Gallstone disease other imaging findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Bile microscopy — Bile microscopy detects microcrystals of cholesterol or amorphous bilirubinate as indirect evidence for the presence of microlithiasis in the bile. It has an overall sensitivity of 65 to 90 percent for identifying patients with gallstones [43-47]. Because of the improved sensitivity of transabdominal ultrasonography for detection of small stones and sludge, there is less need for microcrystal analysis. However, it still has a role in category 4 patients with biliary colic without gallstones on transabdominal ultrasound. However, because obtaining a sample for bile microscopy during endoscopy can take over 45 minutes, we reserve the procedure for patients with a negative EUS.
The test is based upon the theory that patients with cholesterol microlithiasis have bile that is supersaturated with cholesterol and thus have cholesterol monohydrate crystals in their gallbladder bile (picture 1), while those with bilirubinate microlithiasis have amorphous reddish-brown bilirubinate granules in their gallbladders (picture 2) [48,49]. However, the methods for performing the test have not been well standardized, which has led to confusion regarding how to collect and process the bile samples for analysis and what constitutes a positive test.
The proportion of patients with suspected gallstones but negative transabdominal ultrasound found to have microlithiasis varies substantially among reports. A systematic review found that microcrystals accounted for 7 to 79 percent of cases of idiopathic pancreatitis, 83 percent of patients with unexplained biliary-type pain, and 25 to 60 percent of patients with altered biliary and pancreatic sphincter function [50].
While the presence of any cholesterol crystals is theoretically abnormal, to increase specificity, some of the newer reports presume the test to be positive only if more than three crystals are seen per high power field [51]. However, whether findings based upon this approach correlate with clinical outcomes has not been established. As a result, this presumption has not been widely accepted.
Bile collection — Most available studies describe the test as it pertains to the detection of microlithiasis in patients with idiopathic recurrent pancreatitis and have used variable techniques for bile collection, bile processing, and microscopic crystal analysis. Nevertheless, most investigators agree that crystals are formed in the gallbladder where bile is concentrated, so gallbladder bile rather than hepatic bile should be analyzed [28,44,52]. Hepatic bile is significantly less concentrated and thus has a lower yield for the detection of microlithiasis.
Gallbladder bile can be collected using the following techniques:
●Through direct percutaneous puncture of the gallbladder under ultrasound or fluoroscopic guidance. ●During endoscopic retrograde cholangiopancreatography, either through selective gallbladder cannulation or by aspirating bile from the common bile duct after stimulating gallbladder contraction with a slow intravenous infusion of the cholecystokinin (CCK) analogue, sincalide. ●During endoscopy by suctioning bile from the duodenum in the region of the ampulla after gallbladder stimulation with sincalide. In most cases, collection during endoscopy is the simplest and most practical method. Since EUS includes an endoscopic examination, bile collection can be performed during the same session as an EUS, which increases the sensitivity for detecting gallstones over that of EUS alone [40,42]. (See 'Endoscopic ultrasound' above.)
Our approach in patients with biliary colic and a negative EUS is to collect a bile sample during the same endoscopic session as the EUS. Sincalide (0.03 mcg/kg body weight) is given by intravenous drip over 45 minutes; the longer infusion is safer and more effective than a short bolus technique [53]. The tip of the endoscope is positioned next to the ampulla and the bile is aspirated. Bile flow usually starts to accelerate within five minutes of the start of the sincalide infusion. The first 5 to 10 minutes of bile flow is normally light in color and represents common bile duct and hepatic bile. Gallbladder bile is the darker bile that starts flowing several minutes later. We use a commercially available bile collecting catheter with a mushroom tip that we introduce through the working channel of the endoscope and connect to an external suction trap. Once we start to observe dark gallbladder bile being suctioned into the collecting trap, we empty the light colored bile from the trap and begin collecting the dark bile sample. When about 10 to 20 mL of bile has been collected, we stop the Sincalide infusion and conclude the procedure. This typically takes about 30 to 45 minutes from the start of the sincalide infusion to accomplish.
The collected sample of dark bile is incubated at 37°C for 24 hours and then centrifuged at 3000 G for 30 minutes [54]. The supernatant is discarded and the sediment is mixed into the liquid remaining at the bottom of the tube. A drop of that liquid is placed on a slide and examined using a polarizing microscope; a polarizing filter facilitates identification of cholesterol crystals, which exhibit birefringence (they shine against the dark background of the polarizing microscope). The test is considered positive if any cholesterol crystals or amorphous red-brick colored bilirubinate granules are seen.
