| Part oneStudy of normal appendix on multi-slice CTObjective:To study the appearance of normal appendix on multi-slice CT (MSCT) and to improve diagnosis of early appendiceal lesions. Methods:Seventy patients who were ruled out appendicitis, appendectomy and other appendiceal lesions by clinical criteria underwent unenhanced and enhanced MSCT scan. CT scanning parameters were as follows. Tube voltage,120kV; tube current,200mA; collimation,0.6mm; reconstruction slice thickness,1.0mm; reconstruction interval,0.5mm; pitch,1. All patients received100mL of iopromide (370mg I/ml) administered through antecubital vein using power injection at a rate of3mL/s. The acquisition of images started60seconds after the initiation of the injection of intravenous contrast material. The appendix was reconstructed by using multiplanar reformation (MPR) and curved planar reformation (CPR) techniques. The following CT findings were evaluated:appendiceal diameter, thickness of appendiceal wall, maximum depth of the intraluminal appendiceal fluid (MDIAF), appendicolith, gas and periappendiceal appearance. The statistical analysis was performed by using Stata7.0software. The difference in visualizing normal appendix between the unenhanced and enhanced MSCT was compared by corrected Chi-square test. A P value less than0.05was considered statistically significant. Results:The appendix was clearly visualized in66of70(94.3%) patients on unenhanced MSCT and in68of70(97.1%) patients on enhanced MSCT. There was no statistically significance in visualizing normal appendix between the unenhanced and enhanced MSCT (P=0.404). The appendiceal diameter was from3to10mm with mean diameter6.4±1.1mm. The appendiceal diameter more than6mm was seen in36cases. The thickness of appendiceal wall was from1to4mm with mean thickness2.7±0.5mm. The thickness of appendiceal wall more than3mm was seen in18cases. The intraluminal fluid was found in17cases with maximum depth greater than2.6mm seen in4cases. The gas was found in appendiceal lumen in41cases. The appendicolith and calcific appendiceal wall were identified in16and10cases respectively. The periappendiceal fat stranding was not seen in all cases. Conclusion:MSCT with MPR and CPR reconstructions can clearly demonstrate the structure of normal appendix. The commonly used criterion of appendiceal diameter larger than6mm or the thickness of appendiceal wall larger than3mm for acute appendicitis will result in a high false positive. The MDIAF is less than2.6mm. Part twoMulti-slice CT diagnosis of early acute appendicitisObjective:To investigate the value of multi-slice CT (MSCT) in diagnosing early acute appendicitis (AA). Methods:From June2008to June2011, abdomen MSCT images of41patients with acute simple appendicitis confirmed by surgery and pathology were evaluated retrospectively. Thirty-six patients who were ruled out AA and were clinically confirmed normal appendix served as the control groups, with18cases of complicated-normal-appendix (CNA) group and18cases of noncomplicated-normal-appendix (NCNA) group. The appendix was reconstructed by using multiplanar reformation(MPR) and curved planar reformation(CPR) techniques. The differences between early AA and normal appendix in the appendiceal diameter, thickness of the appendiceal wall, maximum depth of the intraluminal appendiceal fluid (MDIAF), abnormal enhancement of the appendiceal wall, appendicolith and the periappendiceal abnormalities were evaluated and compared. For the thickness of the appendiceal wall, the analysis of variance test was performed. For the appendiceal diameter and MDIAF, the rank sum test was used. For the incidence of the thickness of appendiceal wall greater than3mm, abnormal enhancement of appendiceal wall and appendicolith, the Chi-square test was performed. A P value less than0.05was considered statistically significant. Based on the data of appendiceal diameter and MDIAF, receiver operating characteristic (ROC) curves were constructed and used to obtain cutoff values for the appendiceal diameter and MDIAF that best differentiated AA group from the two normal-appendix groups. The sensitivity, specificity and accuracy were calculated respectively. Results:The mean thickness of the appendiceal wall was (2.88±0.62),(2.58±0.50) and (2.73±0.53) mm in early AA, CNA and NCNA groups respectively, with no statistically significant difference among them (F=1.73, P=0.19). The mean appendiceal diameter was (11.37±1.94),(7.03±0.89),(6.75±0.63) mm, and median MDIAF was4.05(2.65～8.50),1.68(0±4.4),0(0±1.9) mm in early AA, CNA and NCNA groups respectively, with statistically significant differences between early AA and the two normal appendix groups (Z=7.02,7.24, P=0.00,0.00, respectively). The abnormal enhancement of appendiceal wall was found in61.1%(11/18) of early AA,16.7%(3/18) of CNA and11.1%(2/18) of NCNA groups respectively, with statistically significant difference between early AA and the two normal appendix groups (χ2=12.83, P=0.00). Using a cutoff value of7.8mm of the appendiceal diameter and2.6mm of MDIAF for the early A A, the sensitivity, specificity and accuracy were97.6%(40/41),91.7%(33/36) and94.8%(73/77), and100.00%(36/36),88.9%(32/36) and94.4%(68/72), respectively. Conclusions:MSCT is particularly useful for the diagnosis of early AA. When appendiceal diameter greater than7.8mm, and MDIAF greater than2.6mm, the early AA can be diagnosed confidently. Part threeMSCT with MPR in differentiating perforated from nonperforated acute appendicitisObjective:To investigate MSCT findings of perforated acute appendicitis (PAA) to discriminate PAA from nonperforated acute appendicitis (NPAA). Methods:Twenty-eight patients with PAA proved by surgery and pathology underwent abdominopelvic MSCT ultrathin-section scan. Thirty-six patients with NPAA served as the control group (18cases of simple AA and18cases of AA with associated periappendiceal inflammation). The appendix was reconstructed by using MPR and CPR techniques. CT findings of the enhancement defect in appendiceal wall, periappendiceal abscess, periappendiceal phlegmon, extraluminal air, extraluminal appendicolith, lateroconal fascial thickening, small bowel wall thichening, cecal wall thichening, ileal wall enhancement, peritoneal enhancement, retrocecal appendix, intraluminal air, ileus, enlargement of lymph node, intraluminal appendicolith between PAA and NPAA were evaluated and compared by using Chi-square test, corrected Chi-square test or Fisher’s exact test based on data characteristics. For appendiceal diameter, the rank sum test was performed. A P value less than0.05was considered statistically significant. Based on the data of appendiceal diameter, receiver operating characteristic (ROC) curve was constructed to depict the curve of those features and to obtain the cutoff value for the appendiceal diameter that best differentiated PAA from NPAA group. The sensitivity, specificity and accuracy were calculated respectively. Results: There were statistically significant differences between PAA and NPAA in enhancement defect in appendiceal wall, abscess, phlegmon, extraluminal air and extraluminal appendicolith (P=0.00,0.00,0.00,0.00and0.02, respectively). Using any one of above five CT findings for the diagnosis of PAA, the sensitivity, specificity and accuracy were96.4%,91.7%and93.8%, respectively. There was a statistically significant difference in the appendiceal diameter between PAA (16.2±3.8mm) and NPAA (11.3±3.1mm). A cutoff value of13.3mm of the appendiceal diameter for PAA could improve the specificity to94.4%. Conclusion:MSCT combining MPR and CPR can accurately differentiate PAA from NPAA, which help surgeon choose optimal management. |
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