contemporary imaging techniques , ultrasound ( us ) being one of them , have contributed to a considerable progress in the diagnosis of pathological changes located in the region of the pancreas . in us examination , one should assess the echogenicity , echostructure , size and shape ( outlines ) of the pancreas . it is possible to detect diffuse ( encompassing the whole parenchyma or its large fragments ) or focal lesions , including solid and cystic ones . us examination of the pancreas for various reasons does not belong to the easiest tests . first of all , this is because of its structure , which is quite complex , and proximity of other anatomical structures . the head of the pancreas is surrounded by the duodenal loop and is localized to the right of the mesenteric vessels and mesenteric - portal confluence . the inferior aspect of the head , called the uncinate process is located to the right of the isthmus of the pancreas which joins the head with the body . the anterior surface of the pancreas is at the right side adjacent to the transverse colon and , further , to the stomach . its superior margin borders the coeliac trunk and the splenic artery which originates from the coeliac trunk . moreover , the pancreas is a large organ located deep in the abdominal cavity in the extraperitoneal space and does not have its own capsule . on examination , it may become covered by the intestine or stomach , which contain air that inhibits adequate assessment . such a situation occurs especially in the course of acute inflammations of abdominal organs and the pancreas as well as during paralytic ileus or postoperative conditions . below , the most common mistakes in ultrasound imaging of the pancreas are presented and divided into three groups : mistakes related to the anatomical structure of the pancreas;mistakes resulting from the contiguity of anatomical structures;mistakes made in the differential diagnosis of pancreatic pathologies . mistakes related to the anatomical structure of the pancreas ; mistakes resulting from the contiguity of anatomical structures ; mistakes made in the differential diagnosis of pancreatic pathologies . the diagnostic errors may result from the lack of a pancreatic capsule ( an evident separation from adjacent organs ) , its anatomical structure and possible anatomical variants as well as from its echostructure and echogenicity . due to the lack of its own capsule , the superior border of the pancreas , which is made up by the inferior wall of the stomach and superior surface of the pancreas , is not visible well . when the posterior wall of the stomach is also indistinct , it might be difficult to assess the size of the pancreas . on the other hand , when the layered structure of the stomach wall is well visible , the proper muscular layer may be misinterpreted as the lumen of the pancreatic duct ( fig . 1 ) . the inferior aspect of the head of the pancreas ( the region of the uncinate process ) may present decreased echogenicity . this is the area of the pancreatic primordium which presents lower echogenicity in comparison to the remaining parenchyma . 2 ) . the image of the pancreatic and common bile ducts may prove helpful in the differential diagnosis since if the tumor in the head of the pancreas is present , they usually undergo dilatation ( fig . 3 ) . furthermore , certain congenital anomalies in the structure of the pancreas may mimic tumor - like masses . an example may be a rare case of pancreas divisum which particularly in the abdominal space may imitate a hypoechoic tumor of the head of the pancreas ( fig . similar us presentations may also result from other anomalies including pancreatic duplications , ectopic pancreas and annular pancreas ( fig . the experience of the examiner and knowledge of possible structural variants of the pancreas are important . if doubts arise , a subsequent step is computed tomography ( ct ) or magnetic resonance imaging ( mri ) . anatomy of the pancreas : stomach (  ) , venous confluence ( zl ) , superior mesenteric artery ( tkg ) , renal vein ( n ) , inferior vena cava ( gd ) , aorta ( a ) . the arrow marks the posterior wall of the stomach developmental variant of the pancreas ; left pancreatic primordium ( zb ) to be differentiated from a focal lesion in the uncinate process ; common bile duct ( pw ) , venous confluence ( zl ) tumor of the head of the pancreas ( tu ) dilated pancreatic duct ( wirsung ) and common bile duct ( pw ) developmental variant of the pancreas aorta , pw  common bile duct , nl  left renal vein ; crosses mark the ventral hypoechoic part of the pancreas developmental variant of the pancreas annular pancreas : zl  confluence , dw  duodenal loop surrounded by normal pancreatic tissue in some patients the lobular architecture of the pancreas is so evident that it raises the suspicions of postinflammatory areas of fibrosis after chronic pancreatitis ( chp ) ( fig . moreover , in the elderly and obese patients , the areas of increased echogenicity observed in the parenchyma are also suggestive of chp . the