key: cord-0005052-zos44qmw authors: Dewit, O.; Fiasse, R.; Vanheuverzwyn, R. title: Apport de l'endoscopie dans la maladie de Crohn date: 2003 journal: Acta Endoscopica DOI: 10.1007/bf03028414 sha: 4195142098f351284cd7a2b4227f654310a95386 doc_id: 5052 cord_uid: zos44qmw Two types of endoscopic lesions are observed in Crohn's disease (CD): active lesions or scars, frequently associated. Following their localization at different sites of the digestive tract, they are defining the type of disease. Ileo-colonoscopy is an important step of the initial characterization of the lesions, completed with biopsies helful for the differential diagnosis between CD and ulcerative colitis or infectious colitis An endoscopy is only repeated in front of a new clinical problem or when a change of treatment is required. In case of severe colitis, colonoscopy may detect septic lesions as well as deep ulcers indicating severe evolution with a bad prognosis. After surgery, in most of the cases ileocolonoscopy detects recurrent lesions whose severity is linked to an unfavourable clinical evolution and permits therapeutic adaptation. Since the risk of colorectal cancer in CD predominant in the colon is probaly underestimated, a systematic colonoscopy after 8 to 10 years of evolution should be performed for the screening of malignant lesions. Colonoscopy is also useful for the treatment of complications of CD, i. e. dilatation of benign strictures, as well as localization and treatment of distal bleeding. Upper digestive tract endoscopy, endosonography, enteroscopy, videocapsule and endoscopic retrograde cholangio-pancreatography are other contributive methods within the field of correct indications. muqueuse avoisinante et efface la vascularisation normalement visible. 9 (Ed~me : aspect << boursouflE >> de la muqueuse et surtout de la sous-muqueuse, rEduisant le calibre de la lumiEre du tube digestif. On note parfois un aspect nodulaire, qui associ6 5 des ulc6rations linEaires, constitue l'image typique en pav6s (<< cobblestone >>) (Fig. 2) . Ulcdr~es 9 UlcErations aphtoi'des : elles sont dvocatrices de la maladie. Ces lesions ont quelques millimEtres, sont punctiformes, a fond blanc et entourEes d'un halo rouge et se trouvent au sein d'une muqueuse normale (Fig. 3) . 9 UlcErations superficielles : de taille et de forme variables, elles peuvent confluer et donner de larges plages ulcErEes longitudinales (en rails) ou en cartes g6ographiques (Fig. 4) . 9 UlcErations profondes : Egalement de taille et de forme variable (Fig. 5 ). Dans les cas graves, l'ulcdration met la musculeuse h nu (aspect striE du fond de l'ulcEre) et dEcolle la muqueuse. Cet aspect tEmoigne de la sEvEritE de la maladie. 9 UlcErations stEnosantes : association d'oedEme et d'ulc6rations emp~chant parfois le passage de l'endoscope (Fig. 6) . Fistules : typiques de la maladie. Elles sont plus frEquentes au niveau de l'intestin grEle qu'au niveau du cElon. L'orifice fistuleux, cedEmateux et ErythEmateux, a quelques millimEtres de diamEtre et est difficile h mettre en Evidence en endoscopie (indication d'un examen radiologique) (Fig. 7 ). 9 Cicatrices d'ulcErations : zones blanch~tres, de formes variables, planes ou dEprimEes, parfois asso-ciEes ~t une convergence des plis ou des valves. 9 Pseudopolypes : correspondent ~ des <, cicatrices hypertrophiques >> de zones ulcErdes. Ils sont de taille et de nombre variables et peuvent parfois rEtrEcir la lumiEre intestinale. 9 StEnoses cicatricielles : de longueur variable, symEtriques, rEguliEres au sein d'une muqueuse peu remaniEe. Darts la MC, ces lesions sont isolEes ou associEes entre elles. Leur localisation contribue 5 dEfinir le type de maladie EtudiEe (ilEale, ilEo-colique, colique, gastro-duodEnale, ano-rectale). Parmi ces diffErents types de lesions, les ulc6rations superficielles et profondes, les stEnoses ulcErEes ou cicatricielles, l'aspect en paves et les pseudopolypes sont les lesions 616mentaires endoscopiques dont la description est la plus reproductible entre dif-fErents observateurs [1, 2[ . Pour cette raison, le GETAID (Groupe d'Etudes Thdrapeutiques des Affections Inflammatoires du tube Digestif) a conqu le CDEIS (<< Crohn's Disease Endoscopic Index of Severity >~) [3] . Dans cet index, 5 zones sont dtudides : l'ilEon, le c6lon droit, le cElon transverse, le c61on gauche et sigmoide, et enfin le rectum. L'opErateur estime pour chaque zone 6tudiEe le pourcentage de la surface lEsionnelle, le pourcentage de surface ulcErEe (superficielles ou profondes) et la presence de stEnoses. En additionnant les diffErents rEsultats selon le modEle 61aborE, l'index est calculE. I1 s'agit 1~ du seul index endoscopique validE dans la MC. I1 est relativement complexe et est utilis6 essentiellement dans l'Evaluation d'essais thErapeutiques. I1 n'y a cependant pas de correlation entre l'activitE clinique Eva-luEe par le << Crohn's Disease Activity Index,> (CDAI), les paramEtres biologiques, le pronostic et cet index endoscopique [4] . L'ilEocoloscopie occupe une place importante dans Ia prise en charge initiale de la MC. Devant un tableau clinique (diarrhEes, sang, douleur...) compatible avec une colite inflammatoire, l'examen endoscopique dEfinit la gravitE et la topographie des lesions. Des prE16vements histologiques compl~tent le diagnostic. Le c61on rEagit souvent de faqon semblable h des agresseurs diffErents, c'est pourquoi le diagnostic final dolt tenir compte de toutes les informations cliniques, biologiques, bactEriologiques et histologiques. Par exemple, Tedesco et at. [5] ont dEmontrE que 38 % des diarrhEes glairo-sanglantes dont l'aspect 6voque une colite inflammatoire idiopathique sont en fair des colites infectieuses. Les infections qui raiment le plus les lesions endoscopiques de MC sont la tuberculose [6] [7] [8] et l'infection it E. Coli O157 : H7 [9] . D'autres bactEries (salmonelles, Yersinia, Chlamydia trachomatis), parasites (amibiase, schistosomiase), ou virus (CMV, HerpEs) se manifestent par des lesions endoscopiques parfois semblables h celles de la MC. Habituellement, lorsque la symptomatologie se prolonge au-del~ de 2 semaines, une maladie inflammatoire de l'intestin est suspectEe, mais certaines colites infectieuses ont aussi une Evolution chronique (TBC, amibiase, campylobacter, etc.). Parmi les autres diagnostics diffdrentiels, citons : les colites ischEmiques en particulier dans leur forme chronique [10] ; les lesions ErythEmateuses des pEridiverticulites, l'ulcEre solitaire du rectum, les colites mEdicamenteuses (aprEs anti-inflammatoires non-stEroi'diens notamment), la maladie du greffon contre l'hEte, les colites neutropEniques, la maladie de Behqet, etc. Les caractEristiques endoscopiques qui permettent de diffErencier la MC de la rectocolite ulcEro-hEmorragique (RCUH) sont rappelEes dans le tableau I. I1 faut souligner qu'il n'est pas toujours ais6 de distin- Des contr61es endoscopiques syst6matiques, ~t intervalles r6guliers, sont habituellement inutiles. L'indication d'un examen de contr61e est de r6pondre une question que pose l'6volution clinique ou biologique d'un patient : 9 Doute sur la nature r6elle de la pouss6e, en particulier en absence de syndrome inflammatoire, pour la distinguer d'autres origines aux sympt6mes (troubles fonctionnels, infection .... ). 9 Impression clinique de r6sistance ~ un traitement. Indication d'utilisation d'une nouvelle classe de m6dicament (immunosuppresseur, anti-TNF, etc.). 9 D6finir la nature inflammatoire ou cicatricielle, b6nigne ou maligne, d'une st6nose suspect6e. 9 Etablir un bilan 16sionnel avant traitement chirurgical afin de ne pas m6sestimer une 16sion pouvant 6tre trait6e dans le m6me temps op6ratoire. Comme la population g6n6rale, le patient atteint d'une MC peut d6velopper un cancer colorectal. Le risque relatif semble plus important dans les formes coliques de la maladie alors qu'il est similaire en cas d'atteinte il6ale isol6e. Ekborn et al. [11] ont 6tudi6 une s6rie de 1655 patients souffrant de MC. Le risque relatif est de 1,0 dans les formes il6ales isol6es, de 3,2 dans les formes il6ocoliques et de 5,6 dans les formes coliques isol6es. Ces r6sultats sont ?~ comparer ~ ceux obtenus par les m~mes auteurs dans la RCUH : 14,2 dans la colite distale et de 33 dans la pancolite. Pour Gillen [12] , le risque de cancer colorectal est vraisemblablement identique dans les deux maladies lorsque l'on consid6re des segments coliques malades 6quivalents et des dur6es d'6volution identiques (RR de 18 pour la MC et de 19 dans la RCUH). I1 ressort de ces 6tudes que le risque de cancer colorectal dans la MC est probablement sous-estim6 en comparaison du risque traditionnellement 6voqu6 dans la RCUH. Diff6rentes 6tudes d6crivent dans la MC une s6quence dysplasie-cancer semblable h celle d6crite dans la RCUH [13] [14] [15] [16] [17] [18] . Friedman et al. [19] d6crivent 16 % de dysplasie ou de cancer dans une population de 260 MC colique suivie aprbs une dur6e de leur maladie de 8 ans ou plus. Dans