IMAGING OF THE ACUTE ABDOMEN CONTENTS Preface xi Emil J. Balthazar Impact of Multislice CT on Imaging of Acute Abdominal Disease 1083 Vikas Kundra and Paul M. Silverman With the advent of multislice CT, higher resolution and more diagnostic images are now available. By transitioning from axial to single-slice helical to now multislice CT scanners, imaging time has been reduced from minutes to seconds. In addition, colli- mation width and computing time have decreased. Increased coverage is now obtained with thinner slices and higher image quality. Although multislice CT has had significant impact in evaluating the entire body, it has been particularly useful for abdominal imaging. Radiologic Diagnosis of Gastrointestinal Perforation 1095 Stephen E. Rubesin and Marc S. Levine Perforations of the gastrointestinal tract have many causes. Holes in the wall of gas- trointestinal organs can be created by blunt or penetrating trauma, iatrogenic injury, inflammatory conditions that penetrate the serosa or adventitia, extrinsic neoplasms that invade the gastrointestinal tract, or primary neoplasms that penetrate outside the wall of gastrointestinal organs. This article provides a radiologic approach for inves- tigating the wide variety of gastrointestinal perforations. General principles about contrast agents and studies are reviewed, and then perforations in specific gastroin- testinal organs are discussed. The Acute Right Lower Quadrant: CT Evaluation 1117 Michael Macari and Emil J. Balthazar This article describes the CT imaging findings of patients presenting with acute right lower quadrant pain. The focus is on appendicitis and current imaging techniques and controversies. The remainder of the article evaluates the most common conditions caus- ing right lower quadrant pain other than appendicitis that can be diagnosed with CT. Adult Intussusception: Diagnosis and Clinical Relevance 1137 Benjamin Y. Huang and David M. Warshauer Adult intussusception is a rare entity. Unlike intussusceptions in childhood, most adult intussusceptions are caused by a definable pathologic lesion, with a significant proportion VOLUME 41 •NUMBER 6 •NOVEMBER 2003 v caused by malignancy, particularly among those involving the colon. Before the advent of noninvasive imaging, most adult intussusceptions were diagnosed surgically or at autopsy, but modern imaging techniques have proved useful in diagnosis and in direct- ing appropriate therapy. Until recently, adult intussusception had been considered pri- marily a surgical condition, but recent data in the radiologic literature suggest that there may be a substantial number of transient, nonneoplastic enteroenteric intussusceptions diagnosed by CT, which do not require operative treatment. CT of Acute Abdominal Aortic Disorders 1153 Sanjeev Bhalla, Christine O. Menias, and Jay P. Heiken Aortic aneurysm rupture, aortic dissection, penetrating atherosclerotic ulcer, acute aortic occlusion, traumatic aortic injury, and aortic fistula represent acute abdominal aortic conditions. Because of its speed and proximity to the emergency department, helical CT is the imaging test of choice for these conditions. MR imaging also plays an important role in the imaging of aortic dissection and penetrating atherosclerotic ulcer. Ultrasound is helpful when CT is not readily available and the patient is unable or too unstable to undergo MR imaging. Because CT is the dominant imaging method for diagnosing acute abdominal aortic conditions, this article focuses on CT tech- niques and manifestations of this group of acute abdominal disorders. Blunt Injury to Mesentery and Small Bowel: CT Evaluation 1171 Patrick W. Hanks and Jeffrey M. Brody CT is widely used in the evaluation of trauma patients. Although the sensitivity for CT detection of solid organ injury is 90% or better, hollow viscous injury has historically been more difficult to identify. Diagnosis of small bowel and mesenteric injury often requires special attention to subtle findings. This article discusses the role of CT in the diagnostic approach to blunt trauma victims, the points of controversy regarding the CT examination technique, the CT findings related to small bowel and mesenteric injury, and the accuracy of imaging diagnosis. Spontaneous Intraperitoneal Hemorrhage: Imaging Features 1183 Koenraad J. Mortele, Vito Cantisani, Douglas L. Brown, and Pablo R. Ros Spontaneous, nontraumatic, intraperitoneal bleeding is a rare but worrisome clinical condition, potentially fatal, which may be related to a vast array of underlying causes. Accurate diagnosis of the cause, organ of origin, extent, and prognosis of