Immediate Postoperative Sonography of Renal Transplants: Vascular Findings and Outcomes

Transcription

1 Genitourinary Imaging Original Research Horrow et al. Sonography of Renal Transplants Genitourinary Imaging Original Research Mindy M. Horrow 1 fshin Parsikia 2 Radi Zaki 2 Jorge Ortiz 2 Horrow MM, Parsikia, Zaki R, Ortiz J Keywords: compartment syndrome, Doppler ultrasound, postoperative, renal transplant DOI: /JR Received November 14, 2012; accepted after revision January 22, Presented as a poster at the 2013 annual symposium of the merican Society of Transplant Surgeons, Miami each, FL. 1 Department of Radiology, Einstein Medical Center, 5501 Old York Rd, Philadelphia, P ddress correspondence to M. M. Horrow (horrowm@einstein.edu). 2 Department of Transplant Surgery, Einstein Medical Center, Philadelphia, P. WE This is a web exclusive article. JR 2013; 201:W479 W X/13/2013 W479 merican Roentgen Ray Society Immediate Postoperative Sonography of Renal Transplants: Vascular Findings and Outcomes OJECTIVE. The purpose of this study was to determine the frequency and types of significant vascular findings on bedside sonography immediately after renal transplantation and which abnormalities would suggest a benefit from early surgical revision. MTERILS ND METHODS. Five hundred seventy-five renal transplant sonograms obtained within 4 hours of surgery were retrospectively reviewed for major vascular abnormalities: lack of renal artery (R) or renal vein (RV) flow, elevated peak systolic velocity (PSV) > 300 cm/s, parvus tardus waveforms, and markedly decreased or no color parenchymal flow. Clinical outcomes of abnormal cases were reviewed, including reoperations and percutaneous interventions. RESULTS. Thirty-two (5.6%) patients underwent repeat surgery within the first week, 16 for nonvascular causes. Forty-seven (8.2%) patients had positive sonography findings. In 16 patients, sonography impacted the decision for reoperation, with 14 confirmed vascular diagnoses: compartment syndrome (n = 7), RV thrombosis (n = 3), R thrombosis (n = 1), R and RV thromboses (n = 2), and vascular steal (n = 1). ll were salvaged except the three RV thromboses. Two patients had no vascular abnormality at surgery. ll 16 had markedly decreased color flow and varying abnormalities of PSV and waveforms. Outcomes of the remaining 31 cases were infarct (n = 1), renal or iliac artery stenoses eventually requiring stents (n = 4), and normalized (n = 26). These 26 had elevated PSV with normal or near-normal color flow. Unpaired Student t tests showed no significant difference in PSV between patients requiring surgery or stents and those who normalized (p = 0.34). CONCLUSION. Immediate postoperative sonography has a spectrum of vascular findings, of which markedly decreased color flow is most likely to benefit from immediate reoperation. lthough sonography is a well-established imaging study for renal transplant dysfunction during the lifetime of the kidney, its routine use immediately after surgery is rarely described in the literature [1]. In most situations, urine output is a good surrogate for graft function, and ultrasound is not routinely performed in the recovery room. s a result, no large studies have addressed the range of vascular findings on sonography immediately after renal transplantation and which of these might benefit from early surgical revision. Renal transplantation is now considered the preferred method of treatment for chronic renal failure. However, the demand for renal transplantation continues to outpace the supply of donor kidneys. This situation stems from the combination of improving medical and surgical techniques for renal transplantation with anticipated graft survival rates at 1 year of 95% and 90%, for living and deceased donors, respectively; an ever-expanding population with end-stage renal disease; and a relatively stagnant rate of kidney donation. etween 1999 and 2008, kidney transplantation operations in the United States increased by 27% from 12,633 to 16,067. During this time, the number of candidates waiting for a renal transplant increased by 75% from 43,632 to 80,972. Since 2008, the number of renal transplantations has plateaued whereas the candidate population continues to increase [2]. In an attempt to meet the increasing need for renal transplants, the pool of donor organs has been expanded to include organs from donors with increasing age, diabetes, hypertension, increased risk of infectious diseases, history of cancer, and infant kidneys. These factors increase the likelihood of poor initial function, delayed graft function, or primary nonfunction. dditionally, the recipients are often older JR:201, September 2013 W479

