CT Imaging of the Biliary System Flashcards
Liver Typical CT Protocol?
Typical CT Protocol?
1 Litre water or iodinated contrast. 100mls IV contrast – 3-5ml/sec. Bolus tracked portal venous – 65-70s post inj.
Many lesions also require (late) arterial phase – 35s – eg: NET, HCC, Renal Cell.
Haemangioma overview, appearance
Haemangioma is the most common benign liver tumour. The size varies from a few millimeters to more than 10 cm.
It is composed of multiple vascular channels lined by endothelial cells. In 60% of cases more than one haemangioma is present.
CT will show haemangiomas as sharply defined masses with the same density as the vessels on NECT and CECT.
The enhancement pattern is characterized by sequential contrast opacification beginning at the periphery as one or more nodular areas of enhancement.
All these areas of enhancement must have the same density as the bloodpool.
This means that in the arterial phase the areas of enhancement must have almost the density of the aorta, while in the portal venous phase the enhancement must be of the same density as the portal vein.
Even on delayed images the density of a haemangioma must be of the same density as the vessels.
Finally most haemangiomas show complete fill in with contrast.
Hepato-Cellular Carcinoma overview, appearance
Sometimes there is rim enhancement and you might mistake them for a haemangioma.
Always look how they present in the other phases and compare with the bloodpool and remember that rim enhancement is never haemangioma.
HCC is a silent tumour, so if patients do not have cirrhosis or hepatitis C, you will discover them at a late stage.
They tend to be very large with a mozaic pattern, a capsule, haemorrhage, necrosis.
HCC becomes isodense or hypoattenuating to liver in the portal venous phase due to fast wash-out. On delayed images the capsule and sometimes septa demonstrate prolonged enhancement.
Thickening of the gallbladder wall overview
Thickening of the gallbladder wall is a relatively frequent finding at diagnostic imaging studies.
A thickened gallbladder wall measures more than 3 mm, typically has a layered appearance on ultrasound, and on CT frequently contains a hypoattenuated layer of subserosal oedema that mimics pericholecystic fluid.
Historically, a thick-walled gallbladder has been regarded as proof of primary gallbladder disease, and it is a well-known hallmark feature of acute cholecystitis.
The finding itself however, is non-specific and can be found in a wide range of gallbladder diseases and extracholecystic pathological conditions.
Contrast-enhanced CT shows a distended gallbladder (arrowheads) with a slightly thickened wall and subtle regional fat-stranding (asterix). There is an impacted obstructing stone in the neck of the gallbladder (arrow)
Causes of thickening – Cholecystitis, Ca, Liver cirrhosis, Hepatitis, Renal failure, Pancreatitis.
Gallbladder carcinoma overview
Gallbladder carcinoma is the fifth most common malignancy of the gastrointestinal tract, and is found incidentally in 1% to 3% of cholecystectomy specimens.
Like other central abdominal pathologies, it is often detected at a late stage of the disease, due to lack of early or specific symptoms.
Gallbladder carcinoma has various imaging appearances, ranging from a polypoid intra-luminal lesion to an infiltrating mass replacing the gallbladder, and it may also present as diffuse mural thickening.
Associated findings such as invasion of adjacent structures, secondary bile duct dilatation, and liver or nodal metastases may help in differentiating a carcinoma from acute or xanthogranulomatous cholecystitis.
In the last few years, an increasing number of reports of port-site metastasis from unsuspected gallbladder cancer have been published and a lot of concern has been expressed that laparoscopic cholecystectomy might adversely affect the prognosis of gallbladder cancer by increasing the risk of port-site and peritoneal seeding.
Pancreas scanning protocol
3 phase scanning essential: uncontrasted to show any calcification
Lesions are hypervascular on arterial and venous phases.
Arterial improves sensitivity to around 88% (~75% on venous)
Pancreatic adenocarcinoma overview
Pancreatic adenocarcinoma has a poor prognosis. Complete resection of the tumour is the only curative treatment.
About 10-15% of all patients with a pancreatic carcinoma will finally undergo resection and only in half of these cases the resection will prove to be radical.
Most pancreatic cancers occur in the head of the pancreas (75%).
A minority is found in the body (15%) and tail (10%).
At the time of diagnosis a pancreatic head carcinoma is usually a little larger than 3 cm.
