CT Pancreas Protocol
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Direct answer
Timing defines the pancreatic protocol CT: a non-contrast phase, a pancreatic (late arterial) phase at roughly 35-45 seconds that maximises pancreatic parenchymal enhancement, and a portal venous phase at 60-70 seconds that maps the mesenteric and portal veins, with water as oral contrast to distend the duodenum. Pancreatic adenocarcinoma appears as a hypodense mass best seen on the pancreatic phase, and resectability is judged by vascular relationships — circumferential encasement of the coeliac axis or superior mesenteric artery over 180 degrees makes a tumour unresectable, while portal or SMV involvement is potentially resectable with venous reconstruction. For acute pancreatitis the emphasis flips: scan at least 72 hours after onset, and grade with the Balthazar CT severity index, which adds necrosis points to inflammation grades.
What you must remember
- Phases: pancreatic parenchymal phase about 35-45 s (tumour-to-parenchyma contrast is greatest), portal venous phase 60-70 s for veins and liver; thin collimation with coronal reformats.
- Adenocarcinoma signature: ill-defined hypodense head-of-pancreas mass, dual duct dilation (pancreatic duct plus common bile duct — the double-duct sign), and abrupt duct cut-off.
- Resectability rules (arteries): tumour abutting or encasing the SMA or coeliac axis by more than 180 degrees is unresectable; less than 180 degrees is borderline resectable.
- Venous criteria: SMV-portal vein occlusion or unreconstructable involvement is unresectable, but short-segment stenosis with a suitable proximal and distal vessel permits venous reconstruction.
- Balthazar CT severity index: inflammation graded A-E (normal gland 0, enlargement 1, peripancreatic inflammation 2, single fluid collection 3, two or more collections 4) plus necrosis (none 0, under 30 per cent 2, 30-50 per cent 4, over 50 per cent 6) — maximum 10; scores above 6 predict complications.
- Acute pancreatitis timing: necrosis demarcates over the first 72 hours, so early CT understages severity; ultrasound first to look for gallstones, CT after 3 days if complications are suspected.
- Water as oral contrast in pancreatic protocol: distends the duodenal C-loop and does not obscure mucosal enhancement, unlike positive contrast.
One patient, two protocols
A 60-year-old with painless jaundice and 8 kg weight loss goes through the tumour protocol. The pancreatic phase shows a 3 cm hypodense mass in the head, double-duct dilation, and fat stranding around the SMA of about 90 degrees; the venous phase shows a patent SMV-portal confluence with a smooth interface. That is a resectable adenocarcinoma — the arterial abutement is under 180 degrees, the vein is clean — so the answer is Whipple's pancreaticoduodenectomy with staging laparoscopy, and biopsy is reserved for unresectable or metastatic disease.
Contrast this with a 35-year-old with gallstone pancreatitis, admitted and improving. Scanning on day 1 would show a fat, indistinct gland and little else; scanning on day 5 shows peripancreatic collections and, say, 40 per cent gland necrosis — Balthazar grade E (4) plus necrosis 30-50 per cent (4) gives a severity index of 8, flagging a patient heading for infected necrosis, step-up drainage and a long stay. Same organ, and the protocol chosen reflects the question asked: characterisation and vascular mapping versus severity and complications.
How the exam frames it
The viva staple is the 180-degree rule — candidates lose marks saying any arterial contact forbids surgery, when resectability in current practice is stratified by degree and by which vessel. The second staple is the CT severity index arithmetic: examiners give an image of necrosis "about one-third of the gland" and expect the number 2, not a paragraph. Indian practice adds a third layer: ileocaecal and pancreatic tuberculosis, tropical pancreatitis and carcinoma in chronic pancreatitis all mimic adenocarcinoma, and a young patient with a pancreatic mass, calcification and duct stones points to tropical chronic pancreatitis — fibrocalculous pancreatic disease recognised in southern India — rather than cancer. Quote the double-duct sign as the sign of a periampullary or head mass, and remember that the commonest cause of acute pancreatitis in Indian series remains gallstone disease, so the ultrasound search for stones precedes the fancy protocol.
Frequently asked questions
Which phases constitute a pancreatic protocol CT for adenocarcinoma?
A non-contrast phase, a pancreatic parenchymal phase at about 35-45 seconds and a portal venous phase at 60-70 seconds, with water orally and thin-slice reformats for vascular assessment.
What CT criteria make a pancreatic tumour unresectable?
Tumour encasement of the superior mesenteric artery or coeliac axis by more than 180 degrees, or unreconstructable superior mesenteric or portal vein involvement, plus distant metastases.
How is the Balthazar CT severity index calculated?
Inflammation is graded 0-4 from normal gland through multiple fluid collections, and necrosis adds 0, 2, 4 or 6 points for none, under 30, 30-50 and over 50 per cent, for a maximum score of 10.
Why should CT for acute pancreatitis severity be delayed 72 hours?
Necrosis takes about three days to demarcate, so early CT understates severity; ultrasound for gallstones comes first and contrast CT follows if deterioration or complications occur.
What is the double-duct sign?
Simultaneous dilation of the common bile duct and pancreatic duct, indicating an obstructing ampullary or pancreatic head lesion, most commonly pancreatic adenocarcinoma.