knowledge concerning possible echostructure and echogenicity variations in the pancreas in healthy persons depending on age and volume of the adipose tissue in the pancreatic parenchyma is fundamental in the differential diagnosis . chp is excluded due to the lack of calcifications and normal presentation of the pancreatic duct . on the other hand , in the initial stage of chp , the fibrous changes in the pancreatic parenchyma are usually discrete . in such cases , lobular parenchyma of the pancreas , undilated pancreatic duct , normal size of the gland , no degenerative changes in the parenchyma , even echo distribution endosonographic image of chronic pancreatitis : the parenchyma of the head and body of the pancreas ( arrows ) is heterogeneous , has enhanced structure ; hyperechoic bands of connective tissue are visible ( fibrosis ) another reason for diagnostic errors might be the course of the splenic artery , which may cross the tail of the pancreas several times and in transverse planes , mimic slight cysts . the doubts , however , are resolved by doppler examination ( power or color doppler ) ( fig . course of the splenic artery ( t ) through the tail of the pancreas  transverse section . color doppler examination the errors in the assessment of the pancreas belonging to this group may result from the contiguity of the caudate lobe of the liver and other organs or intestinal loops that surround the head of the pancreas , the presence of the vessels and bile ducts as well as lymph nodes in the vicinity of the gland . the hypertrophic caudate lobe may have low echogenicity , which might be suggestive of a hypoechoic focal lesion . such a presentation requires the differentiation from a tumorous lesion in the head of the pancreas or from lymphadenopathy ( fig . 9 a , b ) . for this purpose , us examination should be performed in several planes or ct should be conducted . the duodenum filled with semifluid chyme may mimic a hypoechoic tumor of the tail of the pancreas . a similar area may be found in the region of the head of the pancreas when the proximal part of the duodenum undergoes dilatation . in such cases the peristalsis , which causes the  disappearance  of the lesion , should be observed . the cause , however , may also be the tumor of the head of the pancreas or in the region of the suspensory muscle of the duodenum ( ligament of treitz ) or an inflammatory tumor in the course of acute or chronic pancreatitis ( fig . 10 ) . a pancreatic tumor may also be imitated by rare duodenal tumors of adenoma or adenocarcinoma types as well as by hematomas in the wall of the duodenum , particularly in patients treated with anticoagulants . further examples present the duodenal diverticula , particularly the large ones and filled with fluid contents . the lesion mimics a hypoechoic tumor in the region of the head of the pancreas ( arrow ) . neoplastic duodenal tumor ( tu ) involving a half of the intestine periphery and infiltrating the head of the pancreas ( pc ) . the arrow indicates normal five - layer wall of the duodenum , unaffected by the tumor hypoechoic focus in the projection of the tail of the pancreas lesion in the course of acute pancreatitis ( arrow ) ; highly dense , limited fluid area when the left hypochondriac region , the spleen and left kidney are examined , one may visualize a lesion of heterogeneous inner echostructure , which suggests the presence of a tumor in this region . the differential diagnosis should include the tumor of the tail of the pancreas or of the left adrenal gland as well as the stomach filled with fluid contents in a patient who is inadequately prepared for us examination . this may also attest to the dilatation of the stomach caused by a considerable enlargement of the head of the pancreas ( advanced carcinoma of the head or an inflammatory change ) as well as to other types of obstruction of the upper gastrointestinal tract . diagnostic difficulties may also be caused by the presence of the horseshoe kidney , in particular when the isthmus joining the kidneys mimics altered or dilated pancreas . in such cases , the us probe should be placed in several planes in order to reveal the connection in the region of inferior poles of the kidneys . cystic or solid tumors of the pancreas may also be mimicked by a pancreatic pseudoaneurysm which has direct contact with a large artery , such as splenic , gastroduodenal or pancreaticoduodenal arteries , and more rarely with venous vessels such as splenic vein or branches of the superior mesenteric vein . it forms as a result of the damage to the wall of the vessel affected by an inflammatory reaction with consequential blood outflow to the region of the pancreatic parenchyma into the space enclosed in a pseudocapsule . in order to confirm the presence of a vascular lesion , a color and/or power as well as spectral doppler examinations should be performed , although angio - ct is used more often ( fig . when the connection between the pseudoaneurysm and the pancreatic duct exists ( usually in the course of chp or acute