1、阑尾炎的不典型阑尾炎的不典型CT表现表现IntroductionAppendicitis is commonly seen in medical practice,and its preoperative diagnosis is increasingly reliant on imaging,particularly computed tomography(CT),with clinical manifestations and laboratory test results playing a less important role.The imaging-based diagnosis
2、of appendicitis is not always straightforward.To achieve an accurate diagnosis,radiologists must be familiar with atypical as well as characteristic CT appearances of appendicitis.This online presentation reviews:The pathophysiology and etiology of appendicitis,including various causes of secondary/
3、reactive appendicitis and mimics Atypical and complicated cases of appendicitis Advantages and potential pitfalls of using appendiceal caliber and/or appendiceal filling by oral contrast material as diagnostic criteria at CT The importance of comparing current imaging studies with previous studies w
4、hen evaluating early,chronic,and resolving appendicitis2Teaching PointsAn increase in appendiceal caliber between serial CT examinations,even in the absence of adjacent fat stranding,may signal early-stage appendicitis.However,increased appendiceal caliber alone is not a reliable indicator of append
5、icitis and must be considered alongside the patients clinical history and other imaging findings to avoid misdiagnosis.The presence of oral contrast material within the appendix conflicts with a diagnosis of acute appendicitis and can be used as supporting evidence for a nonobstructed appendix in eq
6、uivocal cases,such as when appendiceal mural thickening is seen without substantial periappendiceal fat stranding.Primary appendicitis should be distinguished from secondary or reactive appendicitis,which can be caused by cecal and/or terminal ileal diverticulitis,terminal ileitis,active Crohn disea
7、se,colitis,or an acute gynecologic disease process.Clinical mimics of appendicitis include appendiceal mucoceles and neoplasms.3Learning ObjectivesAfter viewing this presentation,participants should be able to:Discuss the advantages and potential pitfalls of using appen-diceal caliber and/or appendi
8、ceal filling by oral contrast material at CT to determine whether acute appendicitis is present.Recognize the broad spectrum of CT appearances of atypical,complicated,and secondary or reactive appendicitis.List potential mimics of acute appendicitis.4CT ProtocolControversy surrounds the optimal CT p
9、rotocol for evaluating patients with signs and symptoms of acute appendicitis,and the value of intravenous,oral,and rectal contrast agents is debated.At our institution,we routinely administer both oral and intravenous contrast material and acquire 5-mm-thick axial sections with 3-mm coronal and sag
10、ittal reconstructions.The targeted interval between the administration of oral contrast material and scanning is 60 minutes.Alternatives include the use of intravenous contrast material alone,oral contrast material alone,rectal contrast material alone,or no contrast material at all.In many centers,p
11、atients with right lower quadrant pain who are evaluated in the emergency department undergo CT without contrast material.The chosen protocol should satisfy the needs of referring clinicians and be appropriate for the particular patient,although that ideal may be difficult to achieve in emergent set
12、tings.Dose reduction strategies should be used to minimize the patients exposure to radiation while maintaining the image quality needed to achieve a high level of diagnostic accuracy.5Advantages and Disadvantages of Using Oral Contrast Material AdvantagesAllows improved diagnostic accuracy in patie
13、nts with a paucity of intra-abdominal fat and resultant susceptibility to volume averaging of bowel,vessels,and other visceraAllows a decreased number of false-negative findings in certain settingsIn equivocal cases,appendiceal filling can provide supportive evidence for a nonobstructed appendixDisa
14、dvantagesIncreases scanning time,which may delay patient careMay mask appendicolithsLeads to decreased patient satisfaction with the imaging examination(due to unpleasant taste and potential side effects such as nausea,vomiting,and diarrhea)Increases the cost of the imaging examination6Pathophysiolo
15、gy of Acute AppendicitisAppendiceal inflammation leads to appendiceal wall thickening and distention.Possible complications of acute appendicitis include Abscess Gangrene Perforation PeritonitisIn the case shown here,the underlying cause of appendicitis was uncertain,but obstruction of the appendice
16、al lumen by the appendicolith or by lymphoid hyperplasia was suspected to play a role.Figure 1.Coronal CT image shows a dilated fluid-filled appendix with a calcified appendicolith(arrow)and extensive extraluminal fluid and fat stranding(arrowheads)in the right lower quadrant,findings suggestive of
17、perforated appendicitis.7Atypical Location:Normal Variation versus HerniationNormal variationNormal appendix is relatively mobile and may be found in a retrocecal,subcecal,retroileal,preileal,or pelvic siteAmyand herniaHerniation of the appendix into an inguinal herniaOccurs in 6 mmAbnormal appendic
