Sonographic findings of complete tubal abortion

Abstract

Ectopic pregnancies, implantation of a fertilized ovum in any location other than within the endometrial cavity, occur in 1-2% of all pregnancies. Despite current enhanced early diagnosis enabled by serum beta-human choriogonadotropin (hCG) levels and high-resolution ultrasound, this clinical entity continues to account for between 2.7 and 6% of all maternal deaths. The most common site of ectopic implantation is the Fallopian tube (>90% of cases), and less commonly in previous Cesarean scar, ovary, cervix, or the abdomen. Complete tubal abortion refers to a tubal pregnancy having been expelled from the distal portion of the Fallopian tube into the peritoneal cavity and may be associated with either considerable hemorrhage, spontaneous resolution, or rarely serve as an initial nidus for an abdominal pregnancy. We present unusual sonographic findings of a complete tubal abortion in a patient with minimal symptomology.

Introduction

An ectopic pregnancy describes the implantation of a fertilized ovum in any location other than within the endometrial cavity [1], [2]–3]. Ectopic pregnancies occur in approximately 1%-2% of all pregnancies [1–3]. The true incidence of ectopic pregnancy is difficult to ascertain due to both outpatient management of select patients, and spontaneous resolution of this condition in others. Risk factors for ectopic pregnancy include pelvic inflammatory disease (PID), smoking, previous Fallopian tube surgery (including tubal ligation), previous ectopic pregnancy, and infertility [1–4]. Notwithstanding, approximately 50% of women with an ectopic pregnancy do not exhibit any of the above risk factors [5].

Ectopic pregnancies represent a potentially life-threatening condition and despite increased diagnostic modalities including serum beta-human choriogonadotropin (hCG) levels and high-resolution transvaginal ultrasound, ruptured ectopic pregnancy continues to be a significant etiology of maternal death, accounting for between 2.7 and 6% of all maternal deaths [1–5]. The most common site of ectopic implantation is the Fallopian tube (>90% of cases), followed by previous cesarean scar (1%-3%), ovary (1%-3%), cervix (1%) or the peritoneal cavity (1%) [1]. Complete tubal abortion refers to cases in which the ovum completely separates from the tubal wall and is expelled into the peritoneal cavity [6]. Such cases may be associated with pain, peritoneal irritation, considerable intraperitoneal hemorrhage, and shock, or alternatively be asymptomatic with spontaneous resolution [6]. In contrast, an incomplete tubal abortion refers to cases in which the ovum remains attached to the tubal implantation site [6]. The latter, when associated with gradual expulsion of the ovum from the implantation site with concurrent implantation upon peritoneal surfaces is considered a likely nidus of what later may become an abdominal pregnancy. We describe unusual sonographic findings of a complete tubal abortion in a patient with minimal symptomatology.

Case report

A 25-year-old G1P0 initially presented to the emergency room due to a headache. She was in no acute distress and was hemodynamically stable. Her periods were regular with her last menstrual period 6 and 3/7 weeks earlier, and she reported a previous negative cervical cytology assessment. She had been using a copper intrauterine contraceptive device (Miranda) for approximately 2 years prior to her current presentation and attributed her mild chronic lower abdominal discomfort to the presence of a subserous uterine leiomyoma. Her laboratory values were all within the normal range other than a serum beta hCG = 505.7 mIU/mL. Two days later her repeat serum beta hCG = 496.2 mIU/mL.

Transvaginal ultrasound depicted an anteverted uterus devoid of a gestational sac. An IUD was noted in-situ within the endometrial cavity. A subserosal uterine leiomyoma measuring 3.3 × 2.8 × 2.2 cm was noted on the left posterior aspect of the uterus. The left ovary was normal and the right ovary contained a 3.2 × 3.3 × 2.4 cm corpus luteum cyst. Attention was drawn to a moderate amount of free fluid noted in both the anterior and posterior cul-de-sacs. Detailed scanning of the adnexa failed to disclose the presence of a suspected ectopic pregnancy. Continued scanning of the posterior (dependent) cul-de-sac, remote from the adnexa, disclosed the presence of a small sac like structure “floating” in the free fluid (Fig. 1), surrounded by ill-delineated, clot-appearing tissue measuring 3.2 × 3.3 × 2.4 cm in size (Figs. 2 and 3). Magnification of the suspected gestational sac revealed the presence of a yolk sac (Fig. 4). These findings were considered consistent with a likely ruptured or “leaking” tubal pregnancy.

