title: Free air on plain film: Do we need a computed tomography too?
abstract: BACKGROUND
  Standard teaching is that patients with pneumoperitoneum on plain X-ray and clinical signs of abdominal pathology should undergo urgent surgery. It is unknown if abdominal computed tomography (CT) provides additional useful information in this scenario.
  
  
  OBJECTIVE
  The aim of this study is to determine whether or not CT scanning after identification of pneumoperitoneum on plain X-ray changes clinical management or outcomes.
  
  
  METHODS
  Retrospective study carried out over 4 years at a tertiary care academic medical center. All patients in our acute care surgery database with pneumoperitoneum on plain X-ray were included. Patients who underwent subsequent CT scanning (CT group) were compared with patients who did not (non-CT group).
  
  
  METHODS
  The Wilcoxon rank-sum test, t-test and Fisher's exact test were used as appropriate to compare the groups.
  
  
  RESULTS
  There were 25 patients in the non-CT group and 18 patients in the CT group. There were no differences between the groups at presentation. All patients in the non-CT group underwent surgery, compared with 83% (n = 15) of patients in the CT group (P = 0.066). 16 patients in the non-CT and 11 patients in the CT group presented with peritonitis and all underwent surgery regardless of group. For patients undergoing surgery, there were no differences in outcomes between the groups. After X-ray, patients undergoing CT required 328.0 min to arrive in the operating room compared with 136.0 min in the non-CT group (P = 0.007).
  
  
  CONCLUSIONS
  In patients with pneumoperitoneum on X-ray and peritonitis on physical exam, CT delays surgery without providing any measurable benefit.
authors.affiliation: Department of Surgery, Duke University Hospital, Durham, NC, USA ; Department of Global Health and Population, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Carolina V
authors.initials: CV
authors.lastname: Solis
authors.affiliation: Department of Surgery, Division of Trauma, Emergency Surgery and Critical Care, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Yuchiao
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Department of Surgery, Division of Trauma, Emergency Surgery and Critical Care, Massachusetts General Hospital, Boston, MA, USA ; Department of Surgery, Harvard Medical School, Boston, MA, USA.
authors.forename: Marc A
authors.initials: MA
authors.lastname: De Moya
authors.affiliation: Department of Surgery, Division of Trauma, Emergency Surgery and Critical Care, Massachusetts General Hospital, Boston, MA, USA ; Department of Surgery, Harvard Medical School, Boston, MA, USA.
authors.forename: George C
authors.initials: GC
authors.lastname: Velmahos
authors.affiliation: Department of Surgery, Division of Trauma, Emergency Surgery and Critical Care, Massachusetts General Hospital, Boston, MA, USA ; Department of Surgery, Harvard Medical School, Boston, MA, USA.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Fagenholz
keywords: Acute abdomen; computed tomography scan; gastrointestinal perforation; peritonitis; plain film; pneumoperitoneum