title: Can MR measurement of renal artery flow and renal volume predict the outcome of percutaneous transluminal renal angioplasty?
abstract: OBJECTIVE
  Predicting therapeutic benefit from percutaneous transluminal renal angioplasty (PTRA) in patients with renal artery stenosis (RAS) remains difficult. This study investigates whether magnetic resonance (MR)-based renal artery flow measurements relative to renal parenchymal volume can predict clinical outcome following PTRA.
  
  
  METHODS
  The data on 23 patients (13 men, 10 women; age range 47-82 years, mean age 64 years) were analyzed. The indication for treatment was hypertension (n = 18) or renal insufficiency (n = 5). Thirty-four cases of RAS were identified: bilateral disease was manifest in 11 and unilateral disease in 12 patients. The MR imaging protocol included a breath-hold, cardiac-gated cine phase-contrast sequence for renal flow measurement and a fast multiplanar spoiled gradient-echo sequence for renal volume measurement. MR measurements were performed on the day prior to and the day following PTRA. Clinical success was defined as (a) a reduction in diastolic blood pressure > 15% or (b) a reduction in serum creatinine > 20%. Kidneys were categorized as normal volume or low volume. A renal flow index (RFI) was calculated by dividing the renal flow (ml/min) by the renal volume (cm3).
  
  
  RESULTS
  Clinical success was observed in patients. Twelve patients did not benefit from angioplasty. Normal kidney volume was seen in 10 of 11 responders and in 8 of 12 nonresponders, resulting in a sensitivity of 91%, specificity of 33%, a positive predictive value (PPV) of 56% and a negative predictive value (NPV) of 80%. A RFI below a threshold of 1.5 ml/min/cm3 predicted successful outcome with 100% sensitivity, 33% specificity, 58% PPV, and 100% NPV. The combination of normal renal volume and a RFI below 1.5 ml/min/cm3 identified PTRA responders with a sensitivity of 91%, a specificity of 67%, a PPV of 71%, and a NPV of 89%. PTRA resulted in a greater increase in renal flow in responders compared with nonresponders (p < 0.001).
  
  
  CONCLUSIONS
  A combination of cine phase-contrast MR renal flow and parenchymal volume measurements enables identification of patients benefiting from PTRA with a high sensitivity and NPV, but only moderate specificity and PPV.
authors.affiliation: Department of Radiology, University Hospital Zurich, Switzerland. binkert@compuserve.com
authors.forename: C A
authors.initials: CA
authors.lastname: Binkert
authors.forename: J F
authors.initials: JF
authors.lastname: Debatin
authors.forename: E
authors.initials: E
authors.lastname: Schneider
authors.forename: J
authors.initials: J
authors.lastname: Hodler
authors.forename: S G
authors.initials: SG
authors.lastname: Ruehm
authors.forename: M
authors.initials: M
authors.lastname: Schmidt
authors.forename: U
authors.initials: U
authors.lastname: Hoffmann
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000800:Angioplasty, Balloon; D003287:Contrast Media; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D021621:Imaging, Three-Dimensional; D007668:Kidney / Q000473:pathology*; D018810:Magnetic Resonance Angiography; D008279:Magnetic Resonance Imaging; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012077:Renal Artery / Q000473:pathology / Q000503:physiopathology; D012078:Renal Artery Obstruction / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D012079:Renal Circulation; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA