Appendiceal Mucocele Detected under Treatment of Ulcerative Colitis.

A 33-year-old female patient with ulcerative colitis was referred to our outpatient clinic in January 2008 with right lower abdominal pain without bloody diarrhea. Colonoscopy found mild proctosigmoiditis and a submucoal tumor with a maximal diameter of 5 cm in the cecum. Computed tomography revealed a large, hypodense, cystic cylindrical structure extending to the pelvic space. For severe pain, she underwent partial resection of the cecum including the tumor in March 2008. Intraoperatively, the vermiform appendix was swollen like a sausage and compressing the cecum, which accounted for what appeared to be a submucosal tumor like a volcano by endoscopy. Lymphadenectomy was not performed because malignancy was not suspected. In the surgical specimen, the vermiform appendix was spindle-shaped and contained a large quantity of viscous liquid. Postoperative pathological diagnosis was mucinous cystadenoma, and no cancer cells were present in the viscous liquid within the vermiform appendix. The patient left the hospital 7 days postoperatively, and her colitis remains in remission without any complications.

Introduction

When a mass is palpable or detected incidentally by imaging studies in the lower right abdomen in a patient without a history of appendectomy, the possibility of appendiceal mucocele (AM) needs to be considered. AM is a descriptive term for mucinous distension of the appendiceal lumen regardless of the underlying pathology. Four causal pathologic conditions have been reported: retention cyst, mucosal hyperplasia, cystadenoma (or mucinous tumor of unknown malignant potential) and cystadenocarcinoma [1]. In cystadenomas, the most common form, luminal dilatation can reach up to 6 cm and is associated with appendiceal perforation in 20% of cases, resulting in mucinous spillage into the periappendicular area and peritoneal cavity [2,3]. Histological examination of the mucus does not reveal any neoplastic cells, and appendectomy is usually curative [4]. Although underlying malignancies in a mucocele are important for the management, preoperative diagnosis of the etiology of AM is difficult on imaging studies [5]. AM can present in a variety of clinical conditions, but concomitant ulcerative colitis (UC) is extremely rare. We herein report such a patient.

Case Report

A 33-year-old female patient with UC was referred to our outpatient clinic in January 2003. Disease activity was judged moderate by colonoscopy and biopsy. Mesalazine was started orally, and the disease was in remission by May 2003. Since then, she was followed regularly in our department. In January 2008, she was referred again to our outpatient clinic with right lower abdominal pain without bloody diarrhea. Colonoscopy revealed mild proctosigmoiditis and a submucosal tumor with a maximum diameter of 5 cm in the cecum (fig. 1). As the cecum was occupied by the large tumor, the orifice of the vermiform appendix was observed like a volcano. Endoscopic biopsy failed to give histological diagnosis. Computed tomography (CT) revealed a large, hypodense, cystic tube-like structure extending into the pelvic space (fig. 2). An abdominal sonography revealed peculiar onion-skin-like internal echogenicity in the right lower abdomen (fig. 3). Laboratory tests including carcinoembryonic antigen were unremarkable.

Fig. 1

Colonoscopy found a submucoal tumor simulating a volcano with a maximum diameter of 5 cm in the cecum.

Fig. 2

Abdominal CT revealed a large, hypodense, cystic tube-like structure extending into the pelvic space.

Fig. 3

Abdominal sonography revealed peculiar internal echogenicity, onion skin sign, in the right lower abdomen.

Since the dull pain was severe, informed consent was obtained and partial resection of the cecum including the tumor was performed in March 2008. Intraoperatively, the vermiform appendix was swollen like a sausage and compressing the cecum, which accounted for what appeared to be a submucosal tumor simulating a volcano by endoscopy. Lymphadenectomy was not performed because malignancy was not suspected. In the surgical specimen, the vermiform appendix was spindle-shaped, measured 12 cm in length and 3 cm in diameter (fig. 4) and was filled with a large quantity of viscous liquid (fig. 5). Postoperative pathological diagnosis was cystadenoma, and no cancer cells were present in the viscous liquid within or the vermiform appendix or its wall. The patient left the hospital 7 days postoperatively, and her colitis has been in remission without any complication.

Fig. 4

Intraoperative finding. A giant appendix measuring 12 cm in length and 3 cm in diameter.

Fig. 5

Resected specimen. A large quantity of viscous liquid was present in its lumen.

Discussion

AM is a rare pathology of the appendix characterized by a cystic dilatation of the lumen with stasis of mucus. Its incidence ranges between 0.2 and 0.3% of all appendectomies, with a higher frequency in females and in patients more than 50 years of age [6]. Symptoms of AM are nonspecific, but even large lesions up to 4 cm are symptomatic in 75% of patients. The most common presentation is right lower quadrant pain, similar to acute appendicitis; a palpable mass can be found in 50% of cases, whereas urinary dysfunction or hematuria is rarely associated [7]. The diagnosis is difficult on preoperative imaging studies; up to 60% are diagnosed during operations for other conditions [8]. Variable significance of ultrasonography and CT have been reported [5, 9, 10]: ultrasonography can show an elongated hypoechoic mass that is not typical of a cyst. Fine echo spots and/or concentric echogenic layers within the cystic mass, so-called onion skin, are thought to be specific signs for AM [5]. Small lymph nodes or soft tissue in the surrounding fat on CT may suggest the possibility of malignancy [9,10].

In our patient, as she had been under treatment of UC for more than 5 years, AM was detected in the right lower abdomen for severe dull pain. The question arises whether there is a direct link between inflammatory bowel disease (such as UC) and AM. Some authors have suggested that the vermiform appendix or the appendiceal orifice might be involved in UC [11,12]. Although the relation between AM and UC still remains unclear [13,14], inflammation in the cecum may facilitate obstruction of the appendiceal lumen as suspected in our patient.