Pre-rupture diagnosis and conservative surgery for ovarian ectopic pregnancy hidden by an endometrioma, guided by the transvaginal ultrasound "sliding organ sign": a case report and literature review

A 28-year-old Chinese woman (gravida 2 para 1) presented to the emergency department with a 7-day history of intermittent lower abdominal pain and 44 days of amenorrhoea. Her last menstrual period was normal. She had a history of one full-term vaginal delivery and no prior pelvic surgery or contraceptive use. No specific hereditary diseases were reported in the patient’s family history. Physical examination revealed stable vital signs. Abdominal examination revealed mild lower abdominal tenderness without guarding or rebound. Speculum examination revealed a closed cervix without active bleeding. Bimanual examination revealed significant cervical motion tenderness and right adnexal tenderness. A urine pregnancy test conducted in our emergency department was positive, with a haemoglobin concentration of 128 g/L, a serum β-hCG concentration of 6666.0 mIU/mL and a progesterone concentration of 9.88 ng/mL. Transvaginal ultrasound revealed an empty uterine cavity with an endometrial thickness of 15 mm (Fig.  1 A) as well as an endometrioma measuring approximately 2.9 × 2.7 × 2.3 cm (Ovarian–Adnexal Reporting and Data System 2, O-RADS 2) in the right ovary, characterized by thick walls and homogeneous, low-intensity internal echoes presenting a “ground-glass” appearance (Fig.  1 B). Furthermore, a heterogeneous mass measuring approximately 2.0 × 1.9 × 1.7 cm and containing a yolk sac measuring 0.9 × 0.7 × 0.4 cm was detected in the right adnexal region. Under gentle and sustained pressure applied to the right adnexal region using a transvaginal probe, dynamic observation confirmed that the mass moved synchronously with the ovarian tissue without independent mobility, which is consistent with a negative “sliding organ sign.” This finding was confirmed through three repeated assessments (Fig.  1 C). An endometriotic cyst and a gestational sac were determined to co-exist within the right ovary (Fig.  1 D). A distinct corpus luteum blood flow signal was observed in the left ovary (Fig. 1E). On the basis of these findings, the patient was preliminarily diagnosed with a highly suspected right ovarian ectopic pregnancy with an ipsilateral ovarian endometrioma. Fig. 1 ( A ) Transvaginal ultrasound reveals a thickened endometrial lining with no signs of an intrauterine pregnancy. ( B ) A 2.9*2.7*2.3 cm endometriotic cyst is seen within the right ovary. ( C ) A 2.0*1.9*1.7 cm heterogeneous echogenic mass is identified in the right ovary, containing a 0.9*0.7*0.4 cm gestational-sac-like anechoic area with a yolk-sac-like structure inside. ( D ) Co-existence of an endometriotic cyst and a gestational sac within the right ovary. ( E ) A distinct corpus luteum blood flow signal was observed in the left ovary. ( A ) Transvaginal ultrasound reveals a thickened endometrial lining with no signs of an intrauterine pregnancy. ( B ) A 2.9*2.7*2.3 cm endometriotic cyst is seen within the right ovary. ( C ) A 2.0*1.9*1.7 cm heterogeneous echogenic mass is identified in the right ovary, containing a 0.9*0.7*0.4 cm gestational-sac-like anechoic area with a yolk-sac-like structure inside. ( D ) Co-existence of an endometriotic cyst and a gestational sac within the right ovary. ( E ) A distinct corpus luteum blood flow signal was observed in the left ovary. Figure 1 (A) Transvaginal ultrasound reveals a thickened endometrial lining with no signs of an intrauterine pregnancy. (B) A 2.9*2.7*2.3 cm endometriotic cyst is seen within the right ovary. (C) A 2.0*1.9*1.7 cm heterogeneous echogenic mass is identified in the right ovary, containing a 0.9*0.7*0.4 cm gestational-sac-like anechoic area with a yolk-sac-like structure inside. (D) Co-existence of an endometriotic cyst and a gestational sac within the right ovary. (E) A distinct corpus luteum blood flow signal was observed in the left ovary. Although the sonographic signs strongly suggested an ovarian ectopic pregnancy, we recognize that the clinical scenario alone—a positive pregnancy test, an empty uterus, an adnexal mass, and pain—is already sufficient to warrant prompt surgical evaluation [ 1 – 3 ]. Serum CA-125 was not measured in this emergency setting, as it would not have altered the acute management. The advanced ultrasound findings primarily guided our preoperative planning and consent process for ovary-conserving surgery. To confirm the diagnosis, the intrapelvic condition was directly evaluated, and the optimal treatment plan was