Paper - Abdominal pregnancy in a cat (1932)

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Hunter RH. Abdominal pregnancy in a cat. (1932) J Anat. 66: 261-263. PMID 17104372

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This historic 1932 paper by Hunter describes ectopic pregnancy. in the cat

Modern Notes: ectopic pregnancy | cat

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Abdominal Pregnancy in a Cat

By Richard H. Hunter, M.D., M.Cu., Ph.D.

Lecturer in Anatomy, Queen’s University, Belfast

On opening the abdominal cavity of a cat, which had been killed on account of its “strange behaviour,” a number of firm irregularly shaped tumour-like masses were seen attached to the omentum and the intestinal wall. On closer examination a foetal kitten of about full term was also seen, but in a condition of advanced autolysis, and lying free within the peritoneal cavity there were found a number of foetal bones. An X-ray photograph showed that each tumour-like mass contained a foetal kitten, and that this therefore was a case of abdominal pregnancy in a cat.

Cases of abdominal pregnancy in animals are uncommon, and in the literature at my disposal I have been able to find only some half dozen cases in all. Some of them have been stated to be cases of true primary extra-uterine implantation, but though this has recently been stated to occur in the rodents, the evidence produced in support ‘of the cases I have studied appears to be inconclusive and I am more inclined to believe them to be cases in which the foetal sacs have been extruded through a ruptured uterus; and the attachments which are described seem to me to be secondary aseptic inflammatory attachments to the peritoneal surfaces, that is, in none of the cases has there been a clear demonstration of an active placental connection. It is well known that rupture of the uterus does occur in animals. It is commonly due to mal-presentation or to the impaction of a foetus which is too large to pass through the genital passages. In such cases the mother may recover, and after a few months the uterus may show no obvious scar. Simmons was unable to find any cicatrix in the genital canal of a ewe twelve months after such a rupture. Without a most careful examination, both macroscopical and microscopical, a former rupture of the uterus may easily be overlooked and erroneous conclusions drawn.

In the present case studies were first made to decide the presence or absence of a scar.

The specimen as a whole was fixed and hardened in 10 per cent. formalin, and the uterus was then isolated. The blood vessels of both right and left horns were markedly congested. The right uterine horn showed nothing abnormal, but on the left side there was seen, close to the cervical portion, a well-marked “kink.” It is difficult to see how this kink could cause an obstruction to the passage of the foetal kittens, as it did not appear to be bound down by fibrous or other bands; but closer examination revealed an area immediately above it, on the anti-mesenteric border which to the naked eye presented the characters of a cicatrix. This area was cut out and sectioned for microscopic study, and this showed at one place that the continuity of the mucous and muscular walls was broken. Strands of fibrous tissue repaired the break. There is, therefore, in this specimen direct evidence of the rupture of the uterus, and it must be concluded that the foetuses found in the peritoneal cavity were extruded through this rupture, and that the foetal sacs had formed secondary peritoneal attachments.

Fig. 1. Microscopic section through the zone of attachment of the foetal membranes to the gut wall. 1. Placental tissue. 2. Foetal blood vessel. 3. Longitudinal muscle layer. 4. Maternal blood vessel. 5. Circular muscle layer. 6. Gut mucosa.

In each mass the foetus was closely surrounded by the foetal membranes, on the outer surface of which was a dense layer of adventitious fibrinous deposit. The external surface of the sacs to the naked eye appeared to be devoid of blood vessels. None of these sacs contained any free fluid, and the body of each foetus was in close contact with the wall of its sac. The fibrinous exudate would be formed as part of the inflammatory reaction on the expulsion of the foetal sacs through the ruptured uterus. The presence of the foetal sacs alone within the peritoneal cavity would be sufficient to bring about the formation of this exudate. Leopold first showed this to be true by placing fresh foetal sacs in the peritoneal cavity of a rabbit, and in 8 to 9 weeks they were covered with this fibrinous exudate. The amniotic fluid was also absorbed.

Each foetal sac was attached to the gut wall at one side only; the remainder of the zonular placenta had entirely disappeared. Sections of the attached region were prepared to study the détails of the attachment. A microscopic section through the zone of attachment (fig. 1) shows the mucous layer of the gut wall, the muscularis mucosa greatly developed, the circular longitudinal layer of muscle fibres and beyond the last layer true placental tissue. Between the two layers of the circular and longitudinal muscle tissue lies a dilated blood vessel, cut in its long axis, and containing free blood. The placental tissue lies against the outer surface of the longitudinal muscle layer and the remains of the peritoneal covering can be seen. Within the outer layer of muscle tissue are seen small blood vessels. The histological structure of the wall surrounding these vessels is placental epithelium and shows them to be foetal in origin. It must be concluded therefore that there has been an active invasion of the gut wall by the placental tissue. The blood vessels of the foetal system contain blood cells, and in them there is no trace of thrombosis. There is therefore a healthy foetal blood stream within these vessels.

The relations of the foetal and maternal tissues in this specimen are the same as those normally found between the uterine wall and the placenta of carnivores, where the trophoblast penetrates the uterine mucosa after the destruction of the superficial epithelium, with apposition of the foetal and maternal vessels, without any opening of the maternal vessels or the formation of blood sinuses.


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Cite this page: Hill, M.A. (2024, April 13) Embryology Paper - Abdominal pregnancy in a cat (1932). Retrieved from

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