPAM may progress to malignant neoplasia, while CLE does not. Lobectomy is generally indicated for CPAM lesions, while CLE may resolve spontaneously and can often be managed conservatively.

While CPAM-like disease has never been reported in the veterinary literature, there are 11 reports of CLE in dogs. After reviewing these, it is possible that some reported canine cases of CLE may, in fact, represent CPAM-like disease. This case highlights the necessity for histological distinction between these two diseases, and describes a novel condition that may result in spontaneous pneumothorax in dogs.

More details, images and discussion about this case can be found here: http://vetrecordcasereports.bmj.com/content/4/2/e000378.full.

Intubation complication in a rabbit

15 Apr, 16 | by gmills

By Daniel Pang

A report of an unexpected and novel anaesthetic complication in a rabbit, the presence of faecal matter in the oropharynx impeding attempts at intubation, was recently published in Veterinary Record Case Reports.

The incidence of anaesthetic-­ and sedation-­related mortality in apparently healthy rabbits is 1.4 per cent, six to eight times greater than in dogs or cats, and respiratory complications represent a substantial fraction of these deaths.

Unfortunately, undiagnosed respiratory disease and hypoventilation due to anaesthetic agents can cause significant respiratory depression. Endotracheal intubation provides a secure airway, facilitating positive pressure ventilation, reducing the risk of fluid aspiration and limits workplace pollution with anaesthetic gases. However, many rabbits are maintained anaesthetised with a face mask, rather than secure airway, because they are challenging to intubate. They have a relatively large tongue, narrow oral cavity and small glottis, which combine to limit visibility of, and access to, the larynyx. Simpler, novel methods of securing an airway such as supraglottic airway devices (eg, Laryngeal Mask Airway, V­Gel) have shown promise in clinical use.

A healthy, adult New Zealand white rabbit was anaesthetised for a CT scan as part of a larger study evaluating different methods of providing a secure airway to facilitate ventilation. Following induction of general anaesthesia (intramuscular dexmedetomidine and midazolam, followed by intravenous alfaxalone), the rabbit was positioned in sternal recumbency and orotracheal intubation with an endotracheal tube was attempted with a blind technique. Initial attempts at intubation by an experienced anaesthetist were unsuccessful, with intubation finally achieved after five minutes. This contrasted with an average of two minutes to perform intubation in similar rabbits by the same anaesthetist.

The study protocol required CT scans of the oropharynx to be performed before and after intubation. These ‘pre’ and ‘post’ scans allowed us to identify the cause of the difficult intubation: faecal matter present in the oropharynx before intubation, which was pushed caudally to cause a physical obstruction during attempted intubation (Fig 1). This was also confirmed at postmortem examination.

pang pic

FIG 1: CT images (sagittal plane) of a three-month-old New Zealand White rabbit pre-intubation (top) and post-intubation (bottom) with a 2.5 mm ID endotracheal tube. The pre-intubation image shows two areas containing material of mixed gas and soft tissue attenuation. These were confirmed as faecal material at necropsy examination – a discrete faecal pellet in the oral cavity (orange arrow) and dispersed faecal material in the caudal oropharynx, immediately rostral to the larynx (orange arrowheads). The endotracheal tube (green arrowheads) is visible in the post-intubation scan (bottom) passing dorsal to the faecal pellet (orange arrow). The pellet visible in the pre-intubation scan in the oral cavity has migrated caudally to merge with, and compress, the dispersed faecal material in the laryngopharynx

The source(s) of failed orotracheal intubation attempts in rabbits are usually unknown, although there is a tendency to blame anaesthetist inexperience or anatomical impediments. This report identifies a previously undocumented source of a difficult intubation. A pre­anaesthetic examination of the oral cavity in rabbits may be warranted, but is unlikely to rule out the presence of foreign material in the oropharynx.

