5235-96Imaging In Acute Appendicitis: A Review RK JAIN, M JAIN, CL RAJAK, S MUKHERJEE, PP BHATTACHARYYA, MR SHAH Ind J Radiol Imag 2006 16:4:523-532 Key words : Acute appendicitis, Xray, USG, CT INTRODUCTION Acute appendicitis is the most common cause ofemergencyabdominalsurgery(1).Whilethediagnosisofacuteappendicitisisstilllargelythoughttobeaclinicalone,ameaningfulnumberofpatientsarefoundtohavenormalappendicesatsurgery.Theerroneousdiagnosisofthisacuteconditionhasledtoahighrate(8-30%)ofinappropriateremovalofthenormalappendix.Thishighrateneedstobebalancedwiththeproblemofbeingoverrestrictiveinthediagnosisofacuteappendicitis,whichmay allow uncomplicated appendices to progress toperforationandperitonitis(2).However the incidence of acute appendicitis requiringappendectomyhassignificantlydecreasedoverthepastthreeorfourdecade,andthetrendappearstocontinue.Someofthedecreaseinthenumberofappendectomiesisattributabletobetterdiagnosis(3).Withtheavailabilityofhigh-resolutionsonographyandspiralCTitispossibleto bring down these high rates of false positivitysignificantly.Fig.1: Different positions of the appendixANATOMY Thevermiformappendix,ablind-endingtubularstructure,arisesfromtheposteromedialaspectthececuminferiortotheileocecaljunction.Itvariesconsiderablyinlengthandcircumference,theaveragelengthbeingbetween7.5and10cms.Thepositionofthebaseoftheappendixisessentially constant, being found at the confluence ofthethreetaeniaecoliofthececum,whichliesdeeptotheMcBurney'spoint.Thefreeendoftheappendixishoweverfoundinvarietyoflocations.(Fig.1).Thedifferencein appendiceal position influences clinical findingsconsiderably(4).Inunusualcasesofmalrotationofthegut,orfailureofdecentofcecum,theappendixisnotintherightlowerquadrant(5).Theappendixhasitsownmesentry,themesoappendix,arisingfromtheinferiorpartofthemesentryoftheterminalileum,whichattachestothececumandproximalpartofthe appendix. The mesoappendix contains theappendicular artery, a branch of the ileocolic artery.Venousdrainageoftheappendixisviatheileocolicveinsand the right colic vein into the portal system. Thelymphaticdrainageoccurstotheileocolicnodesalongthecourseofthesuperiormesentericarterytotheceliacnodesandcisternachyli.TheafferentnervefibersfromtheappendixaccompanythesympatheticnervestotheT10segmentofthespinalcord,whichexplainswhyinappendicitis is sometimes referred to the periumbilicalarea.On histology, the submucosa contains numerouslymphatic aggregations or follicles. There is a roughparallel between the amount of lymphoid tissue in theappendix and the incidence of acute appendicitis, thepeakforbothoccurringthemidteens(3).PATHOPHYSIOLOGY Appendicitisiscommonlyassociatedwithobstructionoftheappendiceallumenduetofecalith.Obstructionmayalso be secondary to hypertrophy of lymphoid tissue,From the Department of Radiology, Quadra Medical Services Pvt. Ltd.Kolkata.India. Request for Reprints: Ranjit Kumar Jain, Quadra Medical Services Pvt. Ltd. 41, Hazra Road, Kolkata 700019. India. Received 21 May 2006;Accepted 10August 2006 [Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal

524524 RK Jain et al inspissatedbarium,gallstones,worms(ascaris),foreignbodies,ortumor.Followingobstructionoftheappendiceallumen,continuedmucus secretion and inflammatory exudation leads todistension,mucosaledemaandmucosalulcerationalongwith translocation of bacteria to the submucosa. Theswelling of appendix stimulates the nerve endings ofvisceralafferentfibersandthepatientperceivesvisceralperiumbilicalorepigastricpain.Withincreasingintraluminalpressures,furtherdistensionresultsinobstructedlymphaticandvenousdrainageandallows vascular congestion of the appendix. Theinflammatoryprocesssooninvolvestheserosa.Whenthe inflamed serosa of the appendix comes in contactwiththeparietalperitoneum,patientstypicallyexperiencethe classic shift of pain to the right lower quadrant.Intramuralvenousandarterialthrombosesensue,resultingingangrenousappendicitis.Fig. 2. Mucocele of the appendix. (a) Sonogram of the rightlowerquadrantobtainedwithalinear10-6-MHzprobe,showswell