Focal FattyInfiltration

Hyperechoic focal changes are rare. A focal fatty infiltration demonstrates a hyperechoic but regular structure (Fig. 4.54).

Fig. 4.54 Hyperechoic ovoid lesion of the pancreatic head: Focal fatty change.

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Focal Changes

Pancreas

Diffuse Pancreatic Change

Focal Changes

Anechoic Lesion

Hypoechoic Lesion

Isoechoic Lesion

Hyperechoic Lesion

Irregular (Complex Structured) Lesion

Dilatation of the Pancreatic Duct

Chronic Pancreatitis

Focal Chronic Pancreatitis

Pseudocyst/Intracystic Hemorrhage

Cystic Neoplasias (Cystadenoma/Cystadenocarcinoma)

If several or all of the criteria are present, quite often chronic pancreatitis will present a busy picture, where the individual criteria (cyst, fibrosis, calcification, dilated duct) can only be discerned with difficulty or not at all (Fig. 4.55).

Focal Chronic Pancreatitis

Fig. 4.55 Chronic pancreatitis: without the splenic vein as landmark structure (here thrombosed/obliterated), the pancreas is almost impossible to delineate (calipers); the “lively” image is due to ductal ectasia (arrow), here, with calculi, fibrosis, calcification, and microcysts. VC = vena cava; AO = aorta.

Here, too, the texture is heterogeneous, but because of the fibrosis and/or calcification it is micronodular to macronodular. Differential diagnosis has to consider pancreatic cancer (Fig. 4.56).

Fig. 4.56 Mottled hypoechoic/hyperechoic texture of the pancreatic head (P): focal chronic pancreatitis in the head, cut-off of the pancreatic duct (DP) (caution: cancer!).

Fig. 4.57

a Large, symptomatic pancreatic pseudocyst: complex masses in the left upper abdomen. Initial symptoms were caused by mass effects from the cyst.

b Incipient pseudocyst (Z) after acute pancreatitis: complex mass displacing the hepatic artery (AH) and splenic artery (AL). Color duplex. TR = celiac axis.

Cystic neoplasias of the pancreas are rare. Ductal carcinomas comprise approximately 80% of all malignant neoplasms of the pancreas, and some 90% of those are ductal adenocarcinomas. Variants of the cystic neoplasms are (Fig. 4.58):14

●Mucinous cystic neoplasm (MCN)

●Serous cystic neoplasm (serous microcystic adenoma, SMA)

●Intraductal papillary mucinous neoplasm (IPMN)

●Solid pseudopapillary neoplasm (SPN)

Cystadenomas have cystic and solid parts. Until the late 1970s, the spectrum of cystic diseases consisted mainly of serous (microcystic, mostly benign) and mucinous (at the time of diagnosis often malignant) neoplasms. The development and widespread use of new imaging techniques led to the delineation of new categories of cystic pancreatic neoplasms; new entities were described.14

Serous microcystic benign adenoma, mostly found in older women, often presents difficulties in differential diagnosis because of a concomitant duct occlusion. Ultrasound depicts a mainly solid formation with numerous small (honeycomb-like) cysts up to 2 cm in size, whereas in macrocystic adenoma, which occurs mostly in middle-aged women, large cystic formations are immediately detectable. With CDS, tumor vessels are detectable in both types, but more so in microcystic adenoma ( 4.3a–f).

Cystic lesions of the pancreas are summarized in the following outline:

IPMNs are characterized by intraductal proliferation of mucin-producing cells, which are arranged in papillary patterns. In many IPMNs hypersecretion of mucin leads to a cystic dilatation of the involved ducts. In a few IPMNs, focal or diffuse intraductal papillary growth causes duct dilatation ( 4.3 g–k). IPMNs are frequently localized in the main duct of the head region and should be operated at an early stage; those from secondary ducts seem to have a better prognosis.

The most common differential diagnosis of pseudocyst is versus neoplasms with a cystic

Cystic Lesions of the Pancreas

Neoplastic epithelial

Benign

●Serous cystic adenoma

●Mucinous cystic adenoma

Borderline

●IPMN

●Mucinous cystic neoplasm

●Pseudopapillary cystic neoplasm

Malign

●(Serous)/mucinous cystadenocarcinoma

●Intraductal papillary mucinous carcinoma

Nonneoplastic epithelial

●Congenital cyst

●Retention cyst

●Lymphoepithelial cyst

●Duodenal wall cyst

Nonneoplastic nonepithelial

●Pancreatitis-associated pseudocyst

●Parasitic cyst

●Pseudoaneurysm

appearance (cystic ductal carcinoma, MCN and SPN14) (4.3 m–o; Table 4.8). In particular, the SPN may be similar to a pseudocyst ( 4.3 l). Wall thickening in excess of 1 cm, tumor markers in the fine-needle aspirate (CEA, Ca 15.3, Ca 72.4, Ca 19.9) and low amylase and lipase indicate cystic neoplasms. EUS (sensitivity 93%; CT only 36%) and CEUS confirm the diagnosis. In CEUS, necrosis, detritus, and blood clots (see Fig. 4.25) in a pseudocyst can be readily discriminated from solid (vascularized) tumors and septae in cysts ( 4.3c,m).

Mucinous cystadenomas and cystadenocarcinomas are not really distinguishable in US; CDS and CEUS do not give reliable enough values for differentiation, but an invasion into vessels signifies malignancy.

IPM carcinomas demonstrate mural nodulation within the dilated duct wall and parietal

Fig. 4.58 Cystic pancreatic tumors (reproduced from Klöppel and Kosmahl14 with permission from Elsevier).

masses with flow signals. Symptomatic IPMN with mural nodulation greater than 10 mm are mostly malignant. CEUS depicts vascularized septae and hyperenhanced masses (Fig. 4.59).

Table 4.8 provides a summary of cystic lesions of the pancreas, Table 4.9 of the differential diagnoses of diffuse and focal changes in the texture and size of the pancreas.

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