C-IV. Quiz: Learning EUS from Interesting Cases Room C 췌장 성균관대학교의과대학삼성서울병원소화기내과 Jong Kyun Lee Division of Gastroenterology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea 서론 내시경초음파검사 (endoscopic ultrasonography, EUS) 는여러가지췌장질환의감별진단에매우유용하다. 우선주요혈관들을기준으로췌장전체를모두관찰하면서병변을찾는다. 병변을이해하려면정상췌장소견을알아야한다. 정상췌장은균일하고미세한과립상이며 ( 소위소금과후추를뿌려놓은모습 ) 간보다약간밝게보인다. 그러나약간의비균일한부분은정상인에서도보일수있는데, 특히두부는체부나미부에비해비균일하게보인다. 그리고배측췌장이복측췌장에비해좀더밝게보인다. 주췌관의직경은두부, 체부, 미부에서각각 3, 2, 1 mm까지분지췌관은두부외에서는잘보이지않는다. 병변을발견하면초음파탐촉자를천천히움직이면서병변전체를여러번관찰하면서병변의특징, 즉위치, 범위, 모양, 에코양상, 체관, 주변혈관및장기와의관계등을파악함으로써췌장의각종염증성질환, 고형종괴, 낭성병변을감별진단할수있다. 본론 1. 췌장염 급성췌장염에서 EUS는진단목적보다는원인을찾기이해시행된다. 원인미상의재발성췌장염에서 EUS를시행하면미세담석, 분할췌장, 만성췌장염, 작은종양등의원인을발견할수있다. 1,2 만성췌장염의진단에 EUS는췌장실질과췌관의변화를모 두평가할수있고다른영상기법에비해조기변화를민감하게관찰할수있다. 만성췌장염이진단에이용되는지표는 5~13개로다양하다. 3 5 9개의지표를이용할경우 3개이상을만성췌장염의기준으로할때민감도 (83%) 와특이도 (80%) 의균형이가장적당하여진단기준으로많이적용된다 (Table 1). 2007년국제합의모임이있었고 Rosemont classification 을발표하였다. 6 이모임에서는 EUS 소견에대한정의와용어정리, 각지표의중요도순위, 그리고주기준과부기준으로분류하였다 (Table 2, 3). 이와같이함으로써모임에참석한전문가들의각소견에대한일치도가양호하였다 (κ >0.7). 그리고각소견들의중요도에차이를두어진단기준을마련하였다 (Table 4). 이러한기준은복잡한단점은있으나지표들에가중치를둔장점이있다. 2. 췌장선암 EUS의췌장선암발견율은 95~98% 로서 CT나 MRI 등다른검사방법에비해우월하다. 7 9 Multi detector CT (MDCT) 가해상도와 3차원재구성에의해혈관평가가많이향상되었으나 MDCT와의비교연구에서도 EUS가민감도에있어서앞서고있다. 10 EUS의가장큰장점은 2 3 mm까지의작은병변도식 Table 1. Criteria for the Diagnosis of Chronic Pancreatitis by Endoscopic Ultrasound Parenchymal criteria Ductal criteria Hyperechogenic foci Main pancreatic Duct dilation Hyperechogenic strands Duct irregularity Lobularity of contour of gland Hyperechogenic ductal margins Cyst Dilate side branches Stones 제 4 회 EndoFest Korea 235
Table 2. Rosemont Classification: Parenchymal Features of CP Feature Definition Major criteria Minor criteria Histologic correlation Hyperechoic foci with Echogenic structures 2 mm in length and width that shadow Major A Parenchymal based calcifications Lobularity Well circumscribed, 5 mm structures with enhancing rim and Unknown relatively echo poor center A. With honeycombing Contiguous 3 lobules Major B B. Without honeycombing Noncontiguous lobules Yes Hyperchoic foci without Echogenic structures foci 2 mm in both length and width with no Yes Unknown Cysts Anechoic, rounded/elliptical structures with or without septations Yes Pseudocyst Stranding Hyperechoic lines of 3 mm in length in at least 2 different directions with respect to the imaged plane Yes Unknown Table 3. Rosemont Classification: Ductal Features of CP Feature Definition Major criteria Minor criteria Histologic correlation MPD calculi Echogenic structure (s) within MPD with acoustic Major A Stones Irregular MPD contour Uneven or irregular outline and ectatic