2 Horrow et al. 16 with reoperation 7 compartment syndromes 3 renal vein thromboses 1 renal artery thrombosis 2 renal artery and vein thromboses 2 without vascular abnormality at surgery 1 vascular steal from fistula 1 (of 2) pediatric kidneys infarcted and have more comorbidities than in the earlier years of transplantation surgery. The renal transplant population at our institution reflects these shifting demographics. recent review of outcomes in our deceaseddonor renal transplant population found an incidence of 51.3% for delayed graft function, defined as the need for dialysis in the first week after kidney transplantation. The national incidence of delayed graft function is approximately 25% [3]. In addition to general factors such as donor hypotension and prolonged warm ischemia time, significant risk factors specific to our recipient population include frican merican ethnicity, diabetes, and obesity. The combination of increasing numbers of extended donor kidneys and higher-risk recipients has resulted in earlier and more severe acute tubular necrosis (TN). In cases of decreased urine output, we frequently cannot distinguish between TN, which requires supportive care, and a vascular cause that is potentially correctable with surgery. Confirmation of adequate arterial and venous flow is crucial in this susceptible population. ccordingly, we routinely obtain an immediate (within 4 hours) posttransplantation renal sonogram. If critical vascular complications occur, the temporal window of opportunity for salvage is small, and surgery is preferred over percutaneous methods. ecause the vascular abnormalities detected on immediate sonograms might be potentially different from those of later imaging, we were interested in the results of these examinations and, in particular, their potential effect on clinical decisions. Therefore, the purpose of this study was to determine the types of vascular abnormalities on sonography performed within 4 hours of renal transplantation and determine which would suggest a benefit to immediate reoperation. Materials and Methods For this HIP-compliant institutional review board approved retrospective study, informed consent was waived. ll renal transplantation cases at our institution from December 2004 through November 2011 were reviewed. Only those cases with postoperative sonography within 4 hours of surgery were included. Reports were reviewed for any significant vascular abnormality, including: lack of arterial or venous flow, elevated renal artery peak systolic velocity (PSV) greater than 300 cm/s [4], markedly decreased or no parenchymal color flow, and parvus tardus waveforms. Our choice of this PSV threshold was based on our experience with perioperative renal transplant sonography. The highest PSV that appeared technically adequate was used. Elevated 793 Transplants 575 with sonography within 4 hours 47 with one or more positive vascular findings 4 required vascular stents after several months 2 renal artery stenoses: 1 iliac artery stenosis 1 iliac and renal artery stenosis resistive indexes (> 0.8) were not necessarily considered abnormal if color perfusion and velocities were adequate because these findings are common with TN. The images of all abnormal reports were reviewed to make sure that the reported abnormality fit our criteria. Follow-up sonograms of the abnormal cases were also reviewed for changes over time, correlating with any other vascular studies in cases with or without an intervention. ll sonography examinations were performed initially using HDI 5000 units and since 2007 using IU22 units (both Philips Healthcare), acquiring images with 5 2- or 5 1-MHz transducers. routine study included gray-scale imaging, color Doppler imaging starting with standard parameters with increasing sensitivity as needed, and spectral Doppler analysis of the main renal artery at the anastomosis and renal hilum with angle-corrected velocities; peripheral interlobar artery imaging with resistive indexes in the upper, middle, and lower poles; and color and spectral Doppler imaging of the main renal vein and ipsilateral external iliac artery and vein. Perirenal imaging was performed but often limited by bandages, drains, and patient discomfort. Certified sonographers performed all studies during working hours, and radiology residents performed studies after midnight. These residents received at least 2 months of ultrasound training that included real-time scanning. 