Chapter 5: Investigations and Diagnosis

No single clinical variable is completely accurate in predicting the presence of choledocholithiasis. Therefore, the results of a detailed history and physical examination, laboratory evaluations, and diagnostic imaging tests must be taken together when assessing the likelihood that a patient has CBD stones (Nakeeb 2006).

Serum liver function tests (bilirubin, alkaline phosphatase, and transaminases) can be useful in predicting common duct stones. If any one value of the liver profile is elevated, the risk for CBD stones approaches 20%. With two elevated values the risk increases to nearly 40% and with three or more elevated values the risk for CBD stones is nearly 50%. However, between 5% and 7% of patients with normal liver function have CBD stones identified by cholangiography at the time of cholecystectomy. A patient with any one of these indicators has at least ten times the risk of having CBD stones compared with a patient without the risk factor (Abboud et al., 1996).

Serum bilirubin level >10 mg/dL suggests malignant obstruction or coexisting hemolysis. A transient “spike” in serum aminotransferase or amylase (or lipase) levels suggests the passage of a stone (Browning et al., 2006).

It is well known that increased concentrations of CA 19-9 can be found in benign disease of the liver, pancreas and biliary tract, especially in cases with gallstone disease with cholangitis. CA 19-9 levels are associated with biliary obstruction and cholangitis but not with the number and size of stones in patients with choledocholithiasis (Doayan 2011).

Since its introduction in the 1970s, ultrasonographic examination of the biliary tract has become the principal imaging modality for the diagnosis of cholelithiasis. Ultrasonography requires no special preparation of the patient, except for fasting of at least 8 hours, because gallstones are best seen in a distended, bile-filled gallbladder. It involves no ionizing radiation, is simple to perform, and provides accurate anatomic information. It has the additional advantage of being portable and thus available at the bedside of a critically ill patient (Bortoff et al., 2000).

Ultrasound is very sensitive for the diagnosis of gallstones within the gallbladder. Unfortunately, it successfully identifies the presence of CBD stones in only 70% of patients because the distal end of the bile duct is frequently obscured by duodenal or colonic gas. Ultrasound can identify CBD dilation, which can suggest choledocholithiasis. If the extrahepatic bile duct diameter is less than 3 mm, CBD stones are exceedingly rare, whereas a diameter greater than 10 mm in a jaundiced patient predicts CBD stones in more than 90% of cases (Nakeeb 2006).

 

In order to predict the presence of CBD stones more accurately, the combination of clinical, laboratory, and ultrasound risk factors has been used by several investigators. In one study, multivariate logistic regression analysis revealed that when a dilated CBD with stones was found by ultrasound in combination with cholangitis and elevated aspartate transaminase and bilirubin, the likelihood of having stones in the bile duct was 99%. If all these factors were absent, the chance of synchronous choledocholithiasis in patients with cholelithiasis was only 7% (Sarli et al., 2003).

 

With the advent of new three-dimensional (3D) sonographic techniques, additional information may be gained in the evaluation of common duct morphology. Three-dimensional sonography also provides rapid data acquisition and the ability to store raw data for later review. Three-dimensional sonographic measurements of the CBD correlate highly with two-dimensional measurements, validating the use of three-dimensional sonography as a reliable method for evaluation of common bile duct size (Rao et al., 2003).

           Intraoperative ultrasonography can also be used to identify CBD stones at the time of cholecystectomy. In experienced hands, intraoperative ultrasonography has been shown to be comparable to intraoperative cholangiography (IOC) for the diagnosis of CBD stones. Laparoscopic ultrasonography is performed with a high frequency (7.5- to 10-mHZ) probe, and the bile duct is imaged in the transverse and longitudinal planes. The distal bile duct can be visualized in more than 95% of cases (Gurusamy et al., 2010).

              Contrast-enhanced ultrasound (CEUS) is a recently introduced method that is known to have exclusive advantages including cost-effectiveness, real-time imaging, no radiation damage, whilst also being very convenient. In addition to extensive intravenous application, CEUS is also suitable for intracavitary use, one example being voiding ultrasound. Recently, CEUS has even been expanded to be used intraoperatively cholangiography and demonstrates good consistency with IOC (Claudon et al., 2008) percutaneous ultrasound cholangiography (PUSC) comparable to Percutaneous transhepatic cholangiography (PTC)  in depicting the anatomy of the dilated bile duct tree and determining the level of obstruction for patients with obstructive jaundice, hence it expands the capacity of ultrasound in evaluating obstructive bile duct disease and simplifies the procedure of assessing obstructive jaundice (Luyao et al., 2012).

