Isoechoic Lesion

Pancreatic Cancer

Malignant Lymphoma

Focal Pancreatitis

Pancreas Divisum

Annular Pancreas

If the texture of the pancreas is hypoechoic, as evidenced in slim young patients, the texture of pancreatic cancer will be isoechoic and can only be differentiated by its bulging contour and any secondary signs. Cancers of the pancreatic tail and uncinate process are also hard to detect, and at that only in the special planes of the oblique/transverse epigastric views: on the right for the head and on the left for the tail of the pancreas. The obstructed pancreatic duct may be a leading sign (Fig. 4.40).

Fig. 4.40 Malignant tumor (TU) of the pancreatic head: texture isoechoic to the rest of the pancreas (PA).

a Transverse scan.

b Longitudinal scan. AO = aorta, WS = vertebral column, AMS = superior mesenteric artery, CF = venous confluence, DUO = duodenum, A = antrum, DP = pancreatic duct.

While in most cases acute focal pancreatitis appears hypoechoic, chronic focal pancreatitis may be isoechoic with the surrounding pancreatic tissue, and therefore can only be differentiated by focal enlargement and a more macronodular texture. A special form of focal pancreatitis (mainly of the head) is a chronic autoimmune pancreatitis, often characterized by a pancreatic head (or tail12) mass or also by a diffuse pancreatitis. There is a lack of pseudocysts or calculi; the diagnosis is made by antibodies, biopsy, and trial of cortisone therapy (Fig. 4.41, Fig. 4.17b).

Fig. 4.41 Segmental pancreatitis of the head (cursors, P), isoechoic texture.

a Transverse scan.

b Longitudinal scan: Obstruction of the dilated common bile duct (DCH) and cystic duct. DUO = duodenum, WS = vertebral column, AO = aorta, AMS = mesenteric superior artery, VC = vena cava, VP = portal vein, LI LL = left liver lobe, CF = venous confluence.

PancreasDivisum

Pancreas divisum is characterized by a strikingly enlarged head of the pancreas with normal texture, segmental ductal dilatation in the pancreatic body, and the demonstration of two distinct ductal systems in the pancreatic head (Fig. 4.43, Fig. 4.44).

Congenital Anomaly—Pancreas Divisum

During embryological development, the smaller, originally ventral anlage and the larger dorsal anlage fuse. The ventral anlage constitutes the inferior parts of the head and uncinate process of the pancreas, as well as the main pancreatic duct, while from the dorsal anlage emanate the remainder of the pancreatic head, the entire body and tail, and the anlage for the accessory duct of Santorini. The latter may sometimes persist after fusion and drain the pancreatic juice to the minor papilla, or it may resolve and drain into the main pancreatic duct to the papilla of Vater.

Fusion anomalies (complete or incomplete pancreas divisum) are quite common. The accessory duct of Santorini will drain most of the pancreatic juice via the minor papilla, while the main pancreatic duct (of Wirsung) drains part of the pancreatic head and the uncinate process and displays either no (complete pancreas divisum) or only a thin (incomplete pancreas divisum) communication with the main duct (Fig. 4.42). The relative stenosis upstream of the minor papilla may cause recurrent episodes of pancreatitis.

Hyperechoic Lesion

Calcification/Intraductal Calculus

Calcified Splenic Artery

Microcalcification, Fat Necrosis

Intraductal Gas/Stent

Focal Fatty Infiltration