Benign Posttraumatic Pseudopneumoperitoneum.

OBJECTIVE: The objective of our study was to retrospectively determine the anatomic distribution of chest wall ectopic gas resembling pneumoperitoneum (i.e., pseudopneumoperitoneum) and its relationship with trauma mechanisms and clinical outcomes using CT. MATERIALS AND METHODS: Investigators from two separate trauma referral centers screened 492 chest, abdomen, and pelvis CT examinations of patients who had sustained any form of trauma between 2010 and 2015. After excluding 186 patients with recognized causes of ectopic gas, 306 patients (211 men and 95 women; mean age, 44.5 years; range, 6-95 years) remained for analysis by two radiology residents in center 1 and a radiology resident in center 2. Positive cases were reviewed by all investigators, including an experienced fellowship-trained abdominal radiologist. The anatomic location of the pseudopneumoperitoneum, injury severity score, trauma velocity (high speed vs low or unknown speed), trauma mechanism, clinical findings on follow-up, and exploratory laparotomy data were collected for patients with pseudopneumoperitoneum. Two hundred consecutive nontrauma CT examinations from 2015 were selected as control cases by a resident in center 1. The t test and chi-square test were used for determining associations. RESULTS: Pseudopneumoperitoneum was identified in 5.2% of patients, occurring bilaterally adjacent to the lower six costochondral junctions, and was significantly more common with high-velocity trauma than with low-velocity trauma (p = 0.010). None of the patients with pseudopneumoperitoneum had evidence of perforated hollow viscus at surgery (n = 2) or on clinical follow-up (n = 14). No patients had unnecessary surgery due to pseudopneumoperitoneum. CONCLUSION: Pseudopneumoperitoneum is a posttraumatic phenomenon centered near the lower six costochondral junctions. Recognizing these findings may help prevent unnecessary laparotomy in the trauma setting.

Revisiting the surface anatomy of the sciatic nerve in the gluteal region.

The surface anatomy of the sciatic nerve (SN) in the gluteal region is clinically important (e.g., intramuscular injection). Anatomy texts describe the nerve in relation to the posterior superior iliac spine (PSIS), ischial tuberosity (IT), and greater trochanter (GT) but descriptions are inconsistent. The surface anatomy of the SN was determined in relation to these bony landmarks using computed tomography (CT) scans in living adults. One hundred consecutive adult pelvic CT scans (36 females, mean age 76 years) were available for dual consensus analysis. A further 19 adults (9 females, mean age 74 years) underwent pelvic CT scans in both prone and supine positions. The surface projection of the SN along a line between the PSIS and IT and between the IT and GT was measured. The SN was identified in 95% of scans at a mean of 5.2 ± 1.0 cm from the PSIS and 11.4 ± 1.1 cm from the IT. The SN was a mean of 5.8 ± 0.8 cm from the IT and 6.2 ± 1.0 cm from the GT. There were no significant differences in mean positions of the nerve between sides and sexes. A small but clinically irrelevant difference in the surface marking of the SN was found between supine and prone positions with respect to the GT and IT but not in relation to the PSIS and IT. In living adults, the SN lies approximately one-third of the way along a line between the PSIS and IT and half way between the GT and IT.