Presentation
Constipation, general abdominal discomfort. Moderately elevated CRP.
Patient Data
Erect abdominal radiographs:
- marked large and small bowel distension with abnormal gas-fluid levels. Note that several grossly distended large bowel loops overlap, and in these regions (but not elsewhere) both walls of the colon are visible (see magnified key image). This is however not indicative of free gas (Rigler sign), rather its mimicker, the pseudo-Rigler sign. Note that there is no free gas under the diaphragm.
- dense content in the pelvis, representing the distended rectosigmoid bowel filled with fecal matter
- circumscribed, large, mass-like shadowing in the right lower lung zone, which does not silhouette the right heart border, thus is most likely in the lower lobe
Findings are all together in line with large bowel obstruction secondary to rectosigmoid fecal impaction and secondary small bowel ileus. The incidental right lower lung zone mass could represent a malignancy.
Conservative therapy resulted in bowel movements, nevertheless, the patient's symptoms worsened over the next few hours. Therefore a CT was requested.
Magnified and highlighted key images demonstrating the pseudo-Rigler sign where distended loops overlap.
- significant rectosigmoid fecal impaction and distension of the large and small bowel despite multiple bowel movements between the plain film and CT
- no sign of pneumoperitoneum
- confirmation of the right lower lobe mass
Altogether the CT findings are also indicative of large bowel obstruction caused by distal fecal impaction and chronic constipation. The patient was discharged after further conservative management.
Case Discussion
A typical presentation of advanced large bowel obstruction caused by rectosigmoid impaction of fecal matter (fecaloma). The plain film is also a good example of the pseudo-Rigler sign.