Clinical history and questions
View at the display stage of necropsy of a 9 year-old castrated male Labrador dog which suddenly became weak and pale and collapsed during a morning walk with its owner. It retained consciousness, however, and recovered partially at a veterinary clinic where it received supportive treatment. The owners opted for euthanasia after detailed diagnostic workup.
- Describe the abnormalities.
- What underlying disease process/es could produce these changes?
- Make a differential diagnostic list, in order of probability.
- With your preferred diagnosis in mind, what is the pathogenesis of these macroscopic changes?
- Relate the pathology to the clinical signs.
An interpretation of Diagnostic Exercise No. 8 – Roger Kelly
Display stage of necropsy of a dog: euthanasia after an episode of collapse.
Abdominal contents are smeared with free and clotted blood and there is a distinctly yellowish cast to the intra-abdominal fat depots, compared to the white extra-abdominal deposits. There are scattered small, often spherical red to gray nodules up to about 10mm diameter on peritoneal surfaces, particularly those of the omentum. The thorax contains a lot of bloody fluid and the right lung is mostly redder than normal, with the exception of the right middle lobe, which appears to be more fully inflated. The lymphatics on the thoracic surface of the diaphragm are outlined in red. The fat depots beneath peritoneal and pleural membranes are pale yellow, whereas other fat deposits that have been incised are white on section.
Interpretation (basic underlying disease process/es):
Nothing in the history or the image suggests inflammatory disease, unless you are prepared to argue that the nodules might be chronic granulomatous foci, which are most unlikely to bleed spontaneously. Haemorrhage is counted as a degenerative disease, and the nodules are much more likely to be neoplastic, and malignant at that, as they are multiple. A developmental disorder seems intuitively unlikely, so we are left with a combination of neoplasia and degeneration, the latter more likely secondary to the former.
Preferred morphological diagnosis (with differential):
Disseminated intra-abdominal malignancy with secondary haemorrhage.
Traumatic abdominal injury is not supported either by the history or the appearance, although one must always bear in mind the possibility of traumatic splenic rupture, which can also seed the peritoneum with viable explants of normal splenic tissue which can survive indefinitely as small dark red nodules on peritoneum, particularly in the omentum. However, such an event would not lead to intermittent haemorrhage, which is indicated here by the yellowness of the peritoneal fat compared with the other fat depots. This tells you that the peritoneal mesothelium has been in contact with free blood for a week at least; due either to continuous low-grade or to intermittent haemorrhage. What probably happens is that the peritoneal mesothelium has some capacity to phagocytose haemoglobin and convert it to bile pigment, and this gives the colour.
Intra-abdominal haemorrhage, if not immediately fatal, leads first to a large amount of clotted blood in the abdomen, followed within an hour or so by fibrinolysis with liquefaction of most of the blood (except that small proportion in immediate contact with the ruptured tissue). The liquid blood is now free to pass into the diaphragmatic and sternal lymphatics at quite a surprising rate (which is why the diaphragmatic lymphatics are outlined by their blood content), to the extent that the animal in effect receives an autotransfusion, so the recovery shown by this animal under these circumstances is not surprising.