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 .).

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.

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.

[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.

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.

Current and potential renal applications of contrast-enhanced ultrasound.

The combination of microbubble technology and complementary ultrasound techniques has resulted in the development of contrast-enhanced ultrasound (CEUS) and, although initial clinical applications largely focussed on the liver, these are now becoming more diverse. With regard to the kidney, it is a safe, well-tolerated, and reproducible technique, and in selected cases, can obviate the need for computed tomography or magnetic resonance imaging. A clear advantage is the absence of nephrotoxicity. With respect to the current and potential renal applications, it is a useful technique in the evaluation of pseudotumours, acute pyelonephritis, renal tumours, cystic lesions, vascular insults, and renal transplantation. It may also be of value for monitoring the kidney following anti-angiogenic treatment or nephron-sparing interventional techniques for renal tumours. Assessment of microvascular perfusion using time-intensity curves is also likely to have further far-reaching applications in the kidney as well as other organs.

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.

Post-biopsy arteriovenous fistula in transplant kidney: treatment with superselective transcatheter embolisation.

PURPOSE: To evaluate the technical success and therapeutic effect of superselective embolisation of arteriovenous fistulas in renal allografts. MATERIALS AND METHODS: Between 2000 and 2009, 20 patients underwent angiography of 24 AV fistulas (AVF) following percutanous biopsy of the transplanted kidney. Indications for angiography were the diagnosis of AVF by ultrasound and in addition persistent or worsening transplant renal function, or haematuria. Superselective catheterisation of the fistula was performed with a coaxial microcatheter and microcoils were used to occlude the fistula. To assess the short-term effect of embolisation, serum creatinine values were evaluated before embolisation, in the first week after embolisation and after a period of minimum 42 days after the procedure. RESULTS: Angiography identified a single AVF in 16 patients and two AVFs in 4 patients. In 19 patients, successful embolisation was achieved without complications. In one patient, a second session was needed to embolise the AVF completely. The mean serum creatinine level of all patients with embolisation dropped significantly (p=0.0014) from 4.4 mg/dl (range: 1.4-11.6 mg/dl, standard deviation: 3.0) before embolisation to 2.7 mg/dl after embolisation (range: 1.0-7.0mg, standard deviation: 1.8). No patient showed an increase in serum creatinine. Long-term outcomes of the renal allograft revealed a well-functioning allograft in 19/20 patients. One patient returned to haemodialysis due to acute rejection. CONCLUSION: Superselective transcatheter embolisation is a safe and highly effective treatment for AVFs in renal allografts. Renal function was improved in the majority of patients.

Progression of coronary artery calcification and thoracic aorta calcification in kidney transplant recipients.

BACKGROUND: Vascular calcification independently predicts cardiovascular disease, the major cause of death in kidney transplant recipients (KTRs). Longitudinal studies of vascular calcification in KTRs are few and small and have short follow-up. We assessed the evolution of coronary artery (CAC) and thoracic aorta calcification and their determinants in a cohort of prevalent KTRs. STUDY DESIGN: Longitudinal. SETTING & PARTICIPANTS: The Agatston score of coronary arteries and thoracic aorta was measured by 16-slice spiral computed tomography in 281 KTRs. PREDICTORS: Demographic, clinical, and biochemical parameters were recorded simultaneously. OUTCOMES & MEASUREMENTS: The Agatston score was measured again 3.5 or more years later. RESULTS: Repeated analyzable computed tomographic scans were available for 197 (70%) KTRs after 4.40 ± 0.28 years; they were not available for the rest of patients because of death (n = 40), atrial fibrillation (n = 1), other arrhythmias (n = 4), refusal (n = 35), or technical problems precluding confident calcium scoring (n = 4). CAC and aorta calcification scores increased significantly (by a median of 11% and 4% per year, respectively) during follow-up. By multivariable linear regression, higher baseline CAC score, history of cardiovascular event, use of a statin, and lower 25-hydroxyvitamin D(3) level were independent determinants of CAC progression. Independent determinants of aorta calcification progression were higher baseline aorta calcification score, higher pulse pressure, use of a statin, older age, higher serum phosphate level, use of aspirin, and male sex. Significant regression of CAC or aorta calcification was not observed in this cohort. LIMITATIONS: Cohort of prevalent KTRs with potential survival bias; few patients with diabetes and nonwhites, limiting the generalizability of results. CONCLUSION: In contrast to previous small short-term studies, we show that vascular calcification progression is substantial within 4 years in prevalent KTRs and is associated with several traditional and nontraditional cardiovascular risk factors, some of which are modifiable.

Ultrasonographic findings in dual kidney transplantation.