Endoscopic ultrasound (EUS) is a semi invasive test that can be performed with a very low rate of complications (<0.1%).The sensitivity and specificity for the diagnosis of CBD stones by EUS ranges from 92% to 100% and 95% to 100%, respectively. The negative predictive value for EUS is more than 97%.Therefore, when EUS is negative for common duct stones, ERCP or IOC can be avoided (Vilgrain et al., 2001). In a randomized study of 65 patients suspected to have biliary obstruction without cholangitis, EUS-guided biliary intervention was safe, had a high positive predictive value (100%) for bile duct stone and sludge disease, and prevented exposure to the possible complications of ERCP (Lee et al., 2008).

Magnetic resonance cholangiopancreatography (MRCP) has recently been developed as another noninvasive means of imaging the biliary tract. Several studies have shown that MRCP can diagnose CBD stones with a sensitivity of 90%, a specificity of 100%, and an overall diagnostic accuracy of 97%(Nakeeb 2006).  The main advantage of MRCP is that it allows for the direct imaging of the biliary tract without the need for contrast or an invasive procedure. Disadvantages include its high cost, lack of availability, and lack of therapeutic capacity. MRCP has been used to screen patients at low and moderate risk of having common duct stones prior to ERCP. A normal MRCP can avoid the need for an invasive ERCP (Schmidst et al., 2007). MRCP may become more popular as costs are reduced and surgeons become more skilled with laparoscopic techniques for managing CBD stones (Jagadesham et al., 2012).

                MRCP is a reliable and noninvasive evaluation for the detection or exclusion of CBD stones. Rather than indicating a need for CBD exploration, MRCP is more useful in determining when not to explore and for avoiding retained CBD stones in small CBD. No single predictor or combined markers have been found to be the best evidence to include or exclude the presence of CBD stones if the stone is directly inspected by cholangiography (Shiu et al., 2012).

Computerized Tomography (CT) is not well suited for detecting uncomplicated stones, but excellent for detecting complications of choledocholithiasis, such as abscess, perforation of the gallbladder or CBD, and pancreatitis. Spiral CT may prove useful as a noninvasive means of excluding CBD stones; some studies suggest improved diagnostic accuracy when CT is combined with an oral cholecystographic contrast agent (Tseng 2008).

             Another modality of using CT in the diagnosis of choledocholithiasis is computed tomographic intravenous cholangiography (CT-IVC). CT-IVC is highly accurate for detection of ductal calculi, including single small calculi, with a normal or near normal serum bilirubin with a sensitivity and specificity for of 95.6 and 94.3%, respectively (Gibson et al., 2005).

Conventional oral or intravenous cholangiography which is cholangiography after administration of either oral or IV iodinated biliary contrast agents is no longer used routinely in most countries (Wald et al., 2008).

          PTC has been substantially replaced by ERCP and MRCP. Its role now is mostly as part of transhepatic biliary intervention, although occasionally it is used diagnostically (Ozcan et al., 2012). A 22 g Chiba needle is used to puncture the right or left intrahepatic ducts from the right flank or, for left ducts, from an epigastric approach. Any coagulation disorder should be reversed with vitamin K prior to the procedure, which is performed with broad-spectrum IV antibiotic cover and conscious sedation. When the ducts are entered by the needle contrast medium is injected to opacify the biliary tree. Care should be taken to opacify the entire biliary tree. The aspiration of some bile during the procedure reduces the risk of bile leak and endotoxaemia by reducing intraductal pressure. Success rates are close to 100% if the ducts are substantially dilated and about 75% if they are nondilated or only slightly dilated. The major complication rate is about 4% and includes haemobilia, bacteraemia and bile leak (Gossage et al., 2012).

              ERCP has the advantage of providing a therapeutic option at the time CBD stones are identified and is therefore the preferred approach for patients with suspected CBD stones. Skilled endoscopists can successfully cannulate the CBD in approximately 90% to 95% of patients. Complications of diagnostic cholangiography include pancreatitis and cholangitis and occur in up to 5% of patients. ERCP may be unsuccessful in patients with previous gastric surgery (Bilroth II reconstruction), periampullary diverticula, or tortuous biliary ducts. PTC may be used to image the bile ducts if ERCP is unsuccessful (Jagadesham et al., 2012).

