title: Transdiaphragmatic extension of a retroperitoneal lipoma into the intrathoracic extrapleural space via the lumbocostal trigone in a dog.
abstract: METHODS
  An 8-year-old 12.2-kg (26.9-lb) spayed female American Cocker Spaniel was referred for evaluation of abdominal discomfort and a suspected intra-abdominal lipoma with possible invasion into the thorax.
  
  
  RESULTS
  Physical examination revealed a tense abdomen, and the margins of a large abdominal mass could be appreciated. Abdominal imaging revealed a mass of fat opacity in the abdominal and thoracic cavities. Computed tomography with precontrast and postcontrast peritoneograms was used to determine whether the masses connected via a diaphragmatic defect.
  
  
  RESULTS
  Exploratory laparotomy revealed a retroperitoneal lipomatous mass that had focally invaded the hypaxial musculature and had extended across the dorsolateral aspect of the diaphragm via the lumbocostal trigone into the intrathoracic extrapleural space. Surgical resection required transdiaphragmatic thoracotomy. Histologic examination of excised tissue confirmed the preoperative diagnosis of a lipoma. The dog recovered from surgery with no complications and had no disease recurrence for at least 32 months after surgical resection.
  
  
  CONCLUSIONS
  The defect of the lumbocostal trigone is also called the foramen of Bochdalek in humans, and it is recognized as a common location for congenital diaphragmatic hernia. A lumbocostal trigone hernia may be considered as a differential diagnosis for bicavitary masses in dogs, particularly in the absence of a history of trauma.
authors.affiliation: Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Klosterman
authors.forename: Hock Gan
authors.initials: HG
authors.lastname: Heng
authors.forename: Lynetta J
authors.initials: LJ
authors.lastname: Freeman
authors.forename: Michael O
authors.initials: MO
authors.lastname: Childress
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000473:pathology / Q000601:surgery; D004285:Dogs; D005260:Female; D008067:Lipoma / Q000473:pathology / Q000601:surgery / Q000662:veterinary*; D012186:Retroperitoneal Neoplasms / Q000473:pathology / Q000601:surgery / Q000662:veterinary*