Over the last 20 years, interventional nephrology (IN) has become a new and emerging subspecialty of nephrology. The International Society of Nephrology has created an Interventional Nephrology Committee to improve the overall quality of patient care by promoting IN [1]. This has led to many young nephrologists taking the initiative and performing percutaneous endovascular procedures by themselves to avoid unnecessary delays rather than consulting with a variety of specialists.

Financial data from the US Renal Data System suggest that surgeons, radiologists, and nephrologists are responsible for approximately 35%, 30%, and 25%, respectively, of vascular access costs, with the balance being split between anesthesiology and other specialties [2]. Since the establishment of the Korean Study Group for Interventional Nephrology in 2010 which was endorsed by the Korean Society of Nephrology in 2013, some frontier nephrologists interested in IN have performed these endovascular procedures in Korea. The study by Lee and Park [3] reported for the first time the effectiveness and safety of vascular access procedures performed by interventional nephrologists in Korea. The authors showed that the clinical success rate, primary patency rate, and secondary patency rate at 3 months were 89.3%, 56.6%, and 85.7%, respectively. Notably, these results exceeded the recommendations of the Kidney Disease Outcomes Quality Initiative guidelines: a clinical success rate >85% and a primary patency rate at 3 months >40%. However, the success rate of the current study was not conclusive as it did not establish the effectiveness and/or superiority of endovascular interventions by nephrologists according to a large series, showing a clinical success rate >95% by nephrologists in the US as well as by radiologists in Korea [4,5].

The authors also showed that the complication rate was 6.6%, being less than that of another report by interventional radiologists in one of the largest centers in Korea [3,5]. A comparison, however, could be made as complications were both listed (local infection, arterial wall injury, dissection, thromboemboli, fistulas, hematoma, acute occlusion, perforation, vasospasm, renal failure, stroke, myocardial infarct, etc.) and graded [6]. The authors did not describe complications according to the reporting standards of the Society of Interventional Radiology (SIR), although the authors mentioned accordance with the SIR categories in the methods section. Did the authors count and grade hematomas, which may be the most common complication following the endovascular procedures? This appears to be neglected when counting minor complications in the SIR categories. Finally, parameters showing timed components of procedures such as mean procedure times and mean fluoroscopy times should be addressed to determine the effectiveness and safety.

The author declares no conflict of interest.

Sung Gyun Kim

E-mail address: sgkim@hallym.ac.kr (SG Kim)

[1] Interventional Nephrology [Internet]. [cited 2015 Apr 02].Available at: http://www.theisn.org/topics/interventional-nephrology38

[2] Roy-Chaudhury P, Yevzlin A, Bonventre JV, Agarwal A, Almehmi A, Besarab A, Dwyer A, Hentschel DM, Kraus M, Maya I, Pflederer T, Schon D, Wu S, Work J: Academic interventional nephrology: a model for training, research, and patient care. Clin J Am Soc Nephrol 7:521–524, 2012

[3] Lee HS, Park PJ: Clinical outcome of percutaneous thrombectomy of dialysis access thrombosis by an interventional nephrologist. Kidney Res Clin Pract 33:204–209, 2014

[4] Beathard GA, Litchfield T, Physician Operators Forum of RMS Lifeline, Inc: Effectiveness and safety of dialysis vascular access procedures performed by interventional nephrologists. Kidney Int 66:1622–1632, 2004

[5] Goo DE, Kim JH, Park ST, Chang YW, Hwang JH, Kwon KH, Cho DL, Mun C: Usefulness of thromboaspiration with Desilets–Hoffman sheath in thrombosed hemodialysis access graft. J Korean Radiol Soc 51:45–53, 2004

[6] Sacks D, Marinelli DL, Martin LG, Spies JB: Members of the Technology Assessment Committee: Reporting standards for clinical evaluation of new peripheral arterial revascularization devices. J Vasc Interv Radiol 8:137–149, 1997

We appreciate your interest in our recent article entitled “Clinical outcome of percutaneous thrombectomy of dialysis access thrombosis by an interventional nephrologist” [1]. Despite the outcomes of the current study exceeding the guidelines of the Kidney Disease Dialysis Outcomes Quality Initiative [2], the success rate was less than that expected in comparison with representative studies previously reported in the US and Korea [3,4]. Nevertheless, the principle we tried to maintain was that thrombectomy with surgical repair should be placed ahead of stent deployment with percutaneous balloon angioplasty when a better outcome and longer patency could be achieved by surgical revision such as graft interposition or extension. We withdrew percutaneous interventions when stent placement was necessary to treat stenosis, and surgical revision was the preferred option on a long-term basis. These withdrawn cases were regarded as technical failures according to the intention-to-treat principle, explaining why both the success rate and stent deployment rate were relatively lower than other studies.

Over the study period, all complications were inspected and we classified the complications into minor and major in accordance with the criteria from the Society of Interventional Radiology [5]. We performed balloon tamponade for minor venous dissection, and percutaneous embolectomy for distal arterial embolization as described in the article [1]. This description means that the severity of these complications corresponds to Grade 2. There were no complications such as access site hematoma, most likely because we did not approach via the brachial artery, and purse string suture was performed at the introducer site in most cases.

The main purpose of our study was to present that the outcome of endovascular procedures by an interventional nephrologist was also effective and safe. The effectiveness and safety were most likely produced by avoiding unnecessary delays in declotting procedures and the lower level of complication rate. We agree with your opinion that the mean procedure time and mean fluoroscopy time are very important parameters to be inspected. Along with the increasing number of dialysis access procedures performed by interventional nephrologists, further studies will be needed to demonstrate the risk of radiation exposure to patients and medical staff.

None.

Hyung-Seok Lee

E-mail address: pcsacred@gmail.com (HS Lee).

[1] Lee HS, Park PJ: Clinical outcome of percutaneous thrombectomy of dialysis access thrombosis by an interventional nephrologist. Kidney Res Clin Pract 33:204–209, 2014

[2] Vascular Access 2006 Working Group: K/DOQI clinical practice guidelines for vascular access. Am J Kidney Dis 48 (Suppl 1):S176–S247, 2006

[3] Beathard GA, Litchfield T, Physician Operators Forum of RMS Lifeline, Inc: Effectiveness and safety of dialysis vascular access procedures performed by interventional nephrologists. Kidney Int 66:1622–1632, 2004

[4] Goo DE, Kim JH, Park ST, Chang YW, Hwang JH, Kwon KH, Cho DL, Mun C: Usefulness of thromboaspiration with Desilets–Hoffman sheath in thrombosed hemodialysis access graft. J Korean Radiol Soc 51:45–53, 2004

[5] Sacks D, Marinelli L, Martin LG, Spies JB: The Members of the Technology Assessment Committee: Reporting standards for clinical evaluation of new peripheral arterial revascularization devices. J Vasc Interv Radiol 8:137–149, 1997