E d i t o r i a l
Echoendoscopie digestive
V. G I L L A R D Lidge (Belgique)
Endoscopic ultrasonography
En carcinologie, on souligne toute l'importance du staging pr6op6ratoire des tumeurs malignes sur l'impact des d6cisions th6rapeutiques et sur le pro- nostic.
L'endoscopie permet la visualisation directe d'une tumeur et la r6alisation de pr61~vements biopsiques de celle-ci, mais elle n'apporte aucun renseignement sur l'extension en profondeur de la 16sion.
Le CT-scan est utile pour le diagnostic et le bilan d'extension des cancers digestifs, particuli~re- ment en d6montrant l'existence de m6tastases distance, mais il n'est pas fiable pour d6finir l'extension locale de la tumeur primitive.
I1 est impossible d'obtenir une image, en section transversale, de la paroi digestive par l'ultrasono- graphie conventionnelle, par le CT-scan ou par la r6sonance magn6tique nucl6aire, ~ cause de cer- rains probl6mes techniques tels que l'interposition de structures osseuses ou gazeuses, le faible pou- voir de r6solution ou le temps d'acquisition trop 61ev6. L'examen intraluminal contourne ces limita- tions grfice ~i une approche directe de la paroi et des organes adjacents.
L'6choendoscopie, examen non invasif de seconde intention, utilise un transducteur h ultra- sons fix6 ~ l'extr6mit6 d'un endoscope souple.
Grgice h la proximit6 du transducteur, des fr6- quences 61ev6es (7,5 et 12 MHz), procurant une haute r6solution de l'image, pourront 6tre utili- s6es. On obtient ainsi des informations utiles quand les autres techniques d'imagerie m6dicale restent non concluantes.
L'image 6choendoscopique de la paroi digestive se pr6sente comme cinq couches d'6chog6n6icit6 diff6rentes : deux couches hypo6chog6nes et trois couches hyper6chog6nes. Ces cinq couches corres- pondent avec exactitude h la stratification histolo- gique.
Grhce h l'6choendoscopie, il sera possible de r6aliser la stadification des cancers digestifs selon la classification TNM qui est actuellement univer- sellement accept6e.
Cette m6thode d'investigation est plus sensible et plus sp6cifique que toute autre m6thode d'ima- gerie m6dicale invasive actuellement disponible.
In carcinology, the importance of pre-operative staging of malignancy on the therapeutic decision- making and on prognosis should be stressed.
Endoscopy allows direct visualization of a tumor and biopsy sampling but no information is provi- ded as to the depth extend of the lesion.
Thanks to CT-scan, diagnosis and staging o f G1 tract cancer is made possible, especially since CT- scan is able to detect distant metastasis ; however CT-scan is not reliable as to identifying the local extend of the primary cancer.
Cross sectional imaging o f the gut's wall by ultra- sonography, CT-scan or M R I is limited by low resolution, by interferences o f intervening structures and by long acquisition time. Intraluminal scanning overcomes these situations by a direct approach of
the target lesion and obtains a close scanning or intraparietal ,structures.
Endoscopic ultrasonography is a second-level non-invasive investigation ; the equipment consists of an ultrasonic probe connected to the end o f a flexible endoscope. Because of the vicinity of o f the transducer, deep penetration o f the ultrasonic beam is not necessary, which allows higher sonographic frequencies with greater resolution. The information about the gastrointestinal wall obtained by this method is not provided by any other imaging tech- nique.
The major advantage o f E U S is the ability to investigate the intestinal wall and adjacent organs and to evaluate gastro-intestinal tumors according to the T N M classification. EUS of the GI wall
A c t a E n d o s c o p i c a V o l u m e 2 4 - N ~ 1 - 1 9 9 4 1
Cet article des Editions Lavoisier est disponible en acces libre et gratuit sur archives-acen.revuesonline.com
shows the wall to be a five-layered structure of different echogenecities in good correspondance with the real h&tological layers. Then the genetic tissues of a tumor can be decided by studying the relationship between the localization of the tumor inside the wall and the layer structure.
EUS becomes a promising method for the dia- gnosis of extrahepatic eholestasis and for preopera- tive staging of GI tract malignancy, particularly of pancreatic cancer. It will predict, before surgery, the local resectability and presence of satellite lymph nodes. Furthermore it is helpful for the staging and the follow-up of non-Hodgkin's lyre-
phoma. This fairly recent technique can be conside- red as an impressive improvement thanks to its 360 ~ radial scanning with real time dynamic analysis and its direct approach o f the target lesion.
This method is more specific and sensitive than any other invasive radiological exam currently avai- lable.
Tissue characterization still remains the main problem. Nevertheless several medical centers are studying the possibility of characterizing tissues by ultrasonography. . .
2 Volume 24 - N ~ 1 - 1994 Acta Endoscopica
Cet article des Editions Lavoisier est disponible en acces libre et gratuit sur archives-acen.revuesonline.com
