Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

without evidence of an underlying malignancy (39).

Percutaneous gallbladder needle biopsy is usually nondiagnostic, and histologic study of the resected gallbladder is necessary.

Laparoscopic cholecystectomy is difficult and often not successful. Extensive resection is necessary, but this carries a risk of bile duct injury. Intraoperative cholangiography is useful for guidance.

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presence of intraperitoneal fluid. A prospective study in patients with mild disease found US evidence of gallbladder wall thickening in 32%, while with a more severe illness gallbladder wall thickening was seen in 95% (40); a gallbladder wall thickness ≥5mm had a 92% specificity in identifying patients at high risk for hypovolemic shock, while a gallbladder wall thickness between 3 and 5mm was used as a criterion for hospital admission.

Porcelain Gallbladder

The term porcelain gallbladder is applied to a type of chronic cholecystitis containing a calcified gallbladder wall. The prevalence of porcelain gallbladder varies depending on the specific definition used and whether conventional radiographs or CT are employed. In a study of patients with acute abdominal pain operated on for acute cholecystitis, conventional radiography revealed linear gallbladder wall calcifications in slightly under 5% (27).

Occasionally a porcelain gallbladder and xanthogranulomatous cholecystitis coexist; a carcinoma is in the imaging differential diagnosis.

When extensive, these calcifications are detected with most imaging modalities. Still, the diagnosis is not always straightforward because large calcified confluent gallbladder stones have a similar appearance, especially with conventional radiography. In fact, large calcified stones are more common than a porcelain gallbladder.

Ultrasonography reveals a hyperechoic circular gallbladder outline with marked posterior shadowing. In some patients only part of the gallbladder wall is calcified. The sonographic findings are similar to those seen with a gallbladder filled with stones or even emphysematous cholecystitis.

Most authors agree that a porcelain gallbladder is precancerous. Therefore, even in a relatively asymptomatic patient a cholecystectomy is generally recommended. A laparoscopic cholecystectomy is feasible with a porcelain gallbladder.

Dengue Fever

Cholangitis

Acute cholangitis is caused by infection of an obstructed biliary tree, with the obstruction usually secondary to choledocholithiasis. Cholangitis is less common with a malignant obstruction. Occasionally acute cholangitis develops in a setting of bile duct sludge, with sludge presumably leading to intermittent obstruction.

An association probably exists between a peri-Vaterian diverticulum and cholangitis. The risk for cholangitis is increased if the common bile duct drains directly into the diverticulum. Distal duodenal obstruction more often results in pancreatitis rather than cholangitis (Fig. 8.14).

GALLBLADDER AND BILE DUCTS

Typically eosinophilic gastroenteritis involves the stomach and small bowel, although eosinophilic cholangitis also exists. When extensive, imaging reveals marked bile duct wall thickening and lumen narrowing.

Infection

Pyogenic

Most pyogenic cholangitis develops in a setting of choledocholithiasis and, less often, strictures. An occasional patient forms recurrent stones and develops multiple episodes of ascending cholangitis. The bile ducts dilate and bile stasis is evident. Complications include liver abscess and portal vein thrombosis.

Focal or generalized bile duct dilation and strictures are the only consistent imaging finding in pyogenic cholangitis, although many of these patients also have bile duct stones and biliary obstruction. The bile duct wall is thickened and inflamed, identified by CT and MR as increased postcontrast enhancement. Often focal liver enhancement is also evident.

Computed tomography reveals liver inflammatory pseudotumors in some patients with pyogenic cholangitis, consisting of illdefined and hypodense regions; early arterial phase images reveal nodular or wedge-shaped inhomogeneous enhancement, presumably due to chronic inflammation (41). Postcontrast, a central hypodense region is believed to represent chronic inflammation, while septa are secondary to fibroblastic proliferation (42).

An MRCP in recurrent pyogenic cholangitis is able to outline major bile ducts and thus is often superior to direct cholangiography. In one study, MRCP depicted all dilated segments, 96% of duct strictures, and 98% of segments containing calculi (43); direct cholangiography, on the other hand, depicted only about half the dilated segments, ductal strictures, and calculi.

