Intrarenal resistive index after renal transplantation.

BACKGROUND: The intrarenal resistive index is routinely measured in many renal-transplantation centers for assessment of renal-allograft status, although the value of the resistive index remains unclear. METHODS: In a single-center, prospective study involving 321 renal-allograft recipients, we measured the resistive index at baseline, at the time of protocol-specified renal-allograft biopsies (3, 12, and 24 months after transplantation), and at the time of biopsies performed because of graft dysfunction. A total of 1124 renal-allograft resistive-index measurements were included in the analysis. All patients were followed for at least 4.5 years after transplantation. RESULTS: Allograft recipients with a resistive index of at least 0.80 had higher mortality than those with a resistive index of less than 0.80 at 3, 12, and 24 months after transplantation (hazard ratio, 5.20 [95% confidence interval {CI}, 2.14 to 12.64; P<0.001]; 3.46 [95% CI, 1.39 to 8.56; P=0.007]; and 4.12 [95% CI, 1.26 to 13.45; P=0.02], respectively). The need for dialysis did not differ significantly between patients with a resistive index of at least 0.80 and those with a resistive index of less than 0.80 at 3, 12, and 24 months after transplantation (hazard ratio, 1.95 [95% CI, 0.39 to 9.82; P=0.42]; 0.44 [95% CI, 0.05 to 3.72; P=0.45]; and 1.34 [95% CI, 0.20 to 8.82; P=0.76], respectively). At protocol-specified biopsy time points, the resistive index was not associated with renal-allograft histologic features. Older recipient age was the strongest determinant of a higher resistive index (P<0.001). At the time of biopsies performed because of graft dysfunction, antibody-mediated rejection or acute tubular necrosis, as compared with normal biopsy results, was associated with a higher resistive index (0.87 ± 0.12 vs. 0.78 ± 0.14 [P=0.05], and 0.86 ± 0.09 vs. 0.78 ± 0.14 [P=0.007], respectively). CONCLUSIONS: The resistive index, routinely measured at predefined time points after transplantation, reflects characteristics of the recipient but not those of the graft. (ClinicalTrials.gov number, NCT01879124 .).

Extrarenal factors influencing resistance index in stable kidney transplant recipients.

BACKGROUND: Increased intrarenal resistance index (RI) has been associated with decreased long-term allograft and patient survival in kidney transplant recipients. Taking into account the potential role of endothelial dysfunction, systemic inflammation, arteriosclerotic lesions, and left ventricle remodeling, we performed a cross-sectional study that aimed to evaluate extrarenal factors that may have influence on kidney graft RI in a large cohort of stable kidney transplant recipients. METHODS: One hundred seventy-four kidney transplant recipients were enrolled into the study. Mean time after transplantation was 8.4±1.8 years. Echocardiography, carotid ultrasound (intima-media thickness), pulse wave velocity, and Doppler examination of kidney graft were performed. The inflammatory markers, adhesion molecules, and plasma N-terminal prohormone of brain natriuretic peptide concentrations were also measured. Patients were divided into quartile subgroups based on RI value (Q1: RI≤0.68, Q2: RI=0.69-0.72, Q3: RI=0.73-0.76, and Q4: RI≥0.77). RESULTS: The analyzed subgroups were comparable with respect to demographics (except age) and anthropometric parameters as well as comorbidities. The values of age, serum phosphate, pulse wave velocity, left ventricular mass (LVM), and LVM index (LVMI) increased in subsequent RI quartile subgroups. The strongest correlation was found between RI and age, LVM, LVMI, and plasma parathormone concentration and was negative with estimated glomerular filtration rate. In backward stepwise multivariate regression analysis, the RI variability was explained by age, LVMI, and serum phosphate concentration. CONCLUSION: Arterial stiffness and left ventricular hypertrophy may significantly influence the intrarenal vascular resistance measured using Doppler sonography in stable kidney transplant recipients.

Assessment of salivary gland function in patients after successful kidney transplantation using (99m)Tc-pertechnetate salivary gland scintigraphy.

