Abstract
An ectopic fetus was discovered in an 18-month-old uniparous queen that was admitted for an elective ovariectomy. Six months prior she had delivered three healthy kittens. During the preoperative examination, a mass similar in size to a full-term fetus was detected in the abdominal cavity. Ultrasound examination revealed the mass to be an ectopic fetus in the mid-abdominal region. A mummified fetus was removed by laparotomy. No rupture of the uterine wall was visible, but a small necrotic area was present on the left uterine horn, adjacent to the very proximal portion of the uterine horn. The fetus, which was fully developed and covered by a thin membrane, was carefully dissected. Histological examination did not enable us to definitively prove the extra-uterine development of the fetus; however, the ectopic development of the conceptus secondarily expelled into the peritoneal cavity could be assumed.
Extra-uterine pregnancy, also called ectopic pregnancy, is a pregnancy that develops outside the uterine cavity. This disorder is rarely diagnosed in animals but is well known in humans. 1 In the majority of cases it is a fortuitous discovery, due to the absence of clinical signs. There are two distinct types of extra-uterine pregnancies: tubal and abdominal pregnancies. Tubal pregnancy is extremely rare in animals, as a specific factor produced by tubal mucous is suspected to prevent pregnancy development in this area. 2 In animals, tubal pregnancy is mainly described in non-human primates with three published cases for review. 3 Abdominal ectopic pregnancy cases are classified as primary or secondary. Primary abdominal pregnancy occurs when a fertilised oocyte does not reach the uterus but moves into the abdominal cavity. The escaped oocyte then becomes attached on to the peritoneum, omentum, liver, spleen, or the extraluminal of the uterine tube or uterus. Secondary abdominal ectopic pregnancy occurs when the embryo and/or the fetus (more commonly) initially develops in the uterus before entering the abdominal cavity due to the rupture of the uterine wall, which usually results from an external trauma.
This case report describes the diagnosis and management of an ectopic pregnancy in an 18-month-old domestic shorthair queen.
An 18-month-old female domestic shorthair cat was admitted to the Veterinary Campus of Lyon, for a routine ovariectomy. The queen had given birth uneventfully to three healthy kittens 6 months prior. No complications were observed during the delivery and post-partum period. All kittens were successfully weaned. The owner reported that the queen was in oestrus 4 weeks before admission.
On physical examination, the cat was alert with normal vital signs. Abdominal palpation revealed a roughly spherical, 7 cm, firm and irregular mass located in the mid-abdomen. Palpation of the mass did not elicit signs of pain. No other abnormality was observed. An abdominal ultrasonography revealed a moderate amount of free abdominal fluid and a dead fetus in the mid-abdominal region (Fig 1).
Abdominal ultrasonography revealed a moderate amount of free abdominal fluid and a mummified fetus in the mid-abdominal region.
A standard ovariohysterectomy under general anaesthesia was performed. The extra-uterine fetus was wrapped in the omentum and surrounded by a moderate amount of necrotic fat (Fig 2). A 2 mm necrotic area was observed on the left uterine horn (Fig 3), close to the proximal end of uterine horn. The ovaries, the uterine horns and the uterine body had normal macroscopic appearance and were in normal position. The peritoneal membrane and other organs did not show any abnormalities. The mummified fetus was gently dissected from its attachments and removed ‘en bloc’ with the necrotic fat. No additional adhesions were observed.
The extra-uterine mummified fetus was strongly adherent, wrapped into the mesentery and surrounded by a moderate amount of necrotic fat.
A 2 mm necrotic area was observed on the left uterine horn.
Postoperative care was provided including pain management (morphine, 0.1 mg/kg as required). Recovery was uneventful.
Less than an hour after being removed the mummified fetus was dissected. The fetus was surrounded by a thin-walled fibrous capsule (Fig 4). It measured 6.0×3.5 cm. Necropsy showed no abnormalities except generalised autolysis and dehydration (Fig 5). The fetus was fully formed and haired.
The fetus was fully formed with hair and surrounded by a thin-walled fibrous capsule.
Necropsy showed no abnormalities except generalised autolysis of the fetus.
