The renal arterial resistance index and renal allograft survival

Measurement of the intrarenal arterial resistance index for the identification and prediction of diabetic nephropathy

BACKGROUND AND AIMS

High intrarenal resistance index (RI) predicts renal function in several conditions; its use in the prediction of diabetic nephropathy (DN) is little explored. We aimed (1) to compare RI in diabetic and non diabetic hypertensive patients, and (2) to evaluate whether high RI is associated with clinical signs of DN and its progression over time.

DESIGN

observational, prospective.

PARTICIPANTS

92 type 2 diabetic patients and 37 non-diabetic controls aged 40-70, with hypertension and normal renal function. We measured ultrasound RI and, among others, creatinine, estimated glomerular filtration rate and urinary albumin excretion rate (AER) at baseline and after 4.5 years follow-up. Progression of albuminuric state (i.e., transition from baseline normo-microalbuminuria to follow-up micro-macroalbuminuria) was evaluated. RI was significantly higher in diabetic than non-diabetic participants (0.69+/-0.05 vs 0.59+/-0.05, p<0.001). Diabetic patients with RI>or=0.73, i.e., above the 80th percentile of the RI distribution, had significantly higher baseline AER and a more frequent progression of the albuminuric state compared to patients with RI<0.73 (27.7microg/mg [12.1-235.4] vs 15.1microg/mg [8.6-33.4]; 52.9% vs 9.5%, respectively). AER increased significantly from baseline to follow-up in patients with RI>or=0.73 (from 27.7microg/mg [12.1-235.4] to 265.0microg/mg [23.8-1018.1], p<0.01), but not in those with RI<0.73 (from 15.1microg/mg [8.6-33.4] to 16.1microg/mg [10.7-67.2], ns). OR for progression of albuminuric state, adjusted for established predictors of DN, including baseline AER, was 5.01 (1.4-17.7, 95% CI) for patients with RI>or=0.73 vs <0.73. Findings were confirmed in patients with normoalbuminuria at baseline.

CONCLUSIONS

In diabetic patients, high RI (>or=0.73) is associated with features of DN and its progression over time, independent of albuminuria.

Early assessment of renal resistance index and long-term renal function in renal transplant recipients

BACKGROUND

The effect of the intrarenal arterial resistance index (RI) on long-term renal functions is not well known. We examined the predictive value of intrarenal RI on long-term allograft outcomes.

METHODS

We retrospectively investigated 121 stable renal transplant recipients, followed for a mean of 63.21 +/- 19.9 months after renal transplant. Patients with complications during the first six months after transplant were not included. Color Doppler ultrasonography was done to calculate the intrarenal RI within the first four weeks after transplant.

RESULTS

Older recipient age, high pulse pressure, active smoking, and proteinuria were associated with a higher intrarenal RI. Multivariate analyses revealed that renal RI and donor age were independent predictors of allograft outcome. Kaplan-Meier estimates of cumulative graft survival were significantly worse in patients who had an RI of 0.7 or more than they were in patients who had an RI of less than 0.7 (p = .005). Development of chronic allograft nephropathy (CAN) was significantly higher in patients who had an RI of 0.7 or more (p = .02).

CONCLUSIONS

Renal RI determined within the first month after renal transplant predicts long-term allograft function and development of CAN in renal transplant recipients.

[Risk factors for the development of diabetic nephropathy]

INTRODUCTION

Results of epidemiological analysis show that one third of patients with diabetes mellitus develop diabetic nephropathy (DN). Strategies used until now to slow down the progression of DN were initiated when the symptoms of DN were already present.

OBJECTIVE

Our objective was to analyze the prevalence and characteristics of DN and to determine the factors leading to DN.

METHODS

Fifty-two patients with diabetes mellitus (DM)--32 with type 1 aged 32 years and 20 with type 2 aged 59 years--were referred from the Institute of Endocrinology, Diabetes and Metabolic Diseases to the Department of Nephrology for kidney function evaluation. Apart from routine laboratory analyses, glomerular filtration rate was calculated using the MDRD formula (modification of diet in renal disease), the size of the kidney was measured by ultrasound, and kidney volume was calculated using the ellipsoid formula.

RESULTS

Thirty percent of the patients revealed normal (eight patients with DM type 1) or satisfactory kidney function (eight patients with DM type 1) with physiological proteinuria. Microalbuminuria (MAU) or pathological proteinuria (PRT) were found in 10 and 9 patients, respectively, with DM type 1, while decreased kidney function was found in one patient without proteinuria. MAU or PRT were found in four and eight patients, respectively, with DM type 2 and decreased kidney function in four patients without proteinuria. Kidney function was significantly lower in patients with DM type 2 in comparison to DM type 1, while the patients with decreased kidney function had a higher PRT. Compared to DM type 2, in DM type 1 patients, the kidney was longer, and parenchymal artery resistance index was lower in DM type 1 patients compared to DM type 2. Factors associated with DN were patient's age, duration of diabetes, systolic blood pressure, HbA1c and kidney volume.

CONCLUSION

The prevalence of DN among the studied patients was 70%. Treatable factors associated with the development of DN are strict control of blood pressure and glycaemia control.

Relationship between renal resistance index and renal function in liver transplant recipients after cessation of calcineurin inhibitor

End stage renal disease is a major complication after orthotopic liver transplantation (OLT). Vasoconstriction of renal arterial vessels because of calcineurin inhibitor (CNI) treatment plays a pivotal role in the development of renal insufficiency following OLT. Renal resistance can be measured non-invasively by determining the resistance index (RI) of segmental arteries by color-coded duplex ultrasonography, a measure with predictive value for future renal failure. Sixteen OLT patients on long-term CNI therapy were recruited prospectively and randomly assigned either to receive the m-TOR inhibitor sirolimus (SRL) or to continue on CNI treatment, and were followed for one yr. Serum creatinine (crea) declined after conversion to SRL, whereas it tended to increase in patients remaining on CNI (meanDelta crea SRL: -27, -18, -18, -15 micromol/L; meanDelta crea CNI: 4, 5, 8, 11 micromol/L at 1, 3, 6, 12 months, p = 0.02). RI improved after switching to SRL and was lower on SRL than on CNI (meanDeltaRI SRL: -0.04, -0.04, -0.03, -0.03; meanDeltaRI CNI: -0.006, 0.004, -0.007, -0.01 after 1, 3, 6, 12 months, p = 0.016). Individual changes of RI correlated significantly with individual changes of crea (r = 0.54, p < 0.001). Conversion from CNI to SRL can ameliorate renal function accompanied by a reduction of intrarenal RI after OLT.

Resistive index predicts renal prognosis in chronic kidney disease

BACKGROUND

While the clinical validity of Doppler ultrasonography in renal parenchymal disease is still controversial, we have previously reported that the resistive index (RI) and the atrophic index (AI) could estimate tubulointerstitial injury. We aimed to determine whether these indices could estimate renal prognosis in chronic kidney disease (CKD).