Chronic renal failure and its treatment can induce oral health problems and salivary glands dysfunction. The purpose of this study was to assess salivary glands function in patients with kidney transplantation using technetium-99m pertechnetate ((99m)Tc-P) salivary glands scintigraphy. We prospectively studied 34 patients with kidney transplantation (30 males and 4 females,mean age 39.76±11.6 years) and 28 healthy controls (12 males and 16 females, mean age 36.1±9.5 years). Salivary gland scintigraphy was performed nearly 4.4±2.9 years after successful kidney transplantation. Dynamic salivary glands scintigraphy was performed during 25min after the intravenous administration of 185MBq of (99m)Tc-P. Time-activity curves and glands functional parameters were calculated for the parotid and submandibular salivary glands: uptake ratio, maximum accumulation of the radionuclide, and excretion fraction. Statistical analysis of the functional parameters showed no significant differences between patients with kidney transplantation and healthy controls (P>0.05). In conclusion, this study showed that using (99m)Tc-P salivary gland scintigraphy, salivary glands function of patients with successful kidney transplantation do not differ statistically from those in healthy controls.

PET with 18F-FDG-labeled T lymphocytes for diagnosis of acute rat renal allograft rejection.

UNLABELLED: We proposed small-animal PET with (18)F-FDG-labeled T lymphocytes as a new method for image-based diagnosis of acute allogeneic renal transplant rejection (AR) established in a rat model. METHODS: One and 2 h after tail vein injection of 30 × 10(6) ex vivo (18)F-FDG-labeled human T cells into male 10-wk-old uninephrectomized, allogeneically transplanted rats (aTX; Lewis-brown Norway [LBN] to Lewis), whole-body radioactivity distribution was assessed in vivo by small-animal PET (postoperative day 4), and percentage injected dose (%ID) as a parameter of T-cell infiltration was assessed and compared between graft and native kidney. In vivo results were confirmed by autoradiography and staining of human CD3 after postmortem dissection. Syngeneically transplanted rats (sTX) (LBN to LBN), rats with ischemia-reperfusion injury (IRI) (45-min warm ischemia), and rats subjected to acute cyclosporine A (CSA) toxicity (50 mg/kg for 2 d intraperitoneally) served as controls. RESULTS: The accumulation of labeled cells was significantly elevated in allografts with AR (1.07 ± 0.28 %ID), compared with native control kidneys (0.49 ± 0.18 %ID) (P < 0.0001). No differences were found among native controls, sTX, CSA toxicity, and kidneys with IRI. In vivo uptake of (18)F-FDG cells measured in the PET scanner correlated with results obtained by autoradiography, histologic evaluation, and polymerase chain reaction. CONCLUSION: We proposed graft PET imaging using (18)F-FDG-labeled T cells as a new option to detect rat renal AR with a low dose of (18)F-FDG in a noninvasive, fast, and specific manner in rats.

Color Doppler ultrasound-guided transducer compression of post biopsy bleeding of kidney transplants.

BACKGROUND: Color Doppler ultrasound (CDUS) has a potential of early detection of post biopsy bleeding. We describe CDUS guidance in planning, acquisition, and, in the case of bleeding, compression of the needle tract in biopsy procedures of kidney transplants. METHODS: Eighty-three kidney transplant biopsy procedures performed on clinical indication were performed in 71 adult patients, 25 women, mean age 51 years, using CDUS and 18-G biopsy needles. Bleeding needle tracts were compressed using CDUS guidance. RESULTS: CDUS immediately detected blood leakage and facilitated compression of the bleeding needle tract in 34 (41%) of the 83 procedures, including 53 (25%) of 215 needle passes. In 34 bleeding procedures, the mean duration of the longest bleeding time after a needle pass was 124 seconds (median, 20 seconds; range, 3-1440 seconds). In 12 of these procedures (35%), the bleeding time was 30 seconds or more. In six procedures (18%), a bleeding of 120 seconds or more was observed. Complications included seven small hematomas. Five hematomas developed in procedures where the longest duration CD bleeding was 120 seconds or more. CONCLUSIONS: CDUS detects bleeding and facilitates direct transducer compression of the needle tract in a substantial portion of biopsy procedures of kidney transplants. Only minor hematomas occurred.