les cas positifs, 45 % des anomalies 6taient retrouv6es au premier examen et 55 % lors d'examens ult6rieurs r6alis6s tousles 2 ans. IX paraR donc logique de proposer un d6pistage similaire ~ celui de la RCUH : apr6s 8 h 10 ans d'6volution d'une MC colique, r6alisation de 4 biopsies sys-t6matiques tousles 10 cm en plus de l'examen histologique des anomalies endoscopiques observ6es. I1 serait int6ressant de d6finir des sous-groupes devant b6n6ficier davantage de ce type de d6pistage en fonction par exemple de la s6v6rit6 de l'atteinte initiale, de la pr6sence de fistules, d'une colectomie segmentaire diminuant le risque... La fr6quence des coloscopies pourrait ~tre modul6e en fonction de ces sous-groupes de m6me qu'en fonction des anomalies initiales constat6es (absence de dysplasie = espacer les contr61es; dysplasie = renforcer les contr61es et envisager chirurgie). Cette surveillance endoscopique est h r6aliser en phase quiescente de la maladie car la r6action inflammatoire induit des modifications 6pith61iales pouvant ~tre confondues avec la dysplasic recherch6e [20] . L'aspect endoscopique du cancer colorectal (CCR) compliquant les MICI est souvent diff6rent des 16sions n6oplasiques habituelles : plus petite taille, aspect moins bourgeonnant. Le diagnostic pr6coce est difficile. La distinction entre polype ad6no-villeux et pseudopolypes est 6galement difficile. Des biopsies ~ la pince ou une polypectomie sont surtout indiqu6es dans certaines circonstances : diam~tre sup6rieur 1 cm, surface irr6gulibre, h6morragie spontan6e, couleur inhabituelle [21] . Des biopsies autour de la 16sion sont 6galement utiles h la recherche de dysplasie. Un cas particulier est celui des segments coliques exclus (Fig. 8 ). Un travail de Leteurtre et al. du groupe de Lille [22] d6crit 30 % de dysplasie de bas grade ~ l'analyse de 23 pi6ces de proctectomie. Cette intervention avait 6t6 r6alis6e en raison de la persis- Geographically mapped superficial ulcer. tance de sympt6mes aprOs une exclusion rectale d'une dur6e m6diane de 4 ans. D'autres auteurs [23] , qui ont surveill6 25 rectums exclus, ont d6pist6 3 cancers (2 ad6nocarcinomes du rectum et 1 cancer 6pi-dermoide de l'anus). Ces patients doivent donc b6n6ficier d'un contrOle endoscopique r6gulier (tousles 2 ans). La meilleure pr6vention est 6videmment la r6section chirurgicale du segment exclu. Un patient souffrant de maladie de Crohn/~ localisation colique et qui pr6sente une poussEe s6v~re selon les crit6res cliniques classiquement admis (nombre de selles, pr6sence de sang, signes gEn6raux .... ) b6n6ficie d'un examen endoscopique pour deux raisons : --recherche de signes endoscopiques de gravit6 (ulc6rations profondes, mise h nu de la musculeuse...) ; --r6alisation de biopsies ~ la recherche d'une complication infectieuse (parasitaire ou virale) afin d'am61iorer le traitement. Dans les lesions graves, le traitement sera plus ~, agressif, : hospitalisation, corticoides IV, nutrition ent6rale ou parent6rale, infliximab. I1 faut souligner l'excellente correlation entre les signes endoscopiques de gravit6 et le r6sultat anatomopathologique [24] ; ce qui confirme la fiabilit6 de cet examen dans l'estimation globale de la gravit6 de la colite. La pr6sence de signes endoscopiques de gravit6 a une valeur pronostique p6jorative en terme de nombre de fistules et de recours h la chirurgie [25] . Une colite s6v~re non compliquEe (~non chirurgicale~>) ne constitue pas une contre-indication & la rEalisation d'une coloscopie gauche voire totale. Le taux de complications de l'examen en cas de colite grave est faible comme cela a 6t6 d6montr6 dans la R C U H [26] (1 dilatation colique sur 85 examens) et dans la MC [24] (1 m6gac61on et 1 choc toxique sur 78 examens). L'examen doit ~tre r6alis6 par un endoscopiste exp6riment6, avec une insuffiation minimale et une exsuffiation maximale. I1 est interrompu d6s que l'on d6c61e des signes de gravit6. On le r6alise le plus t6t possible et il peut 6tre rdp6t6 si n6cessaire en cas de non-r6ponse au traitement initial pour r66valuer les 16sions et r6orienter le traitement : poursuite ou renforcement du traitement m6dical ou traitement chirurgical. Cela apporte 6galement des indications au chirurgien sur le type de chirurgie la plus adapt6e pour le patient. Environ 80 % des patients atteints de maladie de Crohn subiront une r6section chirurgicale au cours de leur vie [27] . La r6cidive clinique, apr6s r6section chirurgicale survient dans 30 ta 50 % des cas apr6s 5 ans