METHODS

We performed a 2-year follow-up study with an observational cohort of 311 CKD patients. The patients were examined by Doppler ultrasonography to calculate RI and AI to be calculated. Glomerular filtration rate (GFR) was estimated with the abbreviated MDRD study equation every 6 months.

RESULTS

When we divided the patients into three groups by the RI value of 0.65 and 0.70, there were significant differences in the decrease in GFR among the three groups at 24 months. Kaplan-Meier analysis also showed a significant difference among the three groups in the survival rate of worsening renal function, which was defined as a decrease in GFR of at least 20 mL/min 1.73 m(2) or the need for long-term dialysis therapy until the end of the 2-year follow-up. Cox proportional-hazard analysis identified overt proteinuria (> or =1.0 g/g creatinine), high RI (>0.70) and high systolic blood pressure (> or =140 mmHg) as independent predictors of worsening renal function. In contrast, AI was of no significance in evaluating renal prognosis in CKD.

CONCLUSIONS

This study suggested that RI, and proteinuria and hypertension were independent risk factors for the progression of CKD.

Rapid adaptation of the intrarenal resistance index after living donor kidney transplantation

BACKGROUND

Limited data exist concerning changes of renal perfusion directly after kidney transplantation. Colour-coded duplex sonography is the accepted method to assess kidney perfusion after transplantation. A widely used, although unspecific, Doppler parameter is the intrarenal resistance index (RI). The aim of this study was to clarify the influence of different patient- and procedure-related factors on RI before and immediately after living kidney transplantation.

METHODS

In a prospective study, 80 living kidney transplantation donor-recipient pairs were included. RI was measured in the donor 1 to 3 days before nephrectomy and in the recipient during the first hour after transplantation to examine the influence of age, heart rate, duration of cold and warm ischaemia time and immunosuppressive medications.

RESULTS

Mean RI did not differ between donors and recipients. RI correlated with age, both in donors (r = 0.58, P < 0.001) and recipients (r = 0.39, P < 0.001). In recipients, 10 or more years younger than their donors (n = 24), an average decrease of 0.05 in RI compared to the donors' value was observed (P = 0.01). Heart rate, cold and warm ischaemia time and immunosuppressive medications had no influence on the recipient RI. In patients with delayed graft function, a significant increase in RI within 14 days was observed. However, the initial RI was not predictive of graft function.

CONCLUSIONS

The transplanted kidney seems to be able to adjust its RI within a short time despite several potential harmful factors that can occur during the transplantation.

Renal vascular perfusion index in a canine model

Decreased renal perfusion plays an important role in the progression toward renal failure. In this study, a novel measure was proposed to quantify renal perfusion using canine model. Serial renal vascular images at different vascular areas including the whole vascular tree, interlobar, arcuate and interlobular vessels were captured. Image processing software was designed to analyze the changes of power Doppler intensity of colored pixels within regions-of-interest (ROI). For a given ROI, the power Doppler vascular index (PDVI) was found to fluctuate with the cardiac cycle. It was also noted that the power Doppler signals generated by arterial vessels have different fluctuating waveforms and different phase compared with the signal derived from venous vessels. A power Doppler correlation-map was developed to differentiate the arteries and veins in the ROI. Using the serial power Doppler images and the derived flow direction information, the interlobular perfusion can be strongly quantified. The renal vascular perfusion index (RVPI) defined as the ratio of PDVI(max) versus PDVI(min) was significantly higher in the interlobular vessel areas than three other areas for seven healthy dogs. The RVPI resembles the systolic/diastolic (S/D) ratio that commonly reflects arterial hemodynamics. RVPI and power Doppler correlation-map reveal more "dynamic" sense of vascular perfusion and provide a novel approach for the examination of renal function in clinical practice.

Clinical utility of the resistive index in atherosclerotic renovascular disease

OBJECTIVE

This retrospective study examines the relationship between the renal resistive index (RI) and blood pressure and renal function response after open and percutaneous intervention for atherosclerotic renovascular disease (AS-RVD).

METHODS

From March 1997 to December 2005, 86 patients (46 women, 40 men; mean age, 68 +/- 10 years) underwent renal duplex sonography (RDS), including main renal artery and hilar vessel Doppler interrogation, before treatment of AS-RVD. Of these, 56 patients had open operative repair, and 30 had percutaneous intervention. The RI (1-[EDV/PSV]) was calculated from the kidney with the highest peak systolic velocity (PSV). Hypertension response was graded from preprocedural and postprocedural blood pressure measurements and medication requirements. Renal function response was graded by a >or=20% change in estimated glomerular filtration rate (eGFR) calculated from the serum creatinine concentration.

RESULTS

Comorbid conditions, baseline blood pressure, and preoperative renal function were not significantly different between open and percutaneous groups. Baseline characteristics that differed between the percutaneous vs open group were higher mean age (71 +/- 11 years vs 67 +/- 9 years; P = .05), kidney length (11.3 +/- 1.3 cm vs 10.7 +/- 1.2 cm; P = .02), proportion of patients with RI >or=0.8 (50% vs 21%; P = .01), and proportion of bilateral AS-RVD (37% vs 80%; P < .01). After controlling for preintervention blood pressure and extent of repair, postoperative eGFR differed significantly for RI <0.8 or >or=0.8 when all patients (P = .003) and percutaneous intervention (P = .008) were considered. Specifically, eGFR declined from preprocedure to postprocedure in the patients with RI >or=0.8 after percutaneous repair and in the group analyzed as a whole. Neither systolic nor diastolic pressure after intervention demonstrated an association with RI. Considering all patients and both groups, multivariable proportional hazards regression models demonstrated that RI was predictive of all-cause mortality. RI was the most powerful predictor of death during follow-up (hazard ratio, 6.7; 95% confidence interval, 2.6-17.2; P < .001).

CONCLUSION

After intervention for AS-RVD, RI was associated with renal function, but not blood pressure response. A strong, independent relationship between RI and mortality was observed for all patients and both treatment groups.

mToR inhibitors-induced proteinuria: mechanisms, significance, and management

Massive urinary protein excretion has been observed after conversion from calcineurin inhibitors to mammalian target of rapamycin (mToR) inhibitors, especially sirolimus, in renal transplant recipients with chronic allograft nephropathy. Because proteinuria is a major predictive factor of poor transplantation outcome, many studies focused on this adverse event during the past years. Whether proteinuria was due to sirolimus or only a consequence of calcineurin inhibitors withdrawal remained unsolved until high range proteinuria has been observed during sirolimus therapy in islet transplantation and in patients who received sirolimus de novo. Podocyte injury and focal segmental glomerulosclerosis have been related to mToR inhibition in some patients, but the pathways underlying these lesions remain hypothetic. We discuss herein the possible mechanisms and the significance of mToR blockade-induced proteinuria.