[Contrast enhanced ultrasound in renal diseases]. / L'imaging ecocontrastografico nella patologia renale.

Contrast-enhanced ultrasound (CEUS) is one of the most interesting and promising clinical applications of imaging and ultrasound. Thanks to the absence of ionizing radiation, the lack of nephrotoxicity and low cost it has the potential to become a reference in imaging of the kidney. This review, besides providing a brief description of the proper methodology, presents possible applications of CEUS in nephrology and urology, including renal ischemia, the differential diagnosis of cystic and solid lesions, follow-up of ablative therapies, kidney trauma, kidney transplant, inflammatory diseases, ischemic nephropathy and vesicoureteral reflux.

[Ultrasound assessment in renal infections]. / L'ecografia nelle infezioni del rene.

Urinary tract infections (UTIs) are a common clinical problem, especially among women. Ultrasound assessment is indicated in case of complicated UTIs, in particular in children, pregnant women and patients with chronic kidney disease. Even though B-mode imaging alone is rarely diagnostic in case of particular kidney infections such as focal and multifocal acute pyelonephritis, Doppler and power-Doppler (PD) techniques are able to increase its sensitivity. Contrast-enhanced ultrasound (CEUS) further improves the signal-to-noise ratio, thus increasing the diagnostic accuracy of ultrasound in case of renal infectious disease. Recent studies performed on kidney transplant recipients have indeed demonstrated the high sensitivity and specificity of CEUS in diagnosing acute pyelonephritis. Moreover, ultrasonography is a useful diagnostic tool in case of kidney abscesses, emphysematous pyelonephritis, early phases of pyonephrosis, and in the evaluation and monitoring of echinococcal cysts. Ultrasound imaging is less specific in diagnosing xanthogranulomatous pyelonephritis, malacoplakia and renal tuberculosis. Finally, several authors recommend routine ultrasound assessment in HIV patients, given the high incidence of renal complications in this population of patients.

[Parenchymal complications of the transplanted kidney: the role of color-Doppler imaging]. / Le complicanze parenchimali del rene trapiantato: il ruolo dell'eco-color-Doppler.

Kidney transplantation is the treatment of choice for end-stage renal disease, given the better quality of life of transplanted patients when compared to patients on maintenance dialysis. In spite of surgical improvements and new immunosuppressive regimens, part of the transplanted grafts still develop chronic dysfunction. Ultrasonography, both in B-mode and with Doppler ultrasound, is an important diagnostic tool in case of clinical conditions which might impair kidney function. Even though ultrasonography is considered fundamental in the diagnosis of vascular and surgical complications of the transplanted kidney, its role is not fully understood in case of parenchymal complications of the graft. The specificity of Doppler ultrasound is low both in case of acute complications such as acute tubular necrosis, drug toxicity and acute rejection, and in case of chronic conditions such as chronic allograft nephropathy. Single determinations of resistance indices present low diagnostic accuracy, which is higher in case of successive measurements performed during the follow-up of the graft. Modern techniques including tissue pulsatility index, maximal fractional area and contrast-enhanced ultrasound increase the diagnostic power of ultrasonography in case of parenchymal complications of the transplanted kidney.

Relation of resistive and pulsatility indices with graft function after renal transplant.

OBJECTIVES: There are conflicting data regarding the use of some measured indices by Doppler ultrasound such as the resistive index and the pulsatility index in predicting renal allograft dysfunction. This study sought to evaluate the association of early postoperative Doppler indices and 3-month serum creatinine levels in renal transplant recipients. MATERIALS AND METHODS: During a 1-year period, all patients who underwent renal transplant at our hospital were recruited into a prospective study. Doppler ultrasound was performed on all patients 6 days and 3 months after the transplant and the resistive index and the pulsatility index were calculated for each patient. Then, the association between these indices and 3-month outcomes of patients were investigated. RESULTS: Thirty-eight patients including 21 men (mean age, 36.6 ± 13.1 y) were evaluated. There was a positive correlation between the resistive index and the pulsatility index at 6 days after transplant and the serum creatinine measured at the same day (P < .001 and r=0.570 for resistive index; P < .001 and r=0.547 for pulsatility index). There was also a positive correlation between the pulsatility index and the resistive index at 6 days after transplant and 3-month serum creatinine level (P = .009 and r=0.420 for resistive index; P = .009 and r=0.417 for pulsatility index). There were negative correlations between the resistive index and the pulsatility index on the sixth day after surgery and creatinine clearance measured at 6 days and 3 months after transplant. CONCLUSIONS: This study reveals a strong-to-medium correlation between the resistive index and the pulsatility index, serum creatinine level, measured 6 days after transplant.

New normal values not related to age and sex, of glomerular filtration rate by (99m)Tc-DTPA renal dynamic imaging, for the evaluation of living kidney graft donors.

The aim of this study was to investigate the normal values of glomerular filtration rate (GFR) by technetium-99m diaethylene-triamine-pentaacetic acid ((99m)Tc-DTPA) renal dynamic imaging for living kidney graft donors. In a total of 212 candidate donors, GFR was examined using (99m)Tc-DTPA renal dynamic imaging. Donors with GFR≥80mL/(min×1.73m(2)) and as low as with GFR≥70mL/(min×1.73m(2)) but a normal endogenous creatinine clearance rate (CCr) were quantified for living kidney donation. Differences in GFR levels based on sex and age were analyzed using rank correlation coefficient. Out of the 212 candidates, 161 were finally selected as kidney graft donors. The double kidney total GFR between the male and female donor groups, the GFR levels among differently-aged donor groups, and the GFR levels between the elderly (>55 years) and young- and middle-aged (≤55 years) donor groups did not show any significant difference (P>0.05). After kidney donation, renal function measured by blood urea nitrogen (BUN) and serum creatinine of all donors returned to normal within one week, and no serious complications were noticed. In conclusion, renal dynamic imaging by (99m)Tc-DTPA had a good accuracy and repeatability in GFR evaluation for living kidney donors. Candidate donors with GFR between 70mL/(min×1.73m(2)) and 80mL/(min×1.73m(2)) can be selected as kidney donors after strict screening. In living kidney donors GFR is not significantly correlated with age or sex.

Ultrasound image fusion - clinical implementation and potential benefits for monitoring of renal transplants.

PURPOSE: To evaluate the feasibility of US image fusion in the clinical routine and to discuss potential benefits for follow-up after renal transplantation. MATERIALS AND METHODS: 15 patients with a renal transplant were prospectively included in the study. For all of them, a previously performed CT- or MRI-scan covering the renal transplant was available. Each patient was investigated using ultrasound image fusion. Time needed for sucessful implementation of image fusion was registered. Subsequently, quality of image fusion was assessed by two experienced radiologists (10 and 5 years of experience) in consensus using a subjective 5 point rank scale (1 = best). RESULTS: Image fusion was successfully performed in all patients. Time needed for setup of image fusion varied from 45-120 sec (85 ± 5 sec). The score for quality of US image fusion was 1.9 ± 0.7. CONCLUSION: Assessment of renal transplants using US image fusion is feasible and provides several potential benefits for the follow-up of renal transplants.

Cumulative radiation dose from medical imaging in kidney transplant patients.

BACKGROUND: Although many patients undergoing kidney transplant are exposed to multiple examinations that increase cumulative effective doses (CEDs) of ionizing radiation, no data are available characterizing their total longitudinal radiation burden and relating radiation burden with risk factors for more exposure. METHODS: We did a retrospective cohort study of 92 patients (mean age 52 years; range: 20-75 years) who underwent kidney transplant at University Hospital, Novara, Italy, that evaluated all following medical imaging procedures involving ionizing radiation undergone beginning June 2007, and all subsequent procedures through August 2011, at the centre. RESULTS: The mean and median annual CED were 17.2 and 4.9 millisieverts (mSv) per patient-year. The mean and median total CED per patient over the study period were 46.1 and 17.3 mSv, respectively. Twenty-eight and 12% of patients had total CED >50 and 100 mSv, values which are associated with a good or strong evidence of an increased cancer mortality risk, respectively. Computed tomography scanning accounted for 73% of the total CED. The annual CED was significantly higher in incident patients and in patients with ischaemic heart disease and cancer. CONCLUSION: In this institution, multiple testing of kidney transplant patients was common in many patients associated with high cumulative estimated doses of ionizing radiation.

Quantitative elastography of renal transplants using supersonic shear imaging: a pilot study.

PURPOSE: To evaluate the reliability of quantitative ultrasonic measurement of renal allograft elasticity using supersonic shear imaging (SSI) and its relationship with parenchymal pathological changes. MATERIALS AND METHODS: Forty-three kidney transplant recipients (22 women, 21 men) (mean age, 51 years; age range, 18-70 years) underwent SSI elastography, followed by biopsy. The quantitative measurements of cortical elasticity were performed by two radiologists and expressed in terms of Young's modulus (kPa). Intra- and inter-observer reproducibility was assessed (Kruskal-Wallis test and Bland-Altman analysis), as well as the correlation between elasticity values and clinical, biological and pathological data (semi-quantitative Banff scoring). Interstitial fibrosis was evaluated semi-quantitatively by the Banff score and measured by quantitative image analysis. RESULTS: Intra- and inter-observer variation coefficients of cortical elasticity were 20 % and 12 %, respectively. Renal cortical stiffness did not correlate with any clinical parameters, any single semi-quantitative Banff score or the level of interstitial fibrosis; however, a significant correlation was observed between cortical stiffness and the total Banff scores of chronic lesions and of all elementary lesions (R = 0.34, P = 0.05 and R = 0.41, P = 0.03,respectively). CONCLUSION: Quantitative measurement of renal cortical stiffness using SSI is a promising non-invasive tool to evaluate global histological deterioration. KEY POINTS : • Supersonic shear imaging elastography can measure cortical stiffness in renal transplants • The level of cortical stiffness is correlated with the global degree of tissue lesions • The global histological deterioration of transplanted kidneys can be quantified using elastography.

Tissue elasticity estimated by acoustic radiation force impulse quantification depends on the applied transducer force: an experimental study in kidney transplant patients.

OBJECTIVES: Acoustic radiation force impulse (ARFI) quantification estimates tissue elasticity by measuring shear-wave velocity (SWV) and has been applied to various organs. We evaluated the impact of variations in the transducer force applied to the skin on the SWV ultrasound measurements in kidney transplant cortex and ARFI's ability to detect fibrosis in kidney transplants. METHODS: SWV measurements were performed in the cortex of 31 patients with kidney allografts referred for surveillance biopsies. A mechanical device held the transducer and applied forces were equal to a compression weight of 22, 275, 490, 975, 2,040 and 2,990 g. RESULTS: SWV group means were significantly different by repeat measures ANOVA [F(2.85,85.91) = 84.75, P < 0.0005 for 22, 275, 490, 975 and 2,040 g compression weight] and also by pairwise comparisons. Biopsy specimens were sufficient for histological evaluation in 29 of 31 patients. Twelve had grade 0, 11 grade 1, five grade 2 and one grade 3 fibrosis. One-way ANOVA showed no difference in SWV performed with any of the applied transducer forces between grafts with various degrees of fibrosis. CONCLUSION: SWV measurements in kidney transplants are dependent on the applied transducer force and do not differ in grafts with different grades of fibrosis. KEY POINTS: • Acoustic radiation force impulses (ARFI) can quantify tissue elasticity during ultrasound examinations. • Elasticity estimated by ARFI in kidney transplants depends on applied transducer force. • ARFI quantification cannot detect renal allograft fibrosis. • ARFI elasticity estimates may in general vary with applied transducer force.

Acute effects of calcineurin inhibitors on kidney allograft microperfusion visualized by contrast-enhanced sonography.

