Ultrasound signs of pancreatic pathology

Reduction in the size of the pancreas

The pancreas usually decreases in size in older people, but this fact has no clinical significance. In total pancreatic atrophy, the decrease in size occurs in all parts of the pancreas. If there is an impression of isolated atrophy of the tail of the pancreas (the head looks normal), a tumor of the head of the pancreas should be suspected. The head should be examined especially carefully, since chronic pancreatitis in the body and tail can be combined with a slowly growing tumor of the pancreas.

If the pancreas is small, unevenly hyperechoic and heterogeneous in comparison with the liver, the cause is most often chronic pancreatitis.

Diffuse enlargement of the pancreas

In acute pancreatitis, the pancreas may be diffusely enlarged or may be normal in size and hypoechoic in comparison to the adjacent liver. Serum amylase is usually elevated and local intestinal obstruction may be present as a result of intestinal irritation.

If the pancreas is unevenly hyperechoic and diffusely enlarged, this is due to acute pancreatitis against the background of existing chronic pancreatitis.

Local enlargement (non-cystic)

Almost all pancreatic tumors are hypoechoic compared to the normal pancreas. It is impossible to differentiate focal pancreatitis and pancreatic tumor by ultrasound alone. Even if there is an increase in serum amylase, it is necessary to repeat the ultrasound examination in 2 weeks to determine the dynamics. Tumor and pancreatitis can be combined. When there is a mixed echostructure, a biopsy is necessary.

It is impossible to differentiate focal pancreatitis from a pancreatic tumor using ultrasound examination.

Pancreatic cysts

True pancreatic cysts are rare. They are usually solitary, anechoic, smooth-edged, and fluid-filled. Multiple small cysts may be congenital. Pancreatic abscesses or hematomas will have a mixed echogenicity pattern and are often associated with severe pancreatitis.

Pseudocysts resulting from trauma or acute pancreatitis are common; they may enlarge and rupture. Such cysts may be single or multiple. In the early stages, they have a complex echostructure with internal reflections and unclear contours, but over time, these cysts acquire smooth walls, become anechoic, and conduct ultrasound well. Pancreatic pseudocysts can be found in any part of the abdomen or pelvis, displacing from the pancreas. When cysts become infected or damaged, internal echostructures or septa may be determined.

Pancreatic cystadenomas or other cystic tumors usually appear on ultrasound as cystic lesions with multiple septa, with an associated solid component. In microcystadenomatosis, the cysts are very small and poorly visualized.

Parasitic cysts are rare in the pancreas. Perform an ultrasound of the liver and the rest of the abdomen to rule out parasitic disease.

Calcifications in the pancreas

Ultrasound is not the best method for detecting pancreatic calcification. X-ray of the upper abdomen with the patient in the supine position in a direct projection is preferable.

Calcifications within the pancreas may produce an acoustic shadow, but if they are small, they may appear as a separate bright echostructure without an acoustic shadow. Calcification usually occurs as a result of:

1. Chronic pancreatitis. Calcifications are distributed diffusely throughout the pancreas.
2. Pancreatic duct stones. These calcifications are located along the duct.
3. Gallstones in the distal common bile duct may be mistaken for calcifications in the pancreas. However, dilation of the proximal common bile duct is determined.

Dilation of the pancreatic duct

The maximum internal diameter of a normal pancreatic duct is 2 mm, and the duct is best visualized on a transverse scan in the middle third of the pancreatic body. To be sure that you are visualizing the duct, you need to see pancreatic tissue on either side of it. If you do not, the splenic vein posteriorly or the gastric wall anteriorly may be falsely interpreted as the pancreatic duct.

The pancreatic duct walls should be smooth and the lumen clear. When the duct is dilated, the walls become rough; scan not only the head of the pancreas but also the entire biliary tract.

The reasons for the dilation of the pancreatic duct are:

1. Tumor of the head of the pancreas or ampulla of Vater. Both are associated with jaundice and dilation of the biliary tract.
2. Common pancreatic duct stones. Investigate for gallstones and bile duct dilation.
3. Stone in the intrapancreatic duct. The biliary tract should be normal.
4. Chronic pancreatitis.
5. Postoperative strictures after Whipple's procedure or partial pancreatectomy. It is necessary to clarify the anamnestic data from the patient or, if necessary, from the patient's relatives.

The most common errors: during ultrasound examination of the pancreas, an incorrect diagnosis can be made as a result of:

• median location of the gallbladder;
• enlarged lymph nodes;
• retroperitoneal tumors;
• encapsulated ascites or abscess of the abdominal cavity (including splenic abscess);
• liver cysts or tumors;
• mesenteric cysts;
• hematomas around the duodenum;
• partial filling of the stomach. If the stomach contains fluid, it may simulate a pancreatic cyst; if it contains food, it may simulate a tumor. The adjacent intestine may cause similar errors;
• kidney cysts, or kidney tumors, or a distended renal pelvis;
• aortic aneurysms;
• adrenal tumors.