18、eal wall enhancementPeriappendiceal strandingAppendicolith may be present“Arrowhead”sign Focal symmetric thickening of the upper cecal wall where it approaches the obstructed appendiceal orifice,with an arrowhead-shaped collection of oral and/or rectal contrast material Observation of this sign allo
19、ws diagnostic sensitivity of 30%and specificity of 100%,according to Rao et alFigure 23.Arrowhead sign in early-stage appen-dicitis.Coronal CT image shows focal symmetric thickening of the wall of the upper cecum where it approaches the orifice of the obstructed appendix.Note the arrowhead-shaped co
20、llection of oral contrast material(arrow)within the appendix.13Atypical Appendicitis with Normal White Blood Cell CountImportant:Although leuko-cytosis is often associated with acute appendicitis,a normal white blood cell(WBC)count alone does not allow the ex-clusion of appendicitis.When the WBC cou
21、nt is normal or borderline high,concomitant elevation of the absolute neutrophil count(ANC)or percentage of neutrophils supports a diagnosis of acute appendicitis.Figure 24.Atypical acute appendicitis without leuko-cytosis.(a)Coronal CT image shows a dilated 1.4-cm appendix(arrow)with only minimal p
22、eriappendiceal fat stranding in a 59-year-old immunocompetent man with 2 days of right lower quadrant abdominal pain and normal WBC count,ANC,and percentage of neutrophils.(b)Axial CT image shows a mildly dilated 1-cm appendix(arrow)without substantial periappendiceal fat stranding in a 22-year-old
23、immunocompetent man with a normal WBC count and normal percentage of neutrophils but marginally elevated ANC.Pathology reports indicated acute appendicitis in both patients.a.b.14Atypical Appearances:Tip AppendicitisFigure 25.Tip appendicitis.Evaluation of the appendix on coronal CT images reveals a
24、 normal-appearing proximal portion filled with oral contrast material(arrow in a),a nondilated middle portion(arrow in b),and a markedly thickened distal portion(arrow in c)with associated periappendiceal stranding,findings suggestive of tip appendicitis.The diagnosis was confirmed at pathologic ana
25、lysis.a.b.c.Important:Close inspection of the entirety of the appendix,from its origin to its most distal portion,is essential at imaging in order to avoid missing the diagnosis of tip appendicitis.Note that the normal appendiceal tip is bulbous in configura-tion and is expected to be wider in diame
26、ter than the rest of the appendix.15Atypical Appearances:Stump AppendicitisInflammation of residual appendix after appendectomy is known as stump appendi-citis.Surgical resection of the inflamed appendiceal stump with or without invagin-ation,referred to as repeat or completion appendectomy,is usual
27、ly recommended.A recent literature review performed by Kanona et al showed that 37%of cases of stump appendicitis occurred after initial laparoscopic appendectomy and 63%occurred after initial open appendectomy,contrary to earlier reports that suggested an increased incidence rate after appen-dectom
28、y with a laparoscopic approach.The interval between initial appendectomy and repeat appendectomy varied from 9 weeks to 50 years.Rarely,an inflamed epiploic appendage may calcify and mimic stump appendicitis.Figure 26.Stump appendicitis.Axial CT image obtained approximately 2 years after laparoscopi
29、c appendectomy shows a long appendiceal remnant(arrow)with adjacent fat stranding,findings suggestive of stump appendicitis.16Atypical Appearances:Focal Inflammation of AppendixFigure 27.Appendix with rarely seen focal inflammation.Axial(a)and coronal(b)CT images show a 1.5-cm appendix(arrow)contain
30、ing fluid and gas from the middle to the distal portion.These findings are suggestive of an intraluminal abscess in the setting of acute appendicitis.Pathologic analysis showed focal inflammation with a bulging appendiceal luminal wall containing fecal matter.Important:The presence of gas in the app
31、endiceal lumen does not permit the exclusion of appendicitis,and when seen with other features of acute appendicitis,it is suggestive of complicated appendicitis.a.b.17Complicated Appendicitis:PerforationClassic CT findings of perforated appendicitis are Abscess Extraluminal air Extraluminal appendi
32、colithVisualization of one or more appendicoliths increases the probability of appendiceal perforation Appendicoliths may accelerate the rate at which perforation occursFigure 28.Perforated appendicitis.Axial CT image shows an appendicolith(arrow)with an atypical,extraluminal location in the anterio
33、r pelvis,a finding indicative of appendiceal perforation.18Complicated Appendicitis:Perforation(continued)Horrow et al identified five CT findings that collectively yielded 95%sensitivity and specificity for a diagnosis of perforated appendicitis:Extraluminal air Extraluminal appendicolith Abscess P