defined tubular cystic structure with some low- levelluminal echogenicity. (b) Transverse CT scan in anotherpatient obtained with oral contrast material reveals cysticlesion in relation to the cecum suggestive of mucocele.IJRI, 16:4, November 2006 Unrelenting tissue ischemia results in appendicealinfarctionandperforation.Ruptureoftheappendixwithspillageofpusintotheperitonealcavityresultsinlocalizedorgeneralizedperitonitis.Morecommonly,inflamedorperforatedappendixcanbewalledoffbytheadjacentgreateromentumandloopsofsmallbowelresultinginphlegmonousmassorparacecalabscess.Thissequenceisnotinevitableandsomeepisodesofacute appendicitis may resolve spontaneously if theobstructionisrelieved.Rarely,appendicealinflammationresolvesleavingadistendedmucus-filledorgantermedmucoceleoftheappendix.(Fig.2.)CLINICAL MANIFESTATIONS Appendicitisoccursinallagegroups.Itisrareininfantsbut becomes increasingly common in childhood andreachespeakincidenceinthelateteenageyearsandearlytwenties.Sexratioisequalbeforepubertyandmale-to-femaleratiois3:2inteenagersandyoungadults.Theratio again equalizes by the time patients reach theirmidthirties.Noracialpredilectionexistsforappendicitis.Adiagnosisofappendicitisusuallycanbemadeonthebasisofhistoryandphysicalexamination.Symptoms: Painistheprimesymptomofappendicitisandinitiallyislocated in the lower epigastrium or periumbilical area.Thepainsubsequentlylocalizestotherightlowerquadrant,whereitbecomesprogressivelymoresevere.Thisclassicpainsequenceisusualbutnotinvariable.Thedifferenceinappendicealposition,ageofthepatient,anddegreeofinflammation, accounts for variations in the clinicalpresentation.Anorexia nearly always accompanies appendicitis.Nausea, vomiting, and low-grade fever are common.Uncommonly,diarrheaorconstipationmaybeseen.Thesequence of appearance of symptom that is anorexiafollowedbypainandthenvomitinghasgreatdifferentialdiagnosticsignificance3.Ifvomitingprecedestheonsetofpain,thediagnosisshouldbequestioned.Signs: Thecardinalfeaturesofacuteappendicitisarelocalizedabdominaltenderness,rigidity,muscleguarding,painonpercussion,andreboundtenderness.Paininrightlowerquadrantwithpalpationoftheleftlowerquadrant(Rovsingsign)ishelpfulinsupportingaclinicaldiagnosis.Askingthepatienttocoughwillelicitasharppainintherightlowerquadrant(positivecoughsign).Witharetrocecalappendixtheanteriorabdominalfindings[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal525IJRI, 16:4, November 2006 arelessstrikingandtendernessmaybemoremarkedintheflank.Paininrightlowerquadrantwithhyperextensionof the right hip (psoas sign) demonstrates nearbyinflammationwhenstretchingtheileopsoas.Painintherightlowerquadrantwithpassiveinternalrotationoftheflexedrighthip(obturatorsign)indicatesthataninflamedappendixiscontactwiththeobturatorinternus.Laboratory findings: High level of C-reactive protein (>0.8 mg/dL) withleukocytosis and neutrophilia are the most importantlaboratoryfindings6.IMAGING Theclinicalpresentationofappendicitisisvariable.Whiletheclinicaldiagnosismaybestraightforwardinpatientswhopresentwithclassicsignsandsymptoms,atypicalpresentationsmayresultindiagnosticconfusionanddelayin treatment 4. Clinical diagnosis is more confusing inyoungandelderlypatients.Inaddition,manyotherclinicaldisorders present with symptoms similar to those ofappendicitisandthedifferentialdiagnosis3includesthefollowing:AcuteMesentericAdenitisAcutegastroenteritisMeckel'sDiverticulitisIntussusceptionCrohn'sdiseasePerforatedpepticulcerDiverticulitisEpiploicappendagitisUrinarytractinfectionUretericstonePrimaryperitonitisHenoch-SchonleinpurpuraYersiniosisDiseasesoftheMale:TesticulartorsionEpididymitisSeminalvesciculitisGynecologicdisorders:Pelvicinflammatorydisease(PID)OvariancystortorsionEndometriosisRupturedectopicpregnancyRectussheathhematomaCholecystitisSinceaccurateclinicaldiagnosisofappendicitisisdifficult,negativeappendectomyrate7canbeashighas20%.Unnecessarysurgeryforsuspectedappendicitisexposespatients to increased risks, morbidity, and expense 8.Radiological examination can reduce the number ofmisdiagnoses and negative laparotomies and help intreatmentofappendicealabscessesandinpostoperativecomplications.JudicioususeofgradedcompressionUSImaging in Acute Appendicitis525 &CTinpatientswithequivocalclinicalfindingsresultsinlowerfalse-negativeappendectomyrates(4).ConventionalRadiography Thoughplainfilmsarereportedtorevealabnormalitiesin50%ofpatientswithappendicitis(9),theyarenotspecific,notcosteffective,andcanbemisleading(8).Plainfilmsareindicatedfortheevaluationofapatientwithsuspectedappendicitisonlywhenotherdiagnosticprobabilities(e.g.,perforation,intestinalobstruction,ureteralcalculus)arealsoconsidered(8,10).Thevariousplainfilmfindingsthathavebeendescribedinappendicitisareasfollows:(8-11)" Appendicolith." Rightlowerquadrantgas" Increased soft tissue density of the right lowerquadrant" Separationofthececumfromrightextraperitonealfatplanes" Deformity of the cecal and ascending colon gasshadowoccurringduetoadjacentinflammatorymass" Localized ileus with gas in the cecum, ascendingcolonandterminalileum" Effacementoftherightextraperitonealfatline" Gasinperitoneumandretroperitoneum" GasfilledappendixBariumenemaexaminationmaybehelpfulinselectedpatients.Bariumenemaisperformedonanunpreparedbowel gently without any external pressure. Completefilling of a normal appendix effectively excludes thediagnosisofappendicitis.Nonfillingorincompletefillingof the appendix along with mass effect on the cecumsuggestsappendicitis(8),themasseffectbeingduetoabscess/inflammatoryreactionssurroundingtheinflamedappendix. The terminal ileum may be displaced ornarrowedbytheadjacentinflammatorymassandtheremaybethickeningofthemucosalfoldsoftheterminalileum.However,non-fillingofappendixmaybeseeninasmanyas10-20%ofnormalpatients.IthasbeenshownbySeheythatappendixfillsin92%ofnormalchildrenandhencefailureoftheappendixtofillinsymptomaticchildrenisasignificantfinding.Barium enema examination may also be useful inevaluatingcomplexcolonicabnormalitiesdetectedwithcross-sectionalimaging(4).Ultrasonography Ultrasonography (US) is valuable in the diagnosis ofdoubtful cases of appendicitis and is a cost-efficientadjuncttotheclinicalevaluation(12).USisinexpensive,[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal526526 RK Jain et al safe, and widely available. Because US involves noionizing radiation and excels in the depiction of acutegynecologicconditions,itisrecommendedastheinitialimagingstudyinchildren,inyoungwomen,andduringpregnancy8. It has reported sensitivities of 75%-90%,specificities of 86%-100%, accuracies of 87%-96%,positive predictive values of 91%-94%, and negativepredictivevaluesof89%-97%forthediagnosisofacuteappendicitis(4).Useofpreoperativeultrasonographyisalsoassociatedwithoveralllowernegativeappendectomyrate(12).Fig.3.Acuteappendicitisina37-year-oldmanwithright-lower-quadrant pain. (a) Long axis and (b) cross sectional USimages show inflamed appendix as a blind-ended,noncompressible tubular structure filled with fluid andsurrounded by a hypoechoic mass representing phlegmon.GradedcompressiontechniquedescribedbyPuylaert(13)isthestandardmethodforsonographicevaluationofacuteappendicitis.GradedcompressionUS,withslowandgentlemaintainedpressure,allowsforalengthyandsuccessfulevaluationoftheareaofinterestandshowsobstructedappendixasanoncompressibleloopofgut(4).IJRI, 16:4, November 2006 RecentlyBaldisserottoetal(14)hasdescribedtheuseof the noncompressive technique before the gradedcompressionstudy.Thismaysuccessfullyestablishthediagnosisinsomecases,therebyavoidingcompressioninpatientswithabdominalpain.Changeofthepatient'sposition to displace the bowel gas may also help invisualizationoftheappendixdeeplysetintheabdominalcavity without compression. Compression study ishowever,usefulinidentifyingthecasesofappendicitisnotvisualizedatthenoncompressiveexamination.Fig. 4.Appendicitis with appendicolith. (a) Long-axis and (b)cross sectional US image of the right lower quadrant,obtainedwithalinear10-6-MHzprobeina35yearoldwoman,shows the inflamed appendix with an echogenic luminalfocus (between the calipers) with