7 hematomas: 5 required surgery 2 percutaneous drainage 26 did not require vascular intervention 19 no intervention Fig. 1 Flowchart shows outcomes of 793 transplantation procedures. W480 JR:201, September 2013

3 Sonography of Renal Transplants C Fig year-old woman with chronic renal failure who underwent immediate postoperative sonography with findings of main renal artery kink. Compartment syndrome was confirmed on immediate reoperation and kidney was salvaged by repositioning into peritoneal cavity., Oblique sonogram of renal transplant shows significantly elevated peak systolic velocity (PSV) at origin of main renal artery (peak systole 426 cm/s and diastole 191 cm/s) with surrounding color Doppler bruit. Color parenchymal flow is significantly decreased., Sagittal sonogram of kidney shows poor color flow and parvus tardus waveforms in peripheral interlobar arteries. C, Reimaging sonogram after surgery for repositioning into peritoneal cavity shows improved color parenchymal flow and decreased PSV of 180 cm/s. Surgical logs and medical records were searched for all cases of renal transplant patients who returned to the operating room within the perioperative period, considered within 7 days of initial surgery. Surgical findings and outcomes were recorded. Nonsurgical nontransplantation-related complications were not included. The Student t test was used to compare PSV between the group requiring intervention and the group who normalized, with two-sided p < 0.05 considered significant. Results Of the 793 renal transplantations performed during the study period, 575 of the patients underwent immediate postoperative sonography in the recovery room within 4 hours of surgery. Thirty-two patients (5.6%) required some type of reoperation during the perioperative period. total of 47 patients (8.2%) had one or more of the designated Doppler abnormalities on the initial sonogram. Of these, 16 had immediate reoperation on the basis of the Doppler examination and clinical findings. The other 16 reoperations were for nonvascular causes, including 15 with and one with cecal perforation. (Fig. 1). In the nonvascular cases the decision to reoperate was based on clinical or CT findings. Of the 16 vascular cases that were reoperated, surgical outcomes included seven compartment syndrome (1.2%) (Figs. 2 and 3), three RV thromboses, one R thrombosis (Fig. 4), two R and RV thromboses, and one vascular steal of the external iliac artery supplying the renal transplant by a dialysis fistula in the ipsilateral thigh. The sonographic findings and clinical outcomes are included in Table 1. diagnosis of compartment syndrome was made intraoperatively when severe graft hypoperfusion was reversed on opening the incision and decompressing the compartment. We chose intraperitoneal placement of these kidneys as the surgical solution although other procedures, such as placement of a mesh hood, have been used successfully [5]. In all seven cases, the kidney was salvaged with placement into the peritoneal cavity. In the previously reported vascular steal case [6], extremely poor color perfusion with high-resistance waveforms improved dramatically at the bedside during manual compression of the fistula. Surgical Fig year-old man with chronic renal failure who underwent immediate postoperative sonography., Sagittal sonogram of renal transplant with sensitive color settings shows no detectable flow in kidney. Normal color flow is present in adjacent external iliac artery and vein., Reimaging sonogram of kidney after reoperation that confirmed ischemia secondary to compartment syndrome shows improved color flow (same color Doppler settings) after repositioning into peritoneal cavity. JR:201, September 2013 W481