Chronic allograft nephropathy

PURPOSE OF REVIEW

Despite dramatic declines in acute rejection and early graft failure, long-term outcomes after kidney transplantation have improved little during the past 25 years. Most late allograft failure is attributed to chronic allograft nephropathy, but this is a clinicopathological description and not a diagnosis, and its pathogenesis and treatment are largely unknown.

RECENT FINDINGS

Recent studies suggest that acute rejection during the first few months, and calcineurin inhibitor toxicity thereafter, may both contribute to chronic allograft nephropathy. There is also accumulating evidence that injury from antibody-mediated rejection may play an important pathogenic role in at least some patients with chronic allograft nephropathy, particularly those with transplant glomerulopathy. Therapeutic measures, including protocols to reduce calcineurin inhibitor exposure, remain largely unproven.

SUMMARY

Understanding why so many kidney allografts fail, despite effective preventive measures for early acute rejection, is one of the most important areas of research in kidney transplantation today.

Renal transplantation today

BACKGROUND

The first successful renal transplant was carried out more than five decades ago between identical twins. At these early days, acute rejection was the limiting factor.

DISCUSSION

Due to tremendous progress in immunosuppressive therapy and surgical technique, today, renal transplantation is the gold standard therapy for patients with end-stage renal disease. In fact, in comparison with chronic hemodialysis, renal transplantation offers an increase in quality of life while reducing comorbidities associated with dialysis treatment.

RESULTS

Despite numerous beneficial achievements, no further improvement regarding patient outcome can be observed over the last two decades. Graft survival rates remain unchanged. The leading causes for graft loss are chronic allograft nephropathy and death with functioning graft. This might be related to a constant increase of the proportion of donors presenting extended donor criteria as well as a more liberal acceptance of candidates for a renal transplant.

CONCLUSION

In the near future, one has to focus more closely on the posttransplant patient care to minimize factors associated with chronic allograft damage. These include post-transplant diabetes, hyperlipidemia, high blood pressure, cytomegalovirus infection, etc.

Renal vascular imaging: ultrasound and other modalities

Sonographic evaluation of the genitourinary system is a fast, safe, and effective means to detect renal disease. In conjunction with other modalities, Doppler can depict a variety of abnormalities. However, optimization of Doppler techniques and a solid understanding of Doppler threshold criteria are critical for success, whether in the native or transplanted kidney.

Vascular complication and Doppler ultrasonographic finding after renal transplantation

OBJECTIVES

Vascular complications are common after renal transplantation. In this study we correlated Doppler sonographic indices and transplant kidney function.

METHODS

We reviewed data on 244 renal transplant patients. Doppler ultrasonographic evaluation was performed during the first 2 weeks after renal transplantation. We determined resistive index (RI) and pulsatility index (PI) in the interlobar arteries and thrombosis of renal and lower limb veins. Serum creatinine (Cr) and cyclosporine levels were evaluated prior to sonographic assessment.

RESULTS

The mean age of the 142 male and 102 female patients was 36.31 +/- 3.30 years. Prevalence of real artery stenosis was 9.5%. In these patients the mean serum Cr level (2.21 +/- 1.83 mg/dL) was significantly higher than among patients with patent renovascular tributary (1.49 +/- 1.00 mg/dL; P=.03). RI and PI were also significantly correlated with serum Cr(P=.05 and .001, respectively). There was no relationship between cyclosporine level or panel-reactive antibody with RI and PI. Retransplant patients showed higher RI than first renal allograft recipients (0.72 +/- 0.16 vs 0.63 +/- 0.11; P=.006). Serum Cr level was higher among renal allograft recipients with Doppler evidence of thrombosis of the lower limb veins (3.1 +/- 0.98 mg/dL versus 1.56 +/- 1.13 mg/dL; P=.04).

CONCLUSIONS

RI and PI are two valuable Doppler ultrasonographic markers to determine renal allograft function and related vascular complications.

Techniques in interventional radiology: renal CT angiography

Multidetector row CT angiography has become an important tool in the evaluation of patients with suspected renovascular hypertension. The following article presents a review of the published data on accuracy of this method of evaluation as well as a comparison to other diagnostic strategies, in particular, renal MR angiography.

Adjunctive treatment with moxonidine versus nitrendipine for hypertensive patients with advanced renal failure: a cost-effectiveness analysis

BACKGROUND

Systemic hypertension often accompanies chronic renal failure and can accelerate its progression to end-stage renal disease (ESRD). Adjunctive moxonidine appeared to have benefits versus adjunctive nitrendipine, in a randomised double-blind six-month trial in hypertensive patients with advanced renal failure. To understand the longer term effects and costs of moxonidine, a decision analytic model was developed and a cost-effectiveness analysis performed.

METHODS

A Markov model was used to extrapolate results from the trial over three years. All patients started in a non-ESRD state. After each cycle, patients with a glomerular filtration rate below 15 ml/min had progressed to an ESRD state. The cost-effectiveness analysis was based on the Dutch healthcare perspective. The main outcome measure was incremental cost per life-year gained. The percentage of patients progressing to ESRD and cumulative costs were also compared after three years. In the base case analysis, all patients with ESRD received dialysis.

RESULTS

The model predicted that after three years, 38.9% (95%CI 31.8-45.8) of patients treated with nitrendipine progressed to ESRD compared to 7.5% (95%CI 3.5-12.7) of patients treated with moxonidine. Treatment with standard antihypertensive therapy and adjunctive moxonidine was predicted to reduce the number of ESRD cases by 81% over three years compared to adjunctive nitrendipine. The cumulative costs per patient were significantly lower in the moxonidine group 9,858 euro (95% CI 5,501-16,174) than in the nitrendipine group 37,472 euro (95% CI 27,957-49,478). The model showed moxonidine to be dominant compared to nitrendipine, increasing life-years lived by 0.044 (95%CI 0.020-0.070) years and at a cost-saving of 27,615 euro (95%CI 16,894-39,583) per patient. Probabilistic analyses confirmed that the moxonidine strategy was dominant over nitrendipine in over 98.9% of cases. The cumulative 3-year costs and LYL continued to favour the moxonidine strategy in all sensitivity analyses performed.

CONCLUSION

Treatment with standard antihypertensive therapy and adjunctive moxonidine in hypertensive patients with advanced renal failure was predicted to reduce the number of new ESRD cases over three years compared to adjunctive nitrendipine. The model showed that adjunctive moxonidine could increase life-years lived and provide long term cost savings.

Diagnostic Tools for Monitoring Kidney Transplant Recipients

Recent advancements in immunobiology have introduced several new diagnostic tools for monitoring kidney transplant recipients. These have been added to more established tests that, although imperfect, remain important benchmarks of diagnostic utility. Both new and old tests can be characterized with regard to their practicality, and as to whether they detect aberrant function or define the cause of dysfunction. Unfortunately, no current test is both practical and specific to a particular disease entity. Accordingly, the diagnosis of graft dysfunction remains dependent on the proper use and interpretation of many studies. This article reviews the current assays that have been evaluated in the clinic for the diagnosis of renal allograft-related diseases. These are limited to assays based on routinely obtainable samples such as blood, biopsy tissue, and urine. Newer studies are presented, along with more mundane assays, to highlight the practical use of studies regardless of their degree of mechanistic sophistication.

