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Clinical notes

Appendiceal mucocele mistaken for an infected urachal cyst: a differential diagnosis to be taken into account

Daniel A. Pérez Fentes, Melissa Cortegoso González, Ana Puñal Pereira, Antonio Cimadevila García, Serafín Novás Castro, Miguel Blanco Parra Servicio de Urología. Complejo Hospitalario Universitario de Santiago de Compostela. A Coruña, Spain ACTAS UROLÓGICAS ESPAÑOLAS 2009;33(2):205-208

Abstract Objective: To report a case of appendiceal mucocele mistaken for an infected urachal cyst, and to review the differential diagnosis, treatment and prognosis of the disorder. Patient: We report the case of a 74-year-old-male with abdominal pain, fever and dysuria. A hypogastric abscess image was noted at ultrasound and CT. Percutaneous drainage was performed and antibiotic therapy was provided. The opaque enema, colonoscopy and cystoscopy findings were normal. Results: Exploratory laparotomy was performed, with resection of a large cecum-fixed mass, independent of the bladder. Appendectomy and cecectomy were carried out. The pathology report indicated appendiceal mucinous cystoadenoma (mucocele). Conclusions: Appendiceal mucoceles and urachal cysts are uncommon, and mostly asymptomatic. Cystoadenoma or cystoadenocarcinoma mucoceles are large and can reach the midline, leading to confusion with urachal cysts. The diagnosis is established by ultrasound and/or CT. Management is surgical in both cases, avoiding aperture in the case of a mucocele ­ due to the risk of pseudomyxoma peritonei.

Keywords: Mucocele. Urachus. Diagnosis.

Appendiceal mucocele is an obstructive dilatation of the vermiform appendix, with the intraluminal accumulation of mucus. Four presentations are distinguished: simple (retention) mucocele, hyperplastic mucocele, cystoadenoma and cystadenocarcinoma. The latter two can grow large in size, and cystadenocarcinoma has a poor prognosis. In most cases the condition is asymptomatic, though patients may present abdominal pain, a palpable mass, and occasionally also urological manifestations. Urachal cysts are benign and generally asymptomatic lesions clinically manifesting in the case of infection as abdominal pain, a palpable mass, fever, and urological symptoms. We report a case of mucinous cystoadenoma mistaken for and initially treated as an infected urachal cyst. The differential diagnosis between the two conditions is analyzed, along with their treatment and prognosis.

CLINICAL CASE A 74-year old male reported to the Emergency Service with hypogastric pain, fever and dysuria for the previous 48 hours. The personal history revealed arterial hypertension subjected to treatment with captopril, hyperlipidemia treated with atorvastatin, and hyperuricemia managed with allopurinol. Physical examination revealed a palpable, painful mass of large size occupying the hypogastrium and both iliac fossae. The blood tests showed 25,930 leukocytes/mm3 with a strong left shift, and the urine sediment presented 3-5 leukocytes/field, microhematuria, and nitrite positivity at urine strip testing. Abdominal ultrasound showed a possible hypogastric abscess measuring 15 x 9.2 x 7.3 cm in size. The study was completed with abdominopelvic computed tomography, which showed an image with fluid level measuring 15 x 9 x 8 cm in size

located in the hypogastrium, above the bladder dome and in intimate relation to the ileocecal area, compatible with an abscess added to a benign or malignant neoplastic process in the zone (Figs. 1 and 2).



With the tentative diagnosis os infected urachal cyst, percutaneous drainage was carried out with sampling for microbiological study, and intravenous broad-spectrum antibiotic treatment was provided. The serial cultures isolated Leuconostoc spp., Streptococcus intermedius, Clostridium perfringens, Escherichia coli, Bacteroides ovatus, Corynebacterium spp. and Pseudomonas aeruginosa. During admission, a repeat computed tomography can was made, which contributed no further information with respect to the previous scan. An opaque enema was carried out that failed to provide clues to the origin of the disorder; colonoscopy identified no colon alterations; and finally cystoscopy revealed an intact bladder mucosa.

Following the above evaluations, an exploratory laparotomy was decided. Following midline laparotomy, a mass independent of the bladder was observed, intimately adhered to the bowel loops and cecum (Figs. 3 and 4).



Resection was carried out, with accidental aperture of the lesion and the leakage of mucoid contents. The specimen was sent for intraoperative histopathological study, which ruled out malignancy. An ileocecal-appendicular lymphadenectomy was then carried out (with intraoperative freeze-specimen histological confirmation of non-malignancy), together with segmental appendicular-cecal resection. The final pathological diagnosis was appendiceal mucinous cystoadenoma (mucocele). The postoperative course proved favorable, with the exception of surgical wound infection, and discharge was decided one month after the operation. The patient led an independent life and remained asymptomatic until one year after surgery, when he suffered sudden death of cardiac origin.

