title: Robotic percutaneous access to the kidney: comparison with standard manual access.
abstract: OBJECTIVE
  To evaluate the efficiency, accuracy, and safety of robotic percutaneous access to the kidney (PAKY) for percutaneous nephrolithotomy in comparison with conventional manual techniques.
  
  
  METHODS
  We compared the intraoperative access variables (number of access attempts, time to successful access, estimated blood loss, complications) of 23 patients who underwent robotic PAKY with the remote center of motion device (PAKY-RCM) with the same data from a contemporaneous series of 23 patients who underwent conventional manual percutaneous access to the kidney. The PAKY-RCM incorporates a robotic arm and a friction transmission with axial loading system to accurately position and insert a standard 18-gauge needle percutaneously into the kidney. The blood loss during percutaneous access was estimated on a four-point scale (1 = minimal to 4 = large). The color of effluent urine was graded on a four-point scale (1 = clear to 4 = red).
  
  
  RESULTS
  The mean target calix width was 13.5 +/- 9.2 mm in the robotic group and 12.2 +/- 4.5 mm in the manual group (P = 0.57). When comparing PAKY-RCM with standard manual techniques, the mean number of attempts was 2.2 +/- 1.6 v 3.2 +/- 2.5 (P = 0.14), time to access was 10.4 +/- 6.5 minutes v 15.1 +/- 8.8 minutes (P = 0.06), estimated blood loss score was 1.3 +/- 0.49 v 1.7 +/- 0.66 (P = 0.14), and color of effluent urine following access was 2.0 +/- 0.90 v 2.1 +/- 0.7 (P = 0.82). The PAKY-RCM was successful in obtaining access in 87% (20 of 23) of cases. The other three patients (13%) required conversion to manual techniques. There were no major intraoperative complications in either group.
  
  
  CONCLUSIONS
  Robotic PAKY is a feasible, safe, and efficacious method of obtaining renal access for nephrolithotomy. The number of attempts and time to access were comparable to those of standard manual percutaneous access techniques. These findings provide the groundwork for the development of a completely automated robot-assisted percutaneous renal access device.
authors.affiliation: James Buchanan Brady Urological Institute, The Johns Hopkins Medical Institutions, 4940 Eastern Avenue, A3 East, Baltimore, MD 21224, USA. LSU11@jhmi.edu
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Su
authors.forename: Dan
authors.initials: D
authors.lastname: Stoianovici
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Jarrett
authors.forename: Alexandru
authors.initials: A
authors.lastname: Patriciu
authors.forename: William W
authors.initials: WW
authors.lastname: Roberts
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Cadeddu
authors.forename: Sanjay
authors.initials: S
authors.lastname: Ramakumar
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Solomon
authors.forename: Louis R
authors.initials: LR
authors.lastname: Kavoussi
mesh_terms: D016063:Blood Loss, Surgical; D001810:Blood Volume; D004867:Equipment Design; D006801:Humans; D007669:Kidney Calculi / Q000601:surgery*; D007670:Kidney Calices / Q000601:surgery*; D010535:Laparoscopy / Q000379:methods*; D009403:Nephrostomy, Percutaneous / Q000379:methods*; D012371:Robotics; D012449:Safety; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation; D016896:Treatment Outcome