title: Distinction between upper and lower gastrointestinal perforation: usefulness of the periportal free air sign on computed tomography.
abstract: OBJECTIVE
  To evaluate the usefulness of the periportal free air (PPFA) sign on computed tomography (CT) to distinguish upper from lower gastrointestinal (GI) tract perforation.
  
  
  METHODS
  During a 30-month period, we retrospectively analyzed abdominal CT images of 53 consecutive patients with surgically proven GI tract perforation. We divided the patients into two groups, i.e. upper and lower GI tract perforation groups. According to the distribution of free air, we divided the peritoneal cavity into supramesocolic compartment and inframesocolic compartment. We observed the presence or absence of free air in each compartment in each group. When there was free air in the periportal area, it was defined as periportal free air (PPFA) and the sign was positive. To evaluate the usefulness of the PPFA sign, we compared the PPFA sign with the falciform ligament sign and the ligamentum teres sign, both of which are well-known CT signs of pneumoperitoneum. Statistical analyses were performed with univariate and multivariate analyses using SPSS version 11.5 for significant findings among the CT signs.
  
  
  RESULTS
  Free air was seen in supramesocolic compartment in 29 of 30 (97%) patients in the upper GI perforation group and in 17 of 23 (74%) in the lower GI perforation group. Free air in inframesocolic compartment did not show significant difference in either group (p=.16). The PPFA sign was seen in 28 of 30 (93%) patients with upper GI tract perforation, but in only 8 of 23 (35%) patients with lower GI tract perforation (p<.0001). The falciform ligament sign was seen in 24 of 30 (80%) patients with upper GI tract perforation and in 10 of 23 (43%) patients with lower GI tract perforation (p=.020). The ligamentum teres sign was seen in 16 of 30 (53%) patients with upper GI tract perforation and in 2 of 23 (8%) patients with lower GI tract perforation (p=.008). Multivariate logistic regression analysis showed that the PPFA sign was the only variable, which adjusted odds ratio of 15.5 (p=.002).
  
  
  CONCLUSIONS
  The PPFA sign is a useful finding which can help to distinguish upper from lower GI tract perforation. When this sign is present, upper GI tract perforation is strongly suggested.
authors.affiliation: Department of Radiology, Wonkwang University School of Medicine, 344-2 Sinyong-dong, Iksan, Jeonbuk 570-711, South Korea.
authors.forename: Hyun Sun
authors.initials: HS
authors.lastname: Cho
authors.forename: Seong Eon
authors.initials: SE
authors.lastname: Yoon
authors.forename: Seong Hoon
authors.initials: SH
authors.lastname: Park
authors.forename: Hyewon
authors.initials: H
authors.lastname: Kim
authors.forename: Young-Hwan
authors.initials: YH
authors.lastname: Lee
authors.forename: Kwon-Ha
authors.initials: KH
authors.lastname: Yoon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000388:Air; D002648:Child; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007416:Intestinal Perforation / Q000000981:diagnostic imaging*; D008099:Liver / Q000000981:diagnostic imaging*; D041741:Lower Gastrointestinal Tract / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods*; D013272:Stomach Diseases / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D041742:Upper Gastrointestinal Tract / Q000000981:diagnostic imaging*; D055815:Young Adult