Presentation
Abdominal distension.
Patient Data
Intermediate attenuation omental caking and peritoneal nodularity. Small amount of ascites. Subtle right subdiaphragmatic nodules slightly indenting the liver surface.
Tubular mass in the arising from the right lower quadrant containing a few flecks of calcification. The outlines are better seen on the delayed images. The tip of the mass appears discontinuous/has perforated.
Malignant small bowel obstruction due to serosal invasion in the right mid abdomen.
Small left inguinal hernia containing mutinous ascites. Larger right inguinal hernia containing non obstructed ileum.
Ultrasound-guided biopsy
Single ultrasound image shows omental cake in the left lower quadrant which was targeted for biopsy. Biopsy confirmed pseudomyxoma peritonei with signet ring cells.
Case Discussion
Pseudomyxoma peritonei has been caused by rupture of a mucinous neoplasm of the appendix. There can be varying degrees of neoplasia: low grade appendiceal mucinous neoplasm, high-grade appendiceal mucinous neoplasm, and mucinous adenocarcinoma. While liver scalloping is not a major feature in this case, the diagnosis of pseudomyxoma can be made based on the presence of intermediate attenuation mucin-containing ascites and identification of an appendiceal primary tumor.
In this case, a higher grade tumor is favored due to invasion of the small bowel resulting in malignant small bowel obstruction, although evaluation of the primary tumor is needed for definitive histological classification.
The few flecks of calcification can provide a hint of the location of the primary tumor (calcification is a typical feature of mucinous neoplasms), which at first can be challenging to differentiate from small bowel loops. Interestingly, the delayed images help to outline the appendiceal contours and show discontinuity of the tip, indicating rupture.
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