闌尾炎的不典型ct表現(xiàn)

1、Appendicitis:Atypical and Challenging CT Appearances,Introduction,Appendicitis is commonly seen in medical practice, and its preoperative diagnosis is increasingly reliant on imaging, particularly computed tomography (

2、CT), with clinical manifestations and laboratory test results playing a less important role.The imaging-based diagnosis of appendicitis is not always straightforward. To achieve an accurate diagnosis, radiologists must

3、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/reactive appen

4、dicitis and mimicsAtypical and complicated cases of appendicitisAdvantages and potential pitfalls of using appendiceal caliber and/or appendiceal filling by oral contrast material as diagnostic criteria at CTThe impor

5、tance of comparing current imaging studies with previous studies when evaluating early, chronic, and resolving appendicitis,Teaching Points,An increase in appendiceal caliber between serial CT examinations, even in the a

6、bsence of adjacent fat stranding, may signal early-stage appendicitis.However, increased appendiceal caliber alone is not a reliable indicator of appendicitis and must be considered alongside the patient’s clinical hist

7、ory 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

8、 appendix in equivocal cases, such as when appendiceal mural thickening is seen without substantial periappendiceal fat stranding.Primary appendicitis should be distinguished from secondary or reactive appendicitis, whi

9、ch can be caused by cecal and/or terminal ileal diverticulitis, terminal ileitis, active Crohn disease, colitis, or an acute gynecologic disease process.Clinical mimics of appendicitis include appendiceal mucoceles and

10、neoplasms.,Learning Objectives,After viewing this presentation, participants should be able to:Discuss the advantages and potential pitfalls of using appen-diceal caliber and/or appendiceal filling by oral contrast mate

11、rial 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

12、.,CT Protocol,Controversy surrounds the optimal CT protocol for evaluating patients with signs and symptoms of acute appendicitis, and the value of intravenous, oral, and rectal contrast agents is debated.At our institu

13、tion, we routinely administer both oral and intravenous contrast material and acquire 5-mm-thick axial sections with 3-mm coronal and sagittal reconstructions. The targeted interval between the administration of oral con

14、trast 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 center

15、s, patients 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

16、the particular patient, although that ideal may be difficult to achieve in emergent settings.Dose reduction strategies should be used to minimize the patient’s exposure to radiation while maintaining the image quality n

17、eeded to achieve a high level of diagnostic accuracy.,Advantages and Disadvantages of Using Oral Contrast Material,Advantages,Allows improved diagnostic accuracy in patients with a paucity of intra-abdominal fat and resu

18、ltant 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 eviden

19、ce for a nonobstructed appendix,Disadvantages,Increases scanning time, which may delay patient careMay mask appendicolithsLeads to decreased patient satisfaction with the imaging examination (due to unpleasant taste an

20、d potential side effects such as nausea, vomiting, and diarrhea) Increases the cost of the imaging examination,Pathophysiology of Acute Appendicitis,Appendiceal inflammation leads to appendiceal wall thickening and dist

21、ention.Possible complications of acute appendicitis include Abscess GangrenePerforationPeritonitisIn the case shown here, the underlying cause of appendicitis was uncertain, but obstruction of the appendiceal lumen

22、 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

23、 fat stranding (arrowheads) in the right lower quadrant, findings suggestive of perforated appendicitis.,,,,,,Atypical Location: Normal Variation versus Herniation,Normal variationNormal appendix is relatively mobile a

24、nd may be found in a retrocecal, subcecal, retroileal, preileal, or pelvic siteAmyand herniaHerniation of the appendix into an inguinal herniaOccurs in <1% of inguinal hernias (appendicitis is found in 0.13% of ing

25、uinal hernias) Most common in male patientsDe Garengeot herniaHerniation of the appendix into the femoral canalEven rarer than Amyand herniaMost common in female patients,Figures 2–9. Amyand hernia. Coronal CT imag

26、e series shows a fluid-filled and mildly dilated (maximal diameter, 9 mm) appendix (arrow) in an atypical location in the right inguinal canal. These findings could be due to compression at the hernia ring or to a mild m

27、ucocele, but no pathology report or follow-up CT study was available.,Atypical Location: Congenital Rotation Anomalies,Left-sided appendicitis is associated with two congenital anomalies: intestinal malrota-tion and sit

28、us inversus.CT findings of left-sided appendicitis are similar to those of right-sided appendicitis, ex-cept for the difference in the location of the appendix.,Important: Localize the cecum before evaluating the appen

29、dix on CT images. Do not assume that the appendix is normal if it is not seen in the right lower quadrant.,Figures 10–19. Coronal CT image series shows acute appendicitis due to bowel malrotation in the left mid abdomen

30、 (arrow). The cecum is near the midline in the left hemiabdomen, and the duodeno-jejunal junction is in the right upper quadrant, with inversion of the normal relationship between the superior mesenteric artery and vein

31、(not shown).,Utility of Increased Appendiceal Caliber for Diagnosing Appendicitis,a.,b.,c.,Figure 20. Interval increase in appendiceal caliber in serially acquired axial CT studies is suggestive of early acute appendici

32、tis. (a, b) Axial CT scans obtained in an asymptomatic patient for ovarian cancer follow-up show a slight increase in appendiceal diameter from 6 mm at baseline (arrow in a) to 9 mm 3 months later (arrow in b), without s

33、ubstantial adjacent stranding. Viewed in isolation, the appendiceal appearance in b would be equivocal; however, the subtle increase in appendiceal caliber between a and b raises the possibility of very early acute appen