34、hlegmon Defect in mural enhancement(individual feature with the highest sensitivity,at 64%)Figure 29.Perforated appendicitis.Coronal CT image shows disruption of the appen-diceal wall by extraluminal air(arrow),a finding indicative of perforation.19Complicated Appendicitis:Perforation(continued)Figu
35、re 30.Perforated appendicitis with free intraperitoneal and right retroperitoneal air in an 82-year-old woman.Axial(a)and coronal(b)CT images show air collections anterior to the liver,tracking into the retroperitoneal space,along the right paracolic gutter,and into the region of the cecum.Such exte
36、nsive pneumoperitoneum is infrequently seen in cases of appendicitis.a.b.20Complicated Appendicitis:AbscessAbscess is the most frequent complication of perforated appendicitis.A localized abscess occurs if periappendiceal fibrinous adhesions develop before the appendix ruptures.Infection may spread
37、to adjacent structures and spaces,such as the iliopsoas muscles and retroperitoneal tissues,if the abscess is not promptly diagnosed.Figure 31.Perforated appendicitis with a complex multicompartmental abscess extending into the retroperitoneal tissues,right psoas muscle,right iliacus muscle(arrow in
38、 a),and posterior subcutaneous tissues of the right flank(arrow in b).Culture of fluid from the abscess showed Klebsiella infection.a.b.21Complicated Appendicitis:PeritonitisWhen appendiceal rupture occurs before inflammatory adhesions form in early acute appendicitis,peritonitis may result.Peritoni
39、tis secondary to perforated appendicitis is more common in children than in adults because progression from inflammation to perforation is more rapid in children.Contrast-enhanced CT is helpful for distinguishing peritonitis from ascites.Figure 32.Perforated appendicitis with resultant peritonitis i
40、n a 59-year-old woman.Coronal CT image obtained after appendectomy shows enhancing,thickened peritoneum(white arrow)and mild to moderate ascites(black arrow)in the patients abdomen and pelvis.22Complicated Appendicitis:Other Associated FindingsPylephlebitis and pylethrombosisCaused by ascending infe
41、ction along the draining mesenteric-portal venous systemGenitourinary involvementMay result in reactive hydroureter or hydronephrosisGangrenous appendicitisPneumatosis,shaggy appendiceal wall,and patchy areas of mural nonperfusionFigure 33.Pylephlebitis secondary to appendicitis.Axial CT image obtai
42、ned in a patient with appendicitis shows a focal linear region of hypoattenuation in the right hepatic lobe(arrow),a finding that likely represents thrombosis of the distal end of an anterior branch of the right portal vein.23Complicated Appendicitis:Bowel ObstructionBowel obstruction may occur due
43、toNarrowing of the distal ileum because of periappendiceal inflammationAdhesions from appendectomyFigure 34.Axial CT images obtained in the lower abdomen show multiple dilated small bowel loops containing differential air-fluid levels,findings consistent with a small bowel obstruction(arrows in a)se
44、condary to appendicitis(arrow in b).a.b.24Complicated Appendicitis:FistulaA fistula may form from a perforated appendix to adjacent bowel,bladder,vagina,uterus,or skin.Fistulation is a rare com-plication of perforated appendicitis.Figure 35.Coronal CT image shows improving appendicitis with a probab
45、le fistula(arrow)to the adjacent sigmoid colon.25Chronic and Recurrent AppendicitisChronic appendicitisSymptoms last for weeks,months,or yearsRecurrent appendicitisCharacterized by repeated episodes of painIntervals between episodes may vary from weeks to yearsClinical manifestations may be the same
46、 as those of acute or chronic appendicitisFigure 36.Chronic appendicitis.Axial CT images obtained 5 months apart in the same patient show a persistently dilated,fluid-filled appendix(arrow)without substantial adja-cent fat stranding.Even when conservative management of appendicitis fails,the result
47、is not invariably a ruptured appendix.a.b.26Resolving AppendicitisFigure 37.Resolving appendicitis without surgical intervention.Axial CT scans obtained in the same patient at diagnosis(a)and 1 month(b),4 months(c),and 8 months(d)later demonstrate a gradual decrease in caliber of the appendix(arrow)
48、and periappendiceal stranding.No antibiotics were administered for the apparent“cecal mass”found in a,which was no longer seen when the patient presented for CT-guided biopsy(b).The mild dilata-tion of the appendix seen in b may be an equivocal finding in isolation,but when compared with the finding
49、s in previous studies,is suggestive of resolving appendicitis.a.b.c.d.Important:CT evaluation for appendicitis should include a comparison of current images with any available previous studies and with available clinical information to allow accurate differentiation between a normal appendiceal vari
50、ant,early-stage appendicitis,and resolving appendicitis.27Appendectomy MimicsImportant:Do not mistake retained oral contrast material in the appendix for appendicoliths or changes due to appendectomy.Figure 38.Retained barium mimicking changes after appendectomy.(a)Coronal contrast-enhanced CT image