et dans 45 ~ 75 % des cas apr6s 10 ans [28, 29] . L'endoscopie est un bon examen dans l'6valuation de la r6cidive ( Fig. 9 ) : aspect de l'anastomose (ulc6r6e, st6nos6e), atteinte du segment digestif d'amont (si anastomose il6o-colique), voire d'amont et d'aval (si anastomose colo-colique). La r6cidive endoscopique survient pr6cocement. Rutgeerts et al. [28] retrouvent des 16sions il6ales pr6anastomotiques dans 73 % des cas, 1 an apr~s une r6section il6o-caecale. Une 6tude du G E T A I D [30] d6crit des 16sions 3 mois seulement apr6s l'intervention clans 60 % des cas 6tudi6s. L'aspect endoscopique de la r6cidive aurait une valeur pronostique [31] . Apr6s un suivi de 3 ans, l'6volution de ces patients r6v~le qu'il existe une corr61ation entre les 16sions d6crites h l'endoscopie initiale et la r6cidive des sympt6mes cliniques. L'analyse actuarielle permet de pr6dire l'6volution de diff6rents sous-groupes (Tableau II) : 9 Absence ou rares 16sions ~ l'endoscopie initiale (scores i0 h il) : le patient reste asymptomatique dans plus de 90 % des cas apr6s 3 ans et apr6s 6 ans. En d'autres termes, plus la r6cidive endoscopique est importante et pr6coce, plus la maladie est agressive et justifie un traitement ad6quat. Le m o m e n t id6al pour la r6alisation de l'endoscopie postop6ratoire reste cependant ~ d6finir (6-12 mois apr~s l'intervention chirurgicale ?). Dans une s6rie de 980 patients suivis durant 26 ans [32] , la survenue de st6noses chez les patients souffrant de MC avec atteinte colique est estim6e 13,5 %. La majorit6 des st6noses sont b6nignes et peuvent ~tre trait6es par dilatation pneumatique, sous contr61e direct de la vue, via un ballon introduit dans le canal op6rateur de l'endoscope. Les r6sultats des dilatations sont meilleurs dans les st6noses : --courtes (moins de 4 cm de long) ; --mod6r6es (entre 5 et 10 mm de diam~tre) ; --sans angulation ; --isol6es ; --peu inflammatoires. La pression d'insufflation du ballon d6pend du calibre et du mat6riel utilis6 (Fig. 10 ). La dur6e de la dilatation varie de 30 secondes ~ 2 minutes en r6p6tant au besoin la manoeuvre apr6s avoir recen-tr6 le ballon. Le soulagement du patient est imm6diat si la dilatation est efficace et se maintient ~ long terme dans 45 ~ 65 % des cas [33, 34] . Le taux de complication est de 3 g 8 % darts les s6ries publi6es [33, 35] . La combinaison d'une dilatation hydraulique et de l'injection de corticost6roides ~ in loco ~ semble utile : dans une s6rie belge [36] de 13 patients, aucun n'a n6cessit6 de chirurgie compl6mentaire apr6s une surveillance de 47 mois. L'existence d'une st6nose doit faire 6voquer la pos-sibilit6 d'un cancer. Parmi 132 patients avec r6tr6cissement colique [32] , 9 d'entre eux avaient une st6nose maligne soit 6,8 % de l'ensernble des st6noses coliques observ6es. Diff6rents crit~res endoscopiques orientent vers ce diagnostic : st6nose asym6trique, rigide, infranchissable par l'endoscope, ~ bords irr6guliers, nodulaires et friables. L'observation doit ~tre compl6t6e par la r6alisation de biopsies ou de brossages. N6anmoins, si les pr616vements ne r6v61ent pas de cellules n6oplasiques mais que l'aspect endoscopique est 6vocateur, un traitement chirurgical doit ~tre propos6 en raison du risque d'une extension, essentiellement sous-muqueuse, de la tumeur. Ces st6noses malignes ne doivent pas 6tre dilat6es en raison d'un danger de perforation et/ou d'essaimage n6oplasique. Hdmorragie L'h6morragie basse massive est une complication rare (1%) de la maladie de Crohn comme en t6moigne le petit nombre de s6ries publi6es [37, 38] . L'origine de l'h6morragie est plus souvent une ulc6ration colique que il6ale. L'il6ocoloscopie d6finit le site du saignement dans environ 60 % des cas [37] et peut Etre associ6e ?a un traitement h6mostatique. L'endoscopie apporte 6galement des renseignements si un traitement chirurgical imm6diat ou diff6r6 devient n6cessaire. La pr6valence des 16sions 0esophagiennes, gastriques et duod6nales dans la MC est variable d'apr6s les s6ries : 0,5 h 13 % dans les s6ries les plus anciennes et 17 h 75 % dans les s6ries plus r6centes [39] [40] [41] . Cette apparente augmentation de la pr6valence est expliqu6e en partie par la pratique plus fr6quente de l'endoscopie. La pr6valence exacte est difficile d6terminer car il ne s'agit pas toujours d'6tudes bas6es sur l'ensemble d'une population donn6e. Une s6rie franqaise de 129 patients sur une cohorte de 195 patients a 6t6 6tudi6e par endoscopie (eso-gastro-duod6nale : 28 % des