Imaging modalities: which to choose?
Among all instrumental diagnostic methods, computed tomography and magnetic resonance imaging play the leading role:
- MSCT (multislice CT): The most widely used method for detection and staging. It is optimal to use hydro-CT (hydro-MDCT), where the patient drinks water to distend the stomach and duodenum. The examination must be performed in the pancreatic parenchymal and venous phases (with automatic bolus tracking).
- MRI: Has no clear superiority over MSCT in routine practice, but acts as a decisive method for CT-isodense tumors. MRCP (MRCP) is ideal for demonstrating duct architecture.
- Transabdominal ultrasound: Helps in initial evaluation for jaundice (shows biliary duct dilation), but does not rule out a tumor in the body and tail of the gland. Inadequate for staging.
- PET/CT: Limited in initial diagnosis (difficult to distinguish from inflammation), but highly accurate for detecting local recurrences.
Important rule: Never perform biliary stenting (ERCP) prior to CT or MRI. An inserted stent and subsequent cholangitis critically degrade imaging quality and hinder staging.
Direct and indirect signs on tomograms
About 11% of all adenocarcinomas are isodense (blend in density with the glandular tissue). Therefore, diagnosis is based on searching not only for the mass itself, but also for associated changes.
Direct sign: Presence of a hypovascular mass. On CT, it is hypodense, and on MRI (on T1-weighted images with fat suppression) it shows low signal intensity against the background of brightly enhancing normal parenchyma.
Indirect signs (6 warning markers):
- Biliary duct dilation.
- Main pancreatic duct dilation (often with the " abrupt cutoff" sign).
- The "double duct sign" (double duct sign) — simultaneous dilation of the biliary and pancreatic ducts.
- Focal glandular atrophy (proximal to the obstruction).
- Deformation of the organ contour.
- Loss of the normal lobular structure of the parenchyma.
Local Staging
The key task of the radiologist is to determine whether the patient is operable. Vascular invasion is assessed for this purpose:
- Arterial invasion: The tumor involves the vessel by more than 180 degrees of its circumference or causes contour deformation. Involvement of the superior mesenteric artery (SMA), celiac trunk, or common hepatic artery indicates stage T4 (unresectability). Exception: invasion of the splenic artery is not classified as T4, as these vessels are resected together with the spleen in tail cancer.
- Venous invasion: Tumor adherence with dense fibrosis to the superior mesenteric or portal vein causes the specific "tear drop deformity sign" (tear drop deformity sign). Limited venous involvement may be resectable in specialized centers.
Uncinate process tumors are insidious because they frequently encase the SMA even before jaundice develops.
Lymph nodes and distant metastases
When staging pancreatic cancer (8th TNM edition), the following aspects are considered:
- N-stage: Metastases in peripancreatic lymph nodes are designated as N1. However, para-aortic nodes are classified as distant metastases (M1), which precludes radical surgery. Sizing nodes based solely on dimensions reduces diagnostic accuracy.
- M-stage: The most frequent localization of metastases is the liver (better visualized in the venous phase). The appearance of ascites often indicates peritoneal carcinomatosis.
Briefly: answers to topical questions
How to differentiate ductal adenocarcinoma from pancreatic neuroendocrine tumors on CT?
The differential diagnosis of ductal adenocarcinoma and neuroendocrine tumors on CT is based primarily on the pattern of contrast enhancement and the presence of calcifications.
| Sign | Ductal adenocarcinoma | Neuroendocrine tumor |
|---|---|---|
| Contrast enhancement | Hypovascular mass; intense contrast enhancement is not characteristic | Intense contrast enhancement (avid contrast enhancement) |
| Calcification | — | Observed in 22% of tumors |
| Cystic transformation | — | About 20% of pancreatic NETs have a partially cystic structure, and 3% are entirely cystic |
What is the role of endoscopic ultrasound (EUS) in the diagnosis and staging of pancreatic cancer?
Endoscopic ultrasound (EUS) is used for morphological verification and assessment of the local extent of the tumor process.
- Biopsy — useful for obtaining material from indeterminate, non-obstructive masses (diagnostic accuracy for malignancy is 97.6%).
- Resectability assessment — helps determine the anatomical relationship of the tumor to peripancreatic vessels.
The "Three D's" rule for finding isodense cancer: look for Dilation of the biliary ducts, Dilation of the pancreatic duct, and the Double duct sign. If present, look for loss of lobularity and glandular atrophy.
Class and exam questions
Why does the patient drink water before a pancreatic CT scan?
Water is used as a negative oral contrast agent (hydro-CT). It distends the stomach and duodenum without causing beam-hardening artifacts, allowing excellent evaluation of their wall enhancement and detection of tumor invasion.
If the tumor has invaded the splenic artery, is this stage T4?
No. Unlike involvement of the celiac trunk or superior mesenteric artery, invasion of the splenic vessels is not a sign of unresectability. They are resected along with the spleen during distal pancreatectomy.
Can an ERCP and stent placement for jaundice be performed first, followed by a CT scan?
This should be avoided. The stent and concomitant cholangitis cause inflammatory changes that severely degrade CT or MRI image quality, making tumor staging extremely inaccurate.
What else to study on this topic
- Neuroendocrine tumors (NETs): insulinoma and gastroma
- Paraduodenal pancreatitis: differential diagnosis
- Imaging findings after a Whipple resection
- Features of contrast-enhanced ultrasound (CEUS) in pancreatology
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