distal shadowing.It is very important to standardize the examinationtechnique for identification of appendix and therebyavoiding false negative diagnosis. Baldisserotto hassuggested an excellent routine for the actual USexaminationoftherightlowerquadrant,whichwehavefoundveryusefulinourdailypractice.TheUSexaminationoftherightlowerquadrantshouldstartinthetransverseplanefromthetipoftheliverandproceedtowardsthepelvicbrim.Theascendingcolonusuallyisappreciatedbyitsgascontentandhaustralpattern.Intheregionof[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal527IJRI, 16:4, November 2006 thececum,carefulattentionshouldbepaidtoinflammatorychanges in the perienteric fat and the appendix itself.Sagittalandobliqueimagesshouldthenbeobtaineduntiltheentireregionofinteresthasbeenscanned.Detailedimagesareobtainedoftheappendix,ifitisseen.Theexamination is generally begun with a curvilineartransducer appropriate for the patient: a 3.5-MHztransducerforlargepatientsanda5-MHztransducerforthinpatients.Thelineartransducerisusedlatterformoredetailedstudy. Theretrocecalappendicitisisbeststudiedbytheexaminationthroughtherightflank(14).The inflamed appendix is seen as a blind-ended,aperistaltic,noncompressible,tubularstructurethatarisesfromthebaseofthececumhavingadiametergreaterthan6mms.(Fig.3.)Presenceofafecalith(Fig.4)mayaidinarrivingatapositivediagnosis.Fig.5. Classic features of acute appendicitis at US in a 26-year-old man with right lower quadrant pain. (a) Long-axisand (b) cross-sectional US images of the right lowerquadrant obtained with a linear 10-6 MHz transducer showan 8-mm-diameter, blind-ended, tubular structure with alaminated wall. The appendix was not compressible andshowed no peristalsis.Imaging in Acute Appendicitis527 Theovoidshape15ofappendixintransversesectiononUSovertheentireappendiceallengthreliablyrulesoutacute appendicitis while in acute inflammation theappendicealwallthickeningcausesanincreaseoftheouterappendicealdiameterandaroundingoftheshape.Inearlyacuteappendicitis(catarrhalstage)fivelayerscanbeidentified-(Fig.5.)1. central, thin hyperechoic line representing thecollapsedlumenandsuperficialliningofthemucosaoftheappendix,2. hypoechoiclayer(2-3mms)representingedematouslaminapropriaandmuscularismucosa.3. hyperechoicsubmucosa(2-3mms).4. hypoechoicmuscularlayer(2-3-mms).5. outerthinhyperechoiclinerepresentingtheserosa.Inlate(suppurative)stagethelumenoftheappendixisdistendedwithpus/fluidandthereisincreasedthickeningofthesubmucosaandmuscularwallintherangeof3-6mms.Circumferentialcolorinthewalloftheinflamedappendixon color Doppler US images is strongly supportiveevidenceofactiveinflammation(4).(Fig6.)Fig.6. Cross-sectional Color Doppler US image obtainedthrough the base of thick walled appendix in a 74 year oldmale presenting with right lower quadrant abdominal painshowsvirtuallycircumferentialflowinthewalloftheinflamedappendix.Loculated pericecal fluid, phlegmon or abscess,prominentpericecalfatandcircumferentiallossofthesubmucosal layer of appendix are associated withappendicealperforation16.(Fig7.)A significant disadvantage of sonography is that it isoperatordependent.Difficultieswithultrasonographyalsoincludethefactthatanormalappendixmustbeidentifiedtoruleoutacuteappendicitis.Visualizationofanormalappendixismoredifficultinpatientswithalargebody[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal528528 RK Jain et al habitus and when there is an associated ileus, whichproduces shadowing secondary to overlying gas-filledloops of bowel. It may also be not possible on US todifferentiate between appendiceal phlegmon from anabscessandCTmaybehelpfulinthissetting.Computed Tomography Fig. 7. Acute appendicitis with perforation in a 17-year-oldboy presenting with right lower quadrant pain andtenderness. (a) Long-axis and (b) cross sectional USimage, obtained through the right lower quadrant with alinear 10-6-MHz probe, shows the perforated appendix, withdiscontinuity of its wall and surrounded by an abscess.CThasbecomeincreasinglypopularasaneffectivecross-sectionalimagingtechniquefordiagnosingandstagingacuteappendicitis.Itisaquickandaccurateexaminationthatisoperator-independent,isrelativelyeasytoperformand provides images that are easy to interpret.