Tests that are rarely done
Oral cholecystography — Oral cholecystography can diagnose gallstones and assess gallbladder function, but it has largely been replaced by more sensitive and specific tests, such as transabdominal ultrasound [33,55]. It is still occasionally used in patients in whom a high-quality ultrasound examination cannot be obtained (such as in obese patients), to confirm the presence of adenomyomatosis of the gallbladder, and to evaluate patients who are being considered for medical dissolution therapy with ursodeoxycholic acid, in whom it is important to demonstrate stone number and size, relative density of the stones to bile, cystic duct patency, and the gallbladder's concentrating ability. (See "Patient selection for the nonsurgical treatment of gallstone disease".)
An orally administered contrast agent (eg, iopanoic acid, sodium tyropanoate, or calcium ipodate) is given and is absorbed through the intestine, taken up by the liver, and secreted into bile. Gallstones appear as filling defects within the contrast on plain radiographs (image 5). Non-opacification of the gallbladder can occur due to poor absorption from the intestine, impaired liver function, or extrahepatic biliary obstruction. With the currently available oral contrast agents, it is unlikely that the gallbladder will be visualized if the serum bilirubin is greater than 2 to 3 mg/dL.
An approximation of gallbladder motor function can also be obtained using oral cholecystography. The patient is given a fatty meal and serial radiographs are obtained. If the gallbladder is functioning normally, there will be a decrease in gallbladder size over time. Evaluation of the gallbladder motor function is not recommended in patients who have known gallbladder stones since it may induce biliary colic or complications of gallstone disease.
Endoscopic Retrograde Cholangiopancreaticogram (ERCP) Endoscopic retrograde cholangiopancreaticogram (ERCP) is often performed by gastroenterologists or surgeons, and not by radiologists. This test involves putting a tube into the patient's mouth, down the throat, into the stomach, through the duodenum and then, into the common bile duct. ERCP is performed with the patient sedated. Looking through the tube, the gastroenterologist is able to locate the hole in the duodenum where the bile comes in from the common bile duct. A smaller tube or catheter is passed through this hole and contrast material is injected. The contrast agent (dye) also can be injected into the pancreatic duct, showing that ductal system as well. The thick endoscopic tube affords visualization and other things as well. If the problem is a stone in the lower bile duct, the gastroenterologist can often put a basket into the tube and snare the stone and remove it. If the problem is tumor, the endoscopist can insert a biopsy device and remove a small piece of tissue for review by the pathologist. Finally, the endoscopist can help open the connection between the common bile duct and the duodenum by cutting the muscle that encircles the valve (sphincterotomy)—allowing stones that would have been trapped at the junction to flow right on through.
Endoscopic retrograde cholangiopancreatography — Traditionally, ERCP (image 2) was used both as a diagnostic and therapeutic procedure in patients with suspected choledocholithiasis. The sensitivity of ERCP for choledocholithiasis is estimated to be 80 to 93 percent, with a specificity of 99 to 100 percent [28,29]. However, ERCP is invasive, requires technical expertise, and is associated with complications such as pancreatitis, bleeding, and perforation. As a result, ERCP is now reserved for patients who are at high risk for having a common bile duct stone, particularly if there if evidence of cholangitis, or who have had a stone demonstrated on other imaging modalities. (See 'High-risk patients' above and "Endoscopic retrograde cholangiopancreatography: Indications, patient preparation, and complications".)
EUS and MRCP — EUS (image 3) and MRCP (picture 1) have largely replaced ERCP for the diagnosis of choledocholithiasis in patients at intermediate risk for choledocholithiasis. EUS is less invasive than ERCP, and MRCP is noninvasive. Both tests are highly sensitive and specific for choledocholithiasis [30]. Deciding which test should be performed first depends on various factors such as ease of availability, cost, patient-related factors, and the suspicion for a small stone (table 1). (See 'Intermediate-risk patients' above and "Magnetic resonance cholangiopancreatography" and "Endoscopic ultrasound in patients with suspected choledocholithiasis".)
