A case of feline ectopic abdominal fetuses secondary to trauma

Abstract

A multiparous adult cat with a history of prior trauma but no presenting clinical signs was admitted for routine ovariohysterectomy. Uterine abnormalities indicative of trauma were found in addition to 2 ectopic fetuses wrapped in omentum. The ovariohysterectomy was completed and the ectopic fetuses were removed. Recovery was uneventful.

A female, domestic, short-haired, adult calico cat of unknown age was presented to Norwich Veterinary Service for a spay surgery on May 17, 2016. The cat primarily lived outdoors in the owner’s barn, and so a detailed history could not be obtained. The owner noted that the cat had previously given birth to 3 healthy litters each of 3 to 4 kittens, but she was unsure whether the cat was currently pregnant. Approximately 3 to 4 mo earlier, the cat had been stepped on by a cow, but continued to be ambulatory and appeared to be healthy afterwards. The owner was not sure if the cat had been pregnant at the time of the incident. During the preoperative examination, it was not possible to determine pregnancy by palpation and no abnormalities were discovered.

Upon incising into the abdominal cavity, a moderate amount of serosanguinous fluid was found. Gauze was used to soak up most of the fluid and the surgery was continued. After ligation of the left ovarian pedicle, an attempt was made to visualize the right ovarian pedicle and numerous abnormalities were found. First, the right uterine horn was found to have ruptured into 2 sections with a 3-cm gap filled with hemorrhagic tissue (Figure 1). Second, there was an adhesion between the gap and body wall with 3 to 4 circular, soft, fat-like nodules of approximately 1 cm diameter contained within. The adhesion was vascularized and may have attached to a portion of the small intestines, but it was difficult to confirm without more invasive manipulation. The adhesion was ligated and the surgery was continued. Interestingly, the uterus itself was not distended and beyond the abnormalities listed, appeared normal. The right ovarian pedicle and uterine body were then ligated as per standard spay protocols.

Figure 1.

Right uterine horn rupture with approximately a 3-cm gap of hemorrhagic tissue and an adhesion to the ventral body wall containing soft, fat-like nodules of approximately 1 cm diameter.

Prior to closing, the abdomen was thoroughly searched and 2 dead fetuses were found wrapped in well-vascularized omentum in the cranial abdomen (Figure 2). Additionally, there was evidence of blood supply between the spleen and fetuses. Ligations of 3 large omental vessels and 1 splenic vessel were made to remove the fetuses. The fetuses were each approximately 10 cm from crown to rump, had fine hair covering most of the body, and their limbs were bent in abnormal angles. The lighter-colored fetus was especially abnormal, with the caudal half of the body rotated nearly 180°, and a 3-cm crater-like lesion in the abdominal area with an absence of abdominal organs. The patient’s omentum also contained a yellow/tan, amorphous, soft-tissue mass that was 3 to 4 cm in diameter with a ridged surface. None of the fetuses were found with placenta. Additionally, fine dark hairs were found throughout the abdomen. The abdomen was lavaged with sterile saline and 5 mL of a penicillin solution (penicillin G; Fresenius Kabi, Richmond Hill, Ontario) reconstituted to 100 mg/mL before closing the surgical site. The patient was kept in hospital for 3 d and placed on clavulanic acid and amoxicillin tablets (Clavaseptin; Vétoquinol, Lavaltrie, Quebec), 62.5 mg, PO, q12h, for the duration of the cat’s stay.

Figure 2.

Ectopic fetuses ex-situ. The fetuses were 10 cm from crown to rump, fully-haired, and had abnormal body and limb positions. A yellow/tan amorphous mass of approximately 3 to 4 cm with undulating margins was found beside the black and white-haired fetus. Additionally, the black and white-haired fetus’ abdomen had a crater-like lesion and contained no abdominal contents.

At 3 d post-surgery, ventral-dorsal and right lateral abdominal radiographs were taken. A medially displaced healing fracture was identified in the midsection of the wing of the left ilium. No additional fetuses or other abdominal abnormalities were observed on radiographs. Despite this fracture, the patient showed no gait abnormalities at admittance and after surgery. Since the surgery, the patient has returned to the owner’s barn and has had no complications.

Discussion

Ectopic pregnancies are defined as pregnancies that occur outside of the uterus. They are traditionally classified as either abdominal or tubal pregnancies, depending on the site of implantation. There have been no cases of tubal pregnancies in non-primate animals, possibly because of factors inhibiting implantation in the uterine tube and/or lack of maternal recognition of pregnancy (1). However, abdominal pregnancies in cats and other domestic animals have been reported in the literature, albeit uncommonly.