(4, 17)Helical CT has reported sensitivities of 90%-100%,specificitiesof91%-99%,accuraciesof94%-98%,positivepredictivevaluesof92%-98%,andnegativepredictivevalues of 95%-100% for the diagnosis of acuteappendicitis.(4)ItsusehasdecreasedtherateofnegativeappendectomiesandhasdecreasedthenumberofcasesIJRI, 16:4, November 2006 ofappendicealperforation.(17,18)DisadvantagesofCTincludepossibleiodinated-contrast-mediaallergy,patientdiscomfortfromadministrationofcontrast media (especially if rectal contrast media isused),exposuretoionizingradiation,andcost.However,thecostisconsiderablylessthanthatofremovinganormalappendixorhospitalobservation.(8)Technique- there is no consensus on the ideal CTtechniqueforstudyingappendix.TherearedifferentCTprotocolsdependinguponthegenerationofCTscannersused as well as varying from center to center. WhilenonfocusedCTperformedforentireabdomenandpelviswithintravenousandoralcontrastmaterialisthemostpopular approach(4,17), CT evaluation of appendicitiswithouttheuseofintravenouslyadministeredcontrastmaterialisalsoagrowingtrend(2,19,21).Opacificationoftheterminalileumandcecumwithoraland/orrectalcontrast material alone or in combination has beenadvocated4.Howeverlaneetal19donotrecommendtheuseofanycontrastmaterial.Weltmanetal20hasshownthat the use of thin-section (5mms) CT significantlyimprovesthediagnosisofacuteappendicitiscomparedto10mmsections.Weatourclinicprefertoopacifythebowelusingoraland/orrectalcontrastalongwithIVcontrast,andusethinnersections.Image interpretation- the evaluation starts with theidentificationofappendix.Sincethepositionofthececumandascendingcolonishighlyvariable,identificationofthe fatty lips of the ileocecal valve is helpful. Carefulscrutiny of the entire cecum then frequently allowsidentification of the appendix as it arises from theposteromedialborder.Theappendixisfrequentlyseendrapedovertherightexternaliliacarteryandvein.Theright common and external iliac artery and vein aretherefore carefully evaluated from their origins at thebifurcationoftheaortaintothefemoralcanaltoidentifytheoverlyingappendix.Thisusuallyhelpstoavoidthepitfallofnotseeingapelvicappendix.Oncetheappendixisidentified,itisevaluatedforsignofacute appendicitis as described to confirm or excludethediagnosisofacuteappendicitis.Oncetheappendicealregioniscleared,thececumandascendingcolonarecarefully examined for potential involvement by cecalneoplasm (Fig.8), cecal diverticulitis, typhlitis, orsegmental colitis. Diseases that involve primarily thepericolonicfat,suchasprimaryepiploicappendagitisandomentalinfarction,arethenexcluded.Focus is then turned to the terminal ileum and itssubtended mesentery. Gastrointestinal diseases toconsiderinthisanatomiclocationincludeacuteterminalileitis, mesenteric lymphadenitis, Crohn's disease and[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal529IJRI, 16:4, November 2006 tuberculosis. Genitourinary disease then should beexcluded, including acute pyelonephritis, ureteralobstruction,complicationsofovariancystsandmasses,andacutepostpartumovarianveinthrombosis.Inadultpatients, one must also consider acute cholecystitis(which may mimic acute appendicitis if the enlargedgallbladder extends into the right-lower quadrant),pancreatitis,sigmoiddiverticulitis,bowelischemia,andbowelobstruction.Fig. 8. Cecal mass with appendicitis. Coronal reformattedCT scan shows lobulated heterogenous mass of cecumwith involvement of the base of the appendix.Imaging in Acute Appendicitis529 Imaging findings- the normal appendix appears as atubularorringlikepericecalstructurethatiseithertotallycollapsedorpartiallyfilledwithfluid,contrastmaterial,orair.Thenormalappendixhasathicknessof3mmsorless and a diameter of 6mms or less(14,21). Theperiappendicealfatshouldappearhomogeneous,althoughathinmesoappendixmaybepresent.Thefindingofanormal appendix with no fluid in its lumen, normalperiappendiceal fat, and no calcified appendicolithindicatesthattheappendixisnotinflamed.ThemainCTcriteriaforthediagnosisofacuteappendicitisincludeidentificationofathickenedappendixwithatwo-walldiametergreaterthan6.0-7.0mm,periappendicealinflammatory changes, and a calcifiedappendicolith(21).