Ectopic pregnancies occur when a fertilized ovum is implanted outside of the endometrial cavity. Approximately 1.5% to 2.0% of all pregnancies are ectopic,¹ and it is a major cause of maternal death during the first trimester of pregnancy.² Abdominal pregnancies account for approximately 1% of ectopic pregnancies.³ Primary omental pregnancy, in which the greater omentum is the extrauterine site of implantation, is the least common form of abdominal pregnancy, with a reported incidence between 1 in 4857 to 7931 abdominal pregnancies.^4-7 It is reported that maternal mortality from abdominal pregnancy is 7.7 times higher than from tubal ectopic pregnancy, most often resulting from hemorrhagic shock secondary to ectopic pregnancy rupture.^4,8-9 The rarity of an ectopic pregnancy in the omentum and the absence of clinical symptoms often delay diagnosis and proper identification before rupture. We discuss the case of a 23-year-old woman who presented with hemoperitoneum from a ruptured omental ectopic pregnancy that mimicked adnexal implantation. 

A 23-year-old woman (gravida 3, para 2) at 7 weeks gestational age presented to the labor and delivery emergency department with painless, minimal vaginal spotting. On physical examination her vital signs were stable, with blood pressure of 120/88 mm Hg and a pulse rate of 85 beats/min. Her serum β-human chorionic gonadotropin (hCG) level was 433 mIU/mL. The patient denied medical or surgical history aside from 2 uncomplicated vaginal deliveries, a normal menstrual cycle, and no use of contraception, alcohol, or illicit drugs. An osteopathic structural examination (OSE) of the thoracic and lumbar spines, rib cage, and sacrum was performed and revealed that T1-T12 and L1-L5 were neutral, rotated left, and sidebent right and the sacrum was rotated left on a left oblique axis. No Chapman reflex points were identified at this time. Transvaginal ultrasonography revealed a normal uterus and adnexal structures, no free fluid in the pelvis, and no intrauterine pregnancy (IUP). The patient was given the diagnosis of pregnancy of an unknown location, counseled on the possibility of an ectopic pregnancy, and instructed to return for a follow-up evaluation within 48 hours for repeated serum β-hCG level testing. 

The patient did not keep her follow-up appointment, but she returned to the emergency department 2 weeks later with severe abdominal pain over the past 3 hours. She denied any vaginal bleeding, nausea, or vomiting. Her vital signs at the time of presentation were stable (blood pressure, 117/82 mm Hg, and pulse rate, 88 beats/min). However, physical examination revealed diffuse abdominal tenderness, guarding, and signs of acute abdomen with increasing lethargy. An OSE of the thoracic and lumbar spines, rib cage, and sacrum was performed and revealed that T1-T8 and L1-L5 were neutral, rotated left, and sidebent right; T9-T12 were flexed, rotated right, and sidebent right; and the sacrum was rotated left on a left oblique axis. Chapman reflex points were identified anteriorly in the intercostal space between the 9th and 10th and the 10th and 11th ribs near the costochondral junction, bilaterally and posteriorly between the transverse processes of T9 and T10 and T10 and T11, and halfway between the spinous processes and the tips of the transverse processes. 

Transvaginal ultrasonography images revealed an 8-mm endometrial stripe, large amounts of complex fluid with internal echoes around the uterus and both adnexa (most likely representative of a hemoperitoneum) (Figure 1A), and a 0.5-cm left adnexal cystic structure with focal increased vascularity (Figure 1B). Her serum β-hCG level was 333 mIU/mL, and a complete blood cell count revealed a hemoglobin level of 10.9 g/dL, hematocrit of 35%, and a white blood cell count of 19.6 × 10⁹/L. These findings were highly suggestive of a ruptured ectopic pregnancy, and the patient underwent an emergent laparotomy. 

An exploratory laparotomy revealed 1500 mL of hemoperitoneum and a normal uterus with intact ovaries, ligaments, and fallopian tubes. A brownish-red encapsulated soft nodular tissue measuring approximately 2 cm × 2 cm, easily palpated, was clearly seen on the left side of the omentum (Figure 1C). The gestational sac was identified with surrounding blood clots. A left partial omentectomy was also performed with a wide omental excision technique to avoid leaving trophoblastic tissue behind. An examination of the remaining contents of the pelvis and abdominal cavity revealed no abnormal tissue. Histopathologic analysis revealed focally hemorrhagic fibroadipose tissue, reactive lymph nodes, and products of conception consisting of immature chorionic villi in the supporting tissue (Figure 1D). The patient had an uneventful recovery, with down-trending serum β-hCG levels over the course of 2 weeks. 