4 Horrow et al. Fig year-old woman with chronic renal failure who underwent immediate postoperative sonography with minimal demonstrable flow., Initial sonogram with very sensitive Doppler settings shows only minimal color Doppler flow centrally in kidney and spectral Doppler tracing of segmental artery with very low velocity., Reimaging sonogram obtained after arterial thrombectomy and revision of anastomosis shows improved color Doppler flow and normal spectral Doppler tracing in arcuate artery. PSV = peak systolic velocity, EDV = end-diastolic velocity, RI = resistive index. TLE 1: Ultrasound Findings and Clinical Outcomes Patient No. Color PSV (cm/s) RI Waveform Diagnosis Treatment Outcome 1 Poor Parvus tardus Compartment syndrome Surgery Surgical repositioning 2 Poor Parvus tardus Compartment syndrome Surgery Surgical repositioning 3 Poor Parvus tardus Compartment syndrome Surgery Surgical repositioning 4 Poor Parvus tardus Compartment syndrome Surgery Surgical repositioning 5 Minimal 36 1 Normal Compartment syndrome Surgery Surgical repositioning 6 Minimal 40 1 Normal Compartment syndrome Surgery Surgical repositioning 7 None Compartment syndrome Surgery Surgical repositioning 8 Poor Parvus tardus Twist with infarct Surgery Infarcted 9 Poor 140 Reversed diastolic Renal vein thrombosis Surgery Nephrectomy 10 Poor 71 Reversed diastolic Renal vein thrombosis Surgery Nephrectomy 11 Minimal 63 Reversed diastolic Renal vein thrombosis Surgery Nephrectomy 12 Minimal < 5 Renal artery thrombosis Surgery Thrombectomy and arterial revision 13 Poor Parvus tardus Renal artery and vein thrombosis Surgery Thrombectomy and vascular revisions 14 Minimal Normal Renal artery and vein thrombosis Surgery Nephrectomy 15 Poor 70 1 Normal Vascular steal Surgery Ligation of fistula 16 Poor 70 1 Normal cute tubular necrosis Surgery No vascular abnormality at reoperation 17 Poor 5 1 Normal Normal Surgery No vascular abnormality at reoperation 18 Poor Parvus tardus Iliac artery stenosis ngiography Stent at 3 months 19 Normal Normal Renal artery stenosis ngiography Stent at 3 months 20 Poor Parvus tardus Iliac and renal artery stenoses ngiography Stents at 6 months 21 Normal Normal Renal artery stenosis ngiography Stent at 6 months 22 Normal Parvus tardus Renal artery bend a ngiography No treatment 23 Mildly decreased Parvus tardus Renal artery bend a ngiography No treatment (Table 1 continues on next page) W482 JR:201, September 2013

5 Sonography of Renal Transplants TLE 1: Ultrasound Findings and Clinical Outcomes (continued) Patient No. Color PSV (cm/s) RI Waveform Diagnosis Treatment Outcome 24 Normal Parvus tardus Iliac artery stenosis 50 60% ngiography No treatment 25 Normal Normal Hematoma None Reoperation to manage 26 Normal Normal Hematoma None Reoperation to manage 27 Normal Normal Hematoma None Reoperation to manage 28 Mildly decreased Normal Infected hematoma None Percutaneous drainage 29 Normal Normal Hematoma None Conservative management 30 Normal Normal Hematoma None Reoperation to manage 31 Normal Normal Hematoma None Reoperation to manage 32 Normal Normal None No treatment 33 Normal Normal None No treatment 34 Normal Normal None No treatment 35 Normal Normal None No treatment 36 Normal Normal None No treatment 37 Normal Normal None No treatment 38 Normal Normal None No treatment 39 Normal Parvus tardus None No treatment 40 Normal Normal None No treatment 41 Normal Normal None No treatment 42 Normal Normal None No treatment 43 Normal Normal None No treatment 44 Normal Normal None No treatment 45 Normal Normal None No treatment 46 Normal Normal None No treatment 47 Mildly decreased Normal None No treatment Note Dash indicates not applicable. PSV = peak systolic velocity, RI = resistive index. a Renal artery bend is an apparent focal narrowing in a tortuous renal artery but without any pressure gradient and therefore not hemodynamically significant. fistula ligation was required. Two cases with abnormal sonography findings had no vascular complication at reoperation. In one case, the poor flow was attributed to severe TN and function gradually improved. In the second case, the markedly abnormal flow was attributed to poor sonography technique due to a relatively inexperienced imager compounded by dense adhesions and a hernia mesh. There were 31 patients with positive vascular findings who did not undergo reoperation for a vascular cause. Five of these did have a significant vascular complication (Table 1). In four cases the abnormal Doppler findings persisted on follow-up