patients avaient des 16sions parmi lesquelles l'histologie montrait 19 % de granulomes [43] . Chez les enfants, la pr6valence est plus 61ev6e (60 %) et les manifestations cliniques dyspeptiques sont 6galement plus fr6quentes [44] . Toutes les 16sions d6crites dans le tube digestif inf6rieur se retrouvent au niveau du tube digestif sup6rieur. Les plus souvent rencontr6es sont l'6paississement des plis, les 6rosions (Fig. 11) , les ulc6rations longitudinales ou serpigineuses voire des st6noses. Pour ces derni6res, des dilatations pneumatiques ont 6t6 r6alis6es avec succ~s. Les 16sions du tube digestif sup6rieur sont parfois solitaires mais le plus souvent associ6es ~ des 16sions ilEales et/ou coliques. L'int6r~t d'une endoscopie haute syst6matique dans tout bilan initial de maladie de Crohn il6ocolique est incertain mais peut s'av6rer utile dans les colites ind6termin6es oia des biopsies syst6matiques peuvent r6v61er des granulomes, m6me dans une muqueuse macroscopiquement normale. Chez des patients suspects de MC non confirm6e par les examens habituels (endoscopie haute et basse, transit gr~le, ...) l'ent6roscopie est parfois utile au diagnostic. Perez et al. [45] ont ainsi d6crit des 16sions chez 4 patients sur 8 adressfs pour suspicion de MC (retard de croissance chez l'enfant, diarrh6es et douleurs chez l'adulte) et sans an6mie occulte. Le r6sultat de l'ent6roscopie perop6ratoire a une influence directe sur le type de traitement chirurgical dans 10 ~ 61% des cas [46, 47] . Son int6r~t dans la pr6diction de la r6cidive n'est cependant pas d6mon-tr6 m~me en cas de 16sions laiss6es en place lors du traitement chirurgical [48, 49] . L'ent6roscopie est 6galement utile dans la raise au point et le traitement des st6noses j6junales ou il6ales (biopsies-dilatation hydraulique) [50, 51] . Utilis6e depuis 2000, l'6valuation de l'examen du gr~le par vid6ocapsule dans la MC n'a fait l'objet que de rares travaux [52, 53] . Nettement moins invasive que l'ent6roscopie, l'examen doit obligatoirement ~tre pr6c6d6 d'une radiographie de l'intestin gr~le pour exclure une st6nose organique, contre-indication absolue h son utilisation. L'examen pourrait r6v61er des 16sions d6butantes non encore visibles sur les clich6s radiographiques. Trop peu de donn6es existent actuellement pour utiliser cette technique coQteuse en routine (Fig. 12) . Non ulcerated 9 Mucosal erythema : isolated, patchy or distributed as longitudinal bands (Fig. 1) , Erythema is clearly delineated from normal mucosa, deleting completely the normal microvascular pattern. 9 Oedema : the swollen submucosa gives a blistered aspect to the intestinal wall with a narrowing of the lttmen (Fig. 2) . Sometimes the relief is nodular with linear ulcers giving a cobblestone-like pattern. Ulcerated 9 Aphtoid ulcers : these little lesions of a few millimeters appear as white points surrounded by a red ring in a normal mucosa (Fig. 3) . 9 Superficial ulcers : of different size and shape, sometimes confluent, giving large ulcerated areas with an aspect of longitudinal railways or geographic maps (Fig. 4) . 9 Deep ulcerations : also of different size and shape (Fig. 5) . The deep penetration of the ulcer lets sometimes appear the muscular layer (striated aspect of its bottom) and may cause a detachment of the mucosa. The presence of such lesions is a valuable sign of severity. 9 Stenosing ulcerations : oedema associated with ulcerations reduces the diameter of the intestinal lumen, impeding the progression of the endoscope (Fig. 6) . Fistulae : typical of the disease, they are more frequent in the small intestine than in the colon. The orifice of the fistula is edematous and erythematous (Fig. 7) , has often a diameter of a few millimeters and is not easily found at endoscopy (indication of radiological examination). Scars 9 Scars of ulcers : they appear as whitish areas of variable shape, flat or depressed, sometimes associated with a confluence of mucosal folds or valves. With regard to the interobserver agreement, superficial and deep ulcers, ulcerated strictures or scars, cobblestone pattern and pseudopolyps are the elementary lesions whose description is the most reproducible [1, 2] . Taking into account these features the French Association "'GETAID" has proposed a CDEIS, i.e. a "Crohn's Disease Endoscopic Index of Severity" [3] . Five areas were evaluated : ileum, right colon, transverse colon, left colon and sigmoid, finally the rectum. The observer evaluates for each area : the percentage of