In some institutions the initial therapy for acute cholangitis consists of antibiotics and general supportive therapy. With a poor response, especially in a high surgical risk patient, endoscopic or percutaneous biliary drainage is performed to bypass an obstruction. Others believe that early endoscopic biliary drainage is warranted in these patients, and endoscopic drainage should be performed on

an urgent basis. In severe cholangitis, endoscopic biliary drainage is associated with a lower morbidity and mortality than with surgical decompression. Percutaneous transhepatic drainage or surgical drainage is a viable option if endoscopic drainage cannot be performed.

In general, prolonged interventional procedures during the acute phase are associated with increased complications. Excessive catheter manipulation should be avoided, with the aim being to place a biliary drainage catheter proximal to the obstruction.

Yearly surveillance ERCP has been proposed for patients with recurrent bile duct stones who are prone to developing episodes of acute cholangitis (44); stone removal decreases risk of cholangitis.

Hepatolithiasis (Oriental

Cholangiohepatitis)

Hepatolithiasis, previously known as Oriental cholangiohepatitis, recurrent pyogenic cholangitis, and primary intrahepatic stones, is most often encountered in patients from East Asia, with only an occasional non-Oriental patient reported. Prevalence in East Asia varies considerably between countries. The hallmark of this condition is intrahepatic bile duct stones proximal to the confluence of right and left hepatic ducts.

The etiology of hepatolithiasis is not clear. Bile stasis and bacterial infection probably play a role. Some believe that infestation with the parasites Clonorchis sinensis or Ascaris lumbricoides results in an inflammatory reaction that starts a cycle of stasis, stone formation, and strictures, but evidence for such an association is not convincing. In Japan, a congenital basis for these strictures has been raised, with some patients having congenital common bile duct dilation.

Multiple strictures develop and calculi and debris form proximal to these strictures (Fig. 8.15). Both intraand extrahepatic bile ducts eventually dilate, but stones form intrahepatically,more often in the left lobe rather than right lobe ducts. These stones tend to be composed of calcium bilirubinate; they tend to be soft, adhere to the duct wall, and vary in size. Their number

Figure 8.15. Oriental cholangiohepatitis. Computed tomography reveals stones (arrows) within dilated intrahepatic bile ducts.

ranges from several to multiple, in some patients filling most of the visualized bile ducts. In fact, often not all bile ducts are visualized by cholangiography because of segmental obstruction by stones.

This condition is progressive and not curable. Involved liver segments tend to atrophy. Untreated, recurrent cholangitis, liver abscesses, cirrhosis and eventual portal hypertension develop.

Clinically, the diagnosis is readily missed in countries with a low prevalence. Liver enzymes often are only mildly elevated, and the initial ERCP findings are subtle; early on, the extrahepatic ducts tend to appear normal, while a tight intrahepatic stricture prevents visualization of a more proximal stone in a dilated duct.

In some patients the sphincter of Oddi is destroyed, with reflux of gas and intestinal content into bile ducts. At times orally ingested contrast refluxes into the bile ducts. Stones and air bubbles can be confused with each other.

Computed tomography can suggest the diagnosis by detecting dilated intrahepatic bile ducts and stones. Once the diagnosis is suspected, ERC defines the underlying anatomy using, if necessary, a balloon catheter to dilate and obtain adequate filling of intrahepatic ducts. At times percutaneous cholangiography is necessary to outline the full extent of hepatolithiasis. Adequate antibiotic coverage is

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necessary for these procedures because these patients are prone to cholangitis and sepsis.

Not all strictures in oriental cholangitis are benign. These patients are at increased risk for a cholangiocarcinoma. Because of distortion and obstruction by stones, an intrahepatic cholangiocarcinoma is readily overlooked. This tumor infiltrates diffusely and mimics a benignappearing stricture. Imaging in patients with cholangiocarcinoma in a setting of hepatolithiasis reveales irregular ductal strictures or obstruction and lobar atrophy (45); tumors and stones tend to be located in the same lobe. Some of these patients have an intraductal papillary tumor and mucin hypersecretion.