sonography, ultimately requiring percutaneous stents: two R stenoses, one iliac artery stenosis (Fig. 5), and one R and iliac artery stenosis. One case was an infarct of one of two pediatric en-bloc kidneys on day 4 after transplantation. This case was assumed to be a twist of the kidney on its pedicle because the other adjacent kidney remained normal and was able to sustain the patient. The remaining 26 cases in the positive vascular group were all characterized by normal or only mildly decreased color flow in the parenchyma. In three cases with Doppler findings of abnormal waveforms, no intervention was required based upon the angiographic findings (patients 22 24, Table 1). In 23 patients, the only vascular finding was an elevated PSV. On follow-up sonography, these velocities gradually decreased over time, usually several months, although in some patients, the PSV remained greater than 300 cm/s (Fig. 6). Seven of these 25 patients had hematomas, and five of them required reoperation to manage the. Elevated PSV was present in three cases of compartment syndrome, one pediatric kidney with a presumed twist and subsequent infarct, one renal artery thrombosis, and all three with renal artery stenosis, and 25 cases that did not require any vascular intervention. Using the unpaired Student t test, comparison of PSV in cases with (eight cases; mean, 470 ± 105 cm/s; range, cm/s) and without (25 cases; mean, 431 ± 123 cm/s; range cm/s) an anatomic cause showed no statistically significant difference (p = 0.34). Discussion This retrospective review of 575 consecutive renal transplants with sonography performed JR:201, September 2013 W483

6 Horrow et al. within 4 hours of transplantation surgery found 16 cases with such significantly abnormal vascular findings that patients underwent immediate reoperation. Regardless of the specific vascular diagnosis found at surgery, the common finding in this group was extremely poor color Doppler parenchymal flow. Quantitative Doppler parameters were variable, ranging between high and low PSV, and waveforms varied from normal to parvus tardus or reversed diastolic flow. Four patients who required percutaneous vascular interventions several months after transplantation also had significant vascular findings. In most cases, the only abnormality was an elevated PSV with normal or only mildly decreased color flow. This group did not require surgical or percutaneous vascular procedures. On the basis of our data, the finding of poor color parenchymal flow should prompt D Fig year-old man with chronic renal failure and severe atherosclerotic cardiovascular disease. Doppler findings of low normal systolic velocities and parvus tardus waveforms in renal vessels with monophasic waveform in external iliac artery suggest arterial stenosis proximal to renal artery. Subsequent angiography confirmed right common iliac artery stenosis. fter angioplasty and stent placement, renal artery waveforms normalized. RI = resistive index., Transverse sonogram of renal transplant shows parvus tardus waveforms in segmental artery with mildly decreased color flow in kidney., Spectral Doppler sonogram at origin of main renal artery shows low-normal peak systolic velocity (PSV) of 59 cm/s and parvus tardus waveforms. C, Spectral Doppler sonogram of ipsilateral external iliac artery shows monophasic waveform with mild delay in systolic upstroke. Normal external iliac artery waveform should be triphasic. D, Catheter angiogram of aortic bifurcation shows focal stenosis of right common iliac artery (arrow). Measured gradient across stenosis was 21 mm Hg. ngioplasty and stent placement were performed. E, PSV in main renal artery after angioplasty shows normal systolic upstroke, peak systolic velocity of 170 cm/s, and RI of 0.8. consideration of immediate reoperation. lthough there are some Doppler findings that suggest a specific vascular diagnosis, such as reversed diastolic flow in RV thrombosis, it is not always possible to make a specific vascular diagnosis. In particular, there is overlap between some cases of compartment syndrome and renal artery and vein thrombosis. In our population, the most common cause of such poor flow was compartment syndrome, a little known transplantation complication [7, 8]. Retroperitoneal compartment syndrome is considered an analog to abdominal compartment syndrome, in