BACKGROUND: Calcineurin inhibitors induce detrimental vascular remodeling, which may be one cause of chronic allograft failure. Real-time contrast-enhanced sonography (CES) is a relatively new technique in providing quantitative information on microvascular tissue perfusion in kidney allografts in more detail. The purpose of the study was to explore whether acute changes of kidney allograft microperfusion due to the administration of cyclosporine A (CsA) and tacrolimus (Tac) can be evidenced using real-time CES. METHODS: In an explorative single-center clinical trial, renal parenchymal tissue perfusion of 32 stable kidney allograft recipients was evaluated with CES before and 2 hr after the intake of CsA or Tac. In addition to laboratory and clinical parameters, Doppler indices and estimated glomerular filtration rate were measured. RESULTS: Although systolic and diastolic blood pressure and color Doppler indices did not significantly differ, there was a significant decrease of renal blood flow 2 hr after the intake of CsA compared with baseline (4.78±2.31 dB/s, 49%, respectively). In contrast, kidney allograft microperfusion was neither significantly reduced in patients receiving CsA paralleled by calcium channel blockers nor significantly reduced in patients receiving Tac. Furthermore, there was a significant correlation between renal blood flow obtained before drug administration and kidney function. CONCLUSIONS: CES revealed a 49% reduction of kidney allograft microperfusion 2 hr after the intake of CsA, which might be abrogated by calcium channel blockers. In comparison to CsA, Tac did not result in a significant decrease of kidney blood flow.

Left ventricular function in children and adults after renal transplantation in childhood.

BACKGROUND: Renal transplantation improves left ventricular (LV) function, but cardiovascular mortality remains elevated. The aim of this cross-sectional study was to determine whether subclinical abnormalities of LV longitudinal function also persist in patients who underwent renal transplant in childhood. METHODS: Conventional and speckle tracking echocardiography was performed in 68 renal transplant recipients (34 children and 34 adults, median 9.8 years (range 2.0-28.4 years) after first transplantation and 68 age- and sex-matched healthy controls. RESULTS: Mean age at first transplantation was 8.8 ± 4.8 years. Forty-three percent had a pre-emptive transplant. Of the remaining, 70% received haemodialysis and 30% peritoneal dialysis on average for 6.9 months. Thirty-one percent of paediatric and 35% of adult patients had hypertension. LV mass index was increased in adult patients (92 ± 24 vs 75 ± 11 g/m(2), P< 0.01). LV diastolic function and exercise capacity were impaired in both paediatric and adult patients. LV longitudinal peak systolic strain and strain rate were comparable in patients and controls. In multivariate analysis, systolic blood pressure and LV diastolic relaxation were the main covariates of LV peak systolic strain and strain rate (all P < 0.01). CONCLUSIONS: Patients who underwent renal transplantation in childhood have abnormal LV diastolic function and impaired exercise capacity, despite preserved LV longitudinal systolic deformation.

Kidney volume changes in patients with autosomal dominant polycystic kidney disease after renal transplantation.

BACKGROUND: Few studies have investigated whether the volume of native kidney and liver (when combined with polycystic disease) in patients with autosomal dominant polycystic kidney disease (ADPKD) decreases after renal transplantation. METHODS: Changes in the volume of native kidney (bilateral: n=28; unilateral: n=5) and liver (concomitant polycystic disease: n=18) were analyzed in 33 patients with ADPKD, who underwent renal transplantation. Volumetry was retrospectively conducted using simple computed tomography scan data 6 months before transplantation, at the time of transplantation, and 1, 3, and 5 years after transplantation. Volume change was calculated on the basis of the value at the time of transplantation. RESULTS: Mean±standard deviation values of bilateral native kidney volume were 3100±1417 (range: 756 to 6525; median: 2499) cm at the time of transplantation. Kidney volumes were significantly reduced in all but one patient after renal transplantation, decreasing by 37.7% and 40.6% at 1 and 3 years, respectively. The major proportion of the decrease was observed within the first year posttransplantation. In contrast, 16 of 18 patients showed significant increase of liver volumes after renal transplantation. The mean rates of increase were 8.6% and 21.4% at 1 and 3 years, respectively. CONCLUSIONS: As the volume of native polycystic kidneys could be reduced after renal transplantation, resection would be unnecessary if the space for kidney graft is available in the absence of infection, bleeding, or malignancy. When ADPKD is combined with polycystic liver disease, the possibility of intolerable symptoms caused by growing liver cysts should also be taken into account.