Bone metaplasia of the appendix presented with clinical and computed tomography signs of acute appendicitis managed with laparoscopic appendectomy

Abstract

Bone metaplasia or heterotopic ossification of the appendix is an extremely rare condition, which is usually associated with mucinous appendiceal neoplasms. This case describes a young male patient, who presented to the surgical emergency department with clinical and computed tomography signs of acute appendicitis. Laparoscopic appendectomy was performed. The final histopathological examination revealed a bone metaplasia of the distal appendix, without any other associated appendiceal pathology. According to our knowledge and literature review, this is the first such case described in the English literature yet.

INTRODUCTION

Bone metaplasia or heterotopic ossification is a rare finding in the gastrointestinal tract. Usually, it is associated with benign or malignant colorectal epithelial tumours. It has been also described in the appendix in association with the mucin-producing tumours.^[1] This case describes a young male patient, who presented to the surgical emergency department with clinical and abdominal computed tomography (CT) signs of acute appendicitis. Laparoscopic appendectomy was performed. The final histopathological examination revealed a bone metaplasia of the distal appendix, without any other associated appendiceal pathology.

CASE REPORT

A 38-year-old male patient after lung transplantation due to cystic fibrosis was admitted to the abdominal surgical department due to clinical and abdominal CT signs of acute appendicitis. The main symptom was pain in the right lower abdominal quadrant and a slight nausea, without vomiting. There was no fever or any other symptoms. On clinical examination, the abdomen was painful on palpation in the right lower quadrant, serum leucocyte (L) value was normal (7.8 × 10⁹⁄L) and serum C-reactive protein (CRP – 12 mg/L) was mildly elevated. We decided to perform laparoscopy. The patient was placed in a supine position, endotracheally intubated under general anaesthesia. Perioperative antibiotics (gentamicin and metronidazole) were administered. The sterile operative field was prepared in a standard manner. Supraumbilical skin incision was performed, and pneumoperitoneum with the aid of a Veress needle was created. A 10-mm trocar and a camera were introduced into the abdominal cavity above the umbilicus. At laparoscopy, we found macroscopically normal appendix without signs of inflammation or any other associated pathology. There was no obvious thickening of the appendix. There were no adhesions in the abdominal cavity or any obvious enlarged or calcified lymph nodes. We decided to perform appendectomy. In addition, we inserted a 12-mm trocar in the suprapubic region and another 5-mm trocar in the left mesogastrium. A plastic clip was put on the meso-appendix, which was then cut with electrocoagulation. Two plastic clips were put at the base of the appendix, which was then cut between clips. The appendix was placed into the Endobag, which was retrieved from the abdominal cavity through suprapubic trocar. The post-operative course was uneventful. The final histopathological examination revealed a bone metaplasia of the distal appendix, without signs of inflammation or any other associated pathology.

DISCUSSION

A bone metaplasia is a rare histopathological finding in the gastrointestinal tract. Usually, it is associated with benign or malignant colorectal tumours, such as rectal adenocarcinoma, gastric carcinoid and adenomatous and non-adenomatous polyps.^[1–3] Heterotopic ossification has also been reported with other malignancies, including kidney, liver, breast and lung. Heterotopic bone formation in the lung parenchyma can also be associated with idiopathic pulmonary fibrosis.^[4] The abnormal bone formation in the pelvis was also described in a patient, who underwent lung transplantation for alpha-1-antitrypsin-deficient emphysema.^[5] The pathogenesis of bone transformation is not understood, but it is associated with excessive mucin production.^[1,2] Mucin-producing tumours of the appendix can be associated with heterotopic bone formation and this is an extremely rare condition. Mucinous appendiceal neoplasms are uncommon, making up 0.2%–0.3% of all appendectomy specimens.^[2] Only a few cases of heterotopic ossification of the appendix were described in the literature and all were associated with appendiceal mucinous neoplasm.^[2] Our patient had a heterotopic ossification of the distal appendix without any other pathology. There was no inflammation and no tumour. According to our knowledge and literature review, this is the first such case described in the English literature yet. Our patient presented with a typical clinical picture of acute appendicitis, which was confirmed with abdominal CT. Serum L and CRP levels were low; we attributed this to the immunosuppressive therapy due to lung transplantation. Pre-operative diagnosis is difficult. Sometimes, pre-operative CT scan can show areas of calcification within the appendix, but in our case, abdominal CT showed CT signs of acute appendicitis. No calcification within the appendix was described on the abdominal CT. Laparoscopic appendectomy was performed and final diagnosis was set on the basis of the histopathological examination.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.