A Correlation Between Direct and Indirect Doppler Ultrasonographic Measures in Transplant Renal Artery Stenosis

Screening for transplant renal artery stenosis (TRAS) with Doppler ultrasonography (DUS) is increasingly used in the era of kidney transplantation. Direct Doppler study of the stenotic site is a time- consuming and difficult method that requires an angle of interrogation parallel to the vessel. The aim of this study was to assess the correlation between the direct-PSVs (peak systolic velocity at the stenotic site), PSVs/PSVi (PSVi, peak systolic velocity of the adjacent iliac artery)-and indirect-intrarenal arterial resistive index (RI), perfusion index (PI), acceleration time (AT)-DUS findings in the kidney transplant recipients with TRAS. We performed 26 DUS studies of both intrarenal and main renal arteries in 19 TRAS patients (who had PSVs > 150 cm/s, PSVs/PSVi > 2). The mean values of PSVs and PSVs/PSVi were 212 +/- 44.19 cm/s and 2.77 +/- 0.77, respectively. The mean intrarenal RI, PI, and AT were 0.48 +/- 0.065, 0.70 +/- 0.12, and 177.8 +/- 54.6 msec, respectively. A significant negative correlation was found between PSVs and intrarenal RI (Pearson correlation coefficient (r) = -0.4, two-tailed P = .043). No correlation was found between intrarenal PI or AT and the direct DUS findings (P > .05). With a cutoff level of 0.55 for intrarenal resistive index, the sensitivity of this parameter to detect proximal renal arterial stenosis was about 85%. Conclusively, PSVs and intrarenal RI were negatively correlated. Intrarenal resistive index can be used as an screening measure for detection of TRAS.

Renal arterial resistance in septic shock: effects of increasing mean arterial pressure with norepinephrine on the renal resistive index assessed with Doppler ultrasonography

OBJECTIVE

To determine the effects of increasing mean arterial pressure (MAP) on renal resistances assessed by Doppler ultrasonography in septic shock.

DESIGN AND SETTING

Prospective, single-center, nonrandomized, open-label trial in the surgical intensive care unit in a university teaching hospital.

PATIENTS AND PARTICIPANTS

11 patients with septic shock who required fluid resuscitation and norepinephrine to increase and maintain MAP at or above 65 mmHg.

INTERVENTIONS

Norepinephrine was titrated in 11 patients in septic shock during three consecutive not randomized periods of 2 h to achieve a MAP at successively 65, 75, and 85 mmHg.

MEASUREMENTS AND RESULTS

At the end of each period hemodynamic parameters and renal function variables (urinary output, creatinine, clearance) were measured, and Doppler ultrasonography was performed on interlobar arteries to assess the renal resistive index. When increasing MAP from 65 to 75 mmHg, urinary output increased significantly from 76 +/- 64 to 93 +/- 68 ml/h and the resistive index significantly decreased from 0.75 +/- 0.07 to 0.71 +/- 0.06. No difference was found between 75 and 85 mmHg.

CONCLUSIONS

Doppler ultrasonography and resistive index measurements may help determine in each patient the optimal MAP for renal blood flow and may be a relevant end-point to titrate the hemodynamic treatment in septic shock.

Duplex Sonographic Measurements in Allografted Kidneys: A Cross-Sectional Study

OBJECTIVES

The measurement of color Doppler sonography indices, such as resistive index (RI) and pulsatility index (PI), can help in the evaluation of an transplanted kidney. The aim of this study was to determine the correlation between Doppler sonography indices and demographic paraclinical findings in transplanted kidneys.

METHODS

A cross-sectional study was performed on 47 (27 male and 20 female) unrelated living renal transplanted patients.

RESULTS

The mean age, body mass index (BMI), time since transplantation, pulse pressure index (PPI), intrarenal RI and PI were 38 +/- 13 years, 25 +/- 4.5, 48 +/- 31 months, 0.34 +/- 0.06, 0.69 +/- 0.06, and 1.3 +/- 0.3, respectively. There were significant negative correlations between time since transplantation and intrarenal RI and PI (r=-.38, P<.01; r=-.4, P<.01, respectively). There was a significant correlation between patient age, creatinine clearance, and intrarenal RI (r=.30, P=.039; r=.3, P=.043, respectively). There were no significant correlations between intrarenal RI, PI, and BMI, cyclosporine trough level, PPI, recipient and donor sexes, and rejection episodes. Diabetic patients displayed higher RI (0.76 +/- 0.02 vs 0.68 +/- 0.06, P=.048) and patients with serum high-density lipoprotein (HDL) level <40 mg/dL had higher PI than patients with HDL >or= 40 mg/dL (1.6 +/- 0.4 vs 1.2 +/- 0.3, P=.006).

CONCLUSIONS

Intrarenal RIs did not decrease over a few years after transplantation. They can be a useful, feasible predictor of graft function. However, future multicenter trials should be performed to prove the predictive power of RI determination as a marker of renal function.

Color Doppler Findings in Transplanted Kidneys and Remnant Kidneys of Donors 6 to 12 Months After Kidney Transplantation

OBJECTIVES

Ultrasonography and color Doppler have been used extensively in the evaluation of transplanted kidney. The aim of this study was evaluation and comparison of color Doppler sonography findings in the remnant kidney of living donors and the transplanted kidney at 6 to 12 months after kidney transplantation.

METHODS

In a cross-sectional study we evaluated ultrasonographic (US) and color Doppler findings in 20 kidney allograft recipient and donors. Group 1 were unrelated and related kidney donors, and group 2, allograft recipients. Color Doppler US was performed by one sonologist on the remnant kidney of the living donor and the transplanted kidney of the recipient at 6 to 12 months after kidney donation and transplantation. We recorded, kidney size (including length and anteroposterior diameter), cortical thickness, resistive index (RI), and pulsatile index (PI). Statistical analysis was performed using SPSS 13 win (t test) for comparison of the results in donors and recipients. All data are presented as mean values +/- SD with P values less than .05 considered significant.

RESULTS

In group 1, mean age of kidney allograft recipients was 39.92 +/- 11.95 years with male-to-female ratio of 1/2. Mean length, width, and cortical thickness of the transplanted kidney were 120.15 +/- 11.95 mL, 53.65 +/- 7.50 mL, and 8.53 +/- 1.00 mL, respectively. Mean RI and PI were 0.60 +/- 0.08 and 1.02 +/- 0.23, respectively. Mean serum creatinine was 1.23 +/- 0.24 mg/dL. Mean duration of renal transplantation was 7.27 +/- 1.10 months. In group 2, mean age of recipients was 25.63 +/- 3.50 years with male-to-female ratio of 1/10. Mean length, anteroposterior diameter, and cortical thickness were 120.77 +/- 9.28 mL, 53.36 +/- 4.52 mL, and 9.04 +/- 1.27 mL, respectively. Mean RI and PI were 0.60 +/- 0.02 and 1.07 +/- 0.13, respectively. There was no significant difference in the length, anteroposterior diameter, cortical thickness, RI, and PI of donors and transplanted kidneys at 6 to 12 months after transplantation (P>.05). There was a significant increase in both donor and recipient kidney size at 6 to 12 months after transplantation (P<.05).

