Strangulated Small Bowel Obstruction Caused by a Migrated Ring-Shaped Intrauterine Device: Two Case Reports and a Literature Review

Introduction

Small bowel obstruction is a common surgical emergency, and its mortality increases markedly when strangulation occurs. Although adhesions and hernias are the most frequent causes, SBO resulting from migration of an intrauterine device (IUD) is exceedingly rare. Intrauterine devices (IUDs) are widely used long-acting reversible contraceptives with a history of more than 5 decades. They are generally safe, effective, and well tolerated, and many women remain asymptomatic during long-term use. Despite clinical guidelines recommending removal of IUDs after menopause, non-removal remains common. As a result, some IUDs are not removed after menopause, particularly when patients are unaware of the need for removal or lack regular gynecologic follow-up. Long-term retention, however, can lead to complications such as embedment, migration, or perforation, which can present incidentally or with acute symptoms. Given that uterine perforation – the prerequisite for IUD migration – occurs in only 0.05 to 13 per 1000 insertions, subsequent progression to strangulated intestinal obstruction is even more uncommon. As a result, this etiology is often overlooked in clinical practice, particularly when the symptoms of obstruction are atypical, increasing the risk of missed diagnosis, bowel necrosis, and even life-threatening complications.

In this report, we describe 2 consecutive cases encountered within a 6-month period in postmenopausal women who had retained ring-shaped intrauterine devices (IUDs) for more than 30 years. Beyond highlighting the diagnostic challenges associated with this rare condition, this study aims to elucidate the novel “internal herniation” mechanism unique to ringshaped devices – distinct from direct bowel perforation – and to identify postmenopausal uterine atrophy as the key precipitating factor that transforms a long-dormant device into a surgical emergency. This case report is presented in accordance with the SCARE criteria [1].

Case Reports

CASE 1:

A 61-year-old woman presented with a 1-day history of acute-onset abdominal pain, distension, nausea, and vomiting. Physical examination revealed lower abdominal tenderness with rebound and guarding. Vital signs were stable except for tachycardia (102 bpm). Her medical history was notable for intrauterine device (IUD) placement over 30 years prior, with no history of abdominal surgery. Abdominal and pelvic computed tomography (CT) demonstrated segmental small bowel dilatation with air-fluid levels, localized bowel wall thickening with effusions, suggestive of mechanical small bowel obstruction with possible strangulation, and an ectopic ring-shaped IUD (Figure 1A–1E). Laboratory findings included leukocytosis (16.6×109/L; 90.3% neutrophils) and hypokalemia (3.21 mmol/L). Given the signs of peritonitis and suspected strangulated internal hernia, emergency laparoscopy was performed. Intraoperative findings included necrotic ileum and bloody ascites, prompting conversion to laparotomy. A segment of terminal ileum was found herniated through a metallic ring-shaped IUD, resulting in strangulation and necrosis (Figure 1F, 1G). Resection of the necrotic ileum and ileocecal region (total 30 cm) was followed by side-to-side ileo-ascending colon anastomosis. Gynecologic evaluation revealed an atrophic uterus without evidence of acute perforation. Histopathology confirmed transmural necrosis and mesenteric vascular congestion. The postoperative course was stable and uneventful (Figure 1H), except for a wound infection; she was discharged on postoperative day (POD) 17 and remained well during follow-up.

CASE 2:

A 73-year-old woman presented to the emergency department with a 2-day history of lower abdominal pain, exacerbated by physical activity, accompanied by nausea and vomiting. On examination, she was afebrile with stable vital signs except for localized tenderness, rebound, and mild guarding in the left lower quadrant. Her history included intrauterine device (IUD) placement over 40 years prior, with no prior abdominal surgeries. Urgent abdominopelvic CT revealed dilated small bowel loops with air-fluid levels in the left abdomen, localized exudative changes, a ring-shaped radiopaque structure in the abdominal cavity, and free intraperitoneal fluid – findings suggestive of small bowel obstruction with possible strangulation (Figure 2A–2E). Laboratory tests showed leukocytosis (10.89×109/L; 85.7% neutrophils). Emergency exploratory laparotomy revealed approximately 500 mL of hemorrhagic ascites and a migrated ring-shaped IUD in the mid-abdomen. A segment of ileum had herniated through the IUD ring, resulting in strangulation and necrosis (Figure 2F, 2G). The affected bowel (total 50 cm) was resected, and a side-to-side anastomosis was performed using a linear stapler. Uterine exploration revealed no acute perforation, although a suspicious scar was noted. Histopathology confirmed transmural necrosis and hemorrhagic infarction (Figure 2H). The postoperative course was uneventful. The patient was discharged on postoperative day 8 and remained well during follow-up.

Discussion

Strangulated intestinal obstruction is a common and potentially life-threatening surgical emergency characterized by high mortality and complex clinical manifestations. The underlying pathophysiology involves compromised mesenteric blood flow due to bowel strangulation, leading to ischemia and subsequent transmural necrosis if not promptly treated [2,3]. Early and accurate diagnosis, followed by timely surgical intervention, is critical to improving patient outcomes and reducing mortality [4]. While postoperative adhesions and mesenteric arterial stenosis or occlusion are well-established etiologies, strangulated obstruction secondary to IUD migration remains exceedingly rare [5]. To date, 36 cases of IUD-related intestinal obstruction have been reported in China, with only 10 cases documented in the English-language literature worldwide [6–14]. Based on previous case reports (Table 1), intestinal obstruction caused by IUD migration exhibits the following clinical characteristics: the mean age at onset was 56.2 years, whereas patients with ring-shaped IUDs had a higher mean age of 63.57 years. The IUDs had been retained within the pelvic or abdominal cavity for an extended period, averaging over 30 years. The average length of the resected affected bowel segment was approximately 78.3 cm. All cases were treated surgically, and all patients recovered postoperatively. Because most published reports are individual case descriptions, the age discrepancy observed in our cases is derived from limited case-based evidence and lacks support from large-scale datasets. In addition, unlike T shaped IUDs with sharp edges that can penetrate tissues more rapidly, the ring-shaped IUD has a blunt, closed-loop configuration, resulting in a slower and more prolonged transmural migration through the atrophied postmenopausal myometrium [15]. Even when perforation occurs, the device is often covered by the omentum, making small bowel herniation less likely. These factors may collectively contribute to the relatively higher age observed in our cases.

We report 2 cases of IUD-related strangulated small bowel obstruction, both occurring in postmenopausal women who had retained ring-shaped IUDs for several decades and presented to the emergency department with acute abdominal pain. Abdominopelvic CT revealed small bowel obstruction and ectopic IUD in both cases. Intraoperative findings confirmed strangulated ileal herniation through the IUD rings, resulting in ischemic necrosis – 30 cm in Case 1 and 50 cm in Case 2. Both patients underwent successful segmental bowel resection and anastomosis. Histopathological examination showed transmural necrosis and mesenteric vascular congestion.

IUDs are widely used for contraception [15,16]; however, complications arising from device displacement are frequently underrecognized. Displacement refers to deviation from the intended intrauterine position, which can result in partial or complete penetration of the uterine wall [17,18]. Such migration can lead to serious complications, including hemorrhage, uterine perforation, pelvic inflammatory disease, and injury to adjacent organs [18–21]. The reported incidence of uterine perforation associated with IUDs ranges from 0.05 to 13 cases per 1000 insertions [22–24]. Common sites of migration include the bladder wall, intestines, peritoneal cavity, and retroperitoneal space [25–27]. However, migration into the peritoneal cavity resulting in strangulated intestinal obstruction remains poorly defined, with few case reports available. Previous studies suggest that ring-shaped IUDs are more prone to displacement due to their rigid structure and limited flexibility [6]. Despite this, their blunt configuration and small central aperture typically favor omental encapsulation following perforation, which rarely causes intestinal obstruction [28].

The 2 cases presented here offer meaningful clinical evidence that helps clarify this apparent contradiction. Both patients exhibited marked uterine atrophy, and intraoperative findings revealed no evidence of recent perforation, only suspected chronic scarring, indicating a low likelihood of acute perforation. Regarding the mechanism of uterine perforation, intrauterine device (IUD) perforation and subsequent displacement may begin as a chronic, occult process during the perimenopausal period, with the myometrium thinning as the uterus atrophies, but the rigid ring-shaped device retains its original size and shape. The uterus can generate forces up to 50 Newtons [29], sufficient to induce myometrial erosion and facilitate IUD migration into the peritoneal cavity [30,31]. It is plausible that the ring-shaped IUDs in these cases had partially embedded into the myometrium before menopause and gradually migrated into the peritoneal cavity as uterine atrophy progressed thereafter.

