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7 Pancreatitis and Pseudocysts Steffen Rickes and Holger Neye 7.1 Introduction Ultrasonography (US) is a noninvasive imaging modality which is often the first imaging technique in the evaluation of patients with pancreatic diseases. It has undergone significant advances in recent years. In this chapter the value of US in the diagnosis of pancreatitis and pseudocysts will be described and discussed. The article is focused on B-mode US, Doppler sonography and contrast-enhanced ultrasound (CEUS). 7.2 Acute Pancreatitis Acute pancreatitis is a common disease that affects about 300,000 patients per year in America with a mortality of about 7% [1]. The diagnosis is based on clinical and laboratory evaluation. The clinical course of acute pancreatitis varies from a mild transitory form to a severe necrotizing disease. Most episodes of acute pancreatitis are mild and self-limiting. Patients with mild pancreatitis respond well to medical treatment, requiring little more than intravenous fluid resuscitation and analgesia. In contrast, severe pancreatitis is defined as pancreatitis associated with organ failure and/or local complications such as necrosis, abscess formation, or pseudocysts. Severe pancreatitis can be observed in about 20% of all cases, and requires intensive care and sometimes surgical or radiologic intervention. Early S. Rickes () Department of Internal Medicine AMEOS Hospital St. Salvator, Halberstadt, Germany e-mail: rickes@medkl.salvator-kh.de correct assessment of the etiology and the severity of acute pancreatitis allows distinct therapeutic algorithms and can result in better outcome [1]. Advances in imaging modalities have revolutionized the management of patients with acute pancreatitis over the past decade. Contrast enhanced computed tomography (CT) is the criterion standard for diagnosing pancreatic necrosis and peripancreatic collections, as well as for grading acute pancreatitis by the Balthazar system [2]. In recent years the Balthazar grading system has been further developed into the so-called CT severity index (Table 7.1). This index is an attempt to improve the early prognostic value of CT by the intravenous administration of contrast medium. In this way also parenchymal necrosis of the pancreas can be diagnosed [3, 4]. The CT severity index can also be used for other imaging procedures. Table 7.1 Computed tomography grading of severity of acute pancreatitis [2-4]. This system can also be used for other imaging modalities Computed tomography grade (A) Normal pancreas (B) Edematous pancreatitis (C) B plus mild extrapancreatic changes (D) Severe extrapancreatic changes including one fluid collection (E) Multiple or extensive extrapancreatic changes 3 4 Necrosis None One third, Half 0 2 4 6 CT severity index = CT grade+necrosis score Complications 0-3 8% 4-6 35% 7-10 92% M. D’Onofrio (ed.), Ultrasonography of the Pancreas, © Springer-Verlag Italia 2012 0 1 2 Deaths 3% 6% 17% 83 84 Fig. 7.1 Gallstone at the main bile duct at transabdominal US Transabdominal US is the imaging method of choice in patients with acute abdomen due to its wide availability and portability. However, several limitations can be encountered in patients with acute pancreatitis mainly related to abdominal pain, which makes compressions with the probe impossible, and abundant overlying gas owing to a paralytic ileus. Very often a partial or inadequate transabdominal US visualization of the pancreas will result. Therefore, CT is still of paramount importance for the first evaluation of the disease. However, during the course of the disease, US may serve as an excellent imaging tool for short-term follow-up studies. Another potential advantage of US is the good visualization of the biliary system. Biliary stones are the most frequent causes of acute pancreatitis. US can easily detect stones in the gallbladder and in the biliary tract with high diagnostic accuracy (Fig. 7.1). This is very useful to triage patients requiring endoscopic retrograde cholangiopancreatography (ERCP) and sphincterotomy. However, the diagnosis of a bile duct stone with US is obviously influenced by operator skill. One German study demonstrated that experienced examiners achieve a significantly higher diagnostic accuracy for the detection of choledocholithiasis than less experienced investigators (83% versus 64%) [5]. Other studies showed that with endoscopic ultrasonography (EUS) (Fig. 7.2) and magnetic resonance