膵囊胞性疾患のダイナミックCT診断

Dynamic Study for Pancreatic Cystic Disease with Special Reference to Dynamic CT

要旨　膵囊胞性疾患の診断には造影剤を多量に用いるダイナミックCTが有用である．megacysticの腫瘍性囊胞では仮性囊胞との鑑別が問題となる．仮性囊胞では形成された初期は壁が染まらないが，肉芽が形成され線維化が完成すると壁が染まるようになる．しかし壁は薄く比較的均一である．また周囲膵の腫大，石灰化，液体貯溜などの合併所見がみられることも多い．これに対し腫瘍性囊胞では壁はやはりよく染まるが壁は厚く，更に限局肥厚や内腔への隆起像がみられる．ductectaic cystadenomaやadenocarcinomaではダイナミックCTによりブドウのような多房性小囊胞が明らかとなり，粘液の排出もみられる．ダイナミックCTは囊胞の形態を最も忠実に描出できる検査法である．

　Dynamic CT allows measurements of temporal changes in contrast density after bolus administration of contrast material. An ability to demonstrate changes in density of the pancreatic parenchyma and cyst wall make dynamic CT to be a very useful modality for precise diagnosis of pancreatic cystic disease.

　A cystic tumor is demonstrated by dynamic CT to have a well enhanced thick wall of the cyst with thickness or tumor formation. An inflammatory cyst, on the other hand, is shown to have a nonenhanced or enhanced thin wall. Since there is no blood flow in the cyst wall of the pseudocyst, a nonenhanced thin wall is demonstrated in the early phase. On the other hand, enhanced thin wall is demonstrated in the late phase due to granulation and fibrosis.

　In cases of inflammatory cysts, such abnormal findings as swelling of the pancreas, calcification in the pancreas and peripancreatic fluid collection are sometimes observed. Ductectatic cystadenoma or adenocarcinoma is shown to have multiple small cysts in the pancreatic parenchyma and, occasionally, mucus in the duodenum.

　We conclude that dynamic CT is very valuable modality in the diagnosis of pancreatic cystic diseases.