Generally, the initial therapy of these patients is surgical. Stone extraction, various biliary drainage procedures, and, at times, partial hepatectomy are performed. Liver resection is recommended by some surgeons for patients with intrahepatic segmental or subsegmental biliary stenoses. Some perform a partial left lobe resection if bilateral hepatolithiasis and strictures are found; they believe a lobectomy simplifies future treatment and may decrease complications. At times a Roux-en-Y hepaticojejunostomy is performed in order to clear stones. It is important at surgery to ensure that all stones are located and removed. Intraoperative US-guided transhepatic lithotomy is useful to detect residual stones; stones are located by US, and a surgical path is then chosen using US guidance.

A number of endoscopic and percutaneous transhepatic techniques have been developed to deal with these intrahepatic strictures and stones. At times a temporary surgical cutaneous stoma is created, allowing endoscopic access for cholangiography, stricture dilation, and stone removal. Some patients undergo exploration of extrahepatic bile ducts, any accessible stones are removed and a T-tube is inserted; using the T- tube tract for access, strictures are then dilated, stones removed, or electrohydraulic lithotripsy performed. The aim of therapy is complete stone clearance, although stone recurrence is common.

An alternative approach in some patients is percutaneous transhepatic cholangioscopy and lithotripsy. As needed, percutaneous or endoscopic stricture dilation and stone extraction are performed. Smaller intrahepatic stones can be pushed into more central ducts, while

GALLBLADDER AND BILE DUCTS

larger stones are crushed. Stones can also be fragmented using extracorporeal shockwave lithotripsy.

Clonorchiasis

River fluke Clonorchis sinensis larvae migrate from the duodenum into bile ducts where they mature, preferentially residing in smaller intrahepatic ducts. With sufficient infestation, the intrahepatic bile ducts dilate, with essentially unremarkable major intraand extrahepatic ducts. Small duct dilation is probably due to obstruction by these worms. Periductal and ductal inflammation ensue.

The initial abnormality detected by imaging is mild dilation of intrahepatic ducts. Eventually a full spectrum of oriental cholangiohepatitis develops.

Ultrasonography reveals worm aggregates as nonshadowing echogenic masses. Individual flukes are about 10mm in length and thus considerably smaller than an Ascaris worm. Resultant cholangitis often leads to duct wall thickening and increased echogenicity.

Ascariasis

Ascariasis is a common helminthic infestation found worldwide, being especially prevalent in the tropics. In the United States it occurs in the deep South. The adult Ascaris lumbricoides worm lives in the intestinal tract where it produces few symptoms. Biliary obstruction, cholangitis, cholecystitis, pancreatitis, and an intrahepatic abscess are complications if an adult worm migrates into the bile ducts. Biliary ascariasis is more common in children than in adults. Several reports have commented on a sphincterotomy predisposing to biliary infestation.

Computed tomography identifies a worm as a hyperdense tubular structures surrounded by bile. When viewed in a transverse section, the worm has a “bull’s-eye” appearance. Several worms, especially if coiled, appear as an intraluminal tumor.

Ultrasonography reveals a worm as a tubular hyperechoic structure within the bile ducts or gallbladder (Fig. 8.16). At times worm motion is identified. A long curved, tubular, nonshadowing structure containing a hypoechoic center, called the impacted worm sign, is occasionally

Figure 8.16. Biliary ascariasis. Ultrasonography shows a tubular hyperechoic structure (arrow) in the common bile duct. (Courtesy of Ronald O. Bude, M.D., University of Michigan.)

identified in intrahepatic ducts; macerated round worms are seen as focal intraluminal soft tissue masses, with the US appearance mimicking a cholangiocarcinoma.

Magnetic resonance cholangiopancreatography has detected a hyperintense signal inside the worm digestive tract, presumably due to fluid in its gut.

The diagnosis is also established by ERC, and this technique is then used to remove the worm.

Fascioliasis

Most patients with Fasciola hepatica infestations have few symptoms. Occasionally bile duct involvement results in biliary colic or multiple pyogenic liver abscesses. Eosinophilia is common with acute infestation but not a chronic condition. Serologic testing is available.