          The invasive nature of ERCP in addition to its potential complications has limited its use as a diagnostic rather than a therapeutic maneuver. The typical indication for EUS as well as MRCP is the search of choledocholithiasis in patients with a low and intermediate probability of stone disease in order to avoid purely diagnostic ERCP (Schmidst et al., 2007).

         Both ERCP and PTC techniques can be used to directly visualize the biliary tree. A comparison between them is noted in the following table.

Criterion Transhepatic cholangiography Endoscopic cholangiography Success rate >90% with dilated ducts, 70% with nondilated ducts 80 to 90% with either dilated or nondilated ducts Identification of cause of obstruction 90% to 100% 75% to 90% Complications 5%, (range, 3% to 10%) 5% (range, 2% to 7%) Mortality 0.2% to 0.9% 0.1% to 0.2% Expense Less More Skill required Less More Patient selection Proximal lesions, altered gastroduodenal anatomy, failed endoscopic cholangiography Distal lesions, pancreatic pathology, coagulopathy, ascites, failed transhepatic cholangiography

Table (2): Comparison between ERCP and PTC (Nakeeb 2006).  

 

 

 

           IOC can be successfully accomplished in more than 95% of cases. The cholangiogram should be carefully evaluated for filling defects within the ducts, presence of contrast in the duodenum, and the intrahepatic biliary anatomy (Ellison 2005).   

            Debate continues over the need to perform routine IOC at the time of cholecystectomy. Advocates of routine IOC argue that asymptomatic CBD stones can be identified and Bile Ducts Injury (BDI) can be prevented by performing routine IOC. Implementation of routine IOC policy was followed by fewer major BDIs and higher rates of intraoperative CBD stone management (Buddingh et al., 2011).

          Critics of this approach suggest that the incidence of retained stones is no greater when IOC is performed selectively based on clinical and laboratory criteria. The indications for performing IOC during cholecystectomy include: (a) a marginally dilated CBD, (b) a wide cystic duct, (c) palpable CBD stones, (d) elevated serum liver function tests or bilirubin, and (e) a history of pancreatitis or jaundice. If these criteria are strictly followed, approximately 30% of patients will require IOC at the time of cholecystectomy. IOC can identify the size, number, and location of CBD stones in addition to defining biliary anatomy. This information is critical in choosing the most appropriate treatment for CBD stones (Sheffield et al., 2012).

 

Table (3): Summary of imaging modalities in choledocholithiasis (Parks et al., 2005).

Imaging modality	Diagnostic potential	Therapeutic potential	Limitations
Transabdominal ultrasonography	Index investigation in the evaluation of biliary tree obstruction, gallbladder/bile duct stones intrahepatic cysts/abscess/metastases, intra-abdominal collections/free fluid	Percutaneous drainage	More difficult in the obese. Images can be obscured by bowel gas Operator-dependent
Endoscopic ultrasonography	Evaluation of (distal) biliary tree obstruction Bile duct stones. Biopsy (mass/lymph node)	None	Operator-dependent
Laparoscopic ultrasonography	Evaluation of malignant biliary strictures  (size/relationship to portal vein/hepatic arteries/lymph node involvement/liver metastases/peritoneal disease) Biopsy (mass/lymph node)	None	Operator-dependent

 

 

 

Endoscopic retrograde cholangio- pancreatography	Evaluation of biliary tree obstruction Biliary brushings/biopsy Biliary manometry	Sphincterotomy. Stone extraction. Endobiliary stenting (plastic/metal).	Operator-dependent. Technically difficult if previous polya gastrectomy or duodenal diverticulum. Risk of bleeding/duodenal perforation/
Percutaneous transhepatic cholangiography	Evaluation of biliary tree obstruction (particularly hilar cholangiocarcinoma) Bile for cytology	Percutaneous biliary drainage/stenting (plastic/metal).	Operator-dependent. Risk of bleeding/duodenal perforation/ cholangitis
Spiral computed tomography	Diagnosis and staging of disease – newer scanners provide biliary and vascular reconstruction Monitoring response to treatment	Percutaneous drainage	Quality of scanner
Magnetic resonance cholangio- pancreatography	Biliary tree dilatation. Bile duct stones Evaluation of malignant biliary strictures (particularly hilar cholangiocarcinoma) Avoids complications of ERCP	None	Claustrophobia. Contraindicated with iron-containing implants. Small common bile duct stones may be missed. Difficult to interpret if air in the biliary tree.

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