cholangiopancreatography (MRCP) better results can be achieved [6-8]. However, these methods should be used only in patients with suspected choledocholithiasis but without detection of stones at transabdominal US. Finally, interventional procedures, such as aspiration and drainage of fluid collections, may be performed under US guidance. S. Rickes, H. Neye Fig. 7.2 Gallstone (calipers) in the main bile duct at EUS Fig. 7.3 Acute edematous pancreatitis located at the pancreatic head which appears enlarged and hypoechoic at transabdominal US In early pancreatitis, the organ may be of normal size and echotexture. However, in most patients interstitial edema results in an enlargement of the gland and a subsequent hypoechoic appearance (Fig. 7.3). The acute inflammation can be focal or diffuse, depending on the distribution. Focal pancreatitis mostly occurs in the pancreatic head and presents as a hypoechoic mass that is sometimes difficult to differentiate from a tumor. Complications of acute pancreatitis include acute fluid collections representing exudates, peripancreatic tissue necrosis or hemorrhage in various combinations, parenchymal necrosis, and vascular complications. Acute fluid collections are echopoor or echofree. They occur most commonly around the pancreas (Fig. 7.4) and usually spread into both the lesser sac and the anterior pararenal space up to the pericolic region. Furthermore, the enzyme-rich fluid can penetrate into 7 Pancreatitis and Pseudocysts Fig. 7.4 Acute pancreatitis with enlargement of the pancreatic body and fluid collections around the pancreas at transabdominal US 85 Fig. 7.5 Acute pancreatitis with peripancreatic fluid collection and involvement of the left liver lobe at transabdominal US a Fig. 7.6 Necrotizing pancreatitis at transabdominal US. The pancreatic head is destroyed and liquefied. The pancreatic body is enlarged and inhomogeneous. A peripancreatic fluid collection can also be appreciated parenchymal organs, like the spleen or the liver (Fig. 7.5). In acute necrotizing pancreatitis, parts of the pancreas can be destroyed and liquefied (Fig. 7.6). A major problem of conventional US is the detection of non-liquefied parenchymal necrosis because it cannot assess organ perfusion. Through the use of contrast media, however, even at US the vascular behavior of the pancreas can nowadays be examined. At CEUS necrotic areas of the pancreas show no vascular structures (Fig. 7.7). A paper published in 2006 showed that this method produces excellent results in the staging of acute pancreatitis severity [9]. This study demonstrated that the procedure is comparable to CT for the assessment of severe acute pancreatitis and can be recommended as a first-choice imaging procedure, especially when iodinated contrast medium injection is contraindi- b Fig. 7.7 a,b Necrotizing pancreatitis at transabdominal US. a Conventional US. Echopoor region (not liquefied necrosis) at the pancreatic body at B-mode US. A differentiation between necrosis and edema is impossible. b Contrast-enhanced US. The region shows no vascular structures and can therefore be characterized as necrotic cated [9-12]. Ripollés et al. [13] reported that CEUS is comparable to CT in detecting pancreatic necrosis as well as predicting its clinical course and that therefore, 86 when CT is contraindicated, CEUS may be a valid alternative. However, it has to be considered that in this study patients with incomplete US imaging of the pancreas were excluded. In light of the difficulties reported above regarding the exploration of the pancreas in patients with acute pancreatitis, one role of CEUS may be considered not in the first (staging) but in the further evaluation (follow-up) always required in the management of the disease. A positive outcome would be a significant reduction in the number of CT examinations performed. However, when CT is contraindicated, magnetic resonance imaging (MRI), with absolutely the same panoramic view of CT although less available and more expensive, can be used with good results [14, 15]. For instance, if the definition of a fluid collection proves difficult both at US and CT, it can be easily obtainable with MRI [14]. The most important complications of acute pancreatitis are infection of necrosis and vascular complications. Necrotic infection more frequently appears 15–20 days after the clinical onset of acute pancreatitis [16]. The probability of infection increases proportionately to the gravity of the acute