title: Differentiation of Malignant Omental Caking from Benign Omental Thickening using MRI.
abstract: OBJECTIVE
  To determine multi-parametric MRI features that can help differentiate malignant omental caking from benign omental thickening in the setting of portal hypertension.
  
  
  METHODS
  We identified 19 patients with an abnormal omentum on MRI and an available reference standard: 11 patients with portal hypertension and benign omental thickening (9 male, 2 female, mean age 58 ± 6 years) and 8 patients with metastatic omental caking (4 male, 4 female, mean age 61 ± 13 years). Criteria for benign omental thickening were no evidence of malignancy for at least 24 months of follow-up (n = 7), negative ascites cytology (n = 2), or absence of malignancy on pathologic analysis of liver explant (n = 2). Criteria for omental malignancy were positive omental biopsy (n = 6) or ascites cytology (n = 2). Two radiologists (R1 and R2) evaluated characteristics of the thickened omentum on MRI.
  
  
  RESULTS
  Findings occurring with significantly higher frequency in malignant omental caking were hyperintensity on high b-value diffusion-weighted imaging (DWI) (R1 88% vs. 0%, R2 88% vs. 0%), hyperenhancement (R1 75% vs. 0%, R2 75% vs. 0%), and convex outer omental contour (R1 88% vs. 0%, R2 75% vs. 9%) (all p ≤ 0.001); discrete omental nodules were significantly more frequent in malignant omental thickening for R1 (63% vs. 0%, p = 0.005). Features not significantly different between groups included decreased ADC, T2 hyperintensity, vessels coursing through the omentum, moderate/large volume ascites, splenomegaly, and mesenteric edema (all p ≥ 0.058).
  
  
  CONCLUSIONS
  Abnormal signal on DWI, hyperenhancement, and convex outer contour are helpful MRI features to differentiate malignant from benign omental thickening.
authors.affiliation: Department of Radiology, NYU School of Medicine, NYU Langone Medical Center, 550 First Avenue, New York, NY, 10016, USA, ankur.doshi@nyumc.org.
authors.forename: Ankur M
authors.initials: AM
authors.lastname: Doshi
authors.forename: Naomi
authors.initials: N
authors.lastname: Campbell
authors.forename: Cristina H
authors.initials: CH
authors.lastname: Hajdu
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Rosenkrantz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D006975:Hypertension, Portal / Q000209:etiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009852:Omentum / Q000473:pathology*; D010534:Peritoneal Neoplasms / Q000175:diagnosis* / Q000556:secondary; D012189:Retrospective Studies