Migration of an ingested orthodontic retainer into the psoas muscle presenting with radiculopathy-like symptoms

Rationale: Sharp foreign bodies (FBs) can occasionally perforate the gastrointestinal tract and migrate into adjacent structures, but retroperitoneal migration into the psoas muscle is exceedingly rare. Such cases may present with atypical symptoms and pose diagnostic challenges. Patient concerns: A 26-year-old man presented with abdominal pain after swallowing an orthodontic retainer. His abdominal pain improved, but he later developed persistent right lower-limb paresthesia and aching pain that worsened with walking. Diagnoses: Initial computed tomography (CT) demonstrated a metallic FB penetrating a small bowel wall. A diagnostic laparoscopy performed at an outside hospital on day 3 failed to identify the FB. A follow-up CT on day 4 revealed migration of the FB into the right psoas muscle. A repeat CT performed 6 weeks later showed deeper intramuscular migration, correlating with his neurological symptoms. Interventions: A same-day urgent C-arm–assisted laparoscopic exploration was performed. After right colon mobilization and retroperitoneal exposure, the FB was localized using real-time fluoroscopy and completely removed from the psoas muscle. Outcomes: The patient’s neurological symptoms improved immediately after surgery, and resolved at the 2-week follow-up. He remained completely asymptomatic at the 12-month postoperative follow-up. Lessons: Psoas migration of an ingested sharp FB can occur silently without peritonitis and may present with delayed radiculopathy-like symptoms. Persistent or evolving symptoms after an initial negative exploration should prompt repeat CT imaging. C-arm–assisted laparoscopy is a feasible and effective minimally invasive approach for removing migrated retroperitoneal FBs.