determined, followed by diagnostic laparoscopy. Laparoscopic examination revealed approximately 100 mL of haemoperitoneum. The uterus and left adnexa were unremarkable. On gross examination, the right fallopian tube appeared normal in size, shape, and serosal surface, with no adhesions, dilation, or visible abnormalities. No chromotubation was performed to confirm functional patency. The tube was clearly separate from the ovary. The right ovary appeared enlarged and loosely adhered to the pelvic sidewall, without being completely fixed. Following adhesiolysis, a 2-cm dark-red, unruptured mass was identified protruding from the ovarian surface (Fig.  2 A). Evacuation of the mass contents revealed the presence of chorionic villi (Fig.  2 B). During removal of the gestational tissue, the ovarian endometrioma was inadvertently ruptured, releasing a thick, chocolate-coloured fluid consistent with the characteristics of an endometrioma. The cyst wall of the endometrioma was then meticulously excised in a stepwise fashion (Fig.  2 C). Fig. 2 Intraoperative imaging of the right ovary. A : Ovarian pregnancy. B : Evacuation of the mass contents revealed the presence of chorionic villi. C : Capsule of a ruptured ovarian endometrioma Intraoperative imaging of the right ovary. A : Ovarian pregnancy. B : Evacuation of the mass contents revealed the presence of chorionic villi. C : Capsule of a ruptured ovarian endometrioma To maximize the preservation of ovarian function, a suture-based haemostatic strategy was employed; the ovarian cortex was meticulously reconstructed by using 3–0 absorbable sutures to achieve precise haemostasis, while targeted bipolar coagulation was used only for individual, active bleeding points. The surgery lasted 81 min, with an estimated blood loss of 10 mL during the operation. The patient’s postoperative haemoglobin concentration was 122 g/L. Histopathological examination of the resected specimens confirmed the diagnosis. Microscopic examination revealed chorionic villi and trophoblastic tissue embedded within the ovarian stroma (Fig.  3 A), consistent with the characteristics of an OEP. The cyst wall was lined with decidualized endometrial tissue with infiltrating haemosiderin-laden macrophages (Fig.  3 B), confirming the diagnosis of ovarian endometrioma with a decidual change and establishing the co-existence of the two pathologies. The patient’s postoperative course was uneventful; her serum β-hCG levels normalized within 4 weeks post-operatively, and spontaneous menstruation resumed at 6 weeks, indicating well-preserved ovarian function. Fig. 3 Microscopic examination. ( A ) H&E staining (100×): chorionic villi are visible. ( B ) H&E staining (200×): decidualized endometrial tissue is observed Microscopic examination. ( A ) H&E staining (100×): chorionic villi are visible. ( B ) H&E staining (200×): decidualized endometrial tissue is observed

Ovarian ectopic pregnancy (OEP) is defined as the implantation of a gestational sac within the ovarian parenchyma. This rare condition, accounting for 1–3% of all ectopic pregnancies and 0.03–0.09% of all pregnancies [ 1 ], presents unique clinical challenges. The highly vascular and nonmuscular nature of the ovarian stroma predisposes OEP lesions to rapid rupture and life-threatening haemorrhage, making timely diagnosis critical [ 1 , 2 ]. However, preoperative diagnosis remains difficult, as OEPs can mimic the morphological and sonographic features of corpus luteum cysts, ovarian neoplasms, or tubal pregnancies—either intact or ruptured [ 1 , 3 , 4 ]. Ovarian endometrioma is a common subtype of endometriosis. It can induce a chronic inflammatory microenvironment marked by elevated levels of proinflammatory cytokines (e.g., IL-6 and TNF-α) and angiogenic factors such as VEGF [ 5 – 7 ]. This milieu may increase ovarian surface receptivity to trophoblast invasion, potentially contributing to OEP pathogenesis. A meta-analysis confirmed an association between endometriosis and ectopic pregnancy (OR = 2.16–2.66), further highlighting the need for vigilance in this patient population [ 8 ]. However, the classical “ground-glass” echogenicity of an ovarian endometrioma can mask co-existing OEP, creating a diagnostic pitfall that necessitates a high index of suspicion in the assessment of reproductive-age women. To our knowledge, this is the first case in which a preoperative diagnosis of ovarian pregnancy combined with an ovarian endometrioma was highly suspected on the basis of the transvaginal ultrasound “sliding organ sign,” resulting in successful fertility preservation without severe haemorrhage prior to rupture.

