Saw-tooth appearance on barium enema is seen in:
**Core Concept**
The saw-tooth appearance on barium enema is a radiological finding that suggests a specific pathology involving the colon. It is characterized by a series of alternating barium-filled and barium-empty segments, resembling a saw-tooth pattern. This phenomenon is a result of the colon's response to a particular type of obstruction.
**Why the Correct Answer is Right**
The saw-tooth appearance is typically seen in sigmoid volvulus. In this condition, the sigmoid colon twists around its mesenteric axis, leading to a segmental obstruction. As the barium enema is performed, the barium flows into the colon, but the twisting segment prevents it from passing through, resulting in the characteristic saw-tooth pattern. This is due to the intermittent obstruction and reperfusion of the colon, causing the barium to fill and empty the colon in a sequential manner.
**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect as it does not describe a condition that would result in a saw-tooth appearance on barium enema.
**Option B:** This option may be tempting, but it is incorrect because the "lead pipe" sign is typically seen in chronic constipation or Hirschsprung's disease, which does not produce a saw-tooth pattern.
**Option C:** This option is incorrect because a "bird's beak" appearance is typically seen in rectal carcinoma, which does not produce a saw-tooth pattern on barium enema.
**Clinical Pearl / High-Yield Fact**
When interpreting a barium enema, remember that a saw-tooth appearance is highly suggestive of sigmoid volvulus, and this should prompt further investigation, such as CT scan or urgent surgery, to prevent bowel ischemia.
**Correct Answer: C. Sigmoid volvulus.**