the surface bearing lesions, the percentage of surface bearing ulcers (superficial or deep) and the presence of strictures. After addition of these different results, a score can be calculated. This index is the only endoscopic index validated for CD but it is relatively complex and thus restricted to therapeutic trials. However there is no correlation between clinical activity assessed by the Crohn's disease activity index (CDAI), biological parameters, prognosis and the CDEIS [4] . The role of ileocolonoscopy is important when a CD is first taken in care. When clinical symptoms (diarrhea, intestinal bleeding, abdominal pain) are evoking an inflammatory colitis, endoscopy will define the severity of the disease and the topography of the lesions and also permits to sample biopsies useful for the differential diagnosis. Since the colon can react in the same way to different aggressive factors, the final diagnosis must take into account clinical, biological, bacteriological and histological data. For example Tedesco et al. [5] have observed that as much as 38 % of a series of patients with symptoms evoking IBD (diarrhea with blood and mucus, etc.) had in fact an infectious disease. Endoscopically the diseases most mimicking CD are tuberculosis [6] [7] [8] and infection by E. coli 0157:H7 [9] . Other infectious agents, bacteria (Salmonella, Yersinia, Chlamydia trachomatis), parasites (amebiasis, schistosomiasis) or virus (CMV, Herpes) are giving endoscopic lesions quite similar to those observed in Crohn's disease. When symptoms last more than 2 weeks after the onset, an IBD is suspected but some infectious colonic diseases may have a chronic course (tuberculosis, amebiasis, infections by Campylobacter species, etc.). The differential diagnosis must also take into account other chronic evolutions such as ischaemic colitis [10] , peridiverticulitis, solitary rectal ulcer, drug colitis (e.g. NSAIDs), graft-versus-host disease, neutropenic colitis, Behqet disease, etc. Table I summarizes the endoscopic features which contribute to the differential diagnosis between Crohn's disease and ulcerative colitis (UC). This is sometimes difficult, especially when an "ulcerativelike Crohn's disease" is mimicking an ulcerative colitis. In the same way, severe colitis is difficult to assess, particularly at initial flare-up because of the extent and severity of lesions. 9 To define the nature, inflammatory or scar, benign or malignant, of a suspected stricture. 9 To establish an overview of the lesions before a surgical treatment in order to avoid an underestimation of lesions which can be treated by the same operation. Other studies describe a similar evolutive sequence from dysplasia to cancer in CD as in UC [13] [14] [15] [16] [17] [18] . In a group of 260 colonic Crohn' s diseases followed during a period of 8 years or over, 16 % ofdysplasia or cancer have been observed by Friedman et al. [19] . In the subgroup of positive cases 45 % of the anomalies were identified at the first examination, and 55 % during the period o f follow-up examinations performed every 2years. It is thus rational to propose a systematic screening similar to that proposed for UC : after a period of 8 to 10 years of evolution. It is recommended to perform 4 biopsies in any 10 cm of colonic segments in addition to those usually sampled on the observed lesions. For the future, it would be interesting to define subgroups which must benefit in priority from such a screening program, considering for example the severity of the initial presentation, the presence or fistulae, the possible protective effect of a segmental colectomy, etc. In such sub-groups the planning of further colonoscopies would be modulated following the first anomalies screened (i.e. absence of dysplasia = longer intervals between the controls, dysplasia = enhanced endoscopic controls and surgery to discuss). This endoscopic surveillance should be performed during periods of quiescent disease, avoiding pitfalls due to inflammatory epithelial processes mimicking a true dysplasia [20] . is not similar to the common CRC : non protruding, small size lesions, making an early diagnosis more difficult. Moreover the differential diagnosis between adenovillous polyps and pseudo polyps is hard to assess. Biopsies or polypectomy should be performed in the following conditions: diameter of a polyp > 1 cm, irregular surface, spontaneously bloody, atypical color [21] . Biopsies surrounding the lesion are useful to the