this condition can be established with different imaging modalities, such as ultrasound, CT, and MR imaging. This article summarizes the clinical aspects and pathogenesis of the entities causing spontaneous intraperitoneal hemorrhage. The corresponding radiologic features of these conditions are highlighted. Finally, recommendations to perform the imaging modality of choice for each of the abnormalities and key features are provided. Ultrasound and CT Evaluation of Emergent Gallbladder Pathology 1203 Genevieve L. Bennett and Emil J. Balthazar This article provides a review of ultrasound and CT findings in acute conditions of the gallbladder. Although ultrasound or hepatobiliary scintigraphy are usually the initial imaging examinations of choice to evaluate most suspected cases of acute gallbladder pathology, the role of CT in the evaluation of abdominal pain continues to expand. CT allows for more comprehensive evaluation of the abdomen and pelvis and can iden- tify other inflammatory processes that clinically may simulate gallbladder pathology. vi CONTENTS In many instances, CT may be the initial diagnostic procedure performed; it is important to become familiar with the spectrum of CT findings in emergent gallbladder disorders. Furthermore, CT plays an important role in the evaluation of associated complications of these disorders, facilitating prompt diagnosis and appropriate management. Interventional Approach to Pancreatic Fluid Collections 1217 Joseph T. Ferrucci III and Peter R. Mueller Interventional radiologic catheter drainage may be an effective therapeutic approach to fluid collections complicating acute pancreatitis. Pancreatic pseudocysts and abscess are the most common conditions requiring radiologic intervention. Imaging guidance is best performed under CT control allowing precise definition of access route, catheter place- ment, and response. Access routes are chosen to avoid traversing vital intervening struc- tures, especially the pleural space, colon, and small bowel. Optimal results are achieved with the use of large-bore multihole catheters, prolonged duration of drainage, and care- ful collaboration with the surgical team. Ultrasonography of the Acute Abdomen: Gastrointestinal Conditions 1227 Julien B.C.M. Puylaert Although multislice, helical CT is increasingly replacing ultrasonography for the evalua- tion of patients with acute abdominal pain, ultrasound does have certain specific advantages over CT. This article discusses the advantages of ultrasound in imaging of the acute abdomen, exploring such areas as appendicitis, ileocecal Crohn’s disease, infec- tious ileocolitis and infectious ileocecitis, mesenteric lymphadenitis, cecal carcinoma, sig- moid diverticulitis, right-sided colonic diverticulitis, and perforated peptic ulcer. MR Imaging in Abdominal Emergencies 1243 Ivan Pedrosa and Neil M. Rofsky The use of MR imaging in the emergency setting is evolving. Clear indications include situa- tions in need of contrast media when iodinated contrast cannot be administered or to facili- tate assessments in pregnant patients and children when exposure to ionizing radiation is considered unacceptable. The availability of rapid, motion immune sequences now makes MR imaging a feasible study in less cooperative patients extending the range of patients for whom a diagnostic study can be achieved. Further investigations are needed to identify the diagnostic algorithms for which this favorable use holds true. Selective Role of Nuclear Medicine in Evaluating the Acute Abdomen 1275 Lionel S. Zuckier and Leonard M. Freeman Evaluation of the acute abdomen has evolved with the introduction of the high-resolution imaging techniques of CT, ultrasound, and MR imaging, leaving scintigraphic examina- tions a limited although important role based on their noninvasive, physiologic, and functional nature. Bleeding studies can be used to localize noninvasively sites of bleed- ing to regions of the large or small bowel. Pertechnetate studies accurately localize sites of ectopic gastric mucosa. Biliary scintigraphy is helpful in diagnosing patients with acute presentation of biliary disease and is invaluable in analyzing complicated post- cholecystectomy patients. Vascular and traumatic injury of the solid organs can be studied by various functional techniques including biliary and renal scintigraphy. Aniche for infectious imaging has been found in the evaluation of acute appendicitis. CONTENTS vii Complications of Liver Transplantation: Imaging and Intervention 1289 Michael P. Federle and Vibhu Kapoor Orthotopic liver transplantation is the accepted treatment for