Fig. 1.

Sagittal transvaginal image of the cul-de sac. Note the gestational sac surrounded by trophoblastic tissue and blood clots, “floating: in free-fluid (later proven hemoperitoneum), located afar from both adnexa.

Fig. 2.

Magnified sagittal transvaginal sonographic image of the complete tubal aborted gestational sac surrounded by blood clots measuring 1.75 × 1.6 cm in diameter. The faint yolk sac is depicted in the left lateral aspect of the gestational sac.

Fig. 3.

Axial image of Figure 2. The axial diameter of the tubal aborted gestational sac surrounded by blood clots measuring 1.43 cm.

Fig. 4.

Sonographic depiction of the yolk sac (YS) within the gestational sac of the aborted tubal pregnancy, categorically defining gestational sac. Note calipers measuring the yolk sac.

Given the presence of suspected ectopic pregnancy in the presence of free fluid, likely hemorrhage, diagnostic laparoscopy was performed. The presence of 100 mL of blood was noted in the pelvis and blood clots containing tissue were removed. Both Fallopian tubes appeared intact with no evidence of rupture, with the left distal tube appearing mildly hyperemic. The IUD was removed. Histopathology of the tissue removed from the pelvis confirmed organizing blood clots with granulation tissue containing immature chorionic villi consistent with an ectopic pregnancy. The patient's postoperative course was unremarkable, and follow-up serum beta hCG 2 weeks later was negative.

Discussion

The sonographic imaging tenet of an ectopic pregnancy (other than a heterotopic pregnancy) consists of an endometrial cavity devoid of a gestational sac in the presence of a serum beta hCG level above the discriminatory zone (currently considered between 1500 and 3500 mIU/mL) [1,3,7]. The definitive sonographic diagnosis of ectopic pregnancy consists of visualization of a gestational sac containing a yolk sac and/or embryo not located within the endometrial cavity. Following that 8%-31% of patients with suspected ectopic pregnancies will not have sonographic evidence of an intra or extra uterine pregnancy, the term pregnancy of undetermined location (PUL) was coined to include all patients with a positive serum beta hCG value, in the absence of sonographic confirmation of (either an ectopic or intrauterine) pregnancy [1,3]. These patients require meticulous clinical and laboratory (serum beta hCG level and sonographic) follow-up as between 25% and 50% of patients with a PUL will subsequently be determined to have ectopic pregnancies [1].

Systematic English literature search (PubMed, MEDLINE) between 1966 and 2023 utilizing the search terms “prenatal ultrasound,” “ectopic pregnancy” and “tubal abortion” reveals a marked paucity of reports of sonographic findings of tubal abortion [8], [9]–10]. Our case demonstrates that during the sonographic evaluation for possible ectopic pregnancy in which the characteristic finding of a heterogeneous mass typical of an ectopic pregnancy is not visualized in the vicinity of either adnexa, a thorough scan of dependent areas away from the adnexa, including the cul-de-sac must be performed as a gestational sac may be depicted floating among blood clots or free-fluid in this area. Clear depiction of the gestational sac will enable definitive diagnosis of an ectopic pregnancy, will negate the enigmatic diagnosis of a PUL, and ultimately enhance optimal patient care. Clinical management will depend upon the hemodynamic status of the patient, sonographic findings, and may include diagnostic laparoscopy versus continued expectant management with serial serum beta hCG levels, with or without Methotrexate, all to be considered by the clinician and patient.

Patient consent

We have obtained our patient's written informed consent for publishing our Case Report.