Recurrent pyogenic cholangitis is a disease defined by multiple instances of bacterial biliary tract infection, intrahepatic and extrahepatic biliary pigment stone formation, hepatic abscesses, and dilatation and stricturing of the intrahepatic and extrahepatic bile duct. [1, 2]
Digby published the first detailed English-language report of recurrent pyogenic cholangitis in 1930. He described a syndrome consisting of recurring episodes of suppurative cholangitis accompanied by biliary dilatation and pigment stones in the Chinese populace.
Because recurrent pyogenic cholangitis is endemic to areas of Asia, the terms Oriental cholangitis and Oriental cholangiohepatitis were once commonly used to refer to this syndrome. Recurrent pyogenic cholangitis is being recognized with increasing frequency in Western nations. However, even in these locations, it remains predominantly a disease of Asian immigrants.
The initial screening radiologic study of choice is abdominal ultrasonography. It is highly sensitive for ductal stones and ductal dilatation, and it may be helpful in localizing hepatic abscesses or other complications. All patients should undergo abdominal computed tomography (CT) scanning with contrast enhancement. CT scanning allows full assessment of the extent of disease. 
(See the images below.)
Although ultrasonography is an excellent screening test, it is operator dependent and may not demonstrate the full extent of disease. For example, intrahepatic ductal strictures and hepatic lobar atrophy can be missed. CT scanning demonstrates the features of anatomic disease, such as the extent of ductal involvement, the status of the hepatic lobes, and the presence or absence of associated abscesses. On CT scans, isoattenuating features, such as noncalcified stones and biliary sludge, can be missed.
Plain abdominal radiographs may be obtained in the workup of patients presenting acutely with abdominal pain or jaundice. The results are nonspecific and add little to no evidence to support a diagnosis of recurrent pyogenic cholangitis. 
Plain radiographs provide no reliable information to make or refute the diagnosis of recurrent pyogenic cholangitis. If the diagnosis is suspected, and abdominal sonography or CT scanning must be performed as the next step.
Because radiography is insensitive and nonspecific, false-positive or false-negative findings are not well described.
Abdominal CT scanning is the most important noninvasive radiologic study in the diagnosis of recurrent pyogenic cholangitis. It provides a wealth of information pertaining to the extent of disease, and is an invaluable adjunct in therapeutic planning.  (See the image below.)
In a study, Chan and colleagues concluded that CT is sensitive and allows complete radiologic evaluation of recurrent pyogenic cholangitis. Furthermore, they stated that CT was excellent for confirming sonographic findings, evaluating associated masses, and planning therapeutic procedures (eg, hepatic resection, duct manipulation, stone extraction).
In the study, Chan et al used CT to examine 50 patients with recurrent pyogenic cholangitis. Among the patients, 22 had undergone previous surgical procedures including sphincteroplasty or choledochoenterostomy.  A wide range of pathologic features was observed; these included intrahepatic ductal dilatation in all (100%), intrahepatic ductal calculi (74%), common bile duct dilatation (68%), pneumobilia (52%), hepatic segmental atrophy (36%), common bile duct calculi (30%), bile duct strictures (22%), and splenomegaly (14%). Unilobar hepatic disease was seen in 28%. The left lateral segment was most commonly involved.
The authors characterized CT findings demonstrable during acute exacerbations of recurrent pyogenic cholangitis. These included hepatic segmental parenchymal enhancement, hepatic abscess formation, enhancement of duct walls and biloma.
Yoon and colleagues reported 13 inflammatory hepatic pseudotumors detected with CT scanning.  The pseudotumors were 2-7 cm. They appeared as ill-defined, hypoattenuating lesions on nonenhanced scans. With the addition of contrast material, the lesions featured central hypoattenuation with a hyperattenuating or isoattenuating appearance at the periphery in 4 cases. In 9 lesions, multiple hyperattenuating internal septa were noted, as well as a hyperattenuating appearance from the periphery of the mass. All lesions were resected. The histologic findings were consistent with recurrent pyogenic cholangitis.
Findings consistent with portal hypertension, such as splenomegaly and varices, can be demonstrated by CT scan.
Spiral CT data can be reconstructed in a 3-dimensional fashion following the infusion of cholangiographic contrast agents. The reconstruction provides a noninvasive way to specifically image the biliary tree. This technique is called CT cholangiography and has been reported by Klein  and Stockberger.  Although the demonstration of stones and strictures is about as good as that with endoscopic retrograde cholangiopancreatography (ERCP), the technique does not yet have the overall accuracy to serve as a front-line replacement for studies such as ERCP or percutaneous transhepatic cholangiography (PTC).
Degree of confidence
Abdominal CT scanning is currently the most reliable imaging study for ascertaining the complete status of recurrent pyogenic cholangitis. It effectively demonstrates disease in the biliary tree and within the hepatic parenchyma with a high degree of sensitivity and overall accuracy.
Current spiral CT scanners are sensitive for detecting extrahepatic and intrahepatic calculi. More than 90% of intrahepatic stones appear hyperattenuating compared with the nonenhancing hepatic parenchyma.
