胆总管囊肿

【病因病理】

胆管囊肿传统上称为胆总管囊肿,为胆管囊性扩张。病因不明确,可能因胆总管和胰管连接部不正常,胰液反流入胆管引起慢性炎症或胆管壁先天性薄弱等,按囊肿的形态和位置分为5型:I型,胆总管呈囊状、纺锤状或柱状扩张,占80%~90%;Ⅱ型,胆总管单发憩室,占2%；Ⅲ型,十二指肠壁内段胆总管囊状膨出,占1.4%~5%;Ⅳ型,多发性胆管囊肿,位于肝内和肝外,或肝外多发;V型,肝内胆管多发囊状扩张,又称 Caroli病,囊壁可厚2~4mm,由纤维组织构成,一般无上皮层,囊肿大小不等,病程越长则体积越大。

【临床表现】

女性多见,约2/3见于婴幼儿。临床有三大症状:黄疽、腹痛和腹部包块,出现典型三联症者不足30%。婴儿主要症状为黄疽,囊肿远端出现狭窄或扭曲,是产生黄疽的原因,儿童期以腹部包块为主,巨大者可占据右上腹。成人多见腹痛、黄疽及间歇发热,腹痛与继发感染有关,部分患者无明显临床症状,仅于体检时偶然发现。

【影像学表现】

1. 腹部X线平片有时可见右上腹密度均匀软组织阴影,轮廓清晰,并可见邻近充气的胃和肠道受压推移,但诊断存在困难。

2.口服法或静脉法胆囊造影有可能显示胆总管囊肿的轮廓。胆总管憩室充盈后显示与胆总管或肝管有一狭颈,若狭颈开口关闭,则仅见一圆形、光滑压迹,壁内段胆总管囊状影出部可以充盈对比剂而显影。肝内胆管囊状扩张时可以显示多发扩张的肝内胆管,内可有结石影,由于常有黄疽存在,口服或静脉胆系造影常常显影不良,对诊断帮助不大。

3.CT检查

(1)Ⅰ型和Ⅱ型多表现为肝门下方液性密度肿块,密度均匀,边缘光滑,壁薄而均匀,肝内胆管不扩张或轻度扩张,扩张的肝内胆管呈球状或梭形,外周几乎不扩张,若胆总管高度扩张,可压迫邻近的组织器官,如胰腺、胃和胆囊等。

(2)Ⅲ型,小囊肿CT较难诊断。大囊肿表现为液性密度肿块突入十二指肠腔内或壁内，与胆总管相邻近,肝内胆管和胆总管不扩张。

MRCP

(3)Ⅳ型表现为肝内和肝外多发球状或梭形液性密度占位,密度均匀。多发囊肿之间为正常大小的胆管相连,不成比例的扩张胆管与正常胆管相间是与阻塞性胆管扩张鉴别的要点。

(4)V型即 Caroli病:肝内条状或分支状低密度影,代表扩张的肝内胆管。有时可见多个小囊状区域,囊肿一般较小,且与扩张的管状结构相连,可作为与单纯性或先天性肝囊肿鉴别的可靠征象:增强扫描可见低密度囊状区域伴有高密度的圆形血管影,称为“印戒征”。肝门区中心胆管可以不扩张。扩张胆管内可有结石影。

成人胆总管囊肿发生恶性肿瘤的潜在可能性很高,I型最多见,因此对每一例成人胆总管囊肿需要仔细观察有无恶性肿瘤。胆总管囊肿合并恶性肿瘤的主要CT表现为扩张的肝内或肝外胆管壁局限性或广泛性不规则增厚,或出现腔内肿块,增强扫描病灶有不同程度的强化。

4.MR表现  T1W1呈低信号,T2W1呈高信号。形态特征等表现与CT所见相似,发现与囊肿相连的正常胆管是诊断胆管囊肿的要点,MRCP多能显示两者的连接点,且MRCP能显示胆管树全貌并对胆管囊肿进行准确分型,无需对比剂。

The Todani classification of bile duct cysts divides choledochal cysts into five groups.

Classification

Type I

See: type I choledochal cyst

• account for 80-90% of all bile duct cysts

• characterized by fusiform dilation of the extrahepatic bile duct

• a subclassification has been proposed

• Ia: dilatation of extrahepatic bile duct (entire)

• Ib: dilatation of extrahepatic bile duct (focal segment)

• Ic: dilatation of the common bile duct portion of extrahepatic bile duct

Theorized to form as the result of reflux of pancreatic secretions into the bile duct via an anomalous pancreaticobiliary junction. Some believe them to arise from ductal plate anomalies.

Type II

Also known as a bile duct diverticulum. Account for 3% of all bile duct cysts. Saccular outpouchings, representing a true diverticulum, arising from the supraduodenal extrahepatic bile duct or the intrahepatic bile ducts. 

Type III

Also known as a choledochocele:

• account for 5% of all bile duct cysts

• represent protrusion of a focally dilated, intramural segment of the distal common bile duct into the duodenum

Choledochoceles may be successfully managed with endoscopic sphincterotomy, surgical excision, or both, in symptomatic patients.

Type IV

Multiple communicating intra- and extrahepatic duct cysts:

• second most common type of bile duct cysts (10%)

• subdivided into subtypes:

• type 4a: fusiform dilation of the entire extrahepatic bile duct with extension of dilation of the intrahepatic bile ducts

• type 4b: multiple cystic dilations involving only the extrahepatic bile duct

Type V

Also known as Caroli disease, which is a rare form of congenital biliary cystic disease manifested by cystic dilations of intrahepatic bile ducts. Association with benign renal tubular ectasia and other forms of renal cystic disease.

Komi classification of bile duct cysts divides anomalous union of the pancreatico-bile ducts (AUPBD) into three types based on the angle of union of the ducts 1.

Classification

• type I: union of the ducts at a right angle to each other

• type Ia: without dilatation or 

• type Ib: with dilatation of the common channel. 

• type II: union of the ducts with an acute angle between them

• type IIa: without dilatation (IIA) or 

• type IIb: with dilatation of the common channel

• type III: comprises of complex patterns of accessory pancreatic ducts, with or without intricate duct networks

• type IIIc1: tiny communication exists between the main duct and the accessory ducts

type IIIc2: comprises of a common channel made up of common and accessory ducts of equal caliber
type IIIa: is similar to the classic pancreas divisum with biliary dilatation

• type IIIb: characterized by the absence of the Wirsung’s duct

• type IIIc