pancreatitis at clinical and CT evaluation. Infection can be suspected in the presence of gas bubbles produced by anaerobic bacteria within the fluid collections. The detection of gas bubbles within the collections while difficult at US is instead immediate at CT. This is the reason why when infection of necrosis is first suspected CT must be performed again. Pancreatic abscess is a collection of suppurative fluid, surrounded by a fibrous capsule, adjacent to the pancreatic gland. An abscess secondary to acute pancreatitis probably starts off as infection of pancreatic necrosis. An abscess appears later than infection of the necrosis, usually after the fourth week [14]. Surgical necrosectomy or percutaneous debridement can be considered in treating infected pancreatic necrosis. Percutaneous drainage under imaging-guidance is highly efficient in the treatment of pancreatic abscess/infected pancreatic pseudocysts [14]. The mainly fluid content of the lesion explains the excellent clinical success of the procedure. Percutaneous drainage can be carried out under US or CT guidance, although CT is again preferable [14]. The most common vascular complications are thrombosis of the portal venous system, hemorrhage into a pseudocyst, arterial erosions and disruption, formation of collateral vessels or pseudoaneurysms, and rupture of a pseudoaneurysm (see also the paragraph about pseudocysts). In patients with a history of pan- S. Rickes, H. Neye creatitis, the detection of a cystic lesion at US must be further evaluated with Doppler to exclude the presence of vascular complications [14, 17, 18]. The administration of microbubbles could potentially improve the diagnosis of vascular complications. However, CT evaluation remains mandatory for diagnostic confirmation and treatment planning. Angiography, playing no relevant role in the diagnostic phase, has to be immediately used for treating vascular lesions [14]. 7.3 Chronic Pancreatitis Irrespective of its etiology, chronic pancreatitis is described by fibrosis, destruction, and distortion of the pancreatic ducts with loss of parenchyma. The most common cause in Europe is alcohol abuse. Other causes include hereditary, tropical, autoimmune, and idiopathic pancreatitis. The diagnosis of chronic pancreatitis is based on clinical findings, laboratory evaluation of endocrine and exocrine pancreatic function, and imaging findings. Although early morphologic changes of chronic pancreatitis are difficult to recognize at imaging with different techniques, the findings of advanced disease are easily detected [19, 20]. ERCP has long been considered the diagnostic criterion standard in the diagnosis of chronic pancreatitis. However, today ERCP has been replaced by MRCP. MRI is nowadays a powerful noninvasive imaging modality for the study of chronic pancreatitis even in the early phase of the disease [15]. A complete MRI study for chronic pancreatitis includes imaging of the parenchyma before and after the administration of contrast material, and imaging of the duct before and after secretin stimulation to evaluate pancreatic exocrine function through the analysis of the pancreatic fluid output. EUS seems also to be highly sensitive in the detection of early morphologic changes [21]. Technologic advantages and new developments in US (compound and tissue harmonic imaging, high frequency probes, CEUS and elastography) have improved the value of US in the diagnosis of pancreatic diseases [22]. In the US study of chronic pancreatitis, alterations in the size of the pancreas may be seen in about 50% of patients affected by chronic pancreatitis. However, the finding of a gland with normal size does not exclude the diagnosis of chronic pancreatitis. Pancreatic atrophy and focal alterations in size can be easily identified (Fig. 7.8). However, these changes in pancreatic volume are signs of advanced stages of the disease [23]. The 7 Pancreatitis and Pseudocysts Fig. 7.8 Atrophy of the pancreatic parenchyma at transabdominal US in a patient with late-stage chronic pancreatitis. The pancreatic duct is dilated with very small intraductal plugs 87 echogenicity of the pancreas may be increased in chronic pancreatitis due to fatty infiltration and fibrosis, although this sign is not absolutely specific. In fact, it can also be found in obese patients and the elderly. Parenchymal alteration is a more specific sign of chronic inflammation and represented by inhomogeneous and coarse lobulated parenchyma pattern