In contrast, the mechanism of intestinal strangulation differs substantially from that associated with sharp T-shaped devices. Rather than directly perforating the bowel, the ring-shaped IUD serves as a fixed hernia orifice. Chronic inflammation promotes adhesion formation [32], securing the device to the omentum or adjacent bowel loops. During intestinal peristalsis, bowel segments may become entrapped by these adhesive bands or by the ring itself, leading to mechanical obstruction – an internal herniation process. As venous congestion causes the entrapped bowel loop to swell, it becomes irreducible, ultimately progressing to strangulation and the transmural necrosis observed in our patients.

For surgeons, determining the optimal timing for surgical intervention in cases of intestinal obstruction remains challenging, particularly when the etiology of strangulation is unclear [33]. These 2 cases were consecutive patients treated within a 6-month period. In Case 1, the IUD remained confined to the pelvis, and an IUD-related internal herniation was not anticipated preoperatively. Given the patient’s presentation with acute peritonitis, emergency laparoscopy was selected to establish the diagnosis while minimizing surgical trauma. However, the intraoperative discovery of extensive bowel necrosis and dense adhesions rendered laparoscopic manipulation unsafe, necessitating conversion to an open procedure. In Case 2, the surgical strategy was informed by the experience gained from the first case. The IUD was identified preoperatively in a supraumbilical position, and CT imaging demonstrated localized bowel dilatation, fluid accumulation, and clear signs of peritonitis. These findings raised a strong suspicion of bowel necrosis prior to surgery. Consequently, a primary laparotomy was performed to expedite decompression and relieve the obstruction, thereby shortening operative time and reducing the risks associated with prolonged anesthesia and toxin absorption in an older patient. This progression in operative decision making underscores an important principle: although laparoscopy is valuable for diagnostic clarification, primary laparotomy may offer a safer and more efficient approach when strangulation is strongly suspected or when marked bowel distension limits the feasibility of laparoscopic intervention.

While sporadic cases have been documented, the novelty of our report lies in 3 key contributions to the existing literature. First, we encountered 2 such rare cases consecutively within a short 6-month interval. This brief “cluster” suggests that, as China’s population continues to age and the number of women with long-term retained IUDs increases, the true incidence of this complication may be higher than previously estimated and warrants heightened clinical awareness. Second, we identify postmenopausal uterine atrophy not merely as a contributing risk factor but as the primary precipitating event capable of transforming a dormant, decades-old device into a surgical emergency. Third, we clearly delineate the unique “internal herniation” mechanism associated with ring-shaped IUDs, in which the device functions as a fixed hernia orifice rather than directly perforating the bowel, as is more typical with T-shaped devices. Preoperative imaging [34] played a pivotal role in diagnosis, revealing bowel dilation, fluid-filled loops, wall thickening, and IUD displacement. Correlating these radiologic findings with the patient’s clinical history, physical examination, and laboratory results enabled timely surgical intervention. Laparoscopic exploration proved essential in preventing misdiagnosis and guiding appropriate clinical decision-making. Furthermore, these cases highlight the critical importance of patient education regarding the risks associated with long-term IUD retention [35]. To prevent serious and potentially life threatening complications, clinicians should emphasize the importance of timely IUD removal at the onset of menopause. In older women presenting with unexplained abdominal pain, a thorough inquiry into remote contraceptive history is essential. Moreover, for patients with retained IUDs who are poor surgical candidates, we recommend regular abdominal ultrasound surveillance to detect potential device displacement at an early stage.

Conclusions

Although rare, IUD displacement leading to strangulated intestinal obstruction poses serious clinical risks. The pathological process typically begins with mechanical penetration, followed by local inflammation, adhesion formation, and damage to surrounding organs. In cases of intestinal obstruction with unclear etiology, especially in patients with long-term IUD retention, clinicians should maintain a high index of suspicion. A comprehensive evaluation, including imaging studies, is essential to ensure accurate diagnosis, avoid mismanagement, and facilitate timely surgical intervention.