Ultrasound for Vets, by Dr.Kishor Mahind---Pancreas

HOME

The Pancreas:

The normal canine pancreas is difficult to image as it has poorly defined margins, and is often obscured by gas or solid material in the adjacent stomach, duodenum and colon. It requires a high-resolution transducer (5-7.5 MHz) and careful attention to position of the transducer. The animal should be placed in left lateral recumbency, and the transducer placed under the right 13^th rib and angled dorsally with the sound beam approximately parallel to the spine. Once the right kidney has been identified, the transducer is moved slowly medially until the descending duodenum is found.

The right pancreatic lobe lies dorsal and medial to the descending duodenum. If bowel gas is a problem, turn the animal over onto its right side, and repeat the procedure, placing the transducer between the animal and tabletop. The left pancreatic lobe is more difficult to find. Start with the transducer caudal to the left 13^th rib, and search the region caudal to the stomach, medial to the spleen and cranial to the left kidney.

Normal appearance: The normal appearance is often not seen clearly. It has homogenous echogenic texture with poorly defined margins. The pancreatico-duodenal vein runs in the right lobe, parallel to the descending duodenum, and can be used as a landmark.

Abnormal findings: In severe hemorrhagic necrotising pancreatitis, irregular hypoechoic and anechoic areas may be seen in the region of pancreas, representing collections of necrotic tissue and pus. The surrounding mesentery may be hyperechoic due to inflammation and edema. The duodenum tends to be thick walled and atonic, and there may be an associated peritoneal effusion. Secondary biliary obstruction may be noted.

The pancreatic neoplasia, insulinomas, produce spherical or lobular hypoechoic nodules o the ultrasound images. In some cases, relatively small tumors were detectable even in large dogs, usually appearing as focal hypoechoic lesions clearly demarcated from the surrounding pancreatic tissue. A small insulinoma that causes minimal disruption of the surrounding anatomy is more likely to be diagnosed accurately than a large aggressive neoplasm arising in the pancreas, intestine, bile ducts or liver that may destroy or envelop the adjacent organs. The similar ultrasonographic appearance of insulinomas and pathological lymph nodes, both of which appear as small, rounded or lobular, hypoechoic structures, may be another source of error when interpreting ultrasound images. Another potential problem is the overlap between the ultrasonographic signs of pancreatitis and pancreatic neoplasia. Dogs with relatively severe pancreatitis may have hypoechoic or hyperechoic masses like lesion in pancreas, localised peritoneal fluid and local lymphadenopathy and so resemble dog with pancreatic neoplasm. Despite these technical and interpretive difficulties, ultrasound is useful for diagnosis of pancreatic neoplasia because it complements biochemical tests. It is also useful because it makes it possible to detect and localize most small lesions before surgery.

HOME