due to the coexistence of hyperechoic and hypoechoic parts of fibrosis and inflammation, respectively (Fig. 7.9). These findings can be diagnosed presumably with the highest sensitivity at EUS [21, 23, 24]. The most important diagnostic sign of chronic pancreatitis is the presence of calcifications (Fig. 7.10) [25, 26]. These calcifications are calcium carbonate deposits. At US they appear as hyperechoic spots with posterior shading. Small calcifications may be hardly detectable. The diagnosis can be improved by the use of the so-called twinkling artifact (Fig. 7.11). Twinkling artifact is characterized by a rapidly fluctuating mixture of Doppler signals that occurs behind a strongly re- Fig. 7.9 Early-stage chronic pancreatitis at transabdominal US. The pancreatic parenchyma is inhomogeneous and coarse (lobulated parenchyma) a b Fig. 7.10 Chronic pancreatitis at transabdominal US with an increased volume of the pancreatic gland and the presence of multiple calcifications Fig. 7.11 a,b Chronic pancreatitis with small calcifications at percutaneous B-mode US (a, arrows) which generate typically twinkling artifacts at color-Doppler mode (b, arrows) 88 S. Rickes, H. Neye Fig. 7.12 Late-stage chronic pancreatitis at transabdominal US. The pancreatic duct is dilated (5 mm) and shows an irregular course. For better delineation the linear probe is used Fig. 7.13 Early-stage chronic pancreatitis at transabdominal US. The pancreatic duct (arrow) is not dilated but shows an irregular course. For better delineation the linear probe is used flecting granular interface such as pancreatic calcifications [27]. The demonstration of pancreatic calcifications may be improved by the use of harmonic imaging and high resolution US, by using high US beam frequency, increasing US diagnostic accuracy [15]. Intraductal plugs with little or no calcium carbonate deposits appear at US as echoic spots almost without posterior shading (Fig. 7.8). The high spatial and contrast resolution of current US systems allow an accurate identification of pancreatic microcalcifications and microdeposits. Intraductal deposits such as plugs (Fig. 7.8) if not yet calcified can be better identified by means of the US than the CT study. A further important sign of chronic pancreatitis is the dilatation of the main pancreatic duct of more than 3 mm [28, 29] (Fig. 7.12). However, in chronic pancreatitis the main pancreatic duct can also be not yet dilated but irregular in course (Fig. 7.13). Former studies have found that for the sonographic diagnosis of chronic pancreatitis pancreatic duct dilation is the most easily identified sign with a sensitivity of about 60%– 70% and a specificity of about 80%–90% [28, 29]. Focal pancreatitis typically involves the pancreatic head [23]. The differentiation of mass-forming pancreatitis from ductal adenocarcinomas is notoriously problematic due to their similar patterns [12]. Mass-forming pancreatitis usually occurs in patients with a history of chronic pancreatitis and must be differentiated from pancreatic ductal adenocarcinoma. The differential diagnosis with a neoplastic disease may be difficult due to the very similar US features, presenting in most cases as a hypoechoic mass, and also because mass- forming pancreatitis and pancreatic cancer may present with the same symptoms and signs [12]. The presence of small calcifications at US in the lesion may suggest its inflammatory nature, but this is low in specificity [12]. For diagnosis, biopsy is often mandatory. In many cases fine needle aspiration (FNA) or biopsy is in fact still necessary and can be US-guided either percutaneously or endoscopically. CEUS can improve the differential diagnosis between mass-forming pancreatitis and pancreatic adenocarcinoma [30]. In particular, while ductal adenocarcinoma remains hypoechoic in all contrast-enhanced phases, due to its intense desmoplastic reaction with poor mean vascular density of the lesion, the inflammatory mass shows parenchymal enhancement in the early contrast-enhanced phase [12, 30]. The CEUS finding consistent with an inflammatory origin is therefore the presence of parenchymal enhancement similar to that of the adjacent pancreas during the dynamic study. The intensity of this parenchymal enhancement is related to the length of the underlying inflammatory process. It has been observed that, the more the inflammatory process is chronic and longstanding, the less intense is the intralesional parenchymal enhancement, probably in