diagnosis of dysplasia. Excluded colonic segments are a peculiar problem. A study from the Lille Group [22] has revealed 30 % of low grade dysplasia in 23 resected specimens from proctectomy performed for persistent symptoms after a rectal exclusion over a median period of 4 years. In another study [23] in a group of 25 patients followed for excluded segments, 3 cancers have been discovered: 2 rectal adenocarcinoma and 1 anal epidermoid cancer. Patients with excluded colonic or rectal segments have a risk of cancer, as illustrated in Fig. 8 and should undergo every two years a regular endoscopic screening. Otherwise the best prevention is surgical resection. In case of severe flare-up of colonic Crohn' s disease following the classical symptoms (i.e. increased number of stools, bleeding, poor general condition...) a patient may be candidate to colonoscopy for the following reasons: --demonstration of endoscopic markers of severity (deep ulcers, uncovered colonic muscular layer...) ; --sampling of biopsies to rule out an infectious disease (parasites, virus), so improving the therapeutic approach. In case of severe endoscopic lesions the treatment will be more "aggressive" : hospital care, IV corticosteroids, enteral or parenteral nutrition, infliximab. There is an excellent correlation between endoscopic data and histopathological results [24] , which confirms the reliability of endoscopy in the global assessment of severe colitis. The presence of severe lesions bears a bad prognosis with a high incidence of fistulae and an impressive call for surgery [25] . An uncomplicated ("non surgical") severe colitis is not a contraindication for a distal or a total colonoscopy. As it was demonstrated for UC, the rate of complications is low [26] : Around 80 % of the patients suffering from Crohn's disease will undergo a surgical resection during their life [27] . A relapse is observed in 30 % to 50 % of the cases after 5 years and in 45 % to 75 % after 10 years [28, 29] . Endoscopy is the best way to assess a relapse: aspect of the anastomosis (ulcerations, stricture, etc.), lesions of the digestive segment proximal to an ileocolic anastomosis, or lesions above and below in case of colo-colic anastomosis. [28] . A study of the GETAID group has found the same lesions in 60 % of the cases only 3 months after surgery. The endoscopic aspect of the recurrence would have the value of a prognosis marker [31] . After a follow-up of 3 years, a good correlation has been found between the initial aspect of the lesions and the relapse of the symptoms. An actuarial analysis provided the following predictive profile of the sub-groups: 9 Absence or rare lesions at the first endoscopic control (score iO to il) : 90 % of the patients remained asymptomatic after 3 years and also after 6 years. 9 Mild lesions (score i2) : 85 % of the patients remained asymptomatic after 3 years and 60 % after 6 years. 9 More diffuse lesions (score i3): 60 % of the patients remained asymptomatic after 3 years and 15 % after 6 years. 9 Diffuse lesions and anastomotic ulcerations (score i4) : all the patients became symptomatic within the 4 years. Only 30 % of this subgroup were in fact asymptomatic after one year (Table 11) . Score il : rare ileal aphtoid lesions (< or = to 5). Score i2 : multiple ileal aphtoid lesions (> 5) or isolated areas with larger lesions or stomacal lesions. Score i3 : diffuse aphtoid ileitis with inflammatory mucosa. Score i4 : diffuse ileitis with larger ulcerations, nodules and/or stenoses. In other words, the more important is the early morphological recurrence, the more aggressive is the disease, a reason to introduce or to enhance the treatment. Nevertheless the ideal moment for performing the endoscopy remains questionable (6 months after surgery ?). The development of a stricture in patients with Crohn's disease of the colon has been estimated to 13.5 % in a series of 980 patients followed during a period of 26 years [32] . Most of the strictures are benign and can be treated under visual control by hydraulic dilatation using a balloon catheter introduced via the channel operator of the endoscope (Fig. 10) . The ideal stricture to dilate would be short (no more than 4 cm of length) mildly tight (between 5 to 10 mm of diameter), non angulated, single, and with low inflammation. Inflation pressure is directly related to the diameter of the segment and the type of equipment used (Fig. 10) . The time for dilatation is variable: from 30 seconds to 2 