DISCUSSION Appendiceal mucocele, first described by Rokitansky en 18421, is an obstructive dilatation of the

vermiform appendix, with the intraluminal accumulation of mucoid material. It is found in 0.20.7% of all appendectomy pieces, and constitutes a finding in 0.15% of all necropsies1,2. Since acute appendicitis is a frequent surgical emergency, the number of mucoceles diagnosed (mostly on an incidental basis) is relatively important. These lesions tend to manifest at around the fifth decade of life, with no clear gender predilection3 ­ though some authors consider them to be more common in women, while others report a male / female ratio of 2:12. Four clinico-pathological presentations are identified according to the origin of the luminal obstruction: Simple (retention) mucoceles: The obstruction may be caused by an appendicolith. This presentation is characterized by the presence of degenerative epithelial changes without evidence of mucosal hyperplasia or neoplasia. Hyperplastic mucocele: Obstruction is caused by mucosal hyperplasia, without evidence of atypias. These are sessile or pediculate lesions representing colon polyps without malignant potential. Mucinous cystoadenoma: This is the most frequent presentation of appendiceal mucocele (6384%). In this case the epithelium appears dysplastic, of low grade, with a certain degree of atypia. The lesions can become large, and occasionally exceed 6 cm in size. Mucinous cystoadenocarcinoma. This lesion is characterized by high grade cellular dysplasia, and often shows stromal invasion beyond the muscularis mucosae. In the same way as mucinous cystoadenoma, these lesions can grow large in size. The clinical presentation tends to be nonspecific, and most lesions constitute incidental intraoperative or imaging test findings. Fifty-one percent of the patients are asymptomatic. Nevertheless, mucocele may present with abdominal pain (acute or chronic) fundamentally located in the right iliac fossa and hypogastrium, a palpable mass, body weight loss, nausea, vomiting, etc. The literature in turn reports a number of cases with associated urological manifestations: hematuria4, obstructive uropathy5,6,7 or irritative bladder syndrome8. Mucocele may be associated to neoplasms of other intraabdominal organs such as colon adenocarcinoma (0-21%) and ovarian carcinoma (2-24%). As a result, completion of the diagnostic evaluation requires computed tomography, an opaque enema and colonoscopy9,10. Likewise, mucoceles secondary to cystoadenoma or cystoadenocarcinoma have a 20% risk of perforation, with potential progression towards pseudomyxoma peritonei, which dramatically worsens the prognosis. Abdominopelvic computed tomography is the most precise technique for the radiological diagnosis of appendiceal mucocele, and at the same times allows us to discard associated neoplastic processes and the presence of pseudomyxoma peritonei. Computed tomography usually reveals the presence of a cystic mass located in the right iliac fossa, of variable size, low attenuation and wall calcifications2,9,11. The ultrasound findings in turn are characteristic, and a "bull's-eye" or "onion peel" image secondary to the multiple echogenic layers in the dilated appendix may prove pathognomonic. Other imaging techniques of use are magnetic resonance imaging (with findings similar to those of computed tomography), opaque enema (which can reveal a filling defect at appendicular level), colonoscopy (which makes it possible to discard concomitant colon adenocarcinoma - a characteristic feature being the "volcano sign" due to mucocele protrusion within the cecal mucosa, with the appendicular orifice at the center), and echoendoscopy (which is able to confirm the cystic nature of the lesion)3. The management of appendiceal mucocele is surgical. The laparoscopic approach is subject to controversy. Dhage-Ivatury and Sugarbaker11 propose careful exeresis via open surgery instead of adopting a laparoscopic approach, in order to minimize the risk of accidental perforation with mucoid material seeding in the peritoneum and trocar ports. The technique consists of removal of the intact mucocele, an appendectomy and ileocecal-appendicular lymphadenectomy, with histological evaluation of the intraoperative freeze-specimen. If the appendicular stump is affected, cecal resection is required. If the lymphadenectomy findings prove positive, surgery should be extended to include a right hemicolectomy. Lastly, if accidental rupture with leakage of the mucoid materials occurs during surgery, thorough intraperitoneal lavage is required, followed by closure and posterior patient referral to a specialized center for cytoreductive surgery with peritonectomy and intraperitoneal chemotherapy once the diagnosis of pseudomyxoma is confirmed.