The most critical clinical message from this case is clear: any pregnant woman with a suspicious adnexal mass and an empty uterus requires prompt surgical evaluation, regardless of the availability of specialized ultrasound. The clinical triad—positive hCG, an empty uterus, and an adnexal mass—is the non-negotiable trigger for action. In our patient, this triad mandated surgery. The additional ultrasound signs (yolk sac, negative “sliding organ sign”) did not alter the need for surgery but allowed us to diagnose an ovarian pregnancy before rupture, even though it was masked by an endometrioma. When available, such signs are valuable adjuncts for surgical planning and fertility preservation. Ultimately, a high index of suspicion, adherence to core diagnostic principles, and timely minimally invasive surgery are the definitive strategies for ensuring patient safety and preserving future fertility.

Ovarian ectopic pregnancy (OEP) presents a diagnostic challenge because of its rarity and nonspecific clinical presentation. To systematically evaluate the clinical features of OEP co-existing with ovarian endometrioma, we conducted a comprehensive literature search in the PubMed and Scopus databases from January 1950 to December 2025 and identified 7 previously reported studies documenting a total of 8 cases (Table 1 ) [ 9 – 15 ]. Notably, in none of these 8 cases was a diagnosis of OEP highly suspected preoperatively on the basis of dedicated ultrasound signs. The majority of patients presented with haemoperitoneum due to rupture and underwent emergency radical surgery (e.g., salpingo-oophorectomy or hysterectomy), resulting in irreversible loss of ovarian function. Even in cases where some ovarian tissue was preserved [ 10 , 14 , 15 ], preoperative ultrasound did not indicate OEP: in Modawi’s case, the patient underwent elective surgery for an ovarian cyst with incidental intraoperative finding of OEP [ 10 ]; Bryunin’s case was preoperatively suspected to be a tubal ectopic pregnancy [ 14 ]; Aoyagi’s case underwent emergency surgery for ruptured endometrioma without intraoperative recognition of the ectopic gestation [ 15 ]. In stark contrast, the unique value of our case lies in achieving a strongly suspected preoperative diagnosis of OEP before rupture, despite the lesion being completely obscured by an ipsilateral endometrioma. This was accomplished through the deliberate combination of transvaginal ultrasound signs: the identification of a yolk sac and a negative “sliding organ sign”. To our knowledge, this is the first reported case of pre-rupture diagnosis of OEP masked by an endometrioma using these sonographic criteria. Table 1 Summary of confirmed cases of ovarian pregnancy coexisting with ovarian endometrioma Reference Age (y) GA (wk) Clinical Presentation Surgical Findings Surgical Intervention Pathological Findings Fertility Preservation Measures Surgical Timing and Outcome Durburg & Grimes (1958) [ 9 ] 32 ~ 10 Paraumbilical pain, weakness, syncope Massive haemoperitoneum, unidentifiable right ovary, haemorrhagic pelvic mass Laparotomic supracervical hysterectomy + BSO Ruptured ovarian pregnancy, endometriosis with decidual changes None; fertility sacrificed (hysterectomy and BSO) Emergency surgery for rupture and life-threatening haemorrhage; complete loss of reproductive function Modawi (1962) [ 10 ] 35 12 Menorrhagia, backache, lower abdominal dull aching pain for 2 years; regular menses with clots, intermenstrual bleeding Pedunculated right ovarian cyst (grape-fruit size), normal right fallopian tube, no adhesions, bulky uterus Laparotomic right ovarian cyst resection (pedicle clamping/cutting) Primary ovarian twin pregnancy (uniovular), ovarian endometriosis with endometrial glands in cyst capsule, chorionic villi invading ovarian stroma, decidual/luteal cells Conservative resection (ovarian cystectomy); entire ovary preserved Elective surgery for ovarian cyst; uneventful recovery, no reproductive function loss reported Punnonen & Lauren (1982) [ 11 ] (Case 1) NA NA (1st Tri) NA Gestational sac at the ovarian surface Laparotomic USO Ovarian pregnancy, coexisting endometriotic foci None; ovarian function lost (salpingo-oophorectomy) Early surgery, but radical approach without ovarian preservation Punnonen & Lauren (1982) [ 11 ] (Case 2) NA NA (1st Tri) NA Gestational sac at the ovarian surface Laparotomic USO Ovarian pregnancy, coexisting endometriotic foci None; ovarian function lost (salpingo-oophorectomy) Early surgery, but radical approach without ovarian preservation Ohba et al. (1992) [ 12 ] 29 15 Right lower quadrant pain, vaginal spotting (1 week); tender right lower quadrant bulge Unruptured right ovarian mass (intraligamentary), normal fallopian tubes, cul-de-sac “powder burn” (peritoneal endometriosis), appendix