Computed tomography detects hypodense foci scattered in the liver; these lesions resolve after therapy. MRI detects a hyperintense liver capsule in about half of infected patients (46); intrahepatic involvement ranges from hypointense regions on T1-weighted images and hypoto hyperintense on T2-weighted images.

Cholangiography reveals curvilinear radiolucent defects several centimeters long within bile ducts. Rarely, fascioliasis involves the gallbladder. Superimposed biliary calculi, strictures, and regions of fusiform dilation develop with chronic infestation. Differential diagnosis of biliary fascioliasis includes sclerosing cholangitis and infection with other parasites such as

Clonorchis sinensis (flukes are smaller), Ascaris lumbricoides (worms are larger), or Entamoeba histolytica.

Endoscopic sphincterotomy and balloon extraction of parasites are feasible. An endoscopic basket can also be used to remove the worm.

Tuberculosis

Hepatic parenchymal tuberculosis is more common than bile duct involvement. Primary biliary tuberculosis is less common than periportal lymphadenitis and secondary biliary obstruction. In some patients acid-fast bacilli can be aspirated from bile during ERCP.

Actinomycosis

In distinction to pelvic involvement, biliary actinomycosis is rare.

Resection of a cystic duct remnant in an 80-year-old woman with a prior cholecystectomy and closure of a cholecystoduodenal fistula 3 years previously revealed several dense basophilic tumors containing gram-positive branching bacilli, with fluorescent-antibody staining for Actinomyces naeslundii (47); acidfast bacilli staining was negative.

Primary Sclerosing Cholangitis

Clinical

Primary sclerosing cholangitis (PSC) is a chronic cholestatic disease clinically characterized by fatigue, pruritus, and jaundice. The etiology is not known. It can occur at any age, including early childhood; some of these patients have had previous neonatal jaundice.

Primary sclerosing cholangitis is a slowly progressing condition. The diagnosis is suspected by finding a cholestatic biochemical profile and confirmed by imaging of an abnormal biliary tract. In some, the disorder gradually progresses to cirrhosis and hepatic failure, and these patients are considered for liver transplantation.

An initial diagnosis of PSC during pregnancy is probably fortuitous. Liver function does not deteriorate during pregnancy, and

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pregnancy does not have a negative effect on PSC progression.

These patients are at increased risk of developing a cholangiocarcinoma and gallbladder adenocarcinoma.

Associated Conditions

Sclerosing cholangitis does occur as an isolated condition. More typical, especially in younger patients, is an association with inflammatory bowel disease. Liver involvement in patients with ulcerative colitis is not uncommon, although the reported prevalence varies considerably. Part of the confusion is that some patients with ulcerative colitis have nonspecific inflammation surrounding bile ducts; whether such pericholangitis is a variation of sclerosing cholangitis or a separate entity is unknown.

Sclerosing cholangitis developing in a setting of inflammatory bowel disease is still called primary; in spite of such an association, no evidence exists that bowel inflammation results in biliary changes. In fact, in some patients sclerosing cholangitis precedes the clinical detection of inflammatory bowel disease.

In the past, some authors excluded a diagnosis of PSC if bile duct calculi were present. Yet clinically and radiologically some patients have both sclerosing cholangitis and calculi, and bile duct calculi should be considered part of the spectrum of PSC.About 10% of PSC patients have intrahepatic bile duct calculi, and a similar number have chronic pancreatitis. An MR study of patients with PSC detected pancreatic abnormalities in 46%, consisting of a hypointense pancreas on T1-weighted images, hyperintense on T2-weighted images, decreased enhancement during the arterial phase, pancreatic enlargement, pancreatic duct narrowing, and peripancreatic edema or fluid (48).

Some patients with autoimmune hepatitis have cholestasis and bile duct strictures similar to those found in PSC. Occasionally reported are associations of PSC with thymoma and hypogammaglobulinemia, Sjögren’s syndrome, Graves’ hyperthyroidism, systemic lupus erythematosus, and celiac sprue. Sclerosing cholangitis has developed during interferon therapy. Whether Langerhans’ cell histiocytosis, resulting in lung cysts and beaded intrahepatic ducts in infants and a rare adult, is related to PSC is