Abdominal pregnancy: ultrasound diagnosis aided by the balloon of a Foley catheter

Abstract

Clinical diagnosis of an advanced abdominal pregnancy can be difficult, hence various investigations and maneuvers have been described to aid diagnosis. Ultrasound is currently the imaging method of choice. However, with advanced gestation, it might be difficult to see an empty uterus separate from the fetus because of distorted pelvic anatomy and the acoustic shadows cast by fetal bones. We report a case of advanced abdominal pregnancy in which the empty uterus was only clearly demonstrable by ultrasound after the placement of the balloon of a Foley catheter. Abdominal pregnancy is a rare type of ectopic gestation but its frequency is directly related to the frequency of ectopic gestation in the population (1). It can be primary or secondary according to the Studiford criteria, but the latter, in which there is secondary implantation of a primary tubal pregnancy, is more common (2). Abdominal pregnancy is a'life-threatening condition and'hence early and accurate diagnosis is essential to avoid the serious complications associated with it. The clinical presentation of abdominal pregnancy is extremely variable and physical examination by itself may be insufficient for diagnosis. In one reported series, only one of nine women who reached the hospital alive had an accurate preoperative diagnosis of abdominal pregnancy (3). To assist preoperative diagnosis, there is an array of diagnostic procedures including oxytocin stimulation, abdominal X-"ray, hysterosalpingography and ultrasound scan. Ultrasound is currently the imaging method of choice for establishing'the gestational location, but sonographic interpretation'may be difficult especially in advanced cases because of gas within the gastrointestinal tract and distorted pelvic anatomy (4). When sonographic findings are equivocal, magnetic resonance imaging has been suggested (5), or a'repeat of the ultrasound with placement of a sterile Foley bulb into the uterine cavity (6), to confirm the extrauterine position of the pregnancy. We report a case of an advanced abdominal pregnancy that was diagnosed preoperatively by ultrasound with the aid of the balloon of a Foley catheter placed within the uterine cavity. A 21-year-old primigravida was referred to our unit from a primary health center at 32 weeks gestation after 4 years of'infertility with intrauterine fetal death and antepartum hemorrhage. Further evaluation revealed that the first episode of bleeding per vaginam was 7 days prior to presentation. It was slight and was of altered dark blood. There was associated abdominal pain but no history of trauma. The patient had stopped feeling fetal movements since the onset of the bleeding. Except for mild palor, she looked otherwise healthy. Her'pulse was 88 beats/min, and blood pressure was 120/80 mmHg. Her abdomen was enlarged and a symphysiofundal height of 30 cm was obtained. However, it was difficult to delineate the fetal parts because the abdomen was tense with some degree of tenderness. A gentle pelvic examination revealed bloodstained vulva and vagina. The cervix was firm, closed and uneffaced. There was some fullness in the pouch of Douglas. A provisional diagnosis of abruptio placenta (mixed type) was made. The packed cell volume was 31%. A preliminary ultrasound scan in the labor room by one of the obstetricians revealed a singleton, breech fetus with no fetal heart activity. There was reduced liquor volume and the placenta was unusual in appearance with a diffuse location in the “upper uterine pole.” The possibility of an abdominal pregnancy was entertained and the patient was referred to the radiologist for a detailed scan. Using the Philips SDR 2200 with a convex abdominal transducer showed that there was a singleton fetus in breech presentation at 32 weeks gestation with no fetal activity. The placenta was located at what appeared to be the upper uterine pole with degenerative changes. It was difficult to demonstrate an empty uterus separate from the fetus and gestation sac. A Foley catheter was then passed transcervically and the balloon inflated with 30 mL of sterile water. A repeat scan clearly showed three compartments (Fig. 1); the anterior compartment was the full urinary bladder with the balloon of the Foley catheter in situ (C2), the middle and smallest compartment was the empty uterus with the balloon of another Foley catheter within its cavity (C1), while the third and largest posterior compartment contained the fetus and liquor amni. The diagnosis of an advanced extrauterine pregnancy was therefore confirmed. Advanced abdominal pregnancy: the fetus is outside the uterine cavity. C1, balloon of Foley catheter in the uterine cavity; C2, balloon of Foley catheter in the urinary bladder. After resuscitation, the patient had laparotomy with the extraction of a male, macerated fetus from a huge, central, thick-walled gestation sac that was separate from the bulky but empty uterus. There was left hydrosalpinx but a normal left ovary. The right tube and ovary could not be identified because they were matted together with the gestation sac. The placenta was peeled off the posterior aspect of the gestation sac with minimal difficulty and bleeding. Some altered old blood clots were evacuated from the placenta bed. There was no active bleeding. Peritoneal lavage was performed and the abdominal wall was closed in layers. The fetus weighed 2.8 kg. The patient's postoperative recovery was uneventful. She was discharged home on the eighth postoperative day in good health. The clinical diagnosis of advanced abdominal pregnancy can be difficult because of lack of pathognomonic signs and symptoms. The index of suspicion is raised when there are continuous or recurrent abdominal pains in the course of the pregnancy especially if associated with subfertility, tubal surgery and abnormal lie (7). The case presented had some of these features in addition to the abnormal bleeding per vaginam, which led to the initial diagnosis of antepartum hemorrhage. The cause of the bleeding in this patient was the withdrawal of hormones following the death of the fetus and trophoblast, the so-called decidual cast or Arias Stella reaction. Accurate preoperative diagnosis is an important factor in the eventual outcome of the condition. Soft-tissue radiography once occupied the pride of place in the diagnosis of advanced extrauterine pregnancy. Conclusive radiological evidence was provided either by unusual proximity of the fetal parts to the abdominal wall, indicating absence of intervening uterine muscle investing the fetus, or by diffuse calcification in the membranes around a crumpled fetal skeleton (8). Ultrasound is the currently investigation of choice despite difficulties in some cases. The preliminary ultrasound by the'attending obstetrician could not confirm the diagnosis of the abdominal pregnancy because the empty uterus could not be demonstrated separately from the gestation sac. Even at the repeat scan, similar difficulty was encountered until'the placement of the inflated balloon of the catheter within the uterine cavity. Good collaboration between the obstetrician and the radiologist, as was demonstrated in this case, is often rewarding. The other option, where facilities are available, is for such an inconclusive ultrasound scan to be followed by magnetic resonance imaging (4,5). The subsequent care of the patient after the diagnosis was confirmed was along known standards. A perinatal mortality of 75–95% and a maternal mortality of 2–18% have been reported (7). In the case presented, there was already fetal demise before admission but the mother had an uneventful postoperative course and was discharged in good health.