course Yes Unknown Dilated side branches 3 or more tubular anechoic structures each measuring 1 mm in Yes Side branch ectasia width, budding from the MPD MPD dilation 3.5 mm body or >1.5 mm tail Yes MPD dilation Hyperechoic MPD margin Echogenic, distinct structure greater than 50% of entire MPD in the body and tail Yes Ductal fibrosis Table 4. EUS Diagnosis of CP on the Basis of Consensus Criteria I. Consistent with CP A. 1 major A feature (+) 3 minor features B. 1 major A feature (+) major B feature C. 2 major A features II. Suggestive of CP A. 1 major A feature (+) <3 minor features B. 1 major B feature (+) 3 minor features C. 5 minor features (any) III. Indeterminate for CP A. 3 to 4 minor features, no major features B. major B feature alone or with <3 minor features IV. Normal 2 minor features, no major features 별이가능한점하다. 따라서 EUS는 1 cm 이하의작은종양에있어서는확실히 CT나 MRI보다우월한민감도의차이 (100% 대 60~70%) 를보인다. 11 그러나종양의발견에있어서 EUS의제한점도있는데, 만성췌장염이동반된경우, 경계가불분명한형태, 최근에급성췌장염을앓은경우에는종양의발견이어렵다. 12 EUS는종양의범위와주변혈관및림프절의관찰에좋은해상도를가져국소병기평가에도우수하다. 2002년 American Joint Committee on Cancer (AJCC) 에서그전까지주변주요혈관침범을모두 T4로분류했던것을상장간맥정맥 (SMV) 과 Table 5. EUS Criteria for Vascular Invasion by Pancreatic Cancer Loss or irregularity of the interface between tumor and vessel Intravascular tumor growth Non visualization of vessel with collateral circulation 간문맥침범 (PV) 은 T3, 복강동맥 (CA) 과상장간맥동맥 (SMA) 침범은 T4로분류하여 EUS의정확도성적이조금떨어졌으나여전히 T 병기결정에있어서 CT 등다른검사방법에비해좋은성적을보인다. 전체적인 T 병기정확도는 78~94% 이다. 7,8 그러나종양의크기에따라정확도의차이가있어작은종양은 EUS가탁월한정확도를보이나 3 cm 이상의큰종양에서는초음파투과에제한이있어먼쪽의경계나혈관과의관계를알기가어려워 CT보다낮은정확도를보인다. 따라서병기결정에있어서원격전이및 3 cm 이상의큰종양은 CT가, 작은종양은 EUS가우수함으로상호보완적이라고할수있다. EUS에의한혈관침범의기준은 Table 5와같다. 이러한기준에의한 EUS의혈관침범에대한민감도는 42~91%, 특이도는 89~100% 이다. 9 그러나혈관에따라차이가있어, 간문맥과비정맥에대한정확도는 EUS가높은반면에상장간막동맥과복강동맥에대해서는 CT가보다정확하다. N 병기에대한 EUS의정확도는 64~84% 이다. EUS에서악성림프절을시사하는소견은원형, 분명한경계, 1 cm 이상의크기, 저에코이며이 4가지소견을모두보이면악성의가능성 236 The Korean Society of Gastrointestinal Endoscopy
은 80~100% 이다. 13 3. 췌장낭종 췌장의낭성병변은매우다양한데, 임상적으로는가성낭종과신생물성낭종의감별, 장액성낭종과점액성낭종을포함한전암병변의감별, 악성변화여부등을확인하는것이중요하다 (Table 6). 특징적인임상적병력과급, 만성췌장염에동반된가성낭종과일부특징적인모양을보이는장액성낭선종은진단이쉬울수도있으나나머지많은췌장낭종은초음파또는 CT 소견만으로감별하기가쉽지않다. EUS를통해췌장의낭종성병변을감별하고자하는연구가많이있었다. 낭의개수와모양, 낭내부의에코, 낭벽, 격막, 고형종괴유무, 췌관과의관계, 주변췌장실질의변화등을관찰하는것이감별에도움을주며 EUS소견을통한낭성질환의감별정확도는약 80% 정도이다 (Table 7). 14 16 가성낭종은음주력, 췌장염의병력등의임상소견이중요하다. 낭벽은두껍고내부에찌꺼기나출혈에의한에코성물질이보이는경우가많다. 약 70% 에서췌관과연결되어있으나낭이크면확인하기어렵다. 또한주변췌장실질에만성췌 Table 6. Classification of Cystic Pancreatic Lesions Pseudocyst Common cystic pancreatic neoplasms Serous cystadenoma Mucinous cystadenoma IPMN Rare cystic pancreatic neoplasms Solid pseudopapillary tumor Acinar cell cystadenocarcinoma Lymphangioma Hemangioma Paraganglioma Solid tumor with cystic degeneration Pancreatic adenocarcinoma Cystic neuroendocrine tumors Sarcoma True epithelial cysts 장염소견이동반되어있으면감별에도움이된다. 장액성낭선종은 2 cm 이하의작은낭종이 6개이상모여있으며얇은낭벽및격막을가지고중심부분에섬유화 (central scar) 및석회가보이는것이특징이다. 그러나이와같은특징적인모양을보이는경우는 30% 정도이다. 낭종의크기가 2 cm 이상 (macrocystic) 또는개수가 6개이내 (oligocystic) 이며중심석회화없는경우에는다른낭종과감별이어렵다. 반대로수없이미세한낭종과격벽으로구성된경우에는고형성종괴로오인되기도한다. 점액성낭선종은 2 cm 이상크기의단발성또는다발성으로생기며두꺼운낭벽을갖고 15% 에서는가장자리에석회가동반된다. 고형성종괴가동반되면악성을시사한다. 고형성가유두상종양 (solid pseudopapillary tumor, SPT) 은젊은여성의췌장미부에호발하며크기가큰종괴가고형성분과출혈괴사에의한낭성분이같이보이는특징이있다. 그러나이러한소견은 SPT에만국한된것은아니고 SPT가대부분크기가커서 EUS로정확한평가나감별진단은제한적이다. Koito 등은낭종의모양을 6가지로분류하였는데신생물성낭종은 thick wall type, tumor protruding type, thick septal type, microcystic type 중하나였고비신생물성낭종은 thin septal type, simple type에속했다. 17 Sedlack 등은 EUS 소견과수술한병리소견을비교하여 3 mm 이상의두꺼운벽, 두꺼운격막, 고형종괴나주췌관의낭성확장소견등은악성또는악성잠재성낭종 ( 점액성낭선종, IPMN, 낭성내분비종양, 낭성선암 ) 을시사한다고하였다 ( 민간도 91%, 특이도 60%, 정확도 72%). 18 4. 췌관내유두상점액성신생물 (IPMN P) IPMN에서 EUS의역할은다른낭종과의감별, 악성여부, 병변의범위판정등에있다. CT, ERCP, MRCP 등다른다른검사방법으로도대부분에서는쉽게진단된다. 그러나 branch duct type의일부는다른낭종과비슷하게보이는경우가있는데낭종이좀더관형태로나타나고주췌관과연결되어있다. 또악성화를시사하는고형결절이나췌관벽의불규칙한비후 Table 7. EUS Findings of Pancreatic Cystic Lesions Pseudocyst SCN MCN IPMN Location head evenly body/tail head distributed Locularity unilocular multiple small unilocular or multilocular multilocular Wall thick thin thick thin Septae no thin thick no Calcification no central peripheral no Communication with pancreatic duct yes no no yes 제 4 회 EndoFest Korea 237
를관찰할수있고다른검사방법에비해정확도가높다 (92%). EUS에서악성가능성을시사하는소견으로는간결절, 림프절종대, 혈관침범, 10 mm 이상확장된주췌관, 30 mm 이상의분지췌관확장, 고형결절, 췌관벽비후등이있다. 19,20 이러한소견중에서특히작은고형결절, 췌관벽의비후등은다른검사방법으로는알기가어렵다. 따라서수술을하지않고경과관찰하는 IPMN에서 EUS를추적관찰방법의하나로이용하는것은이와같은미세한변화를파악하는데도움이된다. 또한수술을계획하고있는경우에병변이다발성으로분포하거나미만형인경우수술전에절제범위를평가하는데에도 EUS가도움이된다. 이경우관내초음파검사 (intraductal ultrasonography, IDUS) 는좀더고해상도를가지고 ERCP와동시에쉽게시행할수있어절제범위를결정하는데도움이된다. 21 5. 췌장신경내분비종양 신경내분비종양은대부분작고췌장이나주변십이지장, 위벽에위치하여초음파, CT, MRI 등의방법으로는발견율이 50% 이하이다. 반면 EUS의민감도는 82~94% 로서역할이중요하다. 대개경계가좋은저에코의둥근종양으로보이고크기가커지면혼합된에코또는낭성변화를보이기도한다. 임상적으로기능적과비기능적, 단발성과다발성, 췌장내부와외부또는전이여부를아는것이중요하다. CT나 somatostatin receptor scintigraphy (SRS) 는병변이국소적인지전이병변이있는지를아는데중요하며 EUS는췌장내의병변을찾는데다른어떤방법보다도민감도가우수하다. 그리고신경내분비종양의종류에따라그역할이다르다. 인슐린종은주로췌장에위치하여 EUS의진단정확도가높아임상적으로의심되나다른검사방법에서안보이는작은종양과다발성여부를평가하는데도움이된다. 가스트린종은췌장외에존재하는경우도많아 EUS의민감도도떨어지며 SRS를같이시행하면상호보완적이다. 수술전에종양의위치를 tattooing 하는역할로이용되기도한다. 결론 EUS 는췌장의다양한병변을관찰하고감별진단하는데매우유용하다. 그렇게하기위해서는췌장의정상소견을잘이해하고췌장전체를관찰하여야하며병변을천천히여러번관찰하면서특성을잘파악하여야한다. 참고문헌 1. Yusoff IF, Raymond G, Sahai AV. A prospective comparison of the yoeld of EUS in primary vs. recurrent idiopathic acute pancreatitis. Gastrointest Endosc 2004;60:673 678. 