34、dicitis. (c) Repeat CT scan obtained because the patient reported abdominal pain 1 week after b shows the appendix (arrow) with an enlarged diameter of 15 mm and adjacent fat stranding, findings that helped confirm the d

35、iagnosis of appendicitis.,Important: An interval increase in appendiceal caliber over serial CT examina-tions is suggestive of early-stage acute appendicitis even in the absence of adjacent fat stranding.,Limitations of

36、 Appendiceal Caliber for Diagnosing Appendicitis,Figure 21. Variability of appendiceal caliber in two patients with pathology-proved acute appendicitis. (a) Axial CT image obtained in a 23-year-old woman with nausea an

37、d vomiting depicts a normal-caliber 6-mm appendix with indistinct wall (arrow). Minimal anterior pelvic fat stranding also is seen. (b) Cor-onal CT image obtained in a 40-year-old woman with right lower quadrant abdomina

38、l pain shows an unusually large appendix measuring up to 2.1 cm in diameter, with adjacent fat stranding.,Important: Appendiceal caliber alone is not a reliable indicator of appendicitis and must be interpreted within t

39、he context of the patient’s clinical history and other CT findings to avoid misdiagnosis.,a.,b.,Utility of Oral Contrast Material Filling for Diagnosing Acute Appendicitis,The presence of oral contrast material within th

40、e appendix conflicts with a diagnosis of acute appendicitis and can be used as supporting evidence for a nonobstructed appendix in equivocal cases, such as when the appendix is mildly dilated and there is no substantial

41、adjacent fat stranding.Important: Dense oral contrast material can be hard to distinguish from an appendicolith on standard CT images obtained with soft-tissue window and level settings. Use of a bone window will show

42、 an appendicolith to be much denser than oral contrast material.,Figure 22. Mildly dilated, oral contrast mate-rial-filled appendix. Axial CT image shows ap-pendiceal caliber of 7–8 mm and mild mural thickening. Appendi

43、ceal filling by oral contrast material (arrow) and the absence of substantial periappendiceal stranding militate against a di-agnosis of acute appendicitis. The pathology report confirmed that the appendix was non-obstru

44、cted.,Signs of Early-Stage Appendicitis,Appendiceal caliber >6 mmAbnormal appendiceal wall enhancementPeriappendiceal strandingAppendicolith may be present“Arrowhead” signFocal symmetric thickening of the upper c

45、ecal wall where it approaches the obstructed appendiceal orifice, with an arrowhead-shaped collection of oral and/or rectal contrast materialObservation of this sign allows diagnostic sensitivity of 30% and specificity

46、of 100%, according to Rao et al,Figure 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

47、appendix. Note the arrowhead-shaped collection of oral contrast material (arrow) within the appendix.,Atypical Appendicitis with Normal White Blood Cell Count,Important: Although leuko-cytosis is often associated with

48、 acute appendicitis, a normal white blood cell (WBC) count alone does not allow the ex-clusion of appendicitis. When the WBC count is normal or borderline high, concomitant elevation of the absolute neutrophil count (ANC

49、) 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 per

50、iappendiceal 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

51、appendix (arrow) without substantial periappendiceal fat stranding in a 22-year-old immunocompetent man with a normal WBC count and normal percentage of neutrophils but marginally elevated ANC. Pathology reports indicat

52、ed acute appendicitis in both patients.,a.,b.,Atypical Appearances: Tip Appendicitis,Figure 25. Tip appendicitis. Evaluation of the appendix on coronal CT images reveals a normal-appearing proximal portion filled with

53、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

54、diagnosis was confirmed at pathologic analysis.,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 dia

55、gnosis of tip appendicitis. Note that the normal appendiceal tip is bulbous in configura-tion and is expected to be wider in diameter than the rest of the appendix.,Atypical Appearances: Stump Appendicitis,Inflammation

56、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 usually re

57、commended.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 t

58、o earlier reports that suggested an increased incidence rate after appen-dectomy with a laparoscopic approach. The interval between initial appendectomy and repeat appendectomy varied from 9 weeks to 50 years.Rarely, an

59、 inflamed epiploic appendage may calcify and mimic stump appendicitis.,Figure 26. Stump appendicitis. Axial CT image obtained approximately 2 years after laparoscopic appendectomy shows a long appendiceal remnant (arrow

60、) with adjacent fat stranding, findings suggestive of stump appendicitis.,Atypical Appearances: Focal Inflammation of Appendix,Figure 27. Appendix with rarely seen focal inflammation. Axial (a) and coronal (b) CT image

61、s show a 1.5-cm appendix (arrow) containing 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 f

62、ocal inflammation with a bulging appendiceal luminal wall containing fecal matter.,Important: The presence of gas in the appendiceal lumen does not permit the exclusion of appendicitis, and when seen with other features

63、 of acute appendicitis, it is suggestive of complicated appendicitis.,a.,b.,Complicated Appendicitis: Perforation,Classic CT findings of perforated appendicitis areAbscessExtraluminal airExtraluminal appendicolithVis

64、ualization of one or more appendicoliths increases the probability of appendiceal perforationAppendicoliths may accelerate the rate at which perforation occurs,Figure 28. Perforated appendicitis. Axial CT image shows a

65、n appendicolith (arrow) with an atypical, extraluminal location in the anterior pelvis, a finding indicative of appendiceal perforation.,Complicated Appendicitis: Perforation (continued),Horrow et al identified five CT

66、 findings that collectively yielded 95% sensitivity and specificity for a diagnosis of perforated appendicitis:Extraluminal airExtraluminal appendicolithAbscessPhlegmonDefect in mural enhancement (individual feature

67、 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.,Complicated Appendi

68、citis: Perforation (continued),Figure 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