EUS and MRCP for the diagnosis of choledocholithiasis have been evaluated using ERCP as the reference standard:
●A meta-analysis of 27 studies with 2673 patients found that EUS had a sensitivity of 94 percent and a specificity of 95 percent [31]. ●A review of 13 studies found that MRCP had a median sensitivity of 93 percent and a median specificity of 94 percent [32]. Studies have prospectively compared the accuracy of EUS with MRCP in the diagnosis of choledocholithiasis. These have been reviewed in two systemic reviews, both of which showed no significant differences between the two modalities [33,34]. In a pooled analysis of 301 patients from five randomized trials that compared EUS with MRCP, there was no statistically significant difference in aggregated sensitivity (93 versus 85 percent) or specificity (96 versus 93 percent).
MRCP is preferred for many patients because it is noninvasive. However, the sensitivity of MRCP may be lower for small stones (<6 mm, (image 3)) [35], and biliary sludge can be detected by EUS, but generally not by MRCP. As a result, EUS should be considered in patients in whom the suspicion for choledocholithiasis remains moderate to high despite a negative MRCP. (See 'Intermediate-risk patients' above.)
Intraoperative cholangiography — Intraoperative cholangiography has an estimated sensitivity of 59 to 100 percent for diagnosing choledocholithiasis, with a specificity of 93 to 100 percent [29,36,37]. However, it is highly operator-dependent and is not routinely performed by many surgeons [38].
In the era prior to laparoscopic surgery, patients with gallstone disease and suspected choledocholithiasis underwent open cholecystectomy including cholangiography and palpation of the common bile duct and/or open exploration of the common bile duct to diagnose and treat choledocholithiasis. As laparoscopic surgery replaced open surgery as the preferred method for cholecystectomy, exploration of the common bile duct for removal of intraductal stones became technically more challenging. (See "Laparoscopic cholecystectomy", section on 'Evaluation for choledocholithiasis' and "Common bile duct exploration", section on 'Intraoperative cholangiography'.)
With improvements in cholangiography techniques and the use of fluoroscopic rather than static cholangiography, the successful completion rate and accuracy of intraoperative cholangiography have improved over time [39]. In practice, the use of intraoperative cholangiography is highly operator-dependent and may be technically unfeasible in patients with a severely inflamed gallbladder or with a tiny or inflamed cystic duct.
Studies of intraoperative cholangiography during laparoscopic cholecystectomy have shown the following:
●In a review of 13 studies with 1980 patients undergoing laparoscopic cholecystectomy, 9 percent had choledocholithiasis [36]. The success rate for technical completion of intraoperative cholangiography ranged from 88 to 100 percent. Intraoperative cholangiography had a sensitivity of 68 to 100 percent and a specificity of 92 to 100 percent for diagnosing choledocholithiasis. ●In a more recent prospective population-based study, intraoperative cholangiography was routinely attempted in 1171 patients undergoing cholecystectomy [37]. The cholecystectomy was carried out laparoscopically in 79 percent. Intraoperative cholangiography was successful in 95 percent, and choledocholithiasis was identified in 134 patients (11 percent). The sensitivity and specificity of intraoperative cholangiography were 97 and 99 percent, respectively. There is ongoing debate about the routine use of intraoperative cholangiography in all patients undergoing laparoscopic cholecystectomy versus selective use in patients at increased risk for intraductal stones, and practices vary widely among surgeons. Proponents of routine intraoperative cholangiography argue that it permits delineation of biliary anatomy, reduces and identifies bile duct injuries, and identifies asymptomatic choledocholithiasis. Opponents argue that intraoperative cholangiography adds to procedure time and expense. In addition, they argue that asymptomatic common bile duct stones may pass spontaneously and/or have a low potential for causing complications, such that their identification may lead to unnecessary common bile duct exploration and/or conversion to open surgery [40-50].
A 2008 study examined the frequency with which surgeons employ intraoperative cholangiography. In the survey of 1417 surgeons, 27 percent defined themselves as routine intraoperative cholangiography users [38]. Among the routine users, 91 percent reported using intraoperative cholangiography in more than 75 percent of laparoscopic cholecystectomies. Academic surgeons were less often routine users compared with nonacademic surgeons (15 versus 30 percent).
There are no other imaging findings associated with [disease name].
OR
[Imaging modality] may be helpful in the diagnosis of [disease name]. Findings on an [imaging modality] suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].
Other Imaging Findings
- There are no other imaging findings associated with [disease name].
- [Imaging modality] may be helpful in the diagnosis of [disease name]. Findings on an [imaging modality] suggestive of/diagnostic of [disease name] include:
- [Finding 1]
- [Finding 2]
- [Finding 3]