end-stage liver disease. Improvements in surgical techniques and medical therapy have resulted in reduced mor- tality and some types of complications. Patients are, however, still at risk for a variety of vascular, biliary, neoplastic, and other complications, the signs and symptoms of which are often nonspecific. Radiologists can play a key role in diagnosis and management of these complications, as reviewed in this article. Cumulative Index 2003 1307 viii CONTENTS FORTHCOMING ISSUES January 2004 Arthritis Imaging Barbara N. Weissman, MD, Guest Editor March 2004 Emergency Ultrasound Vikram Dogra, MD, Guest Editor May 2004 Cardiac Imaging Martin Lipton, MD, and Lawrence Boxt, MD, Guest Editors RECENT ISSUES September 2003 Advances in Renal Imaging Philip J. Kenney, MD, Guest Editor July 2003 Women’s Imaging: Obstetrics and Gynecology Deborah Levine, MD, Guest Editor May 2003 Multislice Helical CT of the Thorax Phillip M. Boiselle, MD, Guest Editor THE CLINICS ARE NOW AVAILABLE ONLINE! Access your subscription at: http://www.TheClinics.com RadiolClinNAm41(2003)xi–xii Preface Imaging of the acute abdomen EmilJ.Balthazar,MD GuestEditor The only constantin life ischange. imagingmodalityoraprotocolshouldbebasedmainly ontheirreportedaccuracy,sensitivity,andspecificity, —Buddha asmightbeexpected.Inreality,however,theselection processisstronglyinfluencedbypastexperienceand Ithasbeenover10yearssincethepublicationof skills, the quality and availability of equipment, and the last issue of the Radiologic Clinics of North thecostofexamination,andisthereforeofteninstitu- Americadevotedentirelytoimagingacuteabdominal tionallydependent.Intheseventeenthcentury,Francis disorders. Significant advances in technology, new Bacon and the French philosopher Rene´ De´scartes applications,changedprotocols,andconsiderableac- identified observation and analysis, respectively, cumulatedexperiencehavepromptedanupdateofthis astheprimarytoolsthatareessentialintheeffortto importantclinicalsubject. acquirereliablescientificknowledge.Theprocessof The purpose of this new issue is twofold. First, gathering data andanalysis, however, canbebiased, acuteabdominalconditionsthatcanbediagnosedand tinted by our own prejudices, and is not always evaluated rapidly by relatively noninvasive imaging trustworthy.InthewordsofhistorianJacqueBarzun: examinationsarereviewed.Ihavetriedtoavoidover- ‘‘Observationisrarelyneutral;itrestsonpreconcep- lapsandduplicationswhilemaintainingtherelevance tionsandpreperceptions.’’ ofthetopicbyfocusingonpertinent,potentiallylife- I hope that this issue describes what is presently threatening abdominal conditions. Second, this issue availableandwhatisconsideredcurrentstate-of-the- providesanabbreviatedbutcomprehensivepresenta- art in the imaging of acute abdominal conditions. A tionofnewapplicationsofimagingmodalities—such compendium of imaging choices and protocols are asmultidetector(multislice)CT,sonography,andMR described, mainly reflecting the experience and con- imaging—thatwerepreviouslynotavailableorwere victionsofdifferentauthors.Ifoundtheserecommen- notcommonlyusedintheevaluationofpatientswith dations very useful; however, they arenot axioms— acuteabdominalcomplaints. and are certainly not perennial—but are susceptible After perusing through this issue, readers will no to incessant changes and refinements. It is your re- doubt notice that radiologists, based on their experi- sponsibilityasthereader,basedonyourskills,expe- ence and established beliefs, tend to address similar rience, and local factors, to select the appropriate clinical challenges by different means using various imaging modality and the required protocol that, in imagingmodalitiesordistinctlyidiosyncratictechni- your best judgment, will better serve the interest of cal protocols. Theoretically, the selection of a given yourpatients. 0033-8389/03/$ – seefrontmatterD2003ElsevierInc.Allrightsreserved. doi:10.1016/S0033-8389(03)00142-8 xii E.J.Balthazar/RadiolClinNAm41(2003)xi–xii In pursuing my goals, I have been joined and EmilJ. Balthazar,MD helpedbyadistinguishedgroupofleadingacademic Department of Radiology radiologists,allexpertsintheirfield,towhomIextend New York University Schoolof Medicine my affection and gratitude. I am also indebted to 560First Avenue,NB3 W39 BartonDudlick,ourefficientsenioreditor,forhelping New York,NY 10016,USA usmakethisprojectareality. E-mailaddress: [email protected] RadiolClinNAm41(2003)1083–1093 Impact of multislice CT on imaging of acute abdominal disease Vikas Kundra, MD, PhD*, Paul M. Silverman, MD DivisionofDiagnosticImaging,DepartmentofRadiology,TheUniversityofTexas,M.D.AndersonCancerCenter, Box57,Houston,TX77030,USA WiththeadventofmultisliceCT(MSCT),higher the need for cooling; thus, x-rays can be delivered resolution and more diagnostic images are now continuously. With MSCT, the point source is pro- available. By transitioning from axial to single-slice jectedontomultipledetectors,currentlyupto16,inthe helical to now MSCT scanners, imaging time has Zaxisinsteadofthesingledetectorofpriorsystems. been reduced from minutes to seconds. In addition, Therefore,moredataareacquiredwithasinglegan- collimation width and computing time have de- tryrotation. creased. Increased coverage is now obtained with Forimageacquisition,generallythreemajordetec- thinner slices and higher image quality. Although tors designsareused: (1) matrix, whereall detectors MSCT has had significant impact in evaluating the are of the same size; (2) adaptive array, where they entire body, it has been particularly useful for ab- vary from thinner inside to thicker outside; and dominalimaging. (3)hybrid,whereusuallytwosizesareusedwiththe Forexample,differentphasesofenhancementcan thinner detectors located centrally [2]. The first two now be separated more succinctly. Reduced breath- support submillimeter to 5-mm acquisitions modes, holdtimeshaveresultedinmorediagnosticscansby whereas the latter supports submillimeter to 8-mm curtailing motion artifact. Thinner slices have de- acquisitionmodes creasedZ-axisblurringtoallowevaluationofminute Multislicescannersaltertheacquisitionthickness structures, such as blood vessels. Increased comput- byvaryingthenumberofdetectorsused(Fig.2).For ing speed has also shortened reconstruction and example,afour-slicescannerusingthematrixdesign reformation times, enabling selection of the optimal hasaZ-axiswidthof20mmsubdividedinto16equal planeforthestructureinquestion.Clinically,imaging parts of 1.25 mm each. The beam is collimated to findingsonCTincreasethecertaintyofdiagnosisor exciteacertainnumberofrows.Slicesareacquiredin offer an alternative diagnosis to guide patient man- groupsoffour.Ifthecentralfourrowsareused,four agement [1]. slices of 1.25-mm thickness are obtained for total coverageof5mm.Ifthecentraleightareused,every twodetectorsaresummedresultinginaslicethickness Technology of 2.5 mm. If the central 12 are used, every three detectorsaresummedresultinginaslicethicknessof Insimpleterms,MSCTallowsacquisitionofmul- 3.75 mm. If all detectors are used, every four are tiplesliceswithasinglegantryrotation(Fig.1).New summedresultingin5-mmslicescovering20mmin high heat capacity tubes have significantly reduced theZaxis.Forsubmillimeterresolution,thebeamis collimatedacrossdetectors. Withthenew16-slicescanners,16slicesmaybe * Correspondingauthor. obtainedwithasinglegantryrotation,includingatsub- E-mailaddress:[email protected] millimeterresolution.Thisdoesnotincreasethespeed (V.Kundra). ofacquisitionfor5-mmslicescomparedwithafour- 0033-8389/03/$ – seefrontmatterD2003ElsevierInc.Allrightsreserved. doi:10.1016/S0033-8389(03)00117-9 1084 V.Kundra,P.M.Silverman/RadiolClinNAm41(2003)1083–1093 Fig.1.Single-sliceversusMSCT.InsteadofasingledetectorintheZaxisusedinsingle-sliceCT,MSCThasmultipledetectors intheZaxis,providingagreaternumberofimagespergantryrotation. slicescanner(4(cid:1)5mm=20mm)becausethemaxi- In addition to varying collimation at the time of mum width for detection in the Z axis is 20 mm. It acquisition, slice thickness may also be varied by does,however,increasecoveragewhenthinnerslices manipulating how the data are reconstructed. Al- areused.Forexample,at1.25-mmcollimation,afour- though slices can be reconstructed at thicker widths slice scanner covers 5 mm per gantry rotation (4 (cid:1) than those acquired, they cannot be reconstructed 1.25mm=5mm),whereasa16-slicescannercovers thinner. Thus, it is important to select the thinnest 20mmpergantryrotation(16(cid:1)1.25mm=20mm). acquisition widthneeded atthe time ofscanning. Fig.2.Matrixdetector.(A)Inthematrixconfiguration,theZaxisisdividedintoequalparts.Forafour-slicescanner,20mmin theZaxisiscoveredby16detectorseachmeasuring1.25mm.TheX-raybeamiscollimatedtoexposethecentral4,8,12,or 16 detectors. At the time of acquisition, data from the detectors may be added, resulting in slices of varying thickness. For example,byexposingthecentraleightdetectorsandcombiningdatafromeverytwo,four2.5-mmslicesareobtained.(B)Witha 16-slicescanner,16differentacquisitionsmaybeobtainedatsubmillimeterresolutionwithasinglegantryrotation.Intermsof areaintheZaxis,1.25-mmslicescover20mminsteadof5mmbyfour-slicescanners.Becausethetotaldetectorwidthisthe same,thereisnodifferenceinZ-axiscoverageif5-mmslicesareacquired.