Appendiceal Mucocele

May 25, 2007
Surgical Rounds®, January 2006, Volume 0, Issue 0

Nora L. Yip, Chief Resident, Department of General Surgery, University of Connecticut, Farmington, CT; Wayne A. I. Frederick, Assistant Professor of Surgery, Department of Surgery, Director of Surgical Oncology, Carole and Ray Neag Comprehensive Cancer Center, University of Connecticut Health Center, Farmington, CT

Nora L. Yip, MD

Chief Resident Department of General Surgery University of Connecticut Farmington, CT

Wayne A. I. Frederick, MD Assistant Professor of Surgery Department of Surgery Director of Surgical Oncology Carole and Ray Neag Comprehensive Cancer Center University of Connecticut Health Center Farmington, CT

Appendiceal mucoceles are divided into four classifications based on histopathology?retention mucoceles, mucoceles with mucosal hyperplasia, mucinous cystoadenomas, and malignant mucinous cystadenocarcinomas. Treatment is appendectomy with caution regarding a laparoscopic approach. A dreaded complication is pseudomyxoma peritonei, or peritoneal dissemination caused by perforation of the appendix. Recognition and resection of appendiceal mucoceles is important because some are actually malignant cyst?adenocarcinomas, which can rupture and lead to pseudomyxoma peritonei. Patients with benign appendiceal mucoceles have an excellent prognosis, with a reported 5-year survival rate between 91% and 100%; however, the 5-year survival rate drops to 25% to 45% with malignant forms and complications from pseudomyxoma peritonei.1

We report the case of a patient with an appendiceal mucocele who was successfully treated with an appendectomy and discuss the typical symptoms, signs, and features seen on preoperative diagnostic imaging modalities including ultrasonography, barium enema, computed tomography (CT) of the abdomen and pelvis, and colonoscopy.

Case report

A 61-year-old white man presented to the emergency department because of sudden abdominal pain, which he de?scribed as a dull cramp in the lower abdomen that progressed to a sharp, stabbing pain associated with chills. He re?ported no nausea, vomiting, urinary symptoms, or change in bowel habits.

His medical history was significant for gout, hypertension, hypercholesterolemia, gastroesophageal reflux disease, and IgM nephropathy with proteinuria. His surgical history included a kidney biopsy, hemorrhoidectomy, and right inguinal and ventral herniorrhaphies.

The patient had a low-grade fever of 100.2?F, stable vital signs, and was in mild distress with shaking chills. His abdomen was soft and nondistended, with normoactive bowel sounds and no palpable masses, but tender in the suprapubic area. A rectal examination was normal.

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The initial workup showed a white blood cell (WBC) count of 14,300/L, with 86% neutrophils, 1% bands, and a blood urea nitrogen of 26 mg/dL with a creatinine level of 1.6 mg/dL. Urinalysis showed moderate blood with more than 300 mg/dL of protein. Abdominal radiographs revealed mildly dilated loops of small and large bowel but no obstruction nor pneumoperitoneum. Abdominal ultra??sonography revealed a 10-cm, oblong cystic mass in the right lower quadrant (Figure 1). A CT scan of the abdomen and pelvis confirmed a 5 x 4-cm, ovoid, homogenous, soft tissue density below the level of the cecum (Figure 2). There were no in?flammatory changes or free fluid.

The patient was brought to the operating room, a lower midline abdominal in?cision was made, and a large cystic mass was found in the distal appendix. An appendectomy was performed and the patient was discharged to home the following day. Final pathology showed an appendix measuring 14 cm in length with the distal two thirds of the appendix markedly dilated beginning 3.8 cm from the proximal margin (Figure 3). The ap?pendiceal mucocele was lined by dysplastic epithelium extending to the proximal margin of resection, but it contained no infiltrating carcinoma.

Discussion

First described by Rokitansky in 1842, appendiceal mucocele is a cystic mass resulting from a dilated appendiceal lumen caused by abnormal accumulation of mucus. It is a rare clinical condition, accounting for between 0.2% and 0.3% of all appendectomies.1 It occurs in wom?en more frequently than in men, with a reported ratio of 2:1 in people older than 50 years.1

Appendiceal mucoceles are histopath?ologically divided into four groups based on the characteristics of their epithelial lining: (1) retention mucoceles have normal epithelium and mild luminal dilatation caused by pressure from mechanical blockage by a fecalith or scarring from previous inflammation; (2) mucoceles with mucosal hyperplasia have hyperplastic epithelium and mild distention of the lumen without epithelial atypia; (3) mucinous cystoadenomas exhibit some degree of epithelial atypia and marked distention of the lumen; and (4) malignant mucinous cystadenocarcinomas have se?vere luminal distention associated with glandular stromal invasion and/or epithelial cells in peritoneal implants.2

Approximately 25% to 50% of mucoceles are asymptomatic.1,2 Many are discovered incidentally during physical examination as a palpable abdominal mass (15%?50%)1,2 or by radiological imaging for unrelated symptoms. Clini?cal manifestations are nonspecific but may include right lower quadrant abdominal pain, gastrointestinal bleeding, and rarely, urinary symptoms. Other presentations include acute appendicitis, torsion, intussusception, and small bowel obstruction. The worst complication is pseudomyxoma peritonei, or peritoneal dissemination caused by spontaneous or iatrogenic perforation of the appendix.

