Imaging of pancreatic ductal adenocarcinoma - An update for all stages of patient management

Abstract

Background: Pancreatic ductal adenocarcinoma (PDAC) is a common and lethal cancer. From diagnosis to disease staging, response to neoadjuvant therapy assessment and patient surveillance after resection, imaging plays a central role, guiding the multidisciplinary team in decision-planning.

Review aims and findings: This review discusses the most up-to-date imaging recommendations, typical and atypical findings, and issues related to each step of patient management. Example cases for each relevant condition are presented, and a structured report for disease staging is suggested.

Conclusion: Despite current issues in PDAC imaging at different stages of patient management, the radiologist is essential in the multidisciplinary team, as the conveyor of relevant imaging findings crucial for patient care.

Keywords: Neoadjuvant therapy; Neoplasm recurrence, Local; Neoplasm staging; Pancreatic carcinoma; Patient care team.

Fig. 1

Importance of the pancreatic and delayed phases for tumor detection. In the pancreatic phase (A), there is a clear distinction (dashed line) between tumoral tissue (yellow arrow) and pancreatic parenchyma (white arrow). In the portal venous phase (B), the distinction between tumor and normal pancreas is not clear. (C - E) depicts another case, where a pancreatic tumor is ill-defined on the pancreatic (C) and portal venous (D) phases, but well-defined on the delayed phase (E, arrows).

Fig. 2

Typical findings of PDAC. (A) depicts a double duct sign, where both the main pancreatic duct and the biliary tree are dilated (arrows) due to an obstructing tumor in the pancreatic head (dashed line). In (B) there is parenchymal atrophy of the pancreatic tail (arrow), due to an obstructing tumor in the pancreatic body (dashed line). (C) shows a double duct sign in MRCP (white arrows), caused by a presumed obstructing lesion (yellow arrow). (D) reveals an obstructing (white arrow) pancreatic head tumor in a T2-weighted image (yellow arrow).

Fig. 3

Isodense PDAC. This patient presented with dilated main pancreatic duct (A and B, white arrows) and slightly dilated biliary tree, but a pancreatic tumor was not clearly seen on CT on both pancreatic (A) and portal venous (B) phases. MRI clearly identifies the obstructing tumor in the pancreatic head, as observed on DWI (C, yellow arrow) and a double duct sign on MRCP (D, white arrows).

Fig. 4

Diagnostic problem-solving with MRI. This patient presented with dilated main pancreatic duct and biliary tree (A, white arrows), highly suspicious for a pancreatic head tumor (yellow arrow). However, DWI revealed not only a restricting pancreatic head (B, yellow arrow), but also areas of restriction in both kidneys (B, white arrows). These findings prompted the diagnosis of auto-immune pancreatitis, which was confirmed after a 2-week steroid trial.

Fig. 5

(A) is a schematic representation of relevant anatomical structures for PDAC staging. If a tumor is located on the pancreatic head (1), a cephalic duodenopancreatectomy is performed, and if the tumor is located on the pancreatic body and/or tail (2), then a distal pancreatectomy is performed. More extensive tumors might require a total pancreatectomy. (B) is a coronal MIP displaying the relevant blood vessels for PDAC staging, an extremely useful tool for showcasing findings in multidisciplinary team meetings. CT: celiac trunk; HA: hepatic artery (comprises both common hepatic and hepatic proper); LGA: left gastric artery; PV: portal vein; SA: splenic artery; SMA: superior mesenteric artery; SMV: superior mesenteric vein; SV: splenic vein.

Fig. 6

Schematic representation of blood vessel involvement in PDAC staging. (A) tumor-vein contact ≤ 180º (abutment); (B) tumor-vein contact > 180º (encasement); (C) teardrop sign; (D) vessel contour deformity; (E) and (F) arterial abutment and encasement (≤ and > 180º), respectively.

Fig. 7

Venous involvement in PDAC. (A) Tumor-superior mesenteric vein contact < 180º (abutment). (B) Teardrop sign of the superior mesenteric vein (arrow). (D) Portal vein stenosis and deformity (arrows). (D) Superior mesenteric vein occlusion (arrows).

Fig. 8

Arterial variants with surgical implications. (A) depicts the anatomy of a patient with a replaced right hepatic artery (RRHA) originating from the superior mesenteric artery (SMA) and a replaced left hepatic artery (RLHA) originating from the left gastric artery (LGA). The celiac trunk (CT) was encased by the tumor, as represented in (B, dashed line). As arterial collaterals were present between both replaced hepatic arteries, a celiac trunk resection along with tumor resection were performed, and the patient maintained a preserved liver vascularization. (C) represents another patient with the following anatomy: RLHA from LGA, middle hepatic artery (MHA) from CT, and RRHA from SMA. The RRHA was encased by tumor, as shown in (D, dashed line). This allowed tumor resection along with the RRHA, after an embolization procedure for facilitating the development of collaterals.

Fig. 9

Arcuate ligament syndrome. Proximal celiac trunk (CT) stenosis with a hooked appearance (arrow), with pos-stenotic dilatation.

Fig. 10

Importance of MRI for hepatic staging. In a contrast-enhanced CT for PDAC staging (A), no liver lesions were found. The staging MRI clearly revealed hepatic metastases (arrows) with restricted diffusion on DWI (B).

Fig. 11

Metastatic PDAC with peritoneal metastases. (A) reveals a bulky PDAC of the body and tail (dashed line), with hepatic metastases (arrows). There are also peritoneal metastases, as observed with an “omental cake” appearance in the pelvis (B, arrows).

Fig. 12

Response to neoadjuvant therapy. (A) reveals a locally advanced PDAC (dashed line) with common hepatic artery (CHA) encasement up to the celiac trunk bifurcation (CT). After the completion of neoadjuvant chemotherapy, the tumor had reduced in size (B, dashed line), but maintained a long encasement of the CHA. The patient underwent surgery, with an R0 resection.

Fig. 13

Recurrence of PDAC. Two cases of local recurrence of PDAC (dashed lines), in (A) encasing the celiac trunk (CT) and common hepatic artery (CHA), and in (B) encasing the superior mesenteric artery (SMA) and invading the superior mesenteric vein (SMV) with a teardrop sign.