which elevated intraabdominal pressures result in organ dysfunction impacting cardiovascular, respiratory, and renal systems. When this hypertension occurs in the perirenal transplant space, it causes organ ischemia and severe allograft dysfunction that if left unrelieved will result in global infarction and graft E loss. If this finding is detected early, repositioning the kidney into the peritoneum may reverse the process and salvage the transplant. Thus, sonography is crucial both because symptoms are nonspecific and the window of opportunity to relieve the pressure is probably small. The high surgical salvage rate for these patients may be due to our insistence on immediate postoperative imaging of all renal transplants. In our study population, compartment syndrome had an incidence of 1.2%, similar to the 2% reported in the series of all and colleagues [7]. The spectral Doppler findings separated into two distinct groups: those with elevated PSV and distal parvus tardus flow, typical of a hemodynamically significant stenosis; and those with low PSV and normal waveforms. The cause of such variability is unclear but may reflect the timing of the study and how severely compromised the ar- C W484 JR:201, September 2013

7 Sonography of Renal Transplants terial flow had become. In cases such as the patient in Figure 2, the Doppler pattern suggested a vascular kink. These Doppler findings differ from other studies that showed absent or reversed diastolic flow within parenchymal arteries and did not comment on the velocities in the main renal artery [7, 8]. Extremely poor color parenchymal flow also occurred in cases of major arterial or venous thrombosis. Unfortunately, immediate reoperation was less successful in these situations. None of the cases of renal vein thrombosis could be revascularized. One can speculate that these venous thromboses had rapidly involved small as well as large vessels and could not be reversed. Most abnormal vascular cases were characterized only by elevated PSV despite our use of a threshold value of 300 cm/s. Possible reasons for clinically insignificant elevated velocities include edema at the arterial anastomosis, high flow rates through a relatively small vessel due to size mismatch, and difficulty with optimal Doppler scanning technique on immediate postoperative studies [9, 10]. Interestingly, five of the high velocity cases were associated with significant that required surgical intervention. Several criticisms can be made of this study. First, it is a retrospective review, necessarily relying on searches of sonography reports, medical records, discharge summaries, and surgical logs and therefore possibly missing some reoperated cases or some abnormal sonography studies. The inclusion criteria of this study required that the first postoperative sonography be performed within 4 hours of the transplantation surgery. Thus, 118 patients were excluded. The delay in performing the first postoperative Fig year-old woman with chronic renal failure and elevated renal artery velocity immediately after transplantation that decreased spontaneously over time. PSV = peak systolic velocity, EDV = end-diastolic velocity, RI = resistive index., Immediate posttransplantation sonogram shows satisfactory color Doppler flow in kidney., Sonogram shows PSV of main renal artery with elevated velocity of at least 458 cm/s at anastomosis. C, Reimaging sonogram obtained 11 months later shows lower PSV in main renal artery of 307 cm/s. No interventions were performed, and clinical function was adequate. sonography in these patients was likely a random phenomenon related to the availability of personnel and equipment. nother criticism is our choice of 300 cm/s as the upper threshold for normal R velocity. lthough a PSV greater than 200 cm/s is considered suspicious for renal artery stenosis [11, 12], these studies did not address immediate posttransplantation patients. Several small studies have suggested that higher velocities are more common immediately after transplantation, with a decrease over time [10, 13] Nonetheless, follow-up sonography for elevated PSV is advised because we had two cases that were confirmed and the patients treated for renal artery stenosis several months after transplantation. This study might also be criticized for inconsistent quality of the sonograms because