Abdominal pregnancies can be categorized into 2 forms: primary and secondary. Primary abdominal ectopic pregnancies occur when a fertilized oocyte is expelled into the abdomen and implants itself on an abdominal organ such as the omentum or spleen. These have been theorized to occur if a fertilized ovum was present during a spay surgery and excessive handling during surgery allowed the ovum to escape into the abdomen (2). In order to diagnose a primary abdominal ectopic pregnancy, histology is required to show extrauterine placentation onto an abdominal organ. To date, there have been no reports documenting this phenomenon with sufficient histological evidence. Secondary abdominal ectopic pregnancies occur if the oocyte matures into a fetus while it is still in the uterus, then is expelled into the abdominal cavity due to uterine wall rupture and continues its development there. In the available case reports, the diagnosis of these have been based on a history of trauma, evidence of uterine trauma, and gross findings of mummified fetuses in the abdomen (3,4). However, for a confirmed diagnosis, there must be evidence of continued development or viability while in the abdomen (5). In humans, evidence of development in secondary abdominal pregnancy often takes the form of life-threatening hemorrhage caused by the developing fetus. This hemorrhage results from the increase in fetal size within a substitute organ which has a relatively low expansion potential compared to the uterus (6). In cats, although clinical signs are reported in some cases of secondary ectopic pregnancies, none of the case reports have associated intra-abdominal hemorrhage (3–5,7). A possible explanation for this lack of development may be that there is a difference in placental invasion, which describes the degree of fetal trophoblast contact and infiltration into maternal tissues. While humans have the most invasive type, called hemochorial placentation, cats have endotheliochorial placentation, which has only a slight degree of maternal tissue invasion. Thus, from a comparative anatomy perspective, cats are less likely to have ectopic pregnancies due to a difference in their placentation (5,8).

Unfortunately, this case also lacks the histological evidence needed to definitively diagnose an abdominal ectopic pregnancy. Therefore, an ectopic fetus may be a more appropriate diagnosis. Since an ectopic fetus is characterized by its abnormal location, the only requirement for diagnosis is locating the fetus. Since there is lack of evidence to support fetal implantation onto the omental tissues in this patient, the tentative diagnosis is ectopic fetuses. A macroscopic inspection of the fetuses and analysis of the history provides evidence for this diagnosis. Gross inspection of the yellow/tan amorphous mass found in the omentum suggested that it could have been intestinal contents undergoing autolysis. It is possible that the sudden increase in intra-abdominal pressure during the traumatic incident not only caused a uterine rupture, but also directly damaged the fetuses themselves leading to expulsion of one of the fetus’ abdominal contents. Moreover, the fine hairs tracked throughout the abdomen may have been due to the traumatic passage of the fetus from the uterus to the cranial abdomen. These observations all support a diagnosis of ectopic fetuses secondary to trauma.

There has been a wide variety of clinical signs associated with ectopic fetuses. Some reports have described non-specific signs such as fever and vomiting, while others have found the ectopic fetuses incidentally during routine spay surgery or abdominal radiographs (3–5,7). It is unknown if ectopic fetuses directly cause clinical signs due to obstruction, or if initial rupture of the uterus itself causes peritonitis due to release of bacteria from the uterine microflora (3). In this case, the patient was presented with no clinical signs yet had a moderate amount of fluid upon opening its abdomen. It is possible that the ruptured uterine horn remained open to the abdomen, and thus during every estrus cycle, the normal fluid accumulation in the uterus was deposited in the abdomen. Whether this may eventually cause clinical signs is unknown, but given that the patient has had no clinical signs 3 to 4 mo after the incident and the recovery itself was uneventful, it is highly likely that the ectopic fetuses were incidental.

Based on the gross findings, history of the patient, and literature analysis, this patient had an ectopic fetus secondary to abdominal trauma. It is also likely that previous cases diagnosed as secondary abdominal ectopic pregnancies may also be in fact, ectopic fetuses secondary to trauma. However, there are no experimental studies attempting to replicate secondary abdominal ectopic pregnancies in cats or other domestic animals. Non-primate animal models of tubal ectopic pregnancies have been made with some success (9), but currently there are no models of secondary abdominal ectopic pregnancies in domestic animals. This case adds to the database of ectopic fetuses and further illustrates their incidental nature.