title: Nutcracker and SMA syndromes: What is the normal SMA angle in children?
abstract: OBJECTIVE
  The nutcracker and superior mesenteric artery (SMA) syndromes are rare conditions where the left renal vein or duodenum may be compressed by an unusually acute angle between the SMA and aorta, although the normal angle in children is unknown. We measured the SMA angle to define the normal range in children.
  
  
  METHODS
  We retrospectively measured SMA angles, left renal vein (LRV) distance, and duodenal distance (DD) in 205 consecutive pediatric abdominal CT. Total and visceral intra-abdominal fat at the level of the umbilicus were also assessed.
  
  
  RESULTS
  Mean SMA angle was 45.6±19.6° (range 10.6-112.9°), mean LRV distance was 8.6±3.9mm (range 2.0-28.6mm) and mean DD was 11.3±4.8mm (range 3.6-35.3mm). There was a significant but weak correlation between %visceral fat volume (%VF) and SMA angle (R=0.30; p<0.001), LRV distance (R=0.37, p<0.001) and DD (R=0.32; p<0.001).
  
  
  CONCLUSIONS
  There is a wide range of SMA angle, LRV and DD in normal children, which correlated weakly with visceral fat volume. Using a definition of SMA angle <25° would diagnose 9.3% of asymptomatic children with nutcracker syndrome, and using a DD definition of <8mm would diagnose 20% with SMA compression. Our findings suggest exercising caution when attributing these rare syndromes to an absolute SMA angle.
authors.affiliation: Department of Radiology, Box 219, Addenbrooke's Hospital, Cambridge University Teaching Hospitals NHS Foundation Trust, Hills Road, Cambridge, CB2 0QQ, United Kingdom. oja20@owenarthurs.co.uk
authors.forename: O J
authors.initials: OJ
authors.lastname: Arthurs
authors.forename: U
authors.initials: U
authors.lastname: Mehta
authors.forename: P A K
authors.initials: PA
authors.lastname: Set
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004386:Duodenum / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D011860:Radiography, Abdominal / Q000379:methods*; D059228:Renal Nutcracker Syndrome / Q000000981:diagnostic imaging*; D012082:Renal Veins / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013478:Superior Mesenteric Artery Syndrome / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*