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  • BILIARY TRACT AND PANCREAS

    Pancreatic endosonograph y: Clinical TNM staging compared to histology

    TL TIO, MD, Pl 1D

    ABSTRACT: Endosonography has been reported to be effective in the staging of gastrointestinal carcinoma. Pancreatic carcinom::i ts included in the new (1987) TNM classification. Rcscctability is abandoned in favour of depth of tumour invasion. In the author's preoperative study, endosonography was ac• curale for staging of tumour catt>gories, anJ early stages of disease could be distinguished from advanced carcinomas. The presence or absence of regional lymph nodes can be detected. Tissue diagnosis hy biopsy and endosonography- guidcd cytolob'Y is now possible. This imaging technique will become the stand- ard procedure for the staging of pancreatic carcinoma. Can J Gastroenterol 1990;4(9):57l-575

    Key Words: End.osonograJ)hy, Hiswlogy. Pancreatic carcinoma, TNM staging

    L' endosonographie pancreatique: La classification TNM clinique comparee a l'histologie RESUME: On a rapportc l'efficac1te de l'endosonographie dans la classification des cancers gastro-intestinaux. Le cancer du pancreas relcve maintenant de la nouvelle classification TNM (1987). La rcsecabilite a etc abanJonnce et fait place a la profondeur de !'invasion tumorale. Dans notre etude prcopcrawire, l'endosonographie a perm is la classification exactc de.s categories de tumeurs; elle a egalement aide a Jistinguer !es cancers aux premiers stades de leur evolution, des canccn; avances. La presence ou !'absence d'extension aux ganglions lym- phariques a ete decelee. Le diagnostic portanr sur les tissus preleves par cytoponc- tion a l'aiguille echoguidee est desonnais possible. Cette techni4uc d'imagerie deviendra la procedure standard Jans la classification des cancers du pancreas.

    CONVENTIONAL ABDOMINAL ultrasound is a standard imaging technique for evaluation of patients with pancreatic diseases. This proce- dure, however, is often hampered by rhe presence of bowel gas and adipose tis- sue. Endoscopic retrograde cholangio-

    pancreatography (ERCP) is accurate fo r the detection and stag ing of pancreatobiltary abnormal itics. Endo- scopic ul trasonography, genera lly known as endosonography, was developed to improve sonographic im- ages by direct approach co the target of

    Academic Medical Center, Department ofGascroenr.erology-HeJ)atology, Amsterdam, The Netherlands

    Correspondence and re/mnt.1: Dr TL Tiu, Acadenuc Medical Center, Department of Gascroenterology-Hepacology, Meihergdreef 9, l l 05 AZ Amsterdam, The Nerherlarul.s. Telephone 020-566-9111. Fax 020-566-4440

    interest via the gastrointest inal lumen {1-9). Recently, staging of pancreatic carcinoma has been included in the new (1987) TNM classifica ti on ( 10, 11 ). In a prospective stuJy, endo- sonography was performeJ preopcra- t1ve I y to assess the accuracy and limitations of cndosonography in the TNM staging of pancreatic and ampul- lary carcinoma.

    INSTRUMENTS For pancreas endosonography the

    author has been using Olympus echoendoscopes EU-M2 and EU-M3. The latter emits a switchable fre4uency of 7.5 or 12 MHz and a biopsy channel for cndosonography-guided cytology or biopsy or v1deoechocndoscope (VU- M2) (Figure I) . Recently, a small catheter echoprobe which can be intro- duced into the biopsy channel of a for- ward-viewing large calibre gastroscope became avai lable (Figure 2). The specifications of these instruments are summarized in Table I.

    INVESTIGATION TECHNIQUES

    The transgastric approach ,1 llows clear imaging of the body and tail of the pancreas because of the topographic anatomical relationship between the stomach and pancreas (Figure 3 ). For examinatton of che entire head of the pancreas, a transduodenal approach is usually necessary. The configuration of the stomach plays a crucial role for im- aging of che pancreas. A long extended

    572 CAN J GASTROENTEROL VOL 4 No 9 DECEMBER 1990

  • Pancreatic endosonography

    Figure l) An OlymJJUS prototype videoechoeruloscope (VU-M2) with a small echoprobe (e) attached at the tip of a side-viewing duodenoscope (11) . Note the smaller diameter of the echoprobe compared tO the gastrn- scope

    Figure 2) An Olympu., />rototyf,e catheter echoprnhc ( e), which can he introduced through the instrumental channel of a large calilrre ga.mosco/1e

    TABLE 1 Technical data of various Olympus echoendoscopes Echoendoscope EU·M2 EU·M3 VU·M2 (video) Catheter echoprobe Endoscope Side-viewing Side-viewing Side-viewing GIF-ITlO I GIF-IT20 Echoprobe length 42 mm 42 mm 44 mm 140 cm (catheter) Diameter 13 mm 13 mm 10.4 mm 3 mm Frequency 7.5 or 10 MHz 7.5 MHz/ 12 MHz" 7.5 MHz 7 MHz Depth of penetration 10 cm 10 cm/ 3 cm 10 cm 3 cm Axial resolution 0.2 mm 0.2 mm / 0.12 mm 0.2 mm -0.2-0.3 Tile catheter echoprobe Is radial scanning. while oil echoendoscopes ore mechonlcol radial scanning (I 8d5 or 36lf ). Only the EU-M3 hos copob/1/ty for endoU/trosonogrophy-gulded puncture or biopsy. "Switchable frequency

