Intraabdominal Heterotopic Ossification after appendectomy Mimicking Undescended Testicular Tumor: a rare case report and literature review

Reprint requests to: Dr. Ruey-Sheng Chang Department of Medical Imaging, Chia-Yi Christian Hospital. No. 539, Jhongsiao Road, Chiayi 600, Taiwan, R.O.C. Intraabdominal heterotopic ossif ication is a rare sequela of abdominal surgery or trauma. Only a few previous reports have been described in the literature. Here, we report the case of a 20-year-old man who underwent appendectomy 3 years ago and experinced this condition. Initially, he presented with right undescended testis with a palpable mass in the right lower abdomen. Plain radiography and computed tomographic imaging showed peripheral calcified soft tissue mass. Explorative laparotomy for excision was performed and heterotopic ossification was diagnosed by pathologic findings. The characteristic imaging features of this rare entity are discussed and the literature are reviewed. Heterotopic ossification (HO) is the abnormal formation of t rue bone within extraskeletal soft t issues. Classically, many diseases shar ing this common feature were lumped into the category myositis ossificans; however, the term has fallen into disfavor because primary muscle inflammation is not a necessary precursor for such ossification and the ossification does not always occur in muscle tissue. The term HO has largely replaced myositis ossificans in the literature [1]. Mature HO closely resembles normal bone both histologically and radiologically, and thus it differs from dystrophic calcification in soft tissues, in which there is no osteoblastic activity or lamellar bone. Heterotopic ossif ication has been reported in the context of several conditions—most notably total hip arthroplasty and neurologic injuries [2, 3]. However, intraabdominal HO is a rare sequela of abdominal surgery or trauma and of unknown etiology. Here, we present a patient who experienced intraabdominal HO after appendectomy.