title: Non-invasive assessment of renal allograft fibrosis by dynamic sonographic tissue perfusion measurement.
abstract: BACKGROUND
  Chronic allograft nephropathy (CAN) characterized by interstitial fibrosis and tubular atrophy is a major cause of renal transplant failure. The diagnosis can currently only be verified by a graft biopsy.
  
  
  OBJECTIVE
  To evaluate whether non-invasive dynamic color Doppler sonographic parenchymal perfusion measurements are different in grafts with various degrees of biopsy proven renal transplant fibrosis.
  
  
  METHODS
  Forty-nine adult patients were prospectively included. Four patients were excluded. Color Doppler videos from the renal cortex were recorded. Perfusion in the renal cortex was evaluated using a software package which calculates color pixel area and flow velocity, encoded by each pixel inside a region of interest of a video sequence. The software calculates parameters that describe tissue perfusion numerically. Two of these, the perfusion intensity and tissue pulsatility index, were compared to grade of interstitial fibrosis (0-3) in biopsies. Observer agreement was evaluated in a subset of 12 patients.
  
  
  RESULTS
  Of the 45 patients analyzed, 18 patients had grade 0, 18 had grade 1, seven had grade 2 and two had grade 3 fibrosis. The mean perfusion intensity of grade 0 was significantly higher than that of grade 2 and 3 fibrosis in the proximal cortical layer (1.65 m/s vs. 0.84 m/s, P = 0.008). No significant difference was found between grade 0 and grade 1 fibrosis. Perfusion intensity was correlated to estimated glomerular filtration rate (Pearson r 0.51, P = 0.001, R(2) = 0.26 and 0.46, P = 0.001, R(2) = 0.22 in the distal and proximal cortex, respectively). Inter-observer agreement of the perfusion intensity, expressed as intraclass correlation coefficient was 0.69 in the proximal part of the cortex. Intra-observer agreement was 0.85 for observer 1 and 0.82 for observer 2.
  
  
  CONCLUSIONS
  Perfusion intensity assessed by dynamic color Doppler measurements is significantly reduced in allografts with grade 2 and 3 fibrosis compared to allografts without fibrosis. Further studies involving longitudinal assessment of allografts undergoing protocol biopsies would be of interest.
authors.affiliation: Department of Radiology, Oslo University Hospital, Rikshospitalet, Norway. trygve.syversveen@rikshospitalet.no
authors.forename: Trygve
authors.initials: T
authors.lastname: Syversveen
authors.forename: Knut
authors.initials: K
authors.lastname: Brabrand
authors.forename: Karsten
authors.initials: K
authors.lastname: Midtvedt
authors.forename: Erik H
authors.initials: EH
authors.lastname: Strøm
authors.forename: Anders
authors.initials: A
authors.lastname: Hartmann
authors.forename: Audun Elnaes
authors.initials: AE
authors.lastname: Berstad
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001706:Biopsy; D005260:Female; D005355:Fibrosis / Q000000981:diagnostic imaging / Q000473:pathology; D005919:Glomerular Filtration Rate; D006084:Graft Rejection / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007674:Kidney Diseases / Q000000981:diagnostic imaging* / Q000473:pathology; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012984:Software; D018615:Ultrasonography, Doppler, Color