The full article is available here: http://vetrecordcasereports.bmj.com/content/4/1/e000265.full

CSI North Yorkshire

17 Dec, 15 | by gmills

By Tim Hopkins

Raptor persecution is an emotive issue in Britain. In an attempt to increase the population of gamebirds, some unscrupulous gamekeepers (sometimes directed by managers and employers) continue to illegally kill raptors. For conservationists and welfare groups, the shooting, trapping and poisoning of these wild birds represents the worst of the gamebird industry. Aside from the welfare concerns (for both game and raptor) and the disease risks from the release of many millions of captive birds annually, persecution continues to have a significant conservation impact on a number of species, in particular the hen harrier (Circus cyaneus) and golden eagle (Aquila chrysaetos). Historically, some British species were pushed to extinction due to such pressure, although all have since returned to breeding. Parts of the gamebird industry continue to dispute the scale and impact of raptor persecution and believe that the conservationists and welfare bodies are attempting to piecemeal outlaw their traditional hunting sport. For any given incident, the reliability and transparency of a postmortem investigation is paramount.

Veterinary pathologists, police and NGOs are hindered in confirming shooting by decomposition, scavenging and concealment of the carcase by the perpetrator. Furthermore, the identification of ballistic objects within a carcase is rarely enough to prove cause of death – it is often an incidental finding. An article published recently in Veterinary Record Case Reports details a confirmed shooting in an otherwise ambiguous postmortem examination of a hen harrier using advanced imaging techniques.

The bird was fitted with a tracking device as part of Natural England’s Hen Harrier Recovery Project, which enabled its recovery after death. Despite the advanced state of decomposition, a postmortem examination was performed at the Zoological Society of London’s Institute of Zoology. The bird had a broken tibiotarsus, which was radiographed, and minute metallic radio-opacities noted. Without an obvious gross ballistic remnant, the authors needed a diagnostic tool that would determine the composition of the foreign object and its effect on the surrounding tissue. Several modalities were considered but ultimately rejected as they failed to preserve both the foreign body and the microscopic structure of the bone. Histology, for instance, would have provided accurate descriptions of the bony trauma but no information about the chemistry of the object. Conversely, many spectroscopic techniques would have provided accurate descriptions of the metallic object atomic makeup but destroyed the surrounding bone in the process. Scanning Electron Microscopy with x-ray Dispersive Spectroscopy (SEM-EDX) was the only tool that fitted the bill.

 

Fig 1: Plain craniocaudal radiograph of the left tibiotarsus and tarsometatarsus showing three radiodense objects (white and black arrowheads)

Fig 1: Plain craniocaudal radiograph of the left tibiotarsus and tarsometatarsus showing three radiodense objects (white and black arrowheads)

 

SEM-EDX was carried out at the University College London’s Institute of Orthopaedic and Musculoskeletal Science. With great care, the bone was prepared for imaging, which included a thin coat of gold palladium to reduce scatter during scanning. The images were spectacular and conclusive. The fragment had tunnelled into the cortex of the tibiotarsus, fracturing the bone and trabeculae. On its way, it had disintegrated. The fragment was predominantly lead on EDX. The lack of any significant bone resorption or remodelling suggested this injury had resulted in rapid death. Case closed.

That was until we noticed that there were minute amounts of niobium on the spectrum. Niobium is not used in ammunition or firearms manufacture, so where had it come from? The explanation took several months. EDX, like any diagnostic tool, is subject to artefacts, operator error and sensitivity and specificity constraints. After consulting with the University of Bristol’s Department of Earth Sciences, the authors ran the scan data through third party software – DTSA II (Desktop Spectrum Analyser, National Institute for Standards and Technology). DTSA was able to discriminate the spectral peaks and showed that the aforementioned niobium was a misread of the peaks caused by the gold palladium coating. Additionally, it revealed the presence of arsenic and antimony, common additives in lead ammunition manufacture.

This case demonstrates the application of a novel forensic modality to the veterinary field. SEM-EDX has also been used in human forensic science to demonstrate gun shot residue (GSR) – microscopic remnants of the ammunition primer and propellant – on victims, shooters and firearms. This information often forms a vital piece of the investigative puzzle. In the future, it may be possible to determine that an animal was shot by a particular firearm or person by matching the GSR EDX data.

Novel modalities are increasingly important for NGOs and police seeking to stamp out illegal persecution. Confirmation of shooting in such ambiguous cases may increase pressure on the game industry to reform its practices. The imminent use of GSR EDX to match individuals with shooting incidents may be enough to dissuade gamekeepers too.

More details about this case can be found here

 

 

 

Vet Record blog homepage

Vet Record blog

Highlights and insights into the research featured in the Veterinary Record. Visit site



Creative Comms logo

Latest from Vet Record

Latest from Vet Record