pancreatitis  ap ) , bleeding into the gastrointestinal tract may occur . the term hemosuccus pancreaticus denotes an acute condition of the abdomen in which bleeding occurs from the lumen of the vater 's papilla , or more precisely from the system of the excretory ducts of the pancreas . it is difficult to visualize the fragmentary dilatation of the wirsung 's duct in imaging scans . such a presentation in patients with chp is considered specific for this disease and together with the pseudoaneurysm in the projection of the pancreas , it allows for establishing the diagnosis ( doppler or angio - ct examinations are required ) . pancreatic pseudoaneurysm ( arrow ) visualized in color doppler examination  a result of the damage of pancreaticoduodenal artery , a complication of ap the situation is similar in the case a thrombus in the aneurysm of the splenic artery . no signs of flow on doppler examination may lead to an erroneous diagnosis of a hypoechoic focal lesion of the tail of the pancreas ( and more rarely , of the body ) , i.e. in a site that is difficult to interpret in transcutaneous us examinations . diagnosis , it is helpful to visualize it in several planes and after drinking a preparation that will cause the acoustic window enabling to localize the  organ .  ct constitutes a method of choice . lesion caused by lipid infiltration of the mesentery , localized below the normal location of the pancreas in patients with obstructive jaundice , the dilatation of the common bile duct ( cbd ) is encountered . in transverse scans , its considerable enlargement and contents , usually made up from sludge , resemble a tumor of the head of the pancreas ( fig . wide common bile duct and hepatic duct are also characteristic of cholestasis caused by a tumorous lesion in the head of the pancreas . if us is non - diagnostic , further examinations , mainly ct , should be proposed . in the differential diagnosis the cysts of the cbd should also be included , i.e. congenital ductal malformations , which might be mistaken for cystic lesions of the head of the pancreas or cystic neoplastic tumors . dilated common bile duct ( asterisk ) ; to be differentiated from the tumor of the head of the pancreas , dilated wirsung 's duct ( pw ) hypoechoic tumor of the head of the pancreas ( carcinoma  marked with crosses ) . metastases to peripancreatic lymph nodes ( arrows ) enlarged lymph nodes , nodal packages in the projection of the pancreas are in many cases difficult to distinguish from pancreatic tumors ( fig . such a problem might be solved by performing the examination is several planes . in the differentiation between the pancreatic tumor and pathologies in the retroperitoneal space , the pancreatic tumor impresses on the superior mesenteric vein from the superior side and the lesions in the retroperitoneal space  from the inferior side , by which the vessel is moved upwards . in rare cases , one should also bear in mind a similar structure of granulomas in the course of sarcoidosis or castleman 's disease . this particularly concerns the differentiation between inflammatory tumors and focal neoplastic lesions . an erroneous diagnosis may entail improper treatment or decisions to delay or abandon it . . a slight tumor may be difficult to visualize especially with altered , decreased echogenicity of the entire gland . in rare cases , examiners fail to visualize the mass of the tumor ( fig . 17 ) . on the other hand , inflammatory lesions or outcomes of ap also present low echogenicity , which constitutes a basic source of diagnostic errors . malignant lesions may be suspected when the surrounding lymph nodes are enlarged , thrombosis is present or the pancreas is fragmentarily enlarged without changes in its echo - structure . an early symptom of the tumor in the head of the pancreas may also be slight enlargement of the main pancreatic duct to approximately 23 mm . in each instance of such a finding , further , more precise imaging examinations should be recommended , usually ct or eus . visible dilated wirsung 's duct ( arrow ) and slight cysts caused by obstruction in the projection of the tail of the pancreas ( c ) . during surgery carcinoma of the head of the pancreas tru - cut  tissue biopsy ) the assessment of the size of the tumor is also significant in terms of its infiltration into adjacent structures , including vessels , and its resectability . the reason for inhibited assessment of the size may be gases or chyme in the stomach and intestine as well as excessive adiposis of the integuments , greater omentum and mesenteric root . it should be remembered to adequately prepare the patient for the examination , particularly when the pathology of the pancreas is suspected . pancreatic carcinoma is usually poorly vascularized and the vessels are usually visible only on its periphery . similar images are presented by inflammatory tumors , around which contrast enhanced doppler examination reveals areas of necrosis that do not undergo enhancement in relation to normal pancreatic parenchyma . contrast agents usually