2023 Publication Underscores Importance of Transit-time Ultrasound Flow Measurements During Renal Transplantation
In 2022, 42,800 organs were transplanted in U.S. residents. Kidneys were the most common organ transplanted, surpassing 25,000 for the first time ever and accounting for close to 60% of all organ transplants. Acute rejection of the transplanted kidney is a common complication, and can affect up to 1 in 3 recipients. Most rejections occur within six months, but can occur at any time, even years later. In many cases, acute rejection does not cause noticeable symptoms, and is only detected by a blood test.
A 2023 publication from Taiwan1 demonstrates that transit-time ultrasound measurements with the Transonic HT353 provide immediate, objective information about the quality of an arterial or venous graft anastomosis during kidney transplant and can indicate potential technical failure. The clinician’s study included 159 patients (83 males, 76 females, mean age: 44.5 years) who underwent kidney transplantation from 89 living donors and 76 deceased donors between January 2017 to March 2022 at Linkou Chang Gung Memorial Hospital New Taipei City, Taiwan. Early outcomes of the transplant surgery, including postoperative creatinine levels, were assessed separately from living donor and deceased donor kidney transplant patients. Mean graft arterial flows were 480.6 mL/min; mean venous flows were 506.2 mL/min. The clinicians concluded from their study that low graft venous blood flow was significantly associated with delayed graft function (DGF) in living donor kidney transplantation, and high body mass index (BMI) also correlated with delayed graft function in kidney transplant recipients.
Some question why it is so important to measure blood flow during renal transplantation surgery when a transplanted kidney will generally perfuse (“pink up”) quickly to indicate that it is functioning. There are several answers. First, measurements present immediate information about renal circulation. Bretan et al, noted in an early Transonic validation paper that the ultrasonic transit-time Flowprobe accurately measures post-reperfusion renal blood flow and offers a practical and noninvasive method for assessing renal reperfusion injury after transplantation. This can help optimize immunosuppressive strategies to maximize renal recovery2. Moreover, low or decreasing flow could indicate a technical error which, if left uncorrected, could endanger the transplant.3
Secondly, low blood flow could indicate delayed graft function (DGF), which is reported to occur in 25-30 % of kidney transplant cases. DGF is a serious complication that poses a risk factor for long-term graft survival. “Measurements correlate significantly with the occurrence of delayed onset of graft function and the need for post-transplant dialysis.…Immediate information on blood flow data would, therefore, be valuable in critical cases when initiation of antibody prophylaxis is considered on the day of operation, especially in patients with uncertain graft urine production.”4
In 2019, Pravisani R et al, from University of Udine, Udine, Italy, and Soroka University Medical Center, Beer Sheva, Israel, explored the role of the graft hemodynamics in the pathogenesis of DGF via transit-time flow measurement of the correlation between the intraoperative graft flow and kidney transplant outcomes.5 They concluded that the value of intraoperative assessment is early identification of complications or high-risk cases, creating an opportunity for corrective interventions.
Finally, intraoperative flow measurement during renal transplant provides valuable quantitative flow data to include in the operative record of the patient. This information can be particularly valuable in the event of later complications.
To summarize, intraoperative flow measurements during renal transplantation offer surgeons an opportunity to augment their clinical assessment of renal function with solid, objective intraoperative blood flow data that assist in post-surgical decision- making and care.
1 Fan LW, Li YR, Lin KJ, Pan PY, Liu KL, Lin CT, Chiang YJ, Chu SH, Wang HH. The Impact of Intraoperative Graft Blood Flow Measurement on Early Graft Function. Transplant Proc. 2023 May;55(4):782-787.
2 Bretan, P.N. Jr. Lobo, E., Dumitrescu, O., Miller, B., Yen, T.S., “Experimental and Clinical Assessment of Preservation-Induced Reperfusion Injury Comparing Renal Transplant Blood Flow and Renal Endothelin Concentrations,” Transplantation Proceedings 1997;29(8):3520-3521. (1092AH)
3,4 Lundell, A., Persson, N.H., Kallen, R., Ekberg, H., “Impaired Renal Artery Blood Flow at Transplantation Is Correlated to Delayed Onset of Graft Function” Transplant International 1996;9(1)57-61. (685AH)
5Pravisani R, Baccarani U, Langiano N, Meroi F, Avital I, Bove T, Adani GL. Predictive Value of Intraoperative Doppler Flowmetry for Delayed Graft Function in Kidney Transplantation: A Pilot Study. Transplant Proc. 2020 Jun;52(5):1556-1558. (Transonic Reference # 2021-2AH)