Case Presentation: Thoracic duct rupture can be seen in traumatic injuries to the mediastinum, or as a potential complication of thoracic surgical procedures. Rarely, thoracic duct rupture has been associated with severe systemic infections. There have only been a handful of case reports dating back to 1955 of spontaneous, idiopathic thoracic duct ruptures. Most cases of thoracic duct rupture are diagnosed in the setting of chylothorax, although it can also present more subtly as rapid soft tissue swelling in the neck and chest. Thoracic duct cysts are genetic malformations that may predispose a higher risk for spontaneous duct rupture. We report a case of a previously healthy 39 year-old female who presented with spontaneous, acute onset bilateral flank pain and swelling in the left side of her neck. The patient reported that she woke up with an intense, cramping pain in her back and sides just beneath her ribs. She also noticed swelling over her left neck and shoulder that was tender to touch. The patient had no history of trauma or illness and her labs were all within normal range. Infectious work-up was negative. Computed-Tomography (CT) imaging of the neck showed non-specific soft tissue swelling and fluid accumulation from the level of the hyoid bone inferiorly into the supraclavicular fossa and thoracic inlet. CT of the chest and abdomen showed small bilateral pleural effusions. A subsequent thoracentesis revealed chylous fluid. Lymphoscintigraphy was performed that showed delayed activity in the iliac chains and groins consistent with extravasated lymphatic fluid. A diagnosis of thoracic duct rupture was made, and the patient was managed conservatively with a low fat, high protein, medium chain triglyceride (MCT) diet. She showed subsequent improvement in her symptoms and did not require surgical intervention.

Discussion: Although spontaneous thoracic duct rupture is a rarely reported event, it appears to be most commonly reported in female patients. In addition, thoracic duct cysts and malformations also show a distinct bias in the literature toward females. While we did not identify any cyst or malformation in our patient, two previous case reports of spontaneous thoracic duct rupture did show an association with a known preexisting thoracic cyst. Since our patient presented shortly after her thoracic duct rupture, the possibility of a preemptive cyst or malformation cannot be excluded.

Conclusions: Our case highlights the significance of pleural fluid analysis in the setting of effusions with unclear etiologies, as well as the consideration of thoracic duct rupture in patients with spontaneous pleural effusions and/or fluid accumulation anywhere along the ductal tract.