improve the diagnostic accuracy of ultrasound , particularly in the case of hypervascular pancreatic carcinomas which are confirmed in approximately 10% of tested tumors . the increased tissue perfusion is also observed in a certain percentage of neuroendocrine tumors ( net ) or in fragments of large nets ( fig . the application of transducers with higher frequencies and harmonic imaging option also considerably affect the assessment of pancreatic tumor vascularity . still , however , the differentiation between inflammatory lesions from non - vascularized foci of necrosis and poorly vascularized adenocarcinomas , remains a problematic issue . a. hypoechoic focal lesion in the tail of the pancreas ( arrow ) visualized in the transcutaneous ultrasound examination . b. the same lesion after the administration of the contrast agent sonovue  enhanced in the arterial phase ( arrows ) . presentation of the endocrine tumor of the pancreas moreover , a layer of tissue which does not show the presence of neoplastic cells may be found in the surroundings of carcinoma . this is usually related to the increased volume of the stroma , presence of the inflammatory reaction that accompanies the neoplasm and degenerative , necrotic lesions in the enlarging tumor . carcinoma of the head of the pancreas ( hypoechoic area ) lesion surrounded by outer hyperechoic reactive layer . in transcutaneous us examinations , such a layer may cause diagnostic mistakes what is more , secondary neoplastic lesions , such as malignant lymphomas and leukemias , may develop in the pancreas . the gland becomes involved mainly in the course of gastric carcinoma and more rarely in the neoplasms of the duodenum , bile duct and large intestine . furthermore , the more and more common gastrointestinal stromal tumors ( gist ) should be born in mind . they originate from the wall of the gastrointestinal tract , may be localized beyond the lumen of the intestine and frequently adhere to the pancreas . moreover , errors may result from the differentiation between primary lesions in the pancreas and metastases ( fig . the metastases of lung carcinomas , especially small cell lung carcinoma , mammary gland carcinoma and abdominal neoplasms are dominant . the reported cases of metastases also included renal , ovarian , colonic and hepatocellular carcinomas . for the differentiation with primary lesions , us presentation should be interpreted together with other clinical findings . hypoechoic tumor on the border of the body and tail of the pancreas ( arrow ) . single metastatic lesions to the pancreas may be erroneously interpreted as primary lesions in the case of inflammatory lesions in the pancreas , the image of acute and chronic pancreatitis manifests significant differences except for the acute phase of chp in which the changes might be similar or even identical to those in ap . therefore , distinguishing between these two types of pancreatitis becomes possible only after the regression of the acute phase . in the healing process following ap , the pancreas usually returns to its normal state . in the case of chp , however , lesions such as fibrosis , calcifications , pancreatolithiasis and abnormal image of the pancreatic duct persist and determine the diagnosis ( fig . the dilated pancreatic duct may be observed in the course of chronic pancreatitis and in tumors of the head of the pancreas . in the case of a considerable narrowing of the duct ( usually due to pancreatic carcinoma ) , the distally located wirsung 's duct widens to such a degree that it may resemble a large cyst of longitudinal shape . if the wirsung 's duct undergoes fragmentary dilatation , it might be mistaken for the splenic artery crossing the body and tail of the pancreas . the dilated pancreatic duct may also be misinterpreted as the splenic vein . in both case , large calcified concrement in the head of the pancreas ( arrow ) , considerably dilated main duct ( wirsung ) . fibrosis in the region of reduced pancreatic parenchyma tumor of the head of the pancreas ( tu ) , dilated wirsung 's duct ( crosses ) due to cysts , splenic vein (  ) moreover , us images of cysts with dense contents ( necrotic tissue , bleeding into the cyst ) , cystic tumors and solid ones may be similar ( fig . the differentiation is difficult and frequently , the us - guided biopsy determines the diagnosis . similarly to the differentiation between inflammatory and neoplastic lesions , us , or sometimes even ct , is rarely a sufficient criterion and the final opinion concerning the character of the lesion belongs to a cytopathologist upon biopsy ( fig . us - guided aspiration biopsy ( fnab ) enables to minimize false negative results below 10% , particularly when it is controlled by eus . nevertheless , due to a relatively large percentage of false negative cases , it is successively replaced by eus . differentiation of a focal lesion with dense contents ( arrows ) ( inflammatory or neoplastic tumor ? or necrotic lesions ? ) . the patient with the history of ap , during diagnosis large tumorous