(Fig. 9 a). Alobaidi et al(22) hasrecommended the use of bone window settings fordetectingappendicolithswhenevaluatingpatientsforacuteappendicitis,particularlypatientsinwhomevidenceofappendicitisisequivocal.Fig. 9. Classic CT findings of acute appendicitis in a 48-year-old woman who presented with right lower quadrantpain and tenderness. (a) Transverse CT scan obtained withoral contrast material and with 5-mm collimation revealsan obstructing appendicolith within the distended appendix.(b) Caudal helical CT image reveals periappendicealinflammation[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal530530 RK Jain et al Thesizecriteriontodiagnoseappendicitisisespeciallyimportantintheabsenceofperiappendicealinflammation.Benjaminovetal(21)observedthatanupperlimitof6.0mmfornormalappendicealthicknesscanbeusedreliablyatCTonlyiftheluminalcontentisvisualizedbecauseintheabsenceofperiappendicealinflammatorychanges,itisnotpossibletodifferentiateanoncollapsedappendixfilledwithfluidofthesameattenuationasthewallfromathickinflamedappendixifthecontentisnotvisualized.Theysuggested10.0mmastheupperlimitofnormaliftheluminalcontentisnotvisualizedandextraappendicealinflammatorychangesarenotpresent.Patientswithanappendicealthicknessof6.0-10.0mmshouldthereforeundergofurtherexaminationwithrectallyorintravenouslyadministered contrast material or with US to visualizethewallandthuspreventafalse-positivediagnosisofappendicitis.InearlyormildappendicitistheCTfindingsareverysubtle.Theappendixmayappearminimallydistendedassociatedwithahazy,ill-definedincreaseinCTattenuationinthefatimmediatelysurroundingtheappendix.HowevermostpatientswhoundergoCTdemonstrategreaterdegreesofluminal distention and evidence of transmuralinflammation. Circumferential and symmetric wallthickening is nearly always present and is bestdemonstrated on images obtained with intravenouscontrast material enhancement. Periappendicealinflammation(Fig.9b)ispresentin98%ofpatientswithacuteappendicitis.Fig. 10. Transverse CT scan obtained with oral contrastmaterial and with 5-mm collimation in a 13 year old childwith acute appendicitis demonstrates the arrow head signconsisting of a triangle-shaped contrast collection betweenthe thickened cecal apical walls. Surgical explorationrevealed perforated appendicitis.Other important findings include focal cecal apicalthickeningandthearrowheadsign,(Fig.10)whichisseenasanarrowhead-shapedcollectionofcontrastmediumlocalizedtotheupperpartofthececumneartheorificeIJRI, 16:4, November 2006 oftheappendix(23,24).Inflammatorychangesassociatedwith acute appendicitis can cause focal cecal apicalthickening,whichallowscontrastmaterialtoassumetheconfigurationofanarrowheadasitfunnelsatthececalapextothepointoftheobstructedappendicealorifice.Because the sign is formed by the extension ofinflammation from the appendix to the cecum, thearrowheadsignmayallowforplacementofpatientswithappendicitisintotwosurgicalgroups(24):thosewholikelywill do well with standard ligation (arrowhead sign notpresent)andthosewhomayrequirepartialcecectomy(arrowheadsignpresent).Complications- Perforated appendicitis is usuallyaccompanied by pericecal phlegmon or abscessformation.Associatedfindingsincludeextraluminalair,(Fig. 11) marked ileocecal thickening, localizedlymphadenopathy, peritonitis, and small-bowelobstruction.Fig. 11a and b. Transverse CT scan obtained with oralcontrast material and with 5-mm collimation in a 32 year oldwoman with acute appendicitis demonstrates an enlargedthick-walled appendix with an associated cecal apicalthickening and infiltration of surrounding fat. Extraluminal airpocket suggests perforation.[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal

531IJRI, 16:4, November 2006 Iftheabnormalappendixisnotseen,aspecificdiagnosisof appendicitis can be made by identifying anappendicolith within a periappendiceal abscess orphlegmonAlthough a pericecal phlegmon or abscess is stronglysuggestiveofappendicitis,thesearenonspecificfindingsthatmaybeseenwithotherdiseaseentities.Ifsubstantialinflammationispresentwithintherightlowerquadrant,itmaybedifficulttodifferentiateprimaryappendicitiswithsecondaryinflammationofthececumandterminalileumfrom ileocolitis with secondary inflammation of theappendix.CTisofconsiderablevalueinthetreatmentofpatientswho present with a periappendiceal mass and can beusedtoaccuratelystagetheextentofperiappendicealinflammationandtoreliablydifferentiateperiappendicealabscessfromphlegmon,whichisofcriticalimportancetothesurgeon.Manysurgeonsbelievethatthereislittlevalueinattemptingtodrainanonliquefiedphlegmonandpreferinitialnonsurgicaltreatmentwithantibiotictherapyin such cases. Patients with well-defined and well-localizedperiappendicealabscessestypicallybenefitfromCT-directed percutaneous catheter drainage.(4,17)Patients with extensive and poorly defined collectionsusually require immediate surgical exploration andabscessdrainage.MagneticResonanceImaging MRImayalsobeusedinthediagnosisofappendicitisincaseswhereeitherCTiscontraindicatedlikeinpregnancyorinchildrenwhereitisadvisabletoavoidradiation. T1-weightedandT2-weightedturbospin-echosequencesandfat-suppressed inversion recovery turbo spin-echosequences as well as post contrast T1 weightedsequences can be used. On T2-weighted images,inflamedappendixshowmarkedlyhyperintensecenterandaslightlyhyperintensethickenedwallwithmarkedlyhyperintense periappendiceal tissue.(Fig. 12) On postcontrast study, intense contrast enhancement of theinflamed appendiceal wall indicates the presence ofappendicitis. There is also significant enhancement ofsurroundingfatongadolinium-enhancedT1-weightedfat-suppressedspin-echoimages.Mildenhancementcanhoweverbeseeninthenormalappendixandgut.Usingfat-saturationtechnique,contrastdifferences betweentheinflamedappendixandthesurroundingfatisbetterappreciated. However, MRI has inherent limitation indetectingappendicolith.Inflammatorydiseasesofthegut,suchasilealdiverticulitisandCrohn'sdiseasemaymimicappendicitisandmaybecauseforfalse-positivediagnosisofacuteappendicitis.False-negative results usually depend on technique-related limitations, such as inefficient fat saturationImaging in Acute Appendicitis531 causingappendicealwallenhancementtobeobscuredbymesentericfat.Fig.12.AxialT2(a)andT1(b)weightedimagesthroughrightlower quadrant in a 23 year old man presenting with acuteabdomen shows enlarged thick walled inflamed appendixwith periappendiceal inflammationFat-suppressedgadoliniumenhancedMRIimagesaresensitive(97%)andaccurate(95%)inthedetectionofacuteappendicitis25.Incesu, et al (25) found MR imaging superior tosonography in revealing appendicitis. Despite somedisadvantage, MR imaging can also be used aftersuboptimal or nondiagnostic sonography in cases ofsuspectedacuteappendicitis.CONCLUSION Althoughrareininfants,appendicitisiscommoninhumanpopulation.Itisoneofthemostcommoncauseofacuterightlowerquadrantabdominalpainandinmajorityofcases diagnosis of acute appendicitis can largely be[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal532532 RK Jain et al madeonthebasisofhistoryandphysicalexamination.Thoughdecreasing,stillalargenumberofappendicesatsurgeryarefoundtobenormal,leadingtoahighrateofnegativeappendectomies(8-30%).Thisisbecauseofsimilar signs and symptoms of a wide range of acuteabdominalclinicaldisordersandnonspecificlaboratoryandconventionalradiographicfindings.Inrecentyearshoweverwiththeavailabilityofvariouscross-sectionalimagingtechniquesviz.Ultrasonography,SpiralCTandMRI,falsepositivediagnosisofacuteappendicitishasreduced therefore also reducing rate of negativeappendectomies.Theoverallaccuracyofcross-sectionalimagingtechniquesindiagnosingacuteappendicitisvariesfrom87%-98%.Highresolutionsonographyisanmostcommonimagingtechniqueusedindiagnosingappendicitisasitislessexpensive, easily