title: Does ultrasongraphy predict intraoperative findings at cholecystectomy? An institutional review.
abstract: BACKGROUND
  Ultrasonography (US) is the mainstay of biliary tract imaging, but few recent studies have tested its ability to diagnose acute cholecystitis (AC). Our objective was to determine how well a US diagnosis of AC correlates with the intraoperative diagnosis. We hypothesize that US underestimates this diagnosis, potentially leading to unexpected findings in the operating room (OR).
  
  
  METHODS
  This retrospective review included all patients admitted to the acute care surgical service of a tertiary hospital in 2011 with suspected biliary pathology who underwent US and subsequent cholecystectomy. We determined the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of US using the intraoperative diagnosis as the gold standard. Further analysis identified which US findings were most predictive of an intraoperative diagnosis of AC. We used a recursive partitioning method with random forests to identify unique combinations of US findings that, together, are most predictive of AC.
  
  
  RESULTS
  In total, 254 patients underwent US for biliary symptoms; 152 had AC diagnosed, and 143 (94%) of them underwent emergency surgery (median time to OR 23.03 hr). Ultrasonography predicted intraoperative findings with a sensitivity of 73.2%, specificity of 85.5% and PPV of 93.7%. The NPV (52.0%) was quite low. The US indicators most predictive of AC were a thick wall, a positive sonographic Murphy sign and cholelithiasis. Recursive partitioning demonstrated that a positive sonographic Murphy sign is highly predictive of intraoperative AC.
  
  
  CONCLUSIONS
  Ultrasonography is highly sensitive and specific for diagnosing AC. The poor NPV confirms our hypothesis that US can underestimate AC.
authors.affiliation: All authors are from the Department of Surgery, Section of General Surgery, University of Manitoba, Winnipeg, Man.
authors.forename: Shannon
authors.initials: S
authors.lastname: Stogryn
authors.affiliation: All authors are from the Department of Surgery, Section of General Surgery, University of Manitoba, Winnipeg, Man.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Metcalfe
authors.affiliation: All authors are from the Department of Surgery, Section of General Surgery, University of Manitoba, Winnipeg, Man.
authors.forename: Ashley
authors.initials: A
authors.lastname: Vergis
authors.affiliation: All authors are from the Department of Surgery, Section of General Surgery, University of Manitoba, Winnipeg, Man.
authors.forename: Krista
authors.initials: K
authors.lastname: Hardy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002763:Cholecystectomy; D041881:Cholecystitis, Acute / Q000000981:diagnostic imaging*; D006801:Humans; D008350:Manitoba; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000592:standards*; D055815:Young Adult