CONCLUSION

It seems that renal US and Doppler parameters remain stable in the recipient and donor at least upon short-term evaluation. Long-term study with more patients is recommended.

Diurnal blood pressure changes one year after kidney transplantation: relationship to allograft function, histology, and resistive index

Loss of circadian BP change has been linked to target organ damage and accelerated kidney function loss in hypertensive patients with and without chronic kidney disease. Ambulatory BP-derived data from 119 consecutive kidney transplant recipients who presented for the first annual evaluation were examined in relation to allograft function, histology, and ultrasound findings. A total of 101 (85%) patients were receiving antihypertensive medications (median 2), and 85 (71%) achieved target awake average systolic BP (SBP) of <135 mmHg. A day-night change in SBP by 10% or more (dippers) was detected in 29 (24%). Dipping status was associated with younger recipient age, lack of diabetes, low chronic vascular score, and low resistive index. Nondippers and reverse dippers had lower GFR compared with dippers (P = 0.04). For every 10% nocturnal drop in SBP, GFR increased by 4.6 ml/min per 1.73 m(2) (R = 0.3, P = 0.003). Nondippers and reverse dippers were equally common in recipients with normal histology and in those with pathologic findings on surveillance biopsy. On multivariate analysis, percentage of nocturnal fall in SBP and elevated resistive index independently correlated with GFR. This study indicates that lack of nocturnal fall in SBP is related to poor allograft function, high chronic vascular score, and high resistive index irrespective of allograft fibrosis. Further studies are needed to determine whether restoration of normal BP pattern will confer better allograft outcome.

Altered kidney graft high-energy phosphate metabolism in kidney-transplanted end-stage renal disease type 1 diabetic patients: a cross-sectional analysis of the effect of kidney alone and kidney-pancreas transplantation

OBJECTIVE

Diabetes, hypertension, dyslipidemia, obesity, nephrotoxicity of certain immunosuppressive drugs, and the persistence of a chronic alloimmune response may significantly affect graft survival in end-stage renal disease (ESRD) type 1 diabetic patients who have undergone kidney transplant. The aim of this study was to ascertain the impact of kidney alone (KD) or combined kidney-pancreas (KP) transplantation on renal energy metabolism.

RESEARCH DESIGN AND METHODS

We assessed high-energy phosphates (HEPs) metabolism by using, in a cross-sectional fashion, 31P-magnetic resonance spectroscopy in the graft of ESRD type 1 diabetic transplanted patients who received KD (n = 20) or KP (n = 20) transplant long before the appearance of overt chronic allograft nephropathy (CAN). Ten nondiabetic microalbuminuric kidney transplanted patients and 10 nondiabetic kidney transplanted patients with overt CAN were chosen as controls subjects.

RESULTS

Simultaneous KP transplantation patients showed a higher beta-ATP/inorganic phosphorus (Pi) ratio (marker of the graft energy status) versus the other groups, and a positive correlation between beta-ATP/Pi phosphorus ratio and A1C was found. In the analysis limited to the subgroup of normoalbuminuric patients, the difference in beta-ATP/Pi was still detectable in KP patients compared with KD transplantation.

CONCLUSIONS

KP transplantation was associated with better HEPs than in KD transplantation, suggesting that restoration of beta-cell function positively affects kidney graft metabolism.

Gender differences in the renin-angiotensin and nitric oxide systems: relevance in the normal and diseased kidney

Female gender is associated with better renal function and resistance to renal injury, suggesting that an oestrogen-based effect or increased androgenic effects are responsible. Studies in rodents have confirmed a biological basis for this, based on the differential effects of androgens and oestrogens on the normal and diseased kidney. Many researchers in the field believe that the pre-menopausal levels of oestrogen are key to the protection observed in females. The key pressor effects of the renin-angiotensin (RA) system are due to both direct vasoconstrictory properties and alterations in renal control of extracellular fluid volume. Additionally, the RA has been shown to promote diverse aspects of renal injury. RA activity is positively modulated by androgens and antagonized by oestrogens. Nitric oxide (NO) is a potent vasorelaxant with a key role in renal control of extracellular fluid homeostasis. NO can variously have both protective and deleterious effects on renal injury. Endogenous oestrogen has an anti-hypertensive effect as well as protective effects against cell and organ damage, many of which are mediated via increases in NO generation. We examine how the RA- and NO-generating systems may underpin key aspects of gender differences in normal renal function and renal disease.

Enhanced flow velocity after stenting of renal arteries is associated with decreased renal function

BACKGROUND

Atherosclerotic renal artery stenosis (RAS) is frequently treated by angioplasty and stent placement. Duplex sonography is an established noninvasive technique for patient follow-up. There is lack of evidence that routine monitoring of asymptomatic patients with stable blood pressure is needed.

METHODS

Renal duplex sonography was performed in 64 patients who had received percutaneous angioplasty and stenting of an atherosclerotic RAS. Duplex sonographic diagnosis was made by a combination of direct flow measurement in the renal artery and evaluation of intrarenal resistive indices. Renal function was determined by serum creatinine and calculated glomerular filtration rate (GFR).

RESULTS

With a mean follow-up of 28 months after angioplasty, a flow velocity of >2.0 m/s was detected within the stented arteries in 11/64 patients. While the initial blood pressure and GFR as well as the influence of angioplasty on these parameters were not different, the decrease in renal function over time was significantly higher in patients with flow enhancement (annual GFR decrease, 8.0 ml/min vs. 0.8 ml/min; p < 0.05).

CONCLUSION

Follow-up duplex sonography in patients after renal artery stenting detected an unexpectedly high rate of in-stent restenosis associated with enhanced loss of renal function. Routine duplex sonographic follow-up may detect patients at risk of more rapidly declining renal function.

Real-time contrast-enhanced sonography in renal transplant recipients

Conventional colour Doppler ultrasonography (CDUS) is a well-established and the most frequently used imaging procedure to diagnose kidney allograft dysfunction. Unfortunately, this technique is limited to the estimation of the allograft perfusion in large arteries. Early diagnosis of vascular damage, i.e., chronic allograft nephropathy is essential for an early therapeutic intervention. CDUS is still limited in interpreting vascular integrity. In contrast-enhanced sonography (CES) is a feasible technique for quantitative analysis of kidney perfusion and early diagnosis of biopsy proven chronic allograft nephropathy. CES does not provide only quantitative information on microvascular perfusion of the renal allografts but also represents improved diagnostic significance compared with CDUS for the detection of chronic allograft nephropathy.