adherent to mass Laparotomic right USO Ovarian twin pregnancy (autolyzing embryos), ovarian and pelvic endometriosis; a corpus luteum was identified in the ovarian mass periphery None; ovarian function lost (salpingo-oophorectomy) Elective surgery (pre-op suspected malignant ovarian tumor/ectopic pregnancy); uneventful postoperative course Toki et al. (1998) [ 13 ] 29 7 Lower abdominal pain, spotting, amenorrhoea Ruptured left ovarian mass, haemoperitoneum (200 mL) Laparotomic USO Ruptured ovarian pregnancy, microscopic endometriosis with decidual changes None; ovarian function lost (salpingo-oophorectomy) Emergency surgery postrupture; no opportunity for ovarian conservation Bryunin et al. (2022) [ 14 ] 29 ~ 8 (56 days amenorrhoea) Menstrual cycle disorder, right lower abdominal dull pain, sanguinopurulent vaginal discharge (3 days); history of missed abortion Haemoperitoneum (40 mL), right ovarian mass (6 × 5 cm) with heterogenic structure, ovarian/peritoneal endometriotic foci, normal fallopian tubes Laparoscopic right ovarian resection (healthy tissue margins) + endometriotic foci excision Laparoscopically confirmed right-sided intrafollicular ovarian pregnancy, ovarian/peritoneal endometriosis Ovarian resection (marginal, healthy tissue preserved); complete endometriosis excision Emergency surgery (pre-op suspected tubal ectopic pregnancy); minimal blood loss, β-hCG normalized by post-op day 4; intrauterine pregnancy achieved at 9 months post-op with successful delivery Aoyagi et al. (2023) [ 15 ] 34 5.9 Acute hypogastric pain, massive haemoperitoneum Ruptured ovarian endometrioma, haemoperitoneum (1200 mL), no gross ectopic lesion Laparoscopic ovarian cystectomy Ovarian pregnancy, endometrioma with decidual changes, corpus luteum cyst Ovarian cystectomy; ovarian tissue partially preserved but not specifically reconstructed Emergency surgery for rupture; pregnancy not recognized intraoperatively; β-hCG normalized postoperatively Our Case (2025) 28 ~ 6.3 44 days of amenorrhoea, lower abdominal pain Unruptured ovarian mass with a yolk sac, ipsilateral endometrioma, haemoperitoneum (100 mL) Laparoscopic excision of both lesions with ovarian reconstruction Ovarian pregnancy, endometrioma with decidual changes Successful fertility-sparing surgery: ovarian cortex reconstruction with sutures (primary haemostasis), minimal targeted bipolar coagulation to minimize thermal damage Early diagnosis and timely intervention prerupture; menses resumed at 6 weeks, confirming preserved ovarian function Abbrviations: y years, GA gestational age, wk weeks, BSO bilateral salpingo-oophorectomy, USO unilateral salpingo-oophorectomy, LSO left salpingo-oophorectomy, NA not applicable/not available, Tri trimester. Summary of confirmed cases of ovarian pregnancy coexisting with ovarian endometrioma Modawi (1962) [ 10 ] Ohba et al. (1992) [ 12 ] Bryunin et al. (2022) [ 14 ] Abbrviations: y years, GA gestational age, wk weeks, BSO bilateral salpingo-oophorectomy, USO unilateral salpingo-oophorectomy, LSO left salpingo-oophorectomy, NA not applicable/not available, Tri trimester. Before discussing the ultrasound findings, we must emphasize a more fundamental point. The decision to operate on our patient was based solely on the classic clinical triad: positive β-hCG, an empty uterus, and an adnexal mass. This triad alone is sufficient to mandate surgical evaluation (or, in a strictly haemodynamically stable patient, very close observation) regardless of whether advanced sonographic signs are available. The presence of an endometrioma or other complex ovarian pathology must never lower the suspicion of a concurrent ectopic pregnancy. In our case, the transvaginal ultrasound findings (yolk sac and negative “sliding organ sign”) did not drive the decision to operate; rather, they refined the preoperative diagnosis by localizing the pregnancy to the ovary. This knowledge allowed us to counsel the patient specifically for ovary-sparing surgery, prepare for suture-based haemostasis rather than salpingectomy, and minimize intraoperative surprises. Thus, while the clinical triad provides the indication for intervention, meticulous sonography adds value by enabling fertility-preserving precision. The co-existence of OEP and endometrioma is unlikely to be a mere coincidence and suggests shared pathophysiological mechanisms [ 8 ]. Endometriosis creates a chronic pelvic inflammatory state that is rich in proinflammatory cytokines and proangiogenic factors [ 5 , 16 , 17 ]. This milieu can impair tubal function [ 5 ] and, when localized to the ovary by an endometrioma, may fundamentally alter ovarian surface receptivity. The molecular signals (e.g., MMPs and integrins) that enable ectopic endometrial invasion may inadvertently create a “pseudoreceptive” niche for trophoblast