**Here is the provided prompt for this task** A 58-year-old male presents to the emergency department. He was diagnosed with colon cancer (adenocarcinoma, specifically at the splenic flexure) which had a solitary metastatic lesion in the liver. The patient has been on pembrolizumab. They are presenting with worsening epigastric pain, anorexia, nausea, vomiting and labs demonstrating leukocytosis. A CT of the abdomen was performed with intravenous contrast. The following image was obtained, state the broad term for the diagnosis behind the patient's symptoms.
Reading File
Looking at this CT image carefully alongside the clinical context:
CT Findings:
The axial CT with IV contrast shows peripancreatic fat stranding, pancreatic edema, and inflammatory changes around the pancreas — the classic appearance of acute pancreatitis.
Broad Diagnosis: Acute Pancreatitis
More specifically, in this clinical context, this represents immune-mediated (immune-related adverse event) pancreatitis — a known toxicity of checkpoint inhibitor therapy.
Reasoning:
| Feature | Significance |
|---|---|
| Pembrolizumab (anti-PD-1) | Known to cause immune-related adverse events (irAEs) |
| Epigastric pain, nausea, vomiting, anorexia | Classic symptoms of pancreatitis |
| Leukocytosis | Systemic inflammatory response |
| CT findings | Peripancreatic inflammatory changes, edema consistent with acute pancreatitis |
Pembrolizumab is a PD-1 checkpoint inhibitor used in MSI-H/dMMR colorectal cancer. By releasing the brakes on T-cell activity, it can trigger immune-related adverse events (irAEs), including:
- Colitis (most common GI irAE)
- Pancreatitis (less common but well-recognized)
- Hepatitis, pneumonitis, endocrinopathies, etc.
The broad diagnostic term is acute pancreatitis, with the underlying etiology being a checkpoint inhibitor-induced immune-related adverse event (irAE).
Management would involve holding pembrolizumab and initiating high-dose corticosteroids (e.g., methylprednisolone 1–2 mg/kg/day), with supportive care (bowel rest, IV fluids, analgesia).
is there any target or water halo sign here
Reading File
No — the target sign (also called the halo sign or water halo sign) is not present in this CT.
What those signs represent:
Target/Halo/Water halo sign on CT refers to concentric layers seen in a bowel wall or around an organ:
- In bowel: alternating layers of enhancing mucosa, submucosal edema (low density), and outer muscularis/serosa — seen in bowel wall edema, ischemia, Crohn's, or intussusception
- In hepatic/splenic lesions: a hypodense halo around a mass suggesting edema or necrosis
What this image shows instead:
The predominant finding here is centered on the pancreatic region (epigastric/upper abdomen), with:
- Peripancreatic fat stranding — haziness/dirty fat around the pancreas
- Inflammatory exudate in the peripancreatic space
- No distinct layered/target appearance of bowel wall
The target sign would redirect thinking toward bowel pathology (e.g., intussusception, bowel edema, or ischemia). Its absence here, combined with the peripancreatic inflammatory changes and the clinical picture (pembrolizumab, epigastric pain, nausea/vomiting, leukocytosis), keeps acute pancreatitis (irAE) as the diagnosis.
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