title: Renal cortical thickness measured at ultrasound: is it better than renal length as an indicator of renal function in chronic kidney disease?
abstract: OBJECTIVE
  The purpose of our study was to determine whether there is a relationship between renal cortical thickness or length measured on ultrasound and the degree of renal impairment in chronic kidney disease (CKD).
  
  
  METHODS
  From October to December 2007, 25 patients (13 men and 12 women, mean age 73 years) were identified who had CKD but were not on dialysis. The patients were from a single institution and had undergone renal ultrasound and at least three serum creatinines within 90 days. The lowest creatinine was used for estimated glomerular filtration rate (eGFR) calculation using both the Cockcroft-Gault (CG) and the Modification of Diet in Renal Disease Study (MDRD) equations. Ultrasounds were consensus reviewed by three radiologists (2 attendings and a resident) blinded to specific renal function. Cortical thickness was measured in the sagittal plane over a medullary pyramid, perpendicular to the capsule. Length was measured pole-to-pole. Linear regression was used for statistical analysis.
  
  
  RESULTS
  Mean cortical thickness was 5.9 mm (range, 3.2-11.0 mm). Mean length was 10 cm (7.2-12.4 cm). Mean minimum serum creatinine was 2.1 mg/dL (1.1-6.1 mg/dL). Mean eGFR using CG was 34.8 mL/min (10.6-99.4 mL/min) and 36 mL/min (8-66 mL/min) using MDRD. There was a statistically significant relationship between eGFR and cortical thickness using both CG (p < 0.0001) and MDRD (p = 0.005). There was a statistically significant relationship between CG and length (p = 0.003) but not between MDRD and length (p = 0.08).
  
  
  CONCLUSIONS
  Cortical thickness measured on ultrasound appears to be more closely related to eGFR than renal length. Reporting cortical thickness in patients with CKD who are not on dialysis should be considered.
authors.affiliation: Department of Diagnostic Imaging, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, 02903, USA. mbeland@lifespan.org
authors.forename: Michael D
authors.initials: MD
authors.lastname: Beland
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Walle
authors.forename: Jason T
authors.initials: JT
authors.lastname: Machan
authors.forename: John J
authors.initials: JJ
authors.lastname: Cronan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods*; D007668:Kidney / Q000000981:diagnostic imaging*; D007676:Kidney Failure, Chronic / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000379:methods*