The prognosis of appendiceal mucocele depends on its etiology. In the case of simple mucocele, or mucocele secondary to mucosal hyperplasia or cystoadenoma (provided correct treatment is provided), patient survival is 91-100% after 5 years ­ this figure dropping to only 20-25% after 5 years in the case of mucinous cystoadenocarcinoma or pseudomyxoma peritonei2,9. In turn, urachal cysts are benign and likewise infrequent lesions. These cysts are usually diagnosed by antenatal ultrasound. In adult life urachal cysts usually constitute casual ultrasound or surgical findings, since most affected patients are asymptomatic. These lesions also may manifest as a palpable midline mass or, in the case of infection, with suprapubic pain, fever, pyuria or micturition syndrome. Surgical resection is the indicated treatment. However, the optimum treatment remains subject to controversy: according to Yoo et al.12, initial management in the form of percutaneous drainage and antibiotic treatment, with second-stage exeresis, results in fewer complications, with a shorter hospital stay in comparison with primary surgical exeresis. In our case the patient symptoms and computed tomography findings in the form of a large mass located in the region of the midline at supravesical level initially suggested an infected urachal cyst; percutaneous drainage and antibiotic therapy were therefore decided. The intraoperative findings and posterior histopathological confirmation of mucinous cystoadenoma suggest the following reflections: if the hypothesis of an appendiceal mucocele had been taken into account in the differential diagnosis, percutaneous puncture would have been avoided in view of the risk of dissemination. Once puncture was carried out, the fluid obtained should have been sent for cytological study, thus possibly allowing a preoperative diagnosis and better and more precise surgical planning. However, due to the short patient follow-up (death occurring one year after surgery secondary to unrelated causes), we cannot know whether the fact of puncture and accidental surgical aperture of the lesion would have influenced the prognosis.

CONCLUSIONS Appendiceal mucoceles and urachal cysts are infrequent lesions, and in most cases prove asymptomatic. Mucoceles secondary to cystoadenoma or cystoadenocarcinoma may grow large in size, reaching the midline; as a result, they can be mistaken for urachal pathology as a result of their location. The diagnosis is based on the ultrasound and/or computed tomography data, though in some cases imaging techniques are unable to establish a differential diagnosis. A preoperative diagnosis is essential for allowing good surgical planning. Ultimate treatment consists of surgical exeresis in both cases ­ avoiding aperture of the lesion in the case of mucocele, due to the risk of pseudomyxoma peritonei, which seriously worsens the prognosis.

REFERENCES 1. Minni F, Petrella M, Morganti A, Santini D, Marrano D. Giant mucocele of the appendix. Report of a case. Dis Colon Rectum. 2001;44(7):1034-1036. 2. Pereira Arias JG, Ibarluzea González G, Gutiérrez Díez JM, Murueta-Goyena Mendizábal J, Álvarez Martínez JA. Unusual retrovesical cystic lesion: appendiceal mucocele. Arch Esp Urol. 2002;55(5):560-564. 3. Zanati SA, Martin JA, Baker JP, Streutker CJ, Marcon NE. Colonoscopic diagnosis of mucocele of the appendix. Gastrointest Endosc. 2005;62(3):452-456. 4. Vale J, Kirby RS. Hematuria due to mucocele of the appendix. Br J Urol. 1989;63(2):218-219. 5. Parada R, Rosales A, Algaba F, Lluis F, Villavicencio H. Mucocele of the appendix: an unusual cause of obstructive kidney failure. Br J Urol. 1998;82(3):444-445. 6. De Pablo Cárdenas A, Lozano Uruñuela F, Pinós Paul MA, Jiménez Aristu JI, Jiménez Calvo JM, Ruiz Ramo M, et al. Extrinsic ureteral obstruction secondary to appendiceal mucocele. Arch Esp Urol. 2001;54(5):451-454.

7. Ilbeigi P, Lombardo S, Sadeghi-Nejad H. Unusual cause of obstructive uropathy. Int Urol Nephrol. 2005;37(3):505-506. 8. Baskin LS, Stoller ML. Unusual appendiceal pathology presenting as urologic disease. Urology. 1991;38(5):432-436. 9. Rodríguez Alonso A, Suárez Pascual G, Bonelli Martín C, González Blanco A, Lorenzo Franco J, Cuerpo Pérez MA, Nogueira Carballedo C, Alvarez Fernández JC, Nieto García J.Giant retroperitoneal cystic mass: appendiceal mucocele. Actas Urol Esp. 2004;28(4):327331. 10. Roberge RJ, Park AJ. Mucocele of the appendix: an important clinical rarity. J Emerg Med. 2006;30(3):303-306. 11. Dhage-Ivatury S, Sugarbaker PH. Update on the surgical approach to mucocele of the appendix. J Am Coll Surg. 2006;202(4):680-684. 12. Yoo KH, Lee SJ, Chang SG. Treatment of infected urachal cysts. Yonsei Med J. 2006;47(3):423-427.

Correspondence author: Dr. Daniel A. Pérez Fentes Servicio de Urología Hospital Clínico Universitario de Santiago de Compostela. Travesía Choupana s/n - 15706 A Coruña Tel.: 981 950 000 Author e-mail: [email protected] Paper information: Clinical notes Manuscript received: june 2007 Manuscript accepted: july 2007


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