A 40 years old male was brought to the emergency with watery diarrhea. The diagnosis was made on stool cytotoxin assay. On colonoscopy, ulcers, plaques and pseudomembranes were visualized. Patient condition improved drastically after use of metronidazole. CECT finding is given below. What is the name of the sign seen on CECT??

**Core Concept**
The patient presents with symptoms of pseudomembranous colitis, characterized by watery diarrhea, ulcers, plaques, and pseudomembranes in the colon. The diagnosis was made on stool cytotoxin assay, indicating a toxin-mediated infection. The patient's improvement with metronidazole suggests an anaerobic bacterial infection.

**Why the Correct Answer is Right**
Pseudomembranous colitis is often caused by Clostridioides difficile (C. difficile) toxin, which disrupts the normal gut microbiota and leads to inflammation. The appearance of ulcers, plaques, and pseudomembranes is a hallmark of C. difficile infection. The use of metronidazole, an antibiotic effective against anaerobic bacteria, supports this diagnosis. The CECT findings likely reveal thickening of the colonic wall, which is a characteristic feature of pseudomembranous colitis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not describe a characteristic sign of pseudomembranous colitis.
**Option B:** This option is incorrect because it does not match the CECT findings described in the scenario.
**Option C:** This option is incorrect because it does not accurately describe the CECT findings associated with pseudomembranous colitis.

**Clinical Pearl / High-Yield Fact**
The "thumbprinting" sign on CECT, seen in pseudomembranous colitis, is due to submucosal edema and hemorrhage, which causes the colon wall to appear thickened and "thumb-like" on imaging.

**Correct Answer:** C. Thumbprinting sign

✓ Correct Answer: A. Accordion sign