available and free from radiation,howeveritisoperatorandsubjectdependentandrequireslotofexperience.MRIcanalsobeusedinthesettingofpregnancy,otherwiseitexpensive,timeconsumingandcumbersome. Spiral and recently multislice CT hasthereforeemergedasthemosteffectivetoolfordiagnosingappendicitisanditscomplicationsbecauseofitsexcellentresolution.Itprovidesexquisitedetailedanatomicalimagesforreview,andisalsofastandoperatorindependent.References 1. Treutner KH, Schumpelick V. Epidemiology ofappendicitis. Chirurg 1997; 68:1-5[German].2. LaneMJ,LiuDM,HuynhMD,JeffreyRB,Jr,MindelzunRE, and Katz DS. Suspected Acute Appendicitis:Nonenhanced Helical CT in 300 Consecutive Patients.Radiology. 1999; 213: 341-346.3. SchwartzSI.Appendix.InSchwartzSI,SliversGT,SpencesFC, Ed. Principles of Surgery. New York. Mc Graw-Hill,Inc.1994: p- 1307-1318.4. Birnbaum BA, and. Wilson SR. Appendicitis at theMillennium. Radiology. 2000; 215:337-348.5. Moore KL, DalleyAF. Abdomen. In Clinically OrientedAnatomy. Philadelphia. Lippincott Willams & Wilkins.1999: p- 250-254.6. GronroosJM,GronroosP.LeucocytecountandC-reactiveprotein in the diagnosis of acute appendicitis. Br J Surg1999Apr;86(4):501-4.7. ApplegateKE,SivitCJ,SalvatorAE,etal.Effectofcross-sectional imaging on negative appendectomy andperforation rates in children. Radiology 2001; 220:103-107.8. Old JL, Dusing RW, Yap W and Dirks J: Imaging forsuspected appendicitis. American Family Physician2005Jan;71(1).9. Mindelzun RE, McCort JJ.AcuteAbdomen. In MargulisAR,BurhenneHJEd.AlimentaryTractRadiology.StLouis.Mosby. 1989: p-299-302.10. RodrigueG,KanniyanL,GopashettyM,RaoS,ShenoyR.PlainX-RayInAcuteAppendicitisTheInternetJournalofRadiology.2004.3:no2.11. Vaudagna JS and McCort JJ. Plain film diagnosis ofIJRI, 16:4, November 2006 retrocecal appendicitis. Radiology. 1975; 117: 533-536.12. Puig S, Hrmann M, Rebhandl W, Prokop RF-PM andPaya K. US as a Primary Diagnostic Tool in Relation toNegativeAppendectomy.SixYearsExperience.Radiology2003; 226:101-104.13. Puylaert JB. Acute appendicitis: US evaluation usinggraded compression. Radiology 1986; 158:355-36014. Baldisserotto M and Marchiori E. Accuracy ofNoncompressive sonography of children withappendicitis according to the potential positions of theAppendix. AJR 2000; 175:1387-139215. RettenbacherT, HollerwegerA, Macheiner P, GritzmannN, Daniaux M, K Schwamberger, et al. Ovoid Shape ofthe Vermiform Appendix: A Criterion to ExcludeAcuteAppendicitis-Evaluation with US. Radiology 2003;226:95-100.16. Wilson SR. The Gastrointestinal Tract. In Rumak CR,WilsonSR,CharboneauJW,Ed.DiagnosticUltrasound.Mosby. 1998: p- 303-306.17. RaptopoulosV,KatsouG,RosenMP,SiewertB,GoldbergSN, and Kruskal JB. Acute Appendicitis: Effect ofIncreased Use of CT on Selecting Patients Earlier.Radiology 2003; 226:521-526.18. Kaiser S, Frenckner B, and. Jorulf HK. SuspectedAppendicitis in Children: US and CT- A ProspectiveRandomized Study. Radiology 2002; 223:633-638.19. LaneMJ,KatzDS,RossBA,Clautice-EngleTL,MindelzunRE,JeffreyRB,Jr.UnenhancedhelicalCTforsuspectedacuteappendicitis.AJRAmJRoentgenol1997;168:405-40920. WeltmanDI,YuJ,KrumenackerJ,Jr,HuangS,andMohP. Diagnosis of AcuteAppendicitis: Comparison of 5-and10-mmCTSectionsintheSamePatientRadiology.2000; 216:172-177.21. Benjaminov O, Atri M, Hamilton P, and Rappaport D.Frequency of Visualization and Thickness of NormalAppendix at Nonenhanced Helical CT. Radiology 2002;225:400-406.22. Alobaidi M and Shirkhodas A. Value of Bone WindowSettings on CT for RevealingAppendicoliths in PatientswithAppendicitis.AJRAmJRoentgenol2003;180:201-20523. Rexroad JT. The CTArrowhead Sign. Radiology 2003;227:44-45.24. RaoPM,WittenbergJ,McDowellRK,RheaJT,NovellineRA.Appendicitis:useofarrowheadsignfordiagnosisatCT. Radiology 1997. 202:363-366.25. IncesuL,CoskunA,SelcukMB,etal:Acuteappendicitis:MR imaging and sonographic correlation. AJRAm JRoentgenol 1997 Mar; 168(3): 669-74.[Downloadedfreefromhttp://www.ijri.orgonFriday,June17,2011,IP:182.9.17.21]||ClickheretodownloadfreeAndroidapplicationforthisjournal