radiology residents performed some of the studies and radiologists without subspecialty training in ultrasound interpreted others. This lack of experience may have resulted in technically poor measurements of PSV or resistive index or an under- or overreporting of sonography abnormalities, but our impression is that, other than the single technically limited abnormal sonography study with a normal kidney in the operating room, this was not a significant issue. significant criticism is the potential harm that might result by performing immediate postoperative sonography. Two patients with very abnormal studies returned to the operating room but did not require any surgical correction. It is possible that neither of these patients would have been subject to reoperation if sonography had not been performed. In addition, we cannot calculate or account for any additional laboratory testing or imaging studies that were performed solely because of the results of the initial sonography. Furthermore, the findings of this analysis may not be applicable to other transplant centers. oth the variety of sonographic abnormalities and the frequency of perioperative reoperations reflect the demographics of our donor kidneys and transplant recipients and our clinical pathways and decisions. In summary, the most important sonographic finding to recommend immediate surgical intervention after renal transplantation is poor color parenchymal flow. lthough some spectral Doppler patterns are highly suggestive of a specific vascular diagnosis, there is a significant range and variability of findings and a definitive preoperative diagnosis cannot always be made. mong positive cases with extremely abnormal Doppler findings, reoperation was most successful in salvaging cases of compartment syndrome. ecause some Doppler abnormalities, especially elevated PSV with normal color Doppler imaging, resolved spontaneously or were eventually treated by percutaneous procedures, both the severity of sonography findings and the clinical situation must be considered before making a decision regarding urgent reoperation. References 1. Cosgrove DO, Chan KE. Renal transplants: what ultrasound can and cannot do. Ultrasound Q 2008; 24: Organ Procurement and Transplantation Network (OPTN) and Scientific Registry of Transplant Recipients (SRTR) annual data report. Rockville, MD: Department of Health and Human C JR:201, September 2013 W485

8 Horrow et al. Services, Health Resources and Services dmin- 2007; 193: rabrand K, Holdaas H, Gunther, Midtvedt K. istration, Healthcare Systems ureau, Division of 6. Chaudhri Y, Horrow MM, Zaki R. Vascular steal Spontaneous regression of initially elevated peak Transplantation, 2011:4 of renal transplant: sonographic diagnosis. J Ul- systolic velocity in renal transplant artery. Transpl 3. Ortiz J, Parsika, Mumtaz K, et al. Early allograft trasound Med 2006; 25: Int 2011; 24: biopsies performed during delayed graft function 7. all CG, Kirkpatrick W, Yilmaz S, Monroy M, 11. kbar S, Jafri ZH, mendola M, Madrazo L, may not be necessary under thymoglobulin induction. Exp Clin Transplant 2012; 10: Patel U, Khaw KK, Hughes NC. Doppler ultrasound for detection of renal transplant artery stenosis-threshold peak systolic velocity needs to be higher in a low-risk or surveillance population. Clin Radiol 2003; 58: Nguan CY, easley K, Mclister VC, Luke PP. Treatment of renal transplant complications with a mesh hood fascial closure technique. m J Surg Nicolaou S, Salazar. Renal allograft compartment syndrome: an underappreciated postoperative complication. m J Surg 2006; 191: Heer MK, Trevilian PR, Hardy D, Hibberd D. Salvaging kidneys with renal allograft compartment syndrome. Transpl Int 2012; 25:e47 e49 9. Gunther, Foss, Holdaas H, et al. Increased peak systolic velocity in the renal artery of paediatric kidneys transplanted to adult recipients. Nephrol Dial Transplant 2008; 23: Salem R, Kostaki G. Complications of renal transplantation. RadioGraphics 2005; 25: demorais RH, Muglia VF, Mamere E, et al. Duplex Doppler sonography of transplant renal artery stenosis. J Clin Ultrasound 2003; 31: Thalhammer C, schwanden M, Mayr M, Koller M, Steiger J, Jaeger K. Duplex sonography after living donor kidney transplantation: new insights in the early postoperative phase. Ultraschall Med 2006; 27: W486 JR:201, September 2013