attachment and invasion [ 18 , 19 ]. Importantly, our patient had no other identifiable risk factors for ectopic pregnancy (e.g., prior pelvic surgery, pelvic inflammatory disease, or contraceptive use), making the endometrioma the most plausible contributing factor. The differential diagnosis in this case underscores the challenge of accurately identifying ovarian pregnancy within a complex adnexal mass. The core task lies in systematically distinguishing three common acute conditions: tubal ectopic pregnancy, corpus luteum cyst, and ruptured ovarian endometrioma [ 3 , 20 ]. By integrating specific sonographic signs and serological markers, we established a progressive chain of evidence indicating ovarian pregnancy. First, the repeatedly confirmed negative “sliding organ sign” on dynamic ultrasound—where the mass moved synchronously with the ovarian parenchyma without independent mobility—strongly argued against a tubal ectopic pregnancy [ 3 , 4 ]. Second, the clearly identified functional corpus luteum in the contralateral ovary and the well-defined yolk sac within the mass ruled out a diagnosis of a simple corpus luteum cyst. Finally, although a ruptured ovarian endometrioma can also cause acute symptoms and its characteristic “ground-glass” echogenicity may morphologically obscure an adjacent gestational structure, rupture alone cannot explain the sonographically detected yolk sac or the significantly elevated serum β-hCG level. This positioned the endometrioma as a co-existing pathology rather than the primary aetiology. Importantly, ultrasonography provided diagnostic clues that raised strong suspicion in this process, but definitive confirmation relied on laparoscopic exploration and postoperative histopathological examination. Furthermore, the concurrent endometrioma itself was a significant diagnostic confounder. The postoperative pathological finding of decidualized endometriotic tissue—for which progesterone-driven morphological changes can mimic the papillary architecture, solid components, and aberrant vasculature of a malignancy on imaging [ 21 , 22 ]—had the potential to divert diagnostic attention from the ectopic pregnancy and even delay lifesaving intervention. In summary, systematic imaging and clinical indicator analysis can provide crucial direction for the early recognition of ovarian pregnancy, thereby creating a vital opportunity for timely confirmatory laparoscopic intervention. Timely diagnosis was pivotal in preventing severe haemorrhage [ 1 , 2 , 23 ]. Despite the highly vascular ovarian stroma, our patient presented with only 100 mL of haemoperitoneum and an estimated blood loss of 10 mL intraoperatively, indicating that early intervention effectively controlled potential vascular complications. The minimal decrease in haemoglobin concentration (from 128 g/L preoperatively to 122 g/L postoperatively) is further evidence that early intervention successfully limited blood loss. This stable condition enabled a carefully planned, fertility-preserving surgical strategy. The key to our haemostatic technique was the primary reconstruction of the ovarian cortex with fine absorbable sutures, providing definitive anatomical closure as the main haemostatic method. Bipolar electrocautery was employed only for minimal, targeted spots to address discrete bleeding, thereby minimizing thermal damage to the follicular reserve. This suture-dominant approach is fundamental for safeguarding long-term ovarian function [ 23 , 24 ]. This report has several strengths. First, it demonstrates the first successful pre-rupture diagnosis of OEP masked by an endometrioma using the “sliding organ sign” and yolk sac detection. Second, it documents a successful fertility-preserving surgical strategy using suture-based primary haemostasis. Third, the report provides a detailed comparison with all previously reported cases, identified through a comprehensive literature review across two major databases (PubMed and Scopus). Limitations include the following: (1) our work has the inherent limitations of a single case report; (2) serum CA-125 was not measured due to the emergency presentation and clear pregnancy-related diagnosis; (3) tubal patency was assessed by macroscopic appearance only, without chromopertubation; (4) long-term follow-up data on ovarian reserve (e.g., AMH) and subsequent pregnancy outcomes are not yet available; and (5) the “sliding organ sign” is operator dependent, as its interpretation requires the examiner to apply appropriate, sustained pressure and to differentiate true organ adherence from limited mobility due to pain or adhesions. Despite these limitations, our case demonstrates that pre-rupture diagnosis of OEP masked by an endometrioma is feasible with a high index of suspicion and meticulous ultrasound technique.