RESUMEN
OBJECTIVE. In patients with acute cholecystitis (AC), accurate identification of a common bile duct (CBD) stone before cholecystectomy is of concern for surgeons, gastroenterologists, and radiologists. This study evaluates the utility of preoperative MRCP taking into consideration both sonographic findings and biochemical predictors for choledocholithiasis. MATERIALS AND METHODS. Fifty-seven patients (58% women; mean age, 54 years old) with signs of AC on right upper quadrant (RUQ) ultrasound (US) who underwent subsequent MRCP from 2007 to 2017 were identified using a text-based search and retrospectively analyzed, using ERCP as the reference standard. RESULTS. For patients with AC who had a normal CBD diameter on initial RUQ US, we found a significant difference in the total and direct bilirubin levels of patients who had positive (1.94 vs 4.02 mg/dL, respectively; p = 0.013) and negative (0.71 vs 2.13 mg/dL, respectively; p = 0.02) findings for CBD stone on MRCP. ROC curve analysis showed an increased total bilirubin threshold of > 2.3 mg/dL (standard threshold, 1.2 mg/dL), which yielded a negative predictive value (NPV) of 95%. An increased direct bilirubin threshold of > 0.9 mg/dL (standard threshold, 0.2 mg/dL) yielded an NPV of 100%. CONCLUSION. In patients with AC who have a normal CBD diameter on RUQ US, normal or even mildly elevated bilirubin levels below a calculated threshold may obviate preoperative MRCP. Radiologists should be active participants in clinical decision-making; discussion between referring physicians and radiologists regarding biochemical markers and sonographic findings will lead to more appropriate use of preoperative imaging.
RESUMEN
Although most human retrotransposons are inactive, both inactive and active retrotransposons drive genome evolution and may influence transcription through various mechanisms. In humans, three retrotransposon families are still active, but one of these, SVA, remains mysterious. Here we report the identification of a new subfamily of SVA, which apparently formed after an alternative splicing event where the first exon of the MAST2 gene spliced into an intronic SVA and subsequently retrotransposed. Additional examples of SVA retrotransposing upstream exons due to splicing into SVA were also identified in other primate genomes. After molecular and computational experiments, we found a number of functional 3' splice sites within many different transcribed SVAs across the human and chimpanzee genomes. Using a minigene splicing construct containing an SVA, we observed splicing in cell culture, along with SVA exonization events that introduced premature termination codons (PTCs). These data imply that an SVA residing within an intron in the same orientation as the gene may alter normal gene transcription either by gene-trapping or by introducing PTCs through exonization, possibly creating differences within and across species.