Color Doppler indices of renal allografts depend on vascular stiffness of the transplant recipients

A resistance index (RI) of 0.8 or higher was shown to be a strong predictor of kidney allograft and patient survival. Uncertainties persist since the intrarenal RI is closely associated with the vascular stiffness of the allograft recipient. To clarify the diagnostic value of RI further, we analyzed parameters of vascular stiffness of the recipient and intrarenal RI of the renal allograft. In a prospective study laboratory and clinical parameters, pulse wave velocity (PWV), intima media thickness (IMT) and RI were obtained in 76 kidney allograft patients. We found that the RI values significantly correlated with the PWV (p < 0.05) and the recipients age (p < 0.01) but not with the donor age and renal function. Using multiple regression analysis recipient age, PWV, pulse pressure (PP) and IMT were identified as independent factors influencing RI values. For a more correct interpretation of the RI values in renal allografts parameters of vascular stiffness such as IMT, PP or PWV should be included.

Kidney Ultrasound Is Useful Tool in Posttransplant Follow-Up

OBJECTIVES

Renal sonography has been an important imaging tool in surveys of kidney diseases. We reviewed our experience in the finding and management of asymptomatic patients who underwent renal transplantation.

METHODS

We performed baseline graft and native kidney sonography after renal transplantation, as well as annually even if the patient was asymptomatic. At the end of 2004, a total of 326 transplant cases had been annually surveyed. If the findings were positive, they were compared with previous data to determine the need for further examinations and management.

RESULTS

The native kidneys of 105 patients were abnormal. Cysts were detected in 71 cases, 23 of which were bilateral. Stones were found in 15 cases. Polycystic kidney disease was identified in 5. The findings in these 91 patients were the same as before. Moderate hydronephrosis was observed in 14 cases. Nine had native ureteral cancer and underwent nephroureterectomy. Ureteral stricture was found in the other 5 patients. Forty-five grafts were abnormal. Thirty-one showed hydronephrosis and 2 underwent ureteral reimplantation. Asymptomatic stones were found in 2. A new single renal cyst was found in 2 cases; and multiple cysts in one other. Elevated RI on color Doppler was discovered in 12 patients, 4 of whom lost their grafts this year. Serum creatinine values of 6.9 and 2.2 mg/dL were observed in 2 patients.

CONCLUSIONS

Renal sonography screening is useful not only for the graft but also for the native kidney. Hydronephrosis is an important finding. The high possibility of urothelial malignancy should be expected, requiring further examination and sequential follow-up. Elevated RI is a clue to predict graft outcome; rapid deterioration was observed within months.

Early assessment of renal resistance index after kidney transplant can help predict long-term renal function

BACKGROUND

Color Doppler ultrasonography of intrarenal arterial resistance index (RI), performed early after kidney transplant, has proven to reliably predict short-term allograft function. The aim of this study was to assess whether it could also predict long-term renal function.

METHODS

We retrospectively analysed 76 kidney transplant patients who underwent RI assessment within 1 month after the transplant, subdivided into two groups according to RI values, lower (group A) or higher (group B) than its median value (0.635).

RESULTS

Compared with group A subjects, the patients of group B were older at the time of transplant (42 +/- 9 vs 35 +/- 8 years; P = 0.001), the donor age was also older (41 +/- 16 vs 33 +/- 13 years; P = 0.02) and had a slightly higher proteinuria (0.54 +/- 0.5 vs 0.32 +/- 0.2 g/24 h; P = 0.02). Serum creatinine, ciclosporin or tacrolimus trough level, arterial blood pressure, number of human leukocyte antigen (HLA) mismatches, anti-hypertensive medications and incidence of delayed graft function were not significantly different between the two groups. By univariate analysis, RI turned out to directly correlate with the recipient age, donor age and daily proteinuria (P = 0.007, P = 0.0007 and P = 0.02, respectively). Multivariate analysis showed that only donor and recipient age maintained their independent predictive value on RI. Kaplan-Meier analysis, considering a serum creatinine increase >50% as the endpoint of the study, showed a statistically significant different graft survival in the two groups (log-rank test = 5.489; P = 0.01). The univariate relative risk of deterioration of graft function among patients with higher RI was 3.77. Proteinuria and recipient age increased the risk as well.

CONCLUSIONS

Our data seem to suggest that early determination of RI can help predict long-term graft function in kidney transplant recipients.

Reverse diastolic intrarenal flow due to calcineurin inhibitor (CNI) toxicity

Renal calcineurin inhibitor (CNI) toxicity is a frequent side effect of immunosuppression with CNIs in solid organ transplantation, leading to acute and chronic renal failure. Acute CNI toxicity is due to vasoconstriction of the vasa afferens and efferens and vacuolization of smooth muscle cells with medial hyalinosis, leading to vessel lumen narrowing. Our case had an acute renal failure 8 months after deceased donor kidney transplantation under treatment with tacrolimus, sirolimus and prednisolone. In Doppler sonography, we observed reverse diastolic intrarenal blood flow, reflecting intense vessel narrowing. There were histological signs of acute CNI toxicity. Within days of reducing the tacrolimus trough level, renal function improved markedly and Doppler sonography showed orthograde intrarenal blood flow. This is the first case of functional, Doppler sonographic evidence for CNI-induced, rapidly reversible narrowing of intrarenal vessels. This case illustrates the potential role of tacrolimus and sirolimus dosing in combination therapy to produce severe intrarenal vasoconstriction.

Improved diagnosis of early kidney allograft dysfunction by ultrasound with echo enhancer--a new method for the diagnosis of renal perfusion

BACKGROUND

Conventional ultrasound parameters such as the resistance index (RI) are only of limited use in the diagnosis of early allograft dysfunction. We, therefore, performed a prospective study to compare the value of ultrasound contrast media (USCM) with conventional US in the diagnosis of early allograft dysfunction.

METHODS

A total of 48 consecutive kidney recipients underwent US examination after USCM administration 4-10 days after transplantation. Arterial inflow was determined in the interlobar artery and renal cortex using time-intensity curve (TIC) software. The difference in time-to-peak intensity between these two vascular territories was determined, and a perfusion quotient (PQ) was defined as the ratio of TIC increase of interlobar artery to renal cortex. Three patients with segmental loss of renal perfusion demonstrated by Doppler US were excluded.

RESULTS

Nineteen patients had an uneventful clinical course (control group); PQ was 1.2 +/- 0.4. Seven patients with a large perirenal haematoma, without rejection had an increased PQ (P < 0.05) and a prolonged time difference (P < 0.05). Based on clinical and histological criteria, the remaining patients were classified as acute tubular necrosis (ATN) (n = 7), non-vascular rejection (n = 7) or vascular rejection (n = 5). RI determination could not discriminate these groups. Patients with ATN (PQ = 1.6 +/- 0.7) or non-vascular rejection (PQ = 1.1 +/- 0.6) had a lower PQ than patients with vascular rejection (PQ = 2.2 +/- 0.8, P < 0.05). The time difference in all three subgroups was longer compared with controls.