In the past, a correct preoperative diagnosis was difficult, but modern imaging techniques allow for easier recognition of this lesion. Ultra?sonography shows an elongated echo-poor mass with innumerable, fine echo spots in the lesion, suggesting the presence of mucin. The wall of the lesion is indistinct and differs slightly from what one would expect for a cyst wall.3 A barium enema shows failure of the appendix to fill with contrast me?dium, and the cecum or ileal loops are often laterally displaced.2 CT scans of the abdomen and pelvis show a round, cystic, well-encapsulated mass with smooth thin walls without any surrounding inflammation in the right lower quadrant in the anatomic location of the appendix.4,5 The mass does not contain contrast medium and demonstrates low values of attenuation that range from that of water to that of soft tissue, depending on the amount of mucin present. The presence of mural calcifications strongly suggests appendiceal mucocele. Colonoscopy shows a "volcano" sign?an erythematous, soft mass with a central crater from which mucus is discharged.2 Fine-needle aspiration cytology has been advocated in differentiating between benign and malignant forms; however, potential risk of rupture leading to pseudomyxoma peritonei has led to abandoning this technique.

Treatment for appendiceal mucocele is surgical. Resection is important because some lesions are cystadenocarcinomas, which can rupture and result in pseudomyxoma peritonei. An appendectomy is adequate therapy for benign disease, but if malignant disease is demonstrated, such as signs of invasion into the cecum or ileum, a right hemicolectomy should be performed. The abdomen should be carefully explored during laparotomy for other coexisting tumors of the ovaries or gastrointestinal tract.6 All apparent mucinous tissue should be aggressively de?bulked if generalized pseudomyxoma peritonei is found. Intraoperative histologic examination is not always definitive.

Treating this disease laparoscopically is controversial because of the risk of rupture. Gonzalez and colleagues re?ported a case of an appendiceal mucocele caused by a mucinous adenocarcinoma that was resected laparoscopically.7 Nine months later, the patient developed diffuse peritoneal carcinomatosis. An ap?pendiceal mucinous tumor encountered at laparoscopy is a special situation, re?quiring a total atraumatic appendectomy. Manipulating the mucocele may cause spillage of its contents and consideration should be made for conversion to open appendectomy.

The prognosis of patients with benign mucocele is excellent with a 5-year survival rate of 91% to 100%.1 The 5-year survival rate for malignant forms, however, is markedly diminished (25%?45%) due to complications of pseudomyxoma peritonei.

Conclusion

Appendiceal mucocele is an uncommon entity encountered in less than 0.5% of all appendectomies.1 Clinical signs and symptoms are nonspecific and up to 50% of the patients are asymptomatic.1,2 All ap?pendiceal mucoceles are managed surgically with care taken to avoid rupture in the event that the mucocele is actually a malignant process such as a mucinous cystadenocarcinoma. The use of laparoscopy remains controversial and should be undertaken with great care.

References

1. Soweid AM, Clarkston WK, Andrus CH, et al. Diagnosis and management of appendiceal mucoceles. Dig Dis. 1998;16(3): 183-186.

2. Minni F, Petrella M, Morganti A, et al. Giant mucocele of the appendix: report of a case. Dis Colon Rectum. 2001;44(7):1034-1036.

3. Sasaki K, Ishida H, Komatsuda T, et al. Appendiceal mucocele: sonographic findings. Abdom Imaging. 2003;28(1):15-18.

4. Kim SH, Lim HK, Lee WJ, et al. Mucocele of the appendix: ultrasonographic and CT findings. Abdom Imaging. 1998;23(3): 292-296.

5. Zissin R, Gayer G, Kots E, et al. Imaging of mucocoele of the appendix with emphasis on the CT findings: a report of 10 cases. Clin Radiol. 1999;54(12):826-832.

6. Stocchi L, Wolff BG, Larson DR, et al. Surgical treatment of appendiceal mucocele. Arch Surg. 2003;138(6):585-589.

7. Gonzalez Moreno S, Shmookler BM, Sugarbaker PH. Ap?pendiceal mucocele. Contraindication to laparoscopic appendectomy. Surg Endosc. 1998;12(9):1177-1179.