The use of Diagnostic Imaging for Identifying Abnormal Gas Accumulations in Cetaceans and Pinnipeds

Abstract

Recent dogma suggested that marine mammals are not at risk of decompression sickness due to a number of evolutionary adaptations. Several proposed adaptations exist. Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels. Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief. Diagnostic imaging modalities are invaluable tools for the non-invasive examination of animals for evidence of gas and have been used to demonstrate the presence of incidental decompression-related renal gas accumulations in some stranded cetaceans. Diagnostic imaging has also contributed to the recognition of clinically significant gas accumulations in live and dead cetaceans and pinnipeds. Understanding the appropriate application and limitations of the available imaging modalities is important for accurate interpretation of results. The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

Short Update on Dysbaric Osteonecrosis: Concepts and Decompression Management

“…DON does not feature as an immediate complication in persons presenting with symptoms of generalized decompression sickness 9 . The specific lesions of bone necrosis, per se, are not detected by even sophisticated MRI evaluation at the early stages of the dysbaric injury 8,11,16,22 . However, gas bubbles in the marrow can be picked up using MR techniques 8,22 .…”

“…The specific lesions of bone necrosis, per se, are not detected by even sophisticated MRI evaluation at the early stages of the dysbaric injury 8,11,16,22 . However, gas bubbles in the marrow can be picked up using MR techniques 8,22 . Other causes of aseptic bone necrosis being ruled out, lesions specific to DON can take months to develop 1,17,21,[23][24][25][26] .…”

“…Accepted August 2015 ysbarism or musculoskeletal decompression sickness (DCS) is usually observed in people who undergo pointed towards several etiologies of DON [8][9][10][11][12][13] . Given the typical anatomy of vasculature around the end of long bones, it seems plausible that DON is linked to occurrence of micro-embolisms with gas or lipid bubbles following a rapid decrease in surrounding air pressure at those sites 3,10,[14][15][16][17] .…”

Review on diagnostic approach of ultrasound in Veterinary practice

“…This occurs due to the inherent time gain compensation built into most systems to allow increasing amplitude of signals returning from deeper structures to compensate for attenuation (Dennison et al 2012).…”

The physiological consequences of breath-hold diving in marine mammals; the Scholander legacy

“…A more recent study has shown that the gas bubble composition in stranded whales is similar to that from land mammals suffering DCS in experimental dive models (Bernaldo De Quirós et al, 2012). Imaging work in both live and stranded marine mammals indicates that they live with elevated inert gas tensions that cause bubbles to form under certain circumstances (Dennison et al, 2012). This raises some interesting questions: are marine mammals ever at risk of DCS, and if so, could N 2 accumulation limit dive performance (Hooker et al, 2009;Kvadsheim et al, 2012;Sivle et al, 2012)?…”