lesion in the projection of the head of the pancreas . guided fnab of the tumor ; open biopsy channel and hyperechoic needle is visible ( marked with arrows ) cystic tumors of the pancreas constitute a particular diagnostic problem . in this case , the accuracy of the cytological examination constitutes 2777% and only symptomatic lesions and those greater than 56 cm are qualified for the biopsy . what is more , cytological examination does not allow for collecting materials which enable the assessment of other diagnostically important parameters such as the level of neoplastic markers , amylase , lipase , mucin protein as well as viscosity of the fluid from a punctured cyst . verification of preoperative imaging examinations a rare and benign pancreatic tumor is lipoma . its us presentation may indicate carcinoma or , in the case of slight lesions  a cyst . accessory spleen is most frequently localized in the region of the tail or body of the pancreas and shows lower echogenicity than the pancreas . it requires the differentiation with a neuroendocrine tumor , cystic neoplasm , cyst of great density and secondary lesions mainly metastases . in such cases , ct or intraoperative sonography constitute reference examinations that allow for the collection of the material for histopathological tests , assessment of a malignant lesion in terms of its resectability leaving the margin of the pancreatic tissue ( fig . hypoechoic tumor of the body of the pancreas ( arrow ) which needs to be differentiated from a neuroendocrine lesion , secondary tumors and small cyst or cystic tumor the paper presented different anatomical variants of the pancreas , pathological changes of the adjacent structures and diseases of the pancreas itself that might be problematic to diagnose , which may lead to errors in us examination description . sonography is a recognized and valuable diagnostic method . nevertheless , to a large degree , it is also subjective . many of the ultrasound symptoms may not be documented in any objective or quantitative way . this especially refers to the diagnosis of pancreatitis and differentiation of the character of focal lesions based on us presentation . one should bear in mind that a single symptom is of less diagnostic value than a group of symptoms . for instance , fibrosis of the pancreatic parenchyma as a single parameter is not meaningful for chp diagnosis , contrary to the group of symptoms , such as fibrosis , calcifications , pancreatolithiasis or abnormal wirsung 's duct . still , the differential diagnosis of focal solid lesions remains the prime problem of imaging examinations of the pancreas . the major aim of the us examination is early detection of pancreatic neoplasm ( carcinoma ) . improper performance of the examination or a failure to perform a repeated scan when the conditions for the assessment of the pancreas are not favorable or , what is worse , description of normal pancreas when it is not clearly and entirely visible , constitute errors . authors do not report any financial or personal links with other persons or organizations , which might affect negatively the content of this publication and/or claim authorship rights to this publication .
the differential diagnosis of the focal lesions in the region of the pancreas is difficult due to the similarity of clinical and radiological pictures of neoplastic and non - neoplastic lesions . 
 this paper presents the most common causes of errors in ultrasound diagnosis of pancreatic pathologies . 
 attention was paid to the errors resulting from the structural variants of the pancreas and those caused by the neighborhood of intestine , stomach and other organs or vessels . moreover 
 , the article presents mistakes in the interpretation of ultrasound images of normal pancreas as well as its inflammatory and neoplastic lesions . 
 the errors and mistakes in question were divided into three categories : 1 ) mistakes related to the anatomical structure of the pancreas ( anatomical variants , echostructure and echogenicity , course of the splenic artery ) ; 2 ) mistakes related to anatomical structures localized in the vicinity of the pancreas ( caudate lobe of the liver , other organs and intestinal loops surrounding the head of the pancreas , vessels and bile ducts , lymph nodes in the region of the pancreas or duodenal diverticula and tumors ) ; 3 ) mistakes related to the pathologies of the pancreas ( inflammatory and neoplastic lesions including differentiation between inflammatory tumors and malignant masses ) . in spite of the progress of imaging techniques , the differential diagnosis of focal solid lesions remains the prime problem of imaging examinations of the pancreas . 
 the major aim of the ultrasound examination is early detection of pancreatic neoplasm . 
 improper performance of the examination or a failure to perform a repeated scan when the conditions for the assessment of the pancreas are not favorable or , what is worse , description of normal pancreas when it is not clearly and entirely visible , constitute errors .