title: The transitional zone in the tunica media of renal arteries has a maximal length of 10 millimetres.
abstract: BACKGROUND
  The goal of our study was to demonstrate and to determine the length of the transitional zone in the tunica media in renal arteries. The majority of renal artery atherosclerotic stenotic lesions occurs in this segment.
  
  
  METHODS
  Anatomical and histological studies were performed on 26 renal arteries from 13 adults at autopsy (mean age 61.6 years, range 33 to 87 years).
  
  
  RESULTS
  In the macroscopical examination the right renal arteries (RRA) were longer with a median 53.8 mm (range 38 to 65 mm) than the left renal arteries (LRA) with a median 47.6 mm (range 35 to 63 mm), the circumferences were nearly the same: RRA 10.9 mm (range 5 mm to 15 mm) and LRA 11 mm (range 5 mm to 15 mm). Probes for histological examinations were taken from three different regions of each renal artery (origin, 5 mm and 10 mm distal to the origin). We observed a typical elastic arterial structure at the origin and muscular types at the distal 10 mm region. At the distal 5 mm region variable ratios of elastic tissue (ET) and smooth muscle cells (SMC) were found as follows: 15 arteries presented an equal ratio of EM:SMC, 7 arteries presented ET > SMC and 4 arteries presented ET < SMC ratios.
  
  
  CONCLUSIONS
  In this study we confirmed that in renal arteries, a transitional zone (TZ) that is an arterial segment with transition from elastic to muscular type, does exist, involving the maximal length of 10 mm. Further studies on the impact of the biomechanical properties of the transitional zone as a potential localizing factor in renal atherosclerotic disease are justified. In addition, the complex biomechanical behavior of the TZ of the arterial wall should be taken into consideration when interventional procedures are planned.
authors.affiliation: Unité d'Anatomie et de Cytologie Pathologiques, Hôpital Saint-Michel, Paris, France. jkr.janzen@lycosmail.com
authors.forename: J
authors.initials: J
authors.lastname: Janzen
authors.forename: P
authors.initials: P
authors.lastname: Lanzer
authors.forename: K
authors.initials: K
authors.lastname: Rothenberger-Janzen
authors.forename: P N
authors.initials: PN
authors.lastname: Vuong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001161:Arteriosclerosis / Q000473:pathology*; D004547:Elastic Tissue / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000473:pathology; D012016:Reference Values; D012077:Renal Artery / Q000473:pathology*; D012078:Renal Artery Obstruction / Q000473:pathology*; D017540:Tunica Media / Q000473:pathology*