    Figure 3) Anatomic scheme (pnstenar view) shows the relationship between the stomach and the surrounding orgam. sp Spleen; lk Left kid- ney; P Pancreas; l Liver

    stomach provides clear imaging of the entire pancreas. In the case of stomach after partial resection (Billroth I or II}, adequate imaging of the pancreas is dif- ficult or impossible. Patients after a

    Figure 4) Endosonogram of a hypoechoic pancreatic carcinoma (t) obstructing the com- mon hile duct ( cbd) and pancreatic duct ( pd) , a 'double duct lesion.' In Lymph nodes suspected of meta.~tascs

    total gastrectomy should not undergo endosonography because the pancreas cannot he visualized sonographically.

    The most important landmark for a transgastric approach is the splenic vem, which is localized dorsally ad- jacent to the body and tail of the pancreas. The entire ~plen ic vein can be followed from the splennportal con-

    CAN] GASTROENTEROL VOL 4 No 9 0ECEMRER 1990

    fluence to the splenic hilum. By the transduodenal approach, the head of the pancreas is imaged between the duodenal wall and the mesenteric ves- sels. Cross-sectional images ana logous to computed tomography should be made for standardization of cndosono- graphy images.

    INTERPRETATION OF ENDOSONOGRAPHIC IMAGES

    The interpretation of pancreatic carcinoma is comparable to trans- cutaneous ultrasonography. For class- ifying ductular abnormalities, criteria used for the interpretation of ERCP must be incorporateJ. A pancreatic car- cinoma is imaged as a hypoechoic tumour usually obstructing the main W irsung duct associated with a pres- tenotic dilatation of the pancreat ic and common bile ducts. Thus, the cause and extent of the 'double duct lesion' can be imaged (Figure 4). Occasionally in- traducrnl tumours originating from the wall of the pancreatic duct can be found. The intraducral polypoid pat-

    571

  • TIO

    TABLE 2 Endosonography criteria for 1987 TNM classification of pancreatic car- cinoma T Primary tumour Tl Hypoecholc tumour limited to the

    pancreas Tl a Tumour 2 cm or less in greatest

    dimension Tl b Tumour more than 2 cm in

    greatest dimension T2 Hypoechoic tumour extends

    directly to any of the following: duodenum. bile duct. peripan- c reatlc tissue

    T3 Hypoechoic tumour extends to any of the following: stomach, spleen. colon. adjacent large vessels

    Tx Primary tumour cannot be assessed N Regional lymph nodes NO No regional lymph node metastasis Nl Regional lymph node metastasis Nx Regional lymph nodes cannot be

    assessed M Distant metastases MO No distant metastases M 1 Distant metastases: Hepatic

    metastasis, peritoneal dissemi- nation

    Mx Distant metastases cannot be assessed

    Figure 5 ) Endosonogram of an early pancreatic carcinoma (T) extended into the dilated pancreatic duce (PD). P Pancreas; SV Splenic vein

    tern may represent proliferation of the epithelium of the pancreatic duce or the carcinoma itself. Recently, pancreatic carcinoma was incorporated into the new ( 1987) TNM classification (Table 2).

    Staging of distant metastases, how- ever, should be excluded due to the limited penetration depth of ultra- sound. Therefore, liver metastases and peritoneal dissemination may not be imaged.

    574

    Figure 6) A Endosonogram of extensive pancreacic carcmoma (1) wuh retroperitoneal extension adjacent tO the aorta (ao). cv Cava! vein; In Lymph nodes suspected of metastases. B Corresponding computed tomography shows a tumour mass ( t) extending co the aorta ( ao) . cv Cava/ vein; msa Mesenter1c superior arc:ery; sc Stomach; d Duodenum

    CLINICAL TNM ST AGING Pancreatic head carcinoma usually

    causes obstruction of the common bile duct. Thus, obstructive jaundice is the most common clinical symptom. The prognosis, however, remains poor despite advantages of diagnostic modalilies ( 12-14). The size and extent of pancreatic carcinoma may play an important role in the prognosis (15, 16). In contrast, obstructive jaundice due to carcinoma of the body and/or tail of the

    pancreas is rare except when there 1s a very extensive rumour mass. Ampullary carcinomas, however, may cause obstructive jaundice even in the early stage of disease (17). The new (1987) TNM classification should he used for staging carcinomas of the head of the pancreas. Therefore, the common bile duct and duodenum are used as demar- cation marks for T2 carcinoma. Early carcinomas are therefore more fre- quently expected to be found in the

    CAN J GASTROENTEROL VO