CONCLUSIONS

USCM might be superior in the diagnosis of early kidney allograft dysfunction compared with conventional US by means of RI determination. Perirenal haematoma, ATN and vascular rejection are associated with characteristic changes of the TIC.

Antegrade Endopyelotomy for Treatment of Ureteropelvic Junction Obstruction in Transplanted Kidneys

BACKGROUND AND PURPOSE

Little is known about the incidence and treatment of ureteropelvic junction (UPJ) obstruction of renal grafts. We report on three cases treated by endopyelotomy.

PATIENTS AND METHODS

Graft function declined in three patients 98, 135, and 144 days after kidney transplantation. Acute rejection was excluded by renal biopsy. Ultrasonography revealed a dilated collecting system, and a percutaneous nephrostomy tube was placed. An antegrade nephrostogram showed UPJ obstruction. Percutaneous antegrade endopyelotomy was performed with the cold-knife technique, and the area was stented for 6 weeks using a 14F/8.2F Smith endopyelotomy stent.

RESULTS

No intraoperative or postoperative complications occurred. The endopyelotomies were successful, and the creatinine clearances returned to normal.

CONCLUSION

Antegrade endopyelotomy in patients with UPJ obstruction of a renal graft is feasible and effective. Normal kidney function was restored after correction of the obstruction.

Tissue Pulsatility Index: A New Parameter to Evaluate Renal Transplant Perfusion

BACKGROUND

: Chronic allograft nephropathy (CAN) is characterized by loss of parenchymal perfusion. We applied therefore the novel parameter Tissue Pulsatility Index (TPI) to quantify transplant perfusion in the long-term surveillance of renal transplants.

METHODS

: Color Doppler sonographic videos of renal transplants from 38 renal transplant recipients were recorded under defined conditions. TPI was calculated as ratio of the difference of mean systolic and diastolic velocities of the entire region and the average velocity.

RESULTS

: TPI was significantly different between the proximal and distal cortical layers (1.12 vs. 1.56, respectively P=0.000). In patients with elevated creatinine as a measure of compromised function, significantly (P=0.016) higher values (TPI=1.70) were found at distal cortical level compared to patients with normal creatinine (TPI=1.34). After transplantation, TPI rises significantly: 1.10 in 0-1 years vs. 1.41 in 1-2.9 years, P=0.002; 1.10 in 0-1 years vs. 1.37 in 3-4.9 years, P=0.000; 1.10 in 0-1 years vs. 1.31 in 7-8.9 years, P=0.049). TPI declines later on in our population to significantly lowered values in the group more than 9 years after transplantation (1.10 in 0-1 years vs. 0.94 in >9 years, P=0.044).

CONCLUSION

: With the novel TPI, we could demonstrate significant differences between proximal and distal cortical perfusion, between compromised and well-functioning transplants, and could observe significant changes of transplant perfusion at various points at the posttransplantation time scale.

Renal Doppler sonography--update in clinical nephrology

These days renal Doppler sonography has been established as a diagnostic tool of the daily nephrological work-up. Extra- and intrarenal flow signals are obtained for different indications. The intrarenal resistive index is the best examined parameter in the literature. However, the results have to be carefully interpreted, because different hemodynamic factors, such as heart rate, stiffness of the aorta as well as observer-dependent factors may have an impact on the level of the resistive index. The value of this non-invasive technique is discussed in detail for different renal diseases, such as acute and chronic renal failure, renal artery stenosis and for patients after renal transplantation. Being aware of several pitfalls which may lead to false results, nephrologists may use renal Doppler sonography as the first screening method of choice in the diagnostic algorithm.

Real-time contrast-enhanced sonography of renal transplant recipients predicts chronic allograft nephropathy

Real-time contrast-enhanced sonography (RT-CES) can assess microvascular tissue perfusion using gas-filled microbubbles. The study was performed to evaluate the feasibility of RT-CES in detecting chronic allograft nephropathy (CAN) in comparison to color Doppler ultrasonography (CDUS). A total of 26 consecutive renal transplant recipients were prospectively studied using RT-CES and conventional CDUS. Transplant tissue perfusion imaging was performed by low-power imaging during i.v. administration of the sonocontrast Optison. Renal tissue perfusion was assessed quantitatively using flash replenishment kinetics of microbubbles to estimate renal blood flow A *beta (A = peak signal intensity, beta= slope of signal intensity rise). In contrast to conventional CDUS resistance and pulsatility indices, renal blood flow estimated by CES was highly significant related to S-creatinine (r =-0.62, p = 0.0004). Determination of renal blood flow by CES reached a higher sensitivity (91% vs. 82%, p < 0.05), specificity (82% vs. 64%, p < 0.05) and accuracy (85% vs. 73%, p < 0.05) for the diagnosis of CAN as compared to conventional CDUS resistance indices. Perfusion parameters derived from RT-CES significantly improve the early detection of CAN compared to conventional CDUS. RT-CES using low-power real-time perfusion imaging is a feasible method to evaluate microvascular perfusion in renal allograft recipients.

Renal Allograft Hemodynamic and Diameter Changes After Living Donor Transplantation

Renal ultrasound is a valuable tool to measure allograft diameters and hemodynamic changes, some of which may help us to predict ongoing rejection. Longitudinal (L) and horizontal (H) diameters, and resistive index (RI) of intrarenal arteries of kidneys were measured before transplantation in the donor site, as well as 1 week after transplantation in the recipient site (7.5 MHz probe). We excluded patients with acute rejection, delayed graft function, perinephric collection, suspected allograft artery stenosis, or serum creatinine >2 mg/dL. Finally, allograft measurements were compared with the donor parameters. The mean values of L and H diameters in 32 normal allografts were: L 119 +/- 10.4 mm; H 54 +/- 8.4 mm; L/H ratio 2.25 +/- 0.27; RI 0.57 +/- 0.55. The mean values of these measurements when the kidney was in the donor body were: L 110 +/- 9.4 mm; H 44.3 +/- 5.4 mm; L/H ratio 2.97 +/- 0.25; RI 0.61 +/- 0.040. Both L and H diameters were increased significantly after transplantation, but the L/H ratio and RI were decreased significantly (P < .05). The presumed physiologic explanations for these findings in allograft are increased blood flow, decreased intrarenal arterial resistance, stress relaxation, and lack of sympathetic innervation.

Renal Allograft Histopathology in Dog Leukocyte Antigen Mismatched Dogs After Renal Transplantation

OBJECTIVE

To evaluate allograft histopathology in dog leukocyte antigen (DLA)-mismatched dogs undergoing renal transplantation, with transient immunosuppression.

