ORLANDO – Guidelines that attempt to predict whether stones have migrated into the common bile duct appear to get it right, said an investigator at the annual Digestive Disease Week.
A prospective study looking at American Society for Gastrointestinal Endoscopy (ASGE) criteria for evaluating patients with choledocholithiais found that the guidelines correctly predicted the presence of a common bile duct (CBD) stone in 75% of patients deemed to be at high risk, and accurately called the shots in 55% of patients at intermediate risk, reported Dr. Andrew Korson of Beth Israel Deaconess Medical Center in Boston.
Dr. Andrew Korson
The ASGE guidelines are intended to help clinicians decide whether and when an invasive procedure may be warranted, based on certain clinical features, Dr. Korson noted.
"In the past decade there has been heightened awareness of the problem of proper patient selection for endoscopic retrograde cholangiography [ERC] in the setting of suspected choledocholithiasis, and to date there has been no single noninvasive test that has been shown to reliably identify these patients," he said.
The ASGE guidelines stratify patients into high-risk (greater than 50% incidence of choledocholithiasis), intermediate-risk (10%-50% incidence), and low-risk (less than 10% incidence) categories based on the presence of specific predictive features.
Very strong predictors of choledocholithiasis are evidence of a CBD stone on transabdominal ultrasound, clinical ascending cholangitis, and a bilirubin level higher than 4 mg/dL. Strong predictors are a dilated CBD on ultrasound (greater than 6 mm with gallbladder in situ) and a bilirubin level from 1.8 to 4 mg/dL. Moderate predictors are an abnormal liver biochemical test other than bilirubin, age older than 55, and clinical gallstone pancreatitis.
High-risk patients under this classification scheme are those with any very strong predictor or both strong predictors. Patients at low risk are those with no predictors present, and those at intermediate risk are everyone in between.
Only some get stones
Dr. Korson and his colleagues looked at the proportion of patients within ASGE risk categories who actually had choledocholithiasis on ERC.
They enrolled 402 consecutive patients referred to the hospital for ERC for suspected choledocholithiasis.
They considered clinical, radiographic, and biochemical data at initial presentation, and used transabdominal ultrasound to measure the CBD diameter and the presence of echodensities suggestive of stones or, if ultrasound was not performed, CT or magnetic resonance cholangiopancreatography (MRCP) to gather evidence for choledocholithiasis.
The authors used the data to prospectively apply ASGE criteria and risk-stratify the patients.
Endoscopy was performed with either sphincterectomy or balloon sweep at the discretion of the attending gastroenterologist, with the endoscopist blinded to the risk category.
Of the 402 patients enrolled, 69 were excluded for anatomical reasons or because of a lack of complete data, leaving 333 for the final analysis.
Of the 243 patients classified as high risk, 183 (75.3%) were found to have a CBD stone, and 60 (24.7%) had no stone. Of the 88 at intermediate risk, 47 (53.4%) were found on ERC to have a stone, and 41 (46.6%) were not. Neither of the two low-risk patients had a stone.
The investigators determined the positive predictive value (PPV) of the ASGE criteria to be 55% for intermediate-risk patients, and 75% for high-risk patients (P for each less than .001).
In both univariate and multivariate analyses, only radiographic evidence of a CBD stone and elevated liver enzymes (aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase) were significant predictors of risk. Ascending cholangitis, a total bilirubin level above 4 mg/dL, dilated common bile duct, age, and gallstone pancreatitis were not significant independent predictors.
The odds ratio (OR) for choledocholithiasis based on CBD stone on radiographic evidence was 3.56 (P less than .001), and for elevated liver biochemical tests, was 2.26 (P = .03).
In a post hoc univariate analysis, each 10-IU/L increase in ALT, AST, and alkaline phosphatase was associated with a respective odds ratio of 1.01 (P = .04), 1.01 (P =.03), and 1.02 (P = .04) for choledocholithiasis.
Dr. Korson noted that based on the heavy weighting of their sample toward high- and intermediate-risk patients, "further evaluation of factors that separate intermediate- from low-risk patients is warranted."
He acknowledged study limitations, including possible referral bias, because all of the cases were evaluated at a tertiary care center, a high-acuity study population was used, and CT or MRCP was used to detect CBD dilation or a stone when ultrasound was unavailable.
The funding source for the study was not disclosed. Dr. Korson reported having no relevant financial disclosures.