Hepatic segmental atrophy, compensatory hypertrophy, capsular distortion, and complications (eg, abscesses, bilomas, cholangiocarcinomas) are reliably imaged with CT. Other parenchymal infectious complications like acute focal pyogenic hepatitis are easily delineated and appear as persistent parenchymal enhancement in affected segments.
CT is good at detecting peripheral cholangiocarcinomas, as reported by Honda and colleagues  but less reliable (40%) for hilar lesions as described by Soyer and coworkers.  Most central lesions less than 1.5 cm in diameter will be missed by CT scanning. Features of cholangiocarcinoma on CT include hypoattenuation, lack of encapsulation, central scarring, contrast pooling, and capsular retraction.
Hyperattenuating stones become more difficult to image after the hepatic parenchyma is enhanced with the administration of contrast material. Pneumobilia in patients presenting with acute exacerbations or in those who have undergone a biliary-enteric anastomosis for drainage can decrease the sensitivity of the examination. However, this can be remedied by adjusting window width.
Upper gastrointestinal preparation with oral contrast agents should be avoided. This approach may cause contrast material to reflux into the common bile duct and confound the findings of the study.
Examiners should be aware that chronic disease can distort the hepatic parenchyma, with atrophy of affected segments or lobes and compensatory hypertrophy of other areas. This can cause rotation of the liver and alteration of normal anatomical relationships of portal triad structures. The most common hepatic segments that display atrophic changes include the lateral segment of the left lobe and posterior segment of the right lobe.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is being used more frequently than before in the assessment of recurrent pyogenic cholangitis. It can demonstrate all the salient features of the disease, including stones, ductal dilatation and strictures, and hepatic parenchymal disease. Hepatic segmental or lobar atrophy and hypertrophy are easily delineated. Pyogenic hepatitis appears as hepatic parenchymal enhancement on T1-weighted images. Hepatic abscesses and cholangiocarcinomas are both focally hypointense and hyperintense masses on T1- and T2-weighted images, respectively. (See the images below.) [11, 12, 13]
T2-weighted images are well suited for depicting ductal pathology because bile-filled structures produce particularly high signal intensities. According to Brinks and Borello, stones are easily detected as intraductal filling defects, irrespective of their chemical composition.  In comparison, T1-weighted images are better for demonstrating acute suppurative cholangitis, which appears as ductal wall enhancement.
Magnetic resonance cholangiography (MRCP) is a technique that allows 3-dimensional reconstruction and display of the biliary tree. It is most commonly performed by using heavily T2-weighted protocols, which make bile-filled structures appear extremely bright against a hypointense background. Features of recurrent pyogenic cholangitis, such as ductal dilatation, common bile duct stones, and intrahepatic stones, are detected with sensitivities in the range of 80-95%. MRCP accurately depicts sites of obstruction in 85-100% of cases. Reports supporting these rates have been published. [15, 16, 17]
Possible MRCP techniques currently include single-shot rapid acquisition and relaxation enhancement (RARE) and half Fourier acquisition single-shot turbo-spin echo (HASTE) in a single breath-hold with negative oral contrast to decrease the MRCP signal from fluid in the gastrointestinal tract. 
Park and colleagues compared MRCP with direct conventional cholangiography.  A total of 24 patients underwent preoperative MRCP before surgery for recurrent pyogenic cholangitis. Eighteen also underwent preoperative conventional cholangiography. The results were verified by the anatomic findings at surgery.
MRCP was able to depict 100% of hepatic segments with ductal dilatation, 98% of segments with ductal calculi, and 96% of segments with focal strictures. Conventional cholangiography showed 47% of segments with ductal dilatation, 45% with ductal calculi, and 44% with focal ductal strictures. The authors concluded that MRCP was superior to conventional cholangiography for the anatomic evaluation of recurrent pyogenic cholangitis since it can depict the entire biliary tree, even in the presence of ductal obstruction or stenosis.
Degree of confidence
MRI and MRCP are highly sensitive and accurate techniques. They can depict ductal and parenchymal pathology as well as any other radiologic study and are likely to become the studies of choice in recurrent pyogenic cholangitis.
Ductal strictures are usually short (<1 cm) and are easily seen on MRCP in comparison with CT, according to Heffernan and colleagues. 
These techniques do not expose the patient to ionizing radiation and do not require the injection of contrast agents. They also are noninvasive, require no anesthesia, and allow for better visualization of ducts proximal to an obstruction or stenosis.  MRCP also does not increase the risk of biliary sepsis. 
In 1995, Soyer and colleagues described the presence of a hyperintense central scar on T1-weighted images.  This finding and contrast-agent pooling in the mass on late images are more consistent with a cholangiocarcinoma than with other conditions. Data published by Fan and coworkers suggest that MRI is more sensitive than CT in detecting hilar cholangiocarcinomas. 
No normal variants that mimic this disease process have been well described. Various pathologic findings associated with this disease process are better visualized on T1-weighted images than on T2-weighted images or vice versa. These techniques are complementary and should be used together to avoid false-negative results.
