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Type:
Educational Exhibit
Keywords:
Abdomen, Anatomy, Pancreas, CT, MR, Normal variants, Imaging sequences, Congenital
Authors:
R. Ouji1, O. Ghdes2, A. Ali2, I. Kasraoui2, N. Achour2, A. Gaja2, N. Mnif2; 1Oued Ellil/TN, 2TUNIS/TN
DOI:
10.1594/ecr2017/C-2154
Findings and procedure details
1/- Protocol for the exploration of pancreas:
*CT-scan
- The scanning of the pancreas requires a well-established protocol:
⇒An acquisition without contrast injection
⇒An acquisition at pancreatic time (40 to 45 seconds after the beginning of contrast injection): a maximum enhancement of the pancreatic parenchyma
⇒An acquisition at portal time (70 seconds after the beginning of contrast injection)
- In case of suspicion of endocrine tumor,
acquisition at arterial time is necessary
- Axial images,
as well as,
curved and multiplanar reconstructions should be used.
- The CPR mode as well as the minimum intensity projection (min IP) help in the study of pancreatic ducts
*MRI
- A high field machine (> 1 Tesla)
- The production of fine sections
- T1 sequences echo-gradient with fat saturation
- Dynamic sequence in apnea
- à sequences of cholangio-wirsungography 2D and 3D
2/-Congenital malformations and variants:
*Morphological variant
⇒Tuber omentale Fig. 4: -A rounded prominence chiefly on the anterior surface of the neck of the pancreas.
⇒Bifid pancreatic tail: -It’s a rare congenital anomaly.
-On MRI,
it manifests as duplication of the major duct in the body of the pancreas.
*Agenesis and hypoplasia
- Complete agenesis of the pancreas results in severe intrauterine growth retardation and early death
- Partial ventral or dorsal agenesis (hypoplasia) Fig. 5 are also rare.
These are sometimes associated with polysplenia syndrome.
They can be responsible for diabetes and abdominal pain.
- The diagnosis is carried by the CT or MRI which show the absence of a part of the pancreas or a short dorsal pancreas.
*Annular pancreas
- Annular pancreas occurs when a ring of pancreatic tissue surrounds the second portion of the duodenum.
- It may result from adhesion of the ventral bud to the duodenum during duodenal rotation,
resulting in persistent tissue around the duodenum.
- Annular pancreas may cause duodenal obstruction (new born) or pancreatitis symptoms (adult).
- At CT or MRI,
a ring of pancreatic tissue surrounds the second portion of the duodenum,
in continuity with the anatomic pancreas.
- The duct within the encircling tissue usually communicates with the main pancreatic duct but may empty directly into the duodenum.
*Ectopic tissue (heterotopic pancreas)
- It is defined by the presence of pancreatic tissue outside the pancreas and unrelated to it.
- It is found most commonly (80%) in the stomach,
duodenum,
jejunum,
but also in the colon,
esophagus,
gallbladder,
biliary tract,
liver,
spleen,
peritoneum,
mediastinum,
and lung.
- Most often it is located in the submucosa and measures from 0.5 to 2 cm.
- Histologically,
it consists of all or a portion of normal pancreatic elements: acinar,
islet endocrine,
channels realizing a maximum central umbilication.
- The ectopic pancreatic tissue can present all the pathology of a normal pancreas.
- No specific diagnostic features have been shown at multiphasic CT to differentiate ectopic pancreas from other submucosal masses,
and endoscopic ultrasound also has low specificity.
*Pancreas divisum
- Pancreas divisum is the most common congenital anomaly of the pancreas,
with an incidence of 4 to 15%.
- While many congenital anomalies are found coincidentally,
pancreas divisum is clinically important when it is associated with acute recurrent or chronic pancreatitis.
- Pancreas divisum results from failed fusion of the dorsal and ventral ducts during embryonic development.
Pancreatic secretions drain through the duct of Santorini at the minor papilla,
whereas the common bile duct and duct of Wirsung empty normally at the major papilla.
- MRI allow the diagnosis Fig. 6:
⇒The main dorsal duct is in continuity with the duct of Santorini,
crossing the lower common bile duct and emptying into the duodenum
⇒No connection is seen with ventral duct of Wirsung (however,
this duct is not always identified)
- A santorinicele,
or focal dilation of the terminal dorsal duct,
may be present and is thought to develop from obstruction at the minor papilla and relative weakness at the duodenal wall.
*Fatty change of the pancreas Fig. 7
- Fatty change of the pancreas (also known fatty replacement of the pancreas) has been associated with a variety of diseases (Diabetes mellitus,
Cystic fibrosis,
Shwachman-Diamond syndrome),
and with obesity and aging.
- When associated with obesity,
fatty change can be reversed with weight loss.
- The distribution of pancreatic fatty change at imaging is often variable.
*Intrapancreatic accessory spleen
- The accessory spleen has similar enhancement to the anatomic spleen on all CT phases.
Similarly on MRI,
the accessory spleen follows the anatomic spleen signal intensity on all phases,
with decreased signal intensity relative to the pancreas on T1-weighted sequences,
and increased signal intensity relative to the pancreas on T2-weighted sequences.
- Intrapancreatic accessory spleen must be differentiated from hypervascular endocrine tumors.
Generally,
endocrine tumors have more homogeneous arterial enhancement,
with relative washout compared with normal pancreatic tissue on portal venous phase.
- A technetium 99m heat-damaged red blood cell study can be helpful to identify splenic tissue at equivocal CT and MRI cases.