STUDY DESIGN

Prospective study.

ANIMALS

Ten healthy adult mongrel dogs.

METHODS

Reciprocal renal transplantation and bilateral nephrectomy were performed. Immune conditioning consisted of nonmyeloablative (200 cGy), total body irradiation (TBI), bone marrow transplantation (BMT; 7 dogs), cyclosporine (CSA; 15 mg/kg every 12 hours), mycophenolate mofetil (MMF; 10 mg/kg every 12 hours) and intermittent prednisone (1 mg/kg every 12-24 hours). Biopsies were collected at transplantation, during full immunosuppression (44-90 days), and once medications were reduced or discontinued (228-580 days). Biopsies were evaluated for interstitial, tubular, vascular, and glomerular lesions. Blood urea nitrogen, creatinine, serum CSA concentrations, and clinical score were determined at each biopsy.

RESULTS

Seven dogs survived >200 days (mean, 380 days). Transient CSA toxicity was suspected in 6 dogs. Lymphocytic, plasmacytic interstitial inflammation, and tubulitis progressed when immunosuppressive medications were decreased. All 7 dogs had histologic lesions consistent with some degree of allograft rejection at study end.

CONCLUSION

Nonmyeloablative TBI, BMT, and short-term immunosuppression with CSA, MMF, and prednisone allowed renal allograft function and dog survival for >200 days. It appears unlikely that total drug withdrawal will be possible in unrelated DLA-mismatched dogs using this protocol.

CLINICAL RELEVANCE

Transient immunosuppression with MMF, CSA, and prednisone along with BMT and nonmyeloablative TBI may make kidney transplantation a clinical reality for treatment of kidney failure in dogs. Initiating both MMF and CSA at lower dosages may potentially eliminate early renal allograft injury.

The predictive value of renal vascular resistance for late renal allograft loss

The renal artery resistance index (RI), assessed by Doppler ultrasonography, was recently identified as a new risk marker for late renal allograft loss. This finding requires confirmation since RI in that study was not measured at predetermined time points and ultrasonography is operator-dependent. We investigated the predictive value of renal vascular resistance (RVR), a less operator-dependent method as assessed by mean arterial pressure divided by renal blood flow, for the prediction of recipient mortality and death-censored graft loss. RVR was compared to commonly used risk markers such as creatinine clearance (CrCl), serum creatinine (SCreat) and proteinuria (UProt) in 793 first-time cadaveric renal transplant recipients at predetermined time points after transplantation using receiver operating characteristics (ROC) and Cox survival analyses. The present study showed that RVR is a prominent risk marker for recipient mortality and death-censored graft loss. However, the predictive value of RVR for recipient mortality owed mainly to the impact of mean arterial blood pressure. In contrast, RVR constituted more than the sum of its components for death-censored graft loss, but showed less predictive value than SCreat in univariate analysis. As the assessment of RVR is expensive and time-consuming, we believe that RVR holds no clinical merit for the follow-up of renal transplant recipients.

Renal Artery Resistance Index, Thyroid Hormones, and Thyroid Volume in the Early Kidney Transplants Recipients

BACKGROUND

Thyroid hormones could affect renal function, and, on the other hand, renal dysfunction may affect thyroid function. Disturbances of concentrations of thyroid hormones are often associated with thyroid gland enlargement. The aim of the study was to assess the function and morphology of the thyroid (volume and hormones concentration) and kidney function after transplantation (creatinine concentration and resistance index [RI] of transplant artery).

MATERIAL AND METHODS

The group included 13 females, 19 males; aged 19-69 years, mean 44.75 +/- 14.8 years after transplantation with stable graft function. Thyroid volume, renal artery RI, creatinine concentration, and concentrations of T3, rT3, FT3, FT4, and TSH were estimated the day before surgery, and at 1, 3, 6, and 10 days after transplantation.

RESULTS

The statistical analysis revealed a negative correlation between delta RI (difference between RI at 3 and 6 days after transplantation) and serum creatinine concentration, 10 days after transplantation (r = -0.63; P < 0.01). We also observed a negative correlation between creatinine serum concentration at 10 days after transplantation and delta thyroid volume (Delta Vol; r = - 0.48; p < .05), a positive correlation between delta FT4 (Delta FT4) serum concentration, and delta creatinine (Delta Crea; r = 0.73; P < .001).

CONCLUSIONS

The dynamics of RI changes in the transplant kidney artery between 3 and 6 days after transplantation may predict graft function. Together with improved kidney function at 10 days after transplantation, we observed a regression of goiter.

Color Doppler Ultrasonography in the Diagnostic Evaluation of Renal Allografts

Color Doppler ultrasonography of large allograft vessels and renal parenchyma is established firmly in the diagnosis of renal allograft perfusion. While conventional color Doppler ultrasonography has proven itself to be an indispensable, rapid, highly valid and practicable method, e.g. in the diagnosis of allograft artery stenosis or allograft vein thrombosis, the diagnostic usefulness of this method with regard to allograft perfusion is considerably limited. With contrast-enhanced sonography, a simple and readily implementable method that enables the early diagnosis of chronic allograft nephropathy is now available. The timely diagnosis of vascular damage prior to a rise in S-creatinine offers the possibility of early therapeutic intervention and thus at least the potential for the improvement of allograft survival.

Eine neue Methode zur standardisierten Diagnostik nach Nierentransplantation

Ultrasound (US) imaging is an important diagnostic tool following renal transplantation. Unfortunately, due to the heterogeneity of the recipients and their multimorbidity, imaging procedures in the early phase after kidney transplantation are difficult and of limited use. We performed a study to evaluate the use of a contrast enhancer for US examination as a standardized method in the follow-up of kidney transplant recipients.The study included 40 recipients: 32 were examined on the 5th to 7th day following transplantation and 8 patients at the time when clinically suspicious findings occurred (acute rejection, tumor, acute tubular necrosis). Following the intravenous application of the contrast medium, pictures were taken during the arterial and parenchymatous phase and compared with conventional B-mode and power Doppler pictures of the same visual plane. Three examiners assessed different parameters of the transplant organ (max. vascularized area, suspected hematomas, tumors, rejection, acute tubular necrosis). Findings were confirmed by histological results of a biopsy if rejection, tumor, or acute tubular necrosis were suspected. Application of ultrasound contrast medium significantly increased visualization of the vascularized kidney area. Also, US findings in the follow-up after acute rejection therapy corresponded with the clinical course; 19 hematomas could be detected with contrast medium compared to only 9 without. With contrast medium a perfusion deficit was detectable in three patients compared to one patient with power Doppler US. Also, US contrast medium helped to detect tumor vascularization in two patients in whom conventional sonography suspected no abnormality. Ultrasound contrast medium enhancement is a reproducible, reliable, and easy to apply method which is superior to conventional sonography in the follow-up after kidney transplantation. This method is also helpful to detect and control acute rejections and to better visualize hematomas, deficits of perfusion, and tumors.