When tumours of the pancreatic body and tail are diagnosed, they are usually much larger, because they present late with aspecific symptoms.
These tumours are usually irresectable.
Tumours originating in the distal common bile duct or ampulla may also grow into the pancreatic head and together with pancreatic head carcinoma these tumours are often grouped together under the name periampullary tumours. This has some practical value as diagnostic imaging, staging and treatment of all these periampullary tumours is the same.
The early-portal phase is also called the pancreatic phase. It has a scan-delay of 40-50 sec. Water as contrast.
This is the most important phase for detecting and staging a pancreatic tumour.
At that moment the normal pancreatic parenchyma will enhance optimally, because it gets all of its bloodsupply through the arterial and capillary system.
In this phase there is optimal attenuation difference between the hypoattenuating tumour and the normal enhancing pancreatic parenchyma.
Unresectability tumour reasons
Tumour ingrowth into stomach, colon, mesocolon, inferior vena cava or aorta constitute definite criteria for unresectability.
Also the presence of hepatic metastases, peritoneal metastases or para-aortic lymphnode metastases is an absolute sign of unresectability.
Mesenteric lymph node metastases, not immediately adjacent to the pancreas usually also indicate unresectability.
On the left a pancreatic tumour in direct contiguity with the confluence of the portal and superior mesenteric vein.
The tumour surrounds the confluence for more than half the cirumference (>180?).
This tumour was regarded as unresectable.
What is a Pseudocyst
A pseudocyst is a collection of pancreatic fluids adjacent to the pancreas
This patient presented with a gastric outlet obstruction 2 months after an episode of acute pancreatitis.
There is a homogeneous well-demarcated peripancreatic collection in the lesser sac, which abuts the stomach and the pancreas.
The patient did not have fever.
A Pseudocyst is a collection of pancreatic juice or fluid enclosed by a complete wall of fibrous tissue.
It occurs in interstitial pancreatitis and the absence of necrotic tissue is imperative for its diagnosis.
After biochemical confirmation of a tumour, imaging is necessary to locate it.
90% of Phaochromocytomas are in the adrenal glands and 98% within the abdomen.
Extra-adrenal Phaochromocytomas develop in chromaffin tissue of the sympathetic nervous system and can occur anywhere from the base of the brain to the urinary bladder – these are subsequently called paragangliomas.
Common locations for extra-adrenal Phaochromocytomas – close to origin of inferior mesenteric artery, bladder wall, heart, mediastinum and carotid and glomus jugulare tumours.
CT scanning has 85-95% sensitivity and is the imaging modality of choice in detecting tumours >1.0 cm in diameter. MRI ~100%
Surgical resection of the tumour is the treatment of choice and usually results in cure of the hypotension, however…..
The 5yr survival rate for malignant Phaochromocytomas is less than 50%, for non-malignant it is over 95%….but the risk of malignancy is rather higher when children are affected.
TOP: large Phaochromocytoma (Left and centre) and Paraganglioma (right)
BOTTOM: Hypervascular bladder lesion and lymph nodes. Malignant multifocal Phaochromocytoma with lymph node metastases (Black arrow)
After biochemical confirmation of a tumour, imaging is necessary to locate it.
90% of Phaochromocytomas are in the adrenal glands and 98% within the abdomen.
Extra-adrenal Phaochromocytomas develop in chromaffin tissue of the sympathetic nervous system and can occur anywhere from the base of the brain to the urinary bladder – these are subsequently called paragangliomas.
Common locations for extra-adrenal Phaochromocytomas – close to origin of inferior mesenteric artery, bladder wall, heart, mediastinum and carotid and glomus jugulare tumours.
CT scanning has 85-95% sensitivity and is the imaging modality of choice in detecting tumours >1.0 cm in diameter. MRI ~100%
Surgical resection of the tumour is the treatment of choice and usually results in cure of the hypotension, however…..
The 5yr survival rate for malignant Phaochromocytomas is less than 50%, for non-malignant it is over 95%….but the risk of malignancy is rather higher when children are affected.
TOP: large Phaochromocytoma (Left and centre) and Paraganglioma (right)
BOTTOM: Hypervascular bladder lesion and lymph nodes. Malignant multifocal Phaochromocytoma with lymph node metastases (Black arrow)
