Giant appendiceal mucocele as a first manifestation in a patient with silent ulcerative colitis: A case report.

Appendiceal mucocele (AM) is a rare lesion found in only 0.3% of all appendectomies and it is characterized by distention of the appendix by the accumulating intraluminal mucinous material. Four main histopathological subtypes of appendiceal mucocele has been described including: retention cyst, mucosal hyperplasia, mucinous cystadenoma, and cystadenocarcinoma. We report a case of 48-year-old middle eastern female, previously healthy, presented to the primary health center with right iliac fossa discomfort, and referred to our hospital for further evaluation. Contrast enhanced computed tomography of the abdomen and pelvis and focused ultrasonography over the right iliac fossa showed the characteristic CT and sonographic appearance of appendiceal mucocele. An additional incidental note of lack of colonic haustral pattern involving the rectum and descending colon was noted on abdominal CT raising the suspicion of Ulcerative Colitis which was then confirmed by colonoscopy and histopathology. Although no causal relationship between appendicular mucocele and inflammatory bowel disease has been established yet and few case reports had reported appendicular mucocele in patients with ulcerative colitis, close surveillance in these patients, and early recognition of the characteristic imaging features is crucial in preventing dreadful complications like pseudomyxoma peritonei.

Introduction

Appendiceal mucocele is a rare pathology of the appendix caused by accumulation of mucus within a dilated appendix [1]. It has been attributed to 2 main possible pathologic process: increased appendiceal intraluminal pressure secondary to obstruction caused by prior inflammation, mucosal hyperplasia, appendiceal fecoliths, or by an appendiceal tumor such as carcinoid, cystadenoma, and cystadenocarcinoma [2]. Appendiceal involvement in cases of ulcerative colitis is rare and most likely to be secondary to obstructive inflammatory process; however, clear causative relation between the 2 process has not been established.

Case report

A 48-year-old middle eastern female with no significant past medical or surgical history presented to the primary health center with mild discomfort on the right iliac fossa for the last few months. Patient denied any history of vomiting, weight loss, alteration in bowel habit, loss of appetite or rectal bleeding. No history of abnormal vaginal bleeding. Patient was not on any regular medications. Patient was vitally stable and during physical examination a palpable mass was felt in the right lower quadrant and abdominal ultrasound was done there and it showed a large complex right adnexal mass. Patient was referred to our hospital for further investigations. Basic hematological and laboratory work up as well as tumor markers including CA-125, CEA, and Ca19-9 were done and were within normal limits. Contrast enhanced computed tomography of the abdomen and pelvis (Fig. 1) showed an elongated cystic lesion with chicken drumstick appearance lying horizontally and continuous with the base of the cecum likely arising from the appendix. Both ovaries were normal. An incidental note of lack of colonic haustration involving the rectum, descending colon, and up to the level of the splenic flexure of the transverse colon raising the suspicious of chronic Ulcerative colitis (Fig. 1C and D).

Fig.1

(A,B) Contrast enhanced axial and coronal CT images of the abdomen and pelvis showing a large elongated cystic structure resembling the chicken drumstick appearance continuous with the base of the cecum (white arrow). (C,D) Coronal and sagittal images of the abdomen showing lack of colonic haustral pattern involving the descending and sigmoid colon with associated peri-colonic fat stranding (red arrow) suggestive of chronic ulcerative colitis (Color version of the figure is available online.)

Focused ultrasonography of the right iliac fossa (Fig. 2) demonstrate the previously mentioned appendicular avascular cystic lesion with internal alternating echogenic multilayers and a diagnosis of appendicular mucocle was made.

Fig.2

(A) Focused ultrasound of the right lower abdomen shows a large elongated cystic mass at the base of the cecum with internal alternating echogenic multilayers resembling the onion skin appearance (red arrow) suggestive of appendiceal mucocele. Image (B) Color doppler image of the mass shows no internal vascularity (Color version of the figure is available online.)

Further colonoscopy (Fig. 3) was done and it showed superficial mucosal erosions and exudates with loss of the underlying colonic haustral pattern involving the rectum, sigmoid colon as well as the descending colon. Appendicular orifice mucosa was inflamed with no mass could be appreciated. Biopsies were obtained from the colon and histopathology confirmed the diagnosis of ulcerative colitis with no evidence of granulomas or infective agents.

Fig. 3

Spot colonoscopy images showing superficial mucosal erosions and exudates with loss of underlying haustral pattern suggestive of ulcerative colitis.

Patient underwent elective open appendectomy and a large, distended appendix filled with mucinous material with possible mass at the tip of mucocele was noted (Fig. 4). Patient recovered smoothly with uneventful postoperative period so she was discharged with follow-up appointment in the surgical clinic after 2 weeks. Histopathology examination of the resected appendix revealed a low grade appendiceal mucinous neoplasm (Fig. 5).

Fig. 4

Gross pathologic specimen of the resected appendiceal mucocele.

Fig. 5

(A, B). High power histologic images of the appendix showing appendiceal low grade mucinous neoplasm with fibromuscular wall lined by predominantly sloughed lining epithelium with focal intact simple pseudostratified columnar mucinous epithelium lacking cytologic atypia.

Discussion

Appendicular mucocele (AM) is a rare entity that is seen in up to 0.3% of surgically removed appendix [1]. It is a cystic mass resulting from chronic mucinous collection within a dilated appendix and can be benign or malignant in nature [3]. There are 4 general histopathological subtypes including, a simple mucocele (retention cyst), mucosal hyperplasia, mucinous cystadenoma, and mucinous cystadenocarcinoma [1,3,4]. Patients commonly manifest with features of acute appendicitis in up to 50% of the patients. Remaining of the cases present with non–specific symptoms or asymptomatic [5].

Typical CT findings of an appendiceal mucocele include a cystic well-encapsulated mass with wall calcifications containing homogenous low attenuation material and attached to the cecum at the expected location of the appendix [1,4,5]. Mural nodularity and irregular wall thickening are generally suggestive of malignant nature; however, differentiating benign from malignant AM may be difficult, and histologic examination is required [4].

Individuals with inflammatory bowel disease (IBD) and particularly ulcerative colitis, are infrequently diagnosed with appendicular neoplasms, and the relation remains unclear [2,[6], [7], [8], [9]]. It is suggested that the inflammatory nature of the disease can involve the appendiceal orifice and prompt mucin retention within the appendix. Immunologic and genetic causes are also suspected as possible cause for developing AM in this particular group of individuals and is yet to be explored. We reported a case of appendicular mucocele with underlying undiagnosed inflammatory bowel disease(IBD) suggesting the relation between the 2 entities as a result of untreated inflammatory process leading to obstructive development of an AM.

Conclusion

Although rare, patients with IBD may develop appendiceal mucocele as a result of the inflammatory nature of the disease involving the appendiceal orifice leading to retention of mucin in the appendix. It is important to note that this group of individuals are at higher risk of developing malignancy of the colon and appendix may also be involved. Therefore, regular surveillance may be required for possible development of this entity.

Patient consent

A written consent was obtained from the patient for publication of this case and any accompanying images.