title: Bowel wall fat halo sign in patients without intestinal disease.
abstract: OBJECTIVE
  Stratification with a fat layer in the intestinal wall is thought to be a reliable marker for inflammatory bowel disease. We evaluated the presence and frequency of the bowel wall fat halo sign in patients undergoing abdominal CT for clinical indications unrelated to the gastrointestinal tract.
  
  
  METHODS
  We performed a retrospective review of 100 consecutive abdominal and pelvic CT examinations in 61 men and 39 women (mean age, 56 years) with clinical suspicion of renal stone disease. Two radiologists experienced in abdominal imaging performed qualitative and quantifiable assessment of the images. Five segments of the colon (ascending colon, transverse colon, descending colon, sigmoid colon, and rectum) and the terminal ileum (for approximately 1 ft [30 cm]) were evaluated for the presence of the fat halo sign. If the fat halo sign was present, fat density and total wall-thickness assessments were made. Presence or absence of clinical and radiologic signs of inflammatory bowel disease was determined. The Student's t test was used to evaluate the statistical significance, correlating body weight and presence of the halo sign.
  
  
  RESULTS
  The fat halo sign was seen in 21 (21%) of 100 patients. Of the 21 patients with the fat halo sign, six (29%) had renal stone disease and 15 (71%) had no stone disease. The density value of the halo sign ranged from -18 to -64 H (mean, -41 H). The distribution of the fat halo sign was as follows: the terminal ileum, 4%; the ascending colon, 28%; the transverse colon, 34%; the descending colon, 36%; the sigmoid colon, 14%; and rectum, 10%. No patient with this sign had any remote, recent, or subsequently recorded history of inflammatory bowel disease. A statistically significant relationship (p < 0.001) was seen between the presence of the fat halo sign and body weight distribution, with 16 of 21 patients weighing over 200 lb (90 kg).
  
  
  CONCLUSIONS
  In the absence of clinical or radiologic evidence of inflammatory bowel disease, the presence of the fat halo sign may represent a normal finding that is possibly related to obesity.
authors.affiliation: Division of Abdominal Imaging and Intervention, Massachusetts General Hospital, White 270, 55 Fruit St., Boston MA 02114, USA. mharisinghani@partners.org
authors.forename: Mukesh G
authors.initials: MG
authors.lastname: Harisinghani
authors.forename: Jack
authors.initials: J
authors.lastname: Wittenberg
authors.forename: Winnie
authors.initials: W
authors.lastname: Lee
authors.forename: Steven
authors.initials: S
authors.lastname: Chen
authors.forename: Ana Luiza
authors.initials: AL
authors.lastname: Gutierrez
authors.forename: Peter R
authors.initials: PR
authors.lastname: Mueller
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging*; D000368:Aged; D015992:Body Mass Index; D003106:Colon / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007082:Ileum / Q000000981:diagnostic imaging*; D015212:Inflammatory Bowel Diseases / Q000000981:diagnostic imaging*; D007669:Kidney Calculi / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed