Preoperative assessment and treatment of appendiceal mucocele complicated by acute torsion: a case report
© Stark et al.; licensee BioMed Central Ltd. 2014
Received: 14 August 2013
Accepted: 18 November 2013
Published: 2 January 2014
Mucus-producing tumours of the appendix or mucoceles can, if left untreated, lead to dissemination of its contents into the peritoneal cavity causing substantial morbidity to the patient. Symptoms for complicated mucoceles can mimic those of acute appendicitis and the final diagnosis is most likely made intraoperatively. We here present a case that is, to our knowledge, one of only ten described in the literature and the first to characterize torsion of an appendiceal mucocele with abdominal magnetic resonance imaging.
The patient, a 34-year-old Caucasian female presented at the emergency department with acute abdominal pain in the right lower quadrant. Initial diagnostic work-up including ultrasonography and abdominal magnetic resonance imaging showed a large tubular mass at the base of the appendix with indirect signs of torsion. A laparoscopic appendectomy was performed the following day where the finding was confirmed. The patient went on to have an uneventful recovery and was discharged from the hospital on the first postoperative day.
Magnetic resonance imaging is a useful tool in identifying unknown lesions of the appendix and should be considered the primary imaging modality in especially younger patients requiring diagnostic imaging. In this case the preoperative imaging findings aided in choosing the correct timing and treatment option for the patient.
The frequency of primary appendiceal tumours is reported to be 0.5-2% in removed specimens[1–4], mucoceles accounting for only 8% of them. The epithelial lining of the appendix consists of abundant exocrine goblet cells, and thus most tumour types seen in appendiceal samples are mucus producing. Excessive production of mucus by adenomatous tumours leads to the formation of a mucocele and is usually caused by entrapment of mucus and characterized by invasion of mucus into the appendiceal wall. Mucoceles within the appendix are highly heterogenous upon histopathological evaluation and can be classified according to their underlying epithelial neoplastic processes, as proposed by Pai and Longacre. Non-neoplastic or non-epithelial processes, such as inflammation or fecolith obstruction are rare causes of mucocele formation. The majority of mucoceles are fortunately benign in nature[5, 6]. Rupture of these tumors can however lead to dissemination of the abdominal cavity causing localized or generalized pseudomyxoma peritonei. Thorough evaluation of suspicious appendices is therefore necessary in order to exclude rupture and avoid spillage of appendiceal contents into the abdominal cavity during appendectomy. For mucoceles restricted to the appendix simple appendectomy either by open or laparoscopic technique is recommended[2, 7]. Microscopic examination is recommended to ensure negative margins of resection surfaces[6, 7]. Complications for appendiceal mucoceles (AM) consists of inflammation, invagination, obstruction, bleeding, or fistula formation. Here, we present a rare case of AM complicated by acute torsion, characterized by abdominal magnetic resonance imaging (MRI). Preoperative diagnosis of this condition is difficult. Suspicion can however be valuable in choosing the correct timing and treatment option for the patient.
Findings and treatment in reported cases of torsion of appendiceal mucoceles with pre-operative imaging studies
Thin walled appendiceal cyst on US Fluid-filled, tubular appendiceal cyst with slight wall-thickening, mesentery edema and abrupt tapering of the baseof the mucocele on MRI
Well encapsulated mass of unknown origin with intraluminal gas and slight calcifications
Cystic thin-walled lesion with suspected ovarian cyst rupture
Appendiceal fluid filled cyst without contrast enhancement
Dilated fluid-filled appendix negative for oral contrast, abrupt luminal tapering and whorled mesentery
Cystic appendiceal mass with target- like appearance
Cystic lesion with internal echoes of unknown origin
Cesarean section and appendectomy
In our case, the imaging findings were indicative of an appendiceal mucocele. The mesenteric edema and abrupt tapering of the base of the appendix were considered signs of torsion. MRI findings in AM with torsion have not previously been presented in the literature. Based on our findings, the discrimination between simple and complicated mucoceles by imaging is difficult. The patient’s sudden onset of abdominal symptoms and disease presentation were however inconsistent with classical appendicitis and the MRI findings aided in the pre-operative work-up of the patient. Notably, the appendicular wall had already developed necrosis highlighting the risk of rupture. Prompt laparoscopy provided the definitive macroscopic diagnosis and allowed for safe removal of the diseased appendix. Performing the procedure during office-hours ensured access to histopathologic analysis and confirmation that there was no neoplastic involvement of the caecum. The underlying pathology of the mucocele could however not be established on frozen sections. In cases where resection margins are negative and the muocele intact simple appendectomy is considered sufficient. Frozen section analysis can therefore be helpful in cases of AM, although the final histopathological diagnosis requires permanent section analysis. Histologically the large mucocele was confined to the appendix and the luminal side of the intestinal wall with no signs of involvement of the serosa or surrounding compartments. In the necrotic and hemorrhagic specimen no epithelial atypia was observed. Permanent sections of the base of the caecum showed normal intestinal histology without signs of cellular atypia or mucus deposition. The underlying pathology was therefore thought to best represent a mucinous adenoma. In this case simple appendectomy was curative with no need for additional treatments or long-term follow-up.
It is the opinion of the authors that the threshold for performing imaging studies in patients with suspected appendicitis and atypical disease presentation should be low, in order to identify lesions that preferably should be operated on during daytime. To avoid complications and the need for reoperation in cases like the one presented here, the availability of senior surgeon and pathologist consultations during the operation is recommendable. Abdominal MRI is a useful tool in identifying unknown lesions of the appendix and should be considered the primary imaging modality in especially younger patients requiring diagnostic imaging when ultrasonography is inadequate.
Written informed consent was obtained from the patient for publication of this Case Report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
CS is a resident completing his basic surgical training at Päijät-Häme Central Hospital (PHCH) and a PhD student at the University of Turku. BE is a senior surgeon at PHCH. MJ is a consulting radiologist at PHCH.
The study was funded by the authors. There are no additional acknowledgements.
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