The area of the uterine lesion was embedded in paraffin wax and 4 μm thick sections cut at different sites through the lesion (microtome, micron, HM 340 E & HM 355S). All sections were stained with haematoxylin and eosin and observed under direct light microscope (BX51 & DP70 camera; Olympus). Histology of the area of the uterine tissue revealed granulation tissue (Fig 6). Neither placental tissue nor endometrial cells were observed.
Histological appearance of the genital tract showing left ovary (arrows with big dotted), oviduct (black arrows) and proximal left uterine horn (arrows with small dotted) with granulation tissue (arrow-head). Haematoxylin and eosin ×10.
According to the literature, ectopic pregnancy in animals is rare and is mainly reported in cats. Two types of abdominal ectopic pregnancy are recognised in this species. 4–8 In the primary form, the fertilised oocyte enters the peritoneal cavity and is followed by fetal growth and attachment to the mesentery or to an abdominal organ. The primary form results from a wave of antiperistaltic uterine tubal contractions or from tubal obliteration. Oocytes can also be directly fertilised in the abdominal cavity. Although the primary form was reported in some cats, it appears to be anecdotal and is difficult to confirm. 4,5 Such cases may be secondary to physical handling of the fallopian tubes during an ovariohysterectomy performed within 3–4 weeks post coitus, or it might be associated with abnormal anatomy of the genital tract. 9
Secondary abdominal pregnancy is the most commonly reported type in cats and occurs when a fetus is expelled into the abdominal cavity following the rupture of the gravid uterus, either due to external trauma or internal pressure. 8–12 The fetal membranes might become attached to the visceral mesentery, which helps to sustain fetal life for a short time. More often, however, the fetus stays without placental attachment, dies, and undergoes mummification in the abdominal cavity. In our case, the fetus probably grew in the uterus and passed into the abdominal cavity around the time of parturition. It could also be assumed that the small and brownish lesion in the proximal uterine horn is the scar of a uterine rupture. Indeed, granulation tissue, lymphocytes and haemosiderin granules in macrophages were observed on the histological section. Uterine ruptures are rarely reported, which might be due to the rapid healing of endometrial tissues. 10
The present case demonstrates the presence of an ectopic ‘fetus’ and is commonly called an ectopic ‘pregnancy’. Nevertheless, extra-uterine development (ie, ectopic ‘pregnancy’) in cats has not yet been proven. It is worth noting that one living kitten was found in the abdominal cavity of a queen during a surgery, but all the other extra-uterine kittens were dead. 9 In that case, the uterine rupture probably happened just before the surgery, enabling one of the kittens to stay alive. In our case none of the findings indicated the fetus lived after being expelled from the uterus. The lack of placental tissue around the fetus indicated that this ectopic fetus initially developed in utero and then was expelled from the uterus. In humans, the invasiveness of placental tissues along with the development of ectopic endometrial tissue (ie, endometriosis) explains the possibility of true ectopic pregnancies with full extra-uterine fetal development to term. 13
In the present case, diagnosis of the ectopic pregnancy was an incidental finding, similar to previous reports. 8–12 In others cases described in cats, ectopic gestation is usually diagnosed incidentally several weeks after ovariohysterectomy during a routine examination. 8 There are two main explanations for such a delayed diagnosis: the developing fetus is dislodged during the manipulation of the genital tract during ovariohysterectomy, resulting in an ectopic pregnancy post surgery; or, more probably, the fetus formed during a previous pregnancy and was not noticed at the time of surgery. This late diagnosis, sometimes up to 2 years after conception, 14 seems to be due to the absence of clinical signs in the majority of cases. In a few cases, the queen showed non-specific clinical signs, such as anorexia, retching, and vomiting, that were associated with unrelated infections. 10 Sometimes clinical signs related to mechanical interference of the ectopic fetus and abdominal organs or with the necrosis of the ectopic tissue are reported. 15 No clear association exists between the time period the ectopic fetus spent in the abdominal cavity and the development of clinical signs. 3,8
Histological examination of the mummified fetus did not enable us to prove the extra-uterine development of the fetus. Moreover, no signs of ectopic implantation in the abdomen were found. Previous attempts to develop non-primate models of extra-uterine pregnancy have not yet met with success. 3 Therefore, true extra-uterine viable pregnancy does not seem to be possible in cats. 16