relation to the entity of the associated fibrosis. As opposed to this, in mass-forming pancreatitis of more recent onset the enhancement is usually more intense and prolonged [31-34]. Autoimmune pancreatitis is a rare cause of recurrent acute or chronic pancreatitis. It is characterized by periductal inflammation, caused by infiltration of lymphocytes and plasma cells, with evolution to fibrosis [35, 36]. In most cases, the echogenicity is reduced 7 Pancreatitis and Pseudocysts Fig. 7.14 Autoimmune pancreatitis at transabdominal ultrasound with focal enlargements of the pancreatic gland (red arrows) and compression of the pancreatic duct (white arrows) (Fig. 7.14), the gland volume shows focal (Fig. 7.14) or diffuse (sausage-like) enlargement, and the pancreatic duct may be compressed by glandular parenchyma (Fig. 7.14). US findings are characteristic in the diffuse form when the entire gland is involved. In the focal form US features are less characteristic and very similar to those of mass-forming chronic pancreatitis. Focal autoimmune pancreatitis at the pancreatic head is often characterized by the dilation of the common bile duct alone [37]. The vascularization of autoimmune pancreatitis can be demonstrated at CEUS showing relatively intense parenchymal enhancement. CEUS of autoimmune pancreatitis shows fair and often from moderate to marked enhancement in the early contrastenhanced phase, though inhomogeneous [37]. The CEUS findings may be especially useful in the study of focal forms of autoimmune chronic pancreatitis, in which differential diagnosis with ductal adenocarcinoma is a priority [30]. 7.4 Pseudocysts Pseudocyst of the pancreas is a fluid collection that contains pancreatic enzymes, surrounded by a fibrotic wall with no epithelial layer. They are caused by pancreatic ductal disruption following increased luminal pressure, either due to stenosis or calculi obstructing the ductal system, or as a result of parenchymal necrosis. Pseudocysts complicate the course of pancreatitis in 30% to 40% [38], appearing 3-6 weeks or longer following fluid collection organization [15]. At US a pseudocyst is seen as a sharply delineated 89 Fig. 7.15 Pancreatic pseudocyst at transabdominal US and anechoic lesion with distal acoustic enhancement, and it is typically oval or round (Fig. 7.15). Sometimes it may have inclusions (debris), thus simulating a cystic tumor (e.g. cystadenoma or cystadenocarcinoma). Only if there is a history of acute or chronic pancreatitis or there are imaging signs of chronic pancreatitis can the diagnosis of pseudocysts be considered. Pseudocysts must be differentiated from pancreatic cystic tumors, especially mucinous cystadenoma, as they require completely different therapeutic approaches. CEUS can improve the differential diagnosis between pseudocysts and cystic tumors [39, 40]. Differential diagnosis between pseudocysts and cystic tumors of the pancreas is more reliable thanks to the evaluation of the vascularity of intralesional inclusions. Even if characterized by an inhomogeneous content at US, all the inclusions in pseudocysts are always completely avascular, becoming homogeneously anechoic during CEUS examination [40]. In fact, in contrast to CT and MRI the results of the CEUS study of a pseudocyst may be different. Harmonic microbubble-specific software filter all the background tissue signals during CEUS examination and this makes the examination accurate for distinguishing debris from tumoral vegetations. Therefore the accuracy of CEUS in the diagnosis of pseudocyst is high [39]. The wall of the pseudocysts may be more or less vascular at imaging and also at CEUS [39, 40]. Pseudocyst may be followed up if small in size and if not complicated and without involvement of adjacent structures. Otherwise drainage or surgical treatments have to be considered. The surgical approach is recommended if an open communication between the pseudocyst and the ductal system exists. 