minutes, the procedure being repeated if necessary after a correct insertion of the balloon. In case of efficient dilatation, the symptomatic relief is immediately obtained and maintained at long term in 45 to 65 % of the cases [33, 34] . The rate of complications is 3 to 8 % in the published series [33, 35] . Hydraulic dilatation combined with local injection of corticosteroids has been useful: in a Belgian series of 13 patients, none has been operated within a 47 month follow-up period [36] . A stricture can be of malignant origin. Out of 132patients bearing a colonic stricture, 9 had a mali-gnant stenosis, i.e. 6.8 % of the whole group of strictures observed [32] . Different [37, 38] . Colonic ulceration is more frequently responsible than ileal ulceration. Ileocolonoscopy can demonstrate the site of bleeding in 60 % of the cases [37] and can offer an opportunity for an hemostatic procedure. On the other hand endoscopy provides guidelines for a surgical emergency or for a delayed operation. [43] . The prevalence is higher in childhood (60 %) with an increased frequency of dyspeptic symptoms [44] . The proximal lesions described are quite similar to those observed m the distal part. The most frequently encountered lesions are: swelling of the folds, erosions, longitudinal or irregular ulcerations (Fig. 11) , and even strictures for which hydraulic dilatation has been successful. In the majority of cases proximal lesions are combined with ileal or colonic Crohn's lesions. In current practice a systematic proximal endoscopic investigation in a new patient bearing distal lesions of CD is not recommended. However in cases of undetermined colitis, systematic gastroduodenal biopsies may contribute to the diagnosis by revealing granulomas in proximal mucosa with a normal macroscopic aspect. Enteroscopy may be useful in patients suspected of CD, but with diagnosis not confirmed by conventional investigations (upper and lower endoscopy, radiology of the small bowel). In such cases, Perez et al. [45] have observed enteral lesions in 4 patients out of 8 referred for suspicion of CD (delayed growth in a child, diarrhea and abdominal pain in adults) and without occult bleeding. Peroperative enteroscopy has contributed to determine the type of surgery in 10 to 61% of the cases in different series [46, 47] . Its predictive value for recurrence has not been evidenced even in cases of not resected lesions [48, 49] . Finally enteroscopy may be useful for the assessment and the treatment of jejunal or ileal strictures (biopsy-hydraulic dilatation) [5o,51] . Introduced in 2000 this procedure has been poorly evaluated in Crohn's disease and until now rare studies have been published [52, 53] . Less invasive than enteroscopy, videocapsule investigation is absolutely contra-indicated in case of stricture. Therefore a prior radiological examination of the small bowel is mandatory. The method would be able to detect primary lesions not recognized on RX plates (Fig. 12) . A lack of data limits nowadays a routine application of this expensive method in CD. The main targets of endosonography are the complications of Crohn's disease in the anorectal area : diagnosis of abscesses and fistulae, localization in relation to the sphincters, improved visualization of complex tracts [54, 55] . The technique may contribute to the differential diagnosis between CD and UC [56, 57]. The most striking differential feature in case of UC is the thickening of the 2 or 3 first layers of the 5 classically described layers. On the contrary, in CD a secto-rial interruption is frequently observed, and even a reduction of the number of layers indicating a transmural involvement. Therefore, this procedure could be useful in case of undetermined colitis, before considering surgery (ileo-anal or ileo-rectal anastomosis). In a series of patients with Crohn's disease the prevalence of primary sclerosing cholangitis (PSC) This must remain a daily concern for the any gastroenterologist, managing patients suffering .from Crohn's disease, a chronic ailment which may favour the repetition of often inappropriate examinations. Reproductibility of colonoscopic findings in Crohn's disease : a prospective multicenter study of interobserver variation Interobserver variation of colonoileoscopic findings in Crohn's disease Development and validation of an endoscopic index of the severity for Crohn's disease : A prospective multicentre study. 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