INTRODUCTION: Organ shortage has led to using grafts from expanded criteria donors (ECD). Double kidney transplantation is an accepted strategy to increase the donor pool, using organs from an ECD which are not acceptable for single kidney transplantation (SKT). Aim of this retrospective study was to analyse the role of colour Doppler ultrasound (CDUS) in the diagnosis of major surgical complications in DKT, performed with unilateral or bilateral placement. MATERIALS AND METHODS: From 2000 to 2011 we performed 54 DKT. Unilateral placement of both kidneys was done in 26 patients and bilateral DKT in 28, through two separate Gibson incisions (18) or one midline incision (10). Each patient underwent at least 3 CDUS before hospital discharge. The main surgical complications, discovered initially thanks to ultrasound (US), were hydronephrosis from ureteral obstruction, lymphocele and deep venous thrombosis (DVT). RESULTS: Mean follow-up was 42.7 months. Good postoperative renalfunction was demonstrated in 25 patients (46.3%), while delayed graft function occurred in 29 (53.7%). US showed ureteral obstruction requiring surgery in 5 unilateral DKT while no patient subjected to bilateral DKT developed severe hydronephrosis. Lymphoocele, surgically drained, was demonstrated in 6 bilateral DKT with a midline incision, 2 bilateral DKT with two separate incisions and 3 unilateral DKT. CDUS also enabled diagnosis of 2 cases of DVT in ipsilateral DKTs. CONCLUSIONS: CDUS provides useful information in patients with DKT, allowing the detection of clinically unsuspected unilateral diseases. US study of our patients demonstrated that unilateral DKTs are more susceptible to the development of DVT and ureteral stricture, while the incidence of voluminous lymphocele is more frequent in bilateral DKT through a single midline incision. In this scenario, all patients undergoing DKT should be carefully monitored by US after surgery.

Strategies for non-invasive molecular imaging of acute allograft rejection by gamma scintigraphy and positron emission tomography.

The number of patients necessitating treatment for end-stage organ failure, and therefore, the number of allograft recipients, increases. Despite the introduction of new and effective immunosuppressive drugs, acute cellular graft rejection (AR) is still a major risk for graft survival. Hence, early detection and treatment of AR is crucial to limit the inflammatory process and preserve the function of the transplant. Nowadays, AR can only be definitively diagnosed by biopsy. As an invasive procedure, biopsy carries the risk of significant graft injury and is not feasible in patients taking anticoagulant medication. Moreover, limited sampling site (randomly taken exceedingly small portions of tissue) may lead to false negative results, i.e., when rejection is focal or patchy. Thus, in diagnostics, entirely image-based methods would be superior. As AR is characterized by recruitment of activated leukocytes into the transplant several diagnostic strategies exist. We herein review the current approaches (experimental and clinical scenarios with a special focus on renal AR) in noninvasive molecular imaging-based diagnostics of acute AR using either single photon (gamma) imaging or positron emission tomography.

Effects of arteriovenous fistula on clinical, laboratory and echocardiographic findings in renal allograft recipients.

PURPOSE: Left ventricular hypertrophy (LVH) is frequently observed in patients with end-stage renal disease and renal allograft recipients, and is an independent and strong predictor of morbidity and mortality. Presence of a patent arteriovenous fistula (AVF) after renal transplantation may contribute to the persistent LVH. We investigated the clinical, laboratory, and echocardiographic findings in patients with renal transplants with or without AVF. METHODS: A total of 130 renal transplant recipients were included in this study: 60 hemodialysis patients whose fistulas were still functional, 49 hemodialysis patients whose fistulas were spontaneous stopped or closed, and 21 peritoneal dialysis patients who had never had fistulas created. Laboratory parameters were measured and echocardiographic measurements were performed. RESULTS: There were no significant differences regarding smoking status, blood pressures, or NT-proBNP, hs-CRP, iPTH, and TSH levels between the study groups. Left atrial, right atrial diameters, left ventricle end-diastolic diameter, left ventricle end-systolic diameter, interventricular septum thickness (IVST), left ventricle mass index (LVMI), pulmonary artery pressure (PAP), and ejection fraction were similar in the three groups. In correlation analysis, PAP was significantly correlated with serum uric acid and NT-proBNP levels. Also, there were positive and moderate correlations between the serum uric acid and the IVST. CONCLUSION: Patent AVFs have not affected cardiovascular abnormalities such as LVH and LV mass index in patients with renal transplant. Hyperuricemia may be associated with increased PAP and high LVMI.

Multi-detector CT/CT angiogram assessment of acute pancreatic graft dysfunction.

Simultaneous pancreatic-kidney transplantation is the definitive treatment for patients with type 1 diabetes mellitus and renal failure. Pancreatic