90 S. Rickes, H. Neye pancreaticus. An additional issue is whether bleeding is caused by erosion of a vessel wall or because of rupture of a pseudoaneurysm. The splenic artery appears to be the most common artery involved with major bleeding (Fig. 7.17). Helpful information can be obtained by Doppler US [43, 44]. References Fig. 7.16 Pancreatic pseudocyst within the wall of the duodenum at transabdominal US Fig. 7.17 Pseudoaneurysm of the splenic artery. With colorDoppler sonography blood flow can be appreciated within the pseudocyst Pancreatic pseudocysts can involve adjacent organs [14] and the duodenum (Fig. 7.16), stomach and colon. Furthermore, fistulas between pseudocysts and the bile duct system have been reported [41]. The identification of small cystic formations in a thickened duodenal wall on the pancreatic side is however a specific finding for cystic dystrophy of the duodenal wall [42]. Cystic dystrophy of the duodenal wall and groove pancreatitis are in a border site (groove region) between the pancreas and duodenum, a site that can be correctly evaluated with EUS. Bleeding is a further severe complication due to erosion and may occur into the pseudocyst or into the gastrointestinal tract or peritoneal cavity. When bleeding occurs into the pseudocyst, the cyst changes in echogenicity and may enlarge causing pain and pressure effects or blood may pass through the main pancreatic duct into the duodenum, which is known as hemosuccus 1. Rickes S, Uhle C (2009) Advances in the diagnosis of acute pancreatitis. Postgrad Med J 85:208-212 2. Balthazar EJ (1989) CT diagnosis and staging of acute pancreatitis. 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J Gastroenterol Hepatol 19:711 Rickes S, Mönkemüller K, Venerito M, Malfertheiner P (2006) Pseudoaneurysm of the splenic artery. Dig Surg 23:156–158 8 Solid Pancreatic Tumors Christoph F. Dietrich, Michael Hocke, Anna Gallotti and Mirko D’Onofrio 8.1 Introduction 8.2 Pathology and Epidemiology Diagnostic imaging plays a crucial role in the study of pancreatic tumors, with the primary aims being their correct detection and characterization [1, 2]. A further accurate staging is of fundamental importance for treatment planning. Ultrasonography (US) is often the noninvasive imaging modality chosen for the first evaluation of the pancreas, as it is inexpensive, easy to perform and widely available [3]. The more precise and accurate the initial evaluation, the more appropriate the management of the patient will be. In recent decades, the introduction of new technologies has improved the image quality of conventional imaging with very high spatial and contrast resolution [4-6]. Adenocarcinoma is the most common primary malignancy of the pancreas, thus each single pancreatic solid mass detected at US has a high probability of being an adenocarcinoma. Otherwise not all the solid pancreatic masses detected at US are adenocarcinoma [7]. Therefore improving the US capability for the characterization and differential diagnosis will lead to both a faster diagnosis of ductal adenocarcinoma and a more accurate differential diagnosis in respect to other pancreatic tumor histotypes or non-neoplastic mass-forming conditions. This chapter is focused on the actual possibility of detection and characterization, considering the most clinically relevant differential diagnoses, and staging of pancreatic ductal adenocarcinoma by means of US. Ductal adenocarcinoma is the most common primary malignancy of the pancreas, accounting for 80% of malignant pancreatic tumors and almost three-fourths of all pancreatic cancers [8-10]. Macroscopically, pancreatic ductal adenocarcinoma is a white-yellow and firm mass owing to the presence of fibrosis and desmoplasia, with infiltration of the ductal epithelium [7]. Microscopically, it is composed of infiltrating glands surrounded by dense and reactive fibrous tissue [11]. The presence of intratumoral fibrosis and necrosis, typical for highly aggressive types with a reduction in the microvascular density and in perfusion, the presence of perineural invasion and distant metastases (commonly in the liver, lungs, peritoneum and adrenal glands) predict a worse survival [9, 10, 12-14]. In more than 95% of cases, regardless of the site of localization, pancreatic ductal adenocarcinoma is diagnosed at an advanced stage, with locally advanced or metastatic disease requiring palliative therapy [1214]. Only 10 to 20% of patients are candidates for surgery [11]. The prognosis and the treatment approach are based on whether the tumor is resectable or non-resectable at presentation, which is mostly dependent on the time of diagnosis [2]. 8.3 Adenocarcinoma C.F. Dietrich () Department of Clinical Medicine Caritas-Krankenhaus, Bad Mergentheim, Germany e-mail: christoph.dietrich@ckbm.de 8.3.1 Detection The detection of a pancreatic ductal adenocarcinoma at transabdominal US is basically related to both explo- M. D’Onofrio (ed.), Ultrasonography of the Pancreas, © Springer-Verlag Italia 2012 93