福岡徳洲会病院臨床検査科Fukuoka Tokushukai Medical Center
目的：本研究の目的は，急性膵炎の超音波（US）診断を難渋化させる因子を解析し，US診断正診率の向上に寄与することである．
対象と方法：研究対象は2009年12月～2016年10月までに当院にて急性膵炎（acute pancreatitis: AP）と診断された症例で，CTよりもUSが先に施行された124名である．これらをUS診断から後ろ向きに“診断不能群”，“弱い疑い群”，“強い疑い群”の3群に分けた．また，健常コントロール群として600名の正常膵に関して，エコー輝度と腫大の関係を検討し，AP群とも比較した．3群に分けたAP群は各種画像所見（US,CT）や臨床所見を比較した．なお，エコー輝度は輝度0, 1, 2型の3段階に半定量化した．
結果と考察：1）正常膵のUS画像において，特に膵頭部の厚みはエコー輝度と強く関係した（p＜0.001）．また，エコー輝度と膵臓の厚みには正の相関を認めた．2）健常コントロール群とAP群のエコー輝度を比較したところ，両群間に有意差を認め（p＜0.001），AP群で輝度0型が多く，輝度2型が少なかった．また，エコー輝度別に健常コントロール群とAP群の膵臓の厚みを比較したところ，輝度0型と1型では有意にAP群で高値を呈し（p＜0.001），輝度2型でも同様に高値の傾向を示した．3) AP3群間で各種画像所見や臨床所見を比較したところ，“膵のエコー輝度(p=0.026)”，“膵腎周囲fluid貯留(p<0.001)”，“膵周囲脂肪織肥厚(p=0.005)”，“尾部限局だけ膵炎(p=0.007)”のUS所見4項目にのみ有意差を認め，特に“膵腎周囲fluid貯留”はすべての群間で有意差を認めた．
結論：1）急性膵炎においても腫大の判断はエコー輝度別にされるべきである．2）膵腎周囲fluid貯留はもっとも重要な所見であり，これを検出できない場合が最も診断に難渋する．3）尾部限局膵炎は診断に難渋する．
Purpose: We aimed to identify factors complicating diagnostic ultrasound of acute pancreatitis (AP) with the goal of improving the rate of correct diagnosis.
Subjects and Methods: This observational study included 124 patients (98 males and 26 females; age, 56±15 years) among 134 adult subjects with AP who were evaluated at our hospital between December 2009 and October 2016. Ten patients who were examined by computed tomography (CT) prior to ultrasound were excluded. The remaining 124 patients with AP were retrospectively classified into “failed,” “weak,” and “strong” groups based on ultrasound findings. Pancreatic echogenicity and thickness were compared between the AP and control groups. The ultrasound findings of the three AP groups were compared with CT findings and several clinical parameters. The ultrasound characteristics of the normal pancreas were also determined to investigate AP risk factors associated with pancreatic thickness.
Results and Discussion: Among the included factors of echogenicity, sex, and age, multiple regression analysis identified echogenicity and sex as significant AP risk factors (p＜0.001). Echogenicity was significantly lower in the AP group than the control group. Comparison of the pancreatic thickness based on echogenicity between the AP and control groups revealed that the high-level echogenicity of types 0 and 1 was more frequent in the AP group (p＜0.001); a similar trend between the AP groups was observed for type 2 echogenicity as well. There were significant differences in pancreatic echogenicity (p＝0.026), peripancreatic and perinephric fluid (p＜0.001), peripancreatic fat stranding (p＝0.005), and AP localized to the pancreatic tail (p＝0.007) among the three AP groups.
Conclusion: In normal cases, pancreatic thickness was characterized based on a thick appearance with high intensity by ultrasound. In AP, the pancreas was significantly enlarged and hypoechoic. However, the assessment of the pancreas should be based on comparison with normal pancreatic echo brightness. Peripancreatic and perinephric fluid are the most important findings that must be detected for definitive AP diagnosis. Our findings suggest that the diagnosis of AP localized in the pancreatic tail was difficult because of the anatomical approach.
Key words: Ultrasound; acute pancreatitis; pancreatic echogenicity; pancreatic thickness; peripancreatic fluid
© 2019 一般社団法人日本超音波検査学会© 2019 Japanese Society of Sonographers
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