Primary omental pregnancy is the least common form of abdominal pregnancy.⁶ Abdominal pregnancies are a greater risk than tubal ectopic pregnancies because they are usually not detected until a rupture has occurred and subsequent hemorrhagic shock ensues.¹⁰ Before rupture, patients usually present with nonspecific symptoms and have vaginal bleeding less frequently than patients with ectopic pregnancies of tubal origin. 

Osteopathic physicians may use palpatory findings of the musculoskeletal system through an OSE as part of the diagnostic process. These abnormal OSE findings, or somatic dysfunctions, arise due to viscerosomatic reflexes from affected visceral structures.¹¹ In the current case, the OSE findings and the Chapman reflex points identified corresponded to irritation of the small intestine at the jejunum and ileum (Figure 2).¹² These findings, in addition to the transvaginal ultrasonography images, were suggestive of hemoperitoneum, and an ectopic pregnancy of an uncommon location was the diagnosis. Osteopathic concepts in the management of ectopic pregnancy have not been well studied. Smutny et al¹³ state that osteopathic manipulative treatment is contraindicated in ectopic pregnancies because they are surgical emergencies. Nevertheless, this fact does not preclude the use of an OSE as part of the initial physical examination and diagnostic approach, especially because the OSE findings and Chapman reflex points identified were the first diagnostic results that suggested an abdominal location of the ruptured ectopic pregnancy in the current case. 

Laparotomy or laparoscopy can be used to manage a suspected ruptured ectopic pregnancy. Although laparoscopy is less invasive, laparotomy may be the preferred approach in some cases. In the current case, emergent exploratory laparotomy was chosen because of the late presentation of symptoms, the hemoperitoneum, the clinically deteriorating status of the patient, and the aforementioned diagnostic findings that suggested an atypical location of ectopic pregnancy, causing irritation to the small intestine. Laparotomy was superior in this case, as further surgical exploration into the abdominal cavity was required and laparoscopy may have been more difficult and time consuming because of the extensive hemorrhage encountered intraoperatively. Omentectomy was performed via wide omental excision because the true borders of trophoblastic invasion cannot be completely determined grossly. Abdominal pregnancies implanted on a vascular surface have an increased risk of uncontrollable hemorrhage during the procedure, and rapid vascular control during major hemorrhage is easier to establish with laparotomy.¹⁴ 

Abdominal pregnancies can arise as a primary or secondary event. In a primary abdominal pregnancy, the rarest type, the implantation occurs directly on the peritoneal surface, whereas in secondary abdominal pregnancies, the embryo implants primarily on the fallopian tube and is then expelled and reattaches itself on another intra-abdominal surface.¹⁰ Primary abdominal pregnancies have been reported on the omentum, sigmoid colon, posterior peritoneum of the pelvis, spleen, liver, diaphragm, obturator foramen, posterior surface of the uterus, retroperitoneum, and pancreas.¹⁵ Although diagnosis of such pregnancies is challenging, standards have been established by Studdiford to discern abdominal pregnancies from other types of ectopic pregnancies.¹⁶ The criteria include normal bilateral fallopian tubes and ovaries with no recent or remote injury, the absence of any uteroperitoneal fistulas, and pregnancy attached exclusively to the peritoneal surface (early enough to eliminate the possibility of secondary implantation). 

To be properly classified as a primary abdominal pregnancy, histologic evidence of growth of trophoblasts into supporting tissue must be identified. All other cases should be considered secondary abdominal pregnancy.¹⁷ The fact that the patient in the current case had signs of vaginal spotting on initial presentation does not preclude the diagnosis of a primary abdominal pregnancy. Careful intraoperative evaluation revealed a normal uterus and fallopian tubes with intact ligaments and no evidence of adhesions. When the omentum was first encountered and found to be overlying the fallopian tubes, suspicion was low for the ectopic pregnancy to be located in the omentum because hemoperitoneum was present and caused an abnormal appearance of the entire omentum. All 3 Studdiford criteria were met in the current case, thus confirming the presence of a primary omental pregnancy. 

Despite the condition’s rarity, a ruptured primary omental ectopic pregnancy can present similarly to a ruptured ectopic pregnancy of tubal origin, but the former has a substantially higher mortality rate. Diagnosis and proper identification is often delayed because of the lack of presenting signs and symptoms. Ultrasonography has low sensitivity, and clinical examination findings are often benign. An OSE can be helpful in distinguishing the location of visceral abnormality, but further studies are required to evaluate the role of OMT in ectopic pregnancies and accuracy of the correlation between OSE findings and ectopic pregnancies. During surgical exploration in which the uterus, ovaries, and fallopian tubes appear normal and intact, the omentum and abdominal cavity should be carefully examined as a potential implantation site.