2. Tandon M, Topazian M. Endoscopic ultrasound in idiopathic acute pancreatitis. Am J Gastroenterol 2001;96:705 709. 3. Wiersema MJ, Hawes RH, Lehman G, et al. Prospective evaluation of endoscopic ultrasonography and endoscopic retrograde cholangiopancreatography in patients with chronic abdominal pain of suspected pancreatic origin. Endoscopy 1993;25:555 564. 4. Kahl S, Glasbrenner B, Leodolter A, et al. EUS in the diagnosis of early chronic pancreatitis: a prospective follow up study. Gastrointest Endosc 2002;55:507 511. 5. Sahai AV, Zimmerman M, Aabakken L, et al. Prospecive assessment of the ability of endoscopic ultrasound to diagnose, exclude, or establish the severity of chronic pancreatitis found by endoscopic retrograde cholangiopancreatography. Gastrointest Endosc 1998;48:18 25. 6. Catalano MF, Sahai A, Levy M, et al. EUS based criteria for the diagnosis of chronic pancreatitis: the Rosemont classification. Gastrointest Endosc 2009;69:1251 1261. 7. Varadarajulu S, Wallace MB. Applications of endoscopic ultrasonography in pancreatic cancer. Cancer Control 2004;11:15 22. 8. Varadarajulu S, Eloubeidi MA. The role of endoscopic ultrasonography in the evaluation of pancreatico biliary cancer. Gastrointest Endosc Clin N Am 2005;15:497 511. 9. Seicean A, Tantau M, Badea R. The applicability of radial endoscopic ultrasonography in pancreatic diseases. Clinical Imaging 2007;16:77 83. 10. Tamm EP, Loyer EM, Faria SC, et al. Retrospective analysis of dual phase MDCT and follow up EUS/EUS FNA in the diagnosis of pancreatic cancer. Abdominal Imaging 2007;32:660 667. 11. Ahmad NA, Lewis JD, Siegelman ES, et al. Role of endoscopic ultrasound and magnetic resonance imaging in the preoperative staging of pancreatic adenocarcinoma. Am J Gastroenterol 2000; 95:1926 1931. 12. Bhutani MS, Gress FG, Giovaninni M, et al. The no ensosonographic detection of tumor (NEST) study: a case series of pancreatic cancers missed on endoscopic ultrasonography. Endoscopy 2004;36:385 389. 13. Bhutani MS, Hawes RH, Hoffman GJ. A comparison of the accuracy of echo features during endoscopic ultrasound and EUS guided fine needle aspiration for diagnosis of malignant lymph node invasion. Gastrointest Endosc 1997;45:474 479. 14. Brugge WR, Lewandrowski K, Lee Lewandrowski E, et al. Diagnosis of pancreatic cystic neoplasms: A report of the cooperative pancreatic cyst study. Gastroenterol 2004;126:1330 1336. 15. Bhutani M. Role of endoscopic ultrasonography in the diagnosis and treatment of cystic tumors of the pancreas. J 2004;5:266 272. 238 The Korean Society of Gastrointestinal Endoscopy
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