title: Ultrasound-guided core biopsy of small renal masses: diagnostic rate and limitations.
abstract: OBJECTIVE
  To evaluate the feasibility and complications of ultrasound (US)-guided biopsy of small renal masses (SRMs) and to determine factors that contribute to nondiagnostic biopsy specimens.
  
  
  METHODS
  Between June 2004 and May 2011, 58 consecutive patients underwent US-guided core biopsy of a SRM (>1 cm and ≤4 cm) using an 18-gauge core biopsy device. The diagnostic rate, histologic diagnosis, and complications of US-guided core biopsy were assessed. Mann-Whitney U and Fisher exact tests were used to compare diagnostic and nondiagnostic biopsy specimens. Univariate analysis was performed to determine the predictive factors for nondiagnostic biopsy specimens.
  
  
  RESULTS
  There were 59 biopsies of SRMs performed, and the diagnostic rate was 81% (48 of 59). The mass size of diagnostic and nondiagnostic biopsy specimens ranged from 1.2-3.9 cm (2.4 cm±0.7) for diagnostic specimens and from 1.1-3.5 cm (1.9 cm±0.7) for nondiagnostic specimens (P = .024). Of the diagnostic biopsy specimens, 77% (37 of 48) were malignant, and 23% (11 of 48) were benign. Minor complications developed in 20.3% (12 of 59) of biopsies. The lesion size or core number threshold for decreasing diagnostic rate was 2 cm or three cores. A cystic mass, fewer cores (three or fewer cores), an upper pole mass, and a small mass (≤2 cm) significantly predicted a nondiagnostic biopsy specimen (P = .007-.046).
  
  
  CONCLUSIONS
  US-guided core biopsy is a feasible and safe procedure for histologic diagnosis of a SRM. However, nondiagnostic rates may increase when a cystic mass is biopsied, a mass is located in an upper pole mass, a mass is 2 cm or less, and three cores or fewer are sampled.
authors.affiliation: Department of Radiology and Center for Imaging Science, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Sung Yoon
authors.initials: SY
authors.lastname: Park
authors.forename: Byung Kwan
authors.initials: BK
authors.lastname: Park
authors.forename: Chan Kyo
authors.initials: CK
authors.lastname: Kim
authors.forename: Ghee Young
authors.initials: GY
authors.lastname: Kwon
mesh_terms: D000328:Adult; D000368:Aged; D061765:Endoscopic Ultrasound-Guided Fine Needle Aspiration / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity