CASE 357 Published on 04.05.2000

Mucocele of the appendix: US and CT findings

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

S. Lonzi, L. Cambi, S. Mazzeo, D. Caramella

Patient

70 years, male

Categories

No Area of Interest ; Imaging Technique Ultrasound, CT

No Procedure ; No Special Focus ;

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Clinical History

Right flank pain

Imaging Findings

2 months history of abdominal pain in right lower quadrant. No other symptoms or biological alterations were associated. Physical examination showed a mass in the rigth flank. Previous abdominal US interpretation: a renal cyst. We repeated abdominal US and performed spiral CT.

Discussion

Appendicular mucocele is a rare lesion (prevalence in appendectomy specimens at surgery is 0.2-0.3%) caused by abnormal accumulation of mucus: it is a descriptive term without implications as to its nature. By the histological classification we can distinguish three groups: focal or diffuse hyperplasia, mucinous cystadenoma and mucinous cystadenocarcinoma. Possible complications are intussusception or rupture causing pseudomixoma peritonei (it is thought that only a mucinous cystadenocarcinoma may be responsible for this complication). A correct preoperative diagnosis is very difficult, but is necessary in order to prevent rupture at laparotomy, or malignant transformation. Sonography shows differences in mucocele appearance based on the nature of cyst fluid: - Heterogeneous echogenic mass: it is due to gelatinous composition of mucus. - Anechoic cystic mass with posterior enhancement: it is due to homogeneous liquid composition. The most frequent sonographic appearance is a cystic mass with variable internal echoes and consistently excellent through-transmission. CT scans shows well-encapsulated cystic mass with enhanced smooth regular walls in the rigth lower quadrant. Curvilinear or punctate wall calcification may be present. Thick and irregular wall is suggestive for malignant nature of the lesion. The differential diagnosis includes peritoneal cyst, ileocecal duplication, pancreatic pseudocyst, renal cyst, abscess, old hematoma, ovarian cyst and normal fluid-filled terminal ileum loop.

Differential Diagnosis List

Appendicular mucocele (diffuse hyperplasia)

Final Diagnosis

Appendicular mucocele (diffuse hyperplasia)

References

[1] 1) Kim SH, Lim HK, Lee WJ, Lim JH, Byun JY.
Mucocele of appendix: ultasonographic and CT findings. Abdom Imaging. 1998 May-Jun; 23(3):292-6. (PMID: 9569300)

[2] 2) Takahashi S, Furukawa T, Ueda J. Case report: Mucocele of the tip of the appendix. Clin Radiol. 1998 Feb; 53(2): 149-50. (PMID: 9502094)

[3] 3) Wallis JW, Madan A, Shoemaker MC. Giant mucocele of the appendix. AJR Am J Roentgenol 1995 Oct; 165(4): 1013-4. (PMID: 7676956)

[4] 4) Mecek D, Jafry SZ, Madrazo BL. Ultrasound case of the day. Mucocele of the appendix. Radiographics 1992 Nov; 12(6): 1247-9. (PMID: 1439024)

[5] 5) Madwed D, Mindelzum R, Jeffrey RB Jr. Mucocele of the appendix: imaging findings. AJR Am J Roentegenol 1992 Jul; 159(1): 69-72. (PMID: 1609724)

Case information

URL:	https://www.eurorad.org/case/357
DOI:	10.1594/EURORAD/CASE.357
ISSN:	1563-4086

Figure 1

Abdominal US

Longitudinal sonogram of right lower quadrant shows a cystic mass with posterior enhancement measuring 81x53x50 mm. Heterogeneous echogenic material is present in the posterior region.

Figure 2

Spiral CT findings

Unenhanced axial scan. Well-encapsulated cystic mass.

Axial scan after i.v. contrast injection. Cystic mass with regularly enhanced wall.

Enhanced axial scan. The density of the material localized on lower portion of the cyst was not modified by intravenous injection of contrast medium.

Mulitplanar recostructions (MIP algorithm). The recostruction illustrates the extent of cystic mass localized in the anatomical region of the appendix.