Abdominal ultrasonography is the initial screening examination of choice. Ultrasonography is noninvasive and does not expose the patient to ionizing radiation. It is also sensitive for biliary tract pathology. The findings can suggest or confirm the diagnosis in up to 97% of cases of recurrent pyogenic cholangitis, according to Ohto and coworkers. 
Ultrasonography easily demonstrates dilatation of extrahepatic and proximal intrahepatic ducts. Calculi within the extrahepatic biliary radicles and central intrahepatic ducts are readily depicted as described by Lim and colleagues.  The intrahepatic stones are usually hyperechoic compared with the hepatic parenchyma. Sonograms may depict the decreased arborization or truncation of hepatic ducts that typify recurrent pyogenic cholangitis.
Distribution of ductal dilatation as visualized on ultrasonography tends to be unrelated to the location of calculi. This may be secondary to widespread elasticity of the duct walls, as stated by Heffernan and colleagues. 
Features of hepatic parenchymal disease that can be detected with ultrasonography include increased periportal echogenicity, liver abscesses, and bilomas. An associated cholangiocarcinoma appears as a homogeneous, hyperechoic mass, according to Zhang and coinvestigators. 
Ultrasonography can also be used to help guide interventional procedures, such as the aspiration or drainage of bilomas and hepatic abscesses, as well as fine-needle or core biopsy of suspected neoplasms. 
Ultrasonography is the best noninvasive modality for actual imaging of the offending parasites. Flukes are poorly visualized with CT and MRI. With ultrasonography, flukes or clusters of the parasites appear as echogenic foci that are nonshadowing within the bile ducts. Morikawa and associates were able to capture flukes in motion within peripheral bile ducts on M-mode sonograms. 
Lim and colleagues note that flukes are easiest to visualize in the gallbladder.  They sink toward the dependent portion of the organ but can be made to float temporarily with a change in position or transdermal agitation of the gallbladder with the transducer. Flukes in the gallbladder appear fusiform and weakly echogenic and do not produce shadows. [25, 26]
Degree of confidence
The diagnosis of recurrent pyogenic cholangitis can be made with a high degree of confidence in the vast majority of patients. Sonographic findings should be confirmed by another modality, such as CT or MRI. These studies are better at defining the overall extent of hepatic parenchymal and intrahepatic ductal disease.
Distal intrahepatic ductal and parenchymal disease can be difficult to image with ultrasonography. Patients with acute exacerbations of recurrent pyogenic cholangitis can present with pneumobilia, which obscures details of the ductal system. The presence of ductal air along with a dilated duct packed with stones can appear like an abscess in the acute setting. Also, because the stones in recurrent pyogenic cholangitis are pigment stones, they may be isoechoic and therefore missed by sonographic examination. As always, ultrasonography is highly operator dependent.
Radionuclide studies are not typically used in the diagnostic algorithm for recurrent pyogenic cholangitis. Their results are nonspecific and do not yield enough information upon which to base treatment strategy. While the studies may demonstrate some extrahepatic ductal abnormalities well, they are poor choices for delineating the location and extent of intrahepatic disease.
Before the advent of sophisticated CT and MRI techniques, direct contrast cholangiography was considered essential in the diagnosis of recurrent pyogenic cholangitis and in the assessment of the disease's extent. It can still provide critical information about location and extent of stones and ductal dilatation and strictures.
Classic cholangiographic findings of recurrent pyogenic cholangitis include ductal dilatation, which is frequently most marked in the extrahepatic duct; dilatation of the proximal central intrahepatic ducts with associated abrupt truncation of more peripheral ducts; and filling defects in contrast agent–filled ducts, which represent the presence of stones.
Khuroo and coworkers published findings of direct contrast cholangiography in 227 patients with recurrent pyogenic cholangitis.  Baseline cholangiographic abnormalities included biliary calculi and sludge, bile duct dilatation and strictures. Only 21 patients had cholangiographic evidence of prior parasite infestation.
A cohort of 55 patients in the study underwent serial cholangiography at intervals of about 18 months. In this subgroup, symptoms and cholangiographic abnormalities resolved in 25 who underwent successful endoscopic sphincterotomy and extraction of biliary calculi. In the remaining patients, recurrent pyogenic cholangitis reoccurred, and the cholangiographic findings worsened over time.
ERCP and PTC are the most common clinical approaches to cholangiography. Both of these are invasive procedures and have low, but not negligible, complication rates. In addition, Sherman and Lehman reported inability to cannulate the common bile duct in 5-10% of attempted ERCP studies. 
Degree of confidence
Cholangiography demonstrates ductal disease and the presence of stones with relatively high sensitivity and specificity. This is especially true of the extrahepatic and more centrally located intrahepatic bile ducts. Weaknesses include inability to detect disease distal to strictures and an inherent inability to image the hepatic parenchyma. CT scanning is required to provide information about the extent of hepatic parenchymal disease. This is particularly critical if hepatic resection is planned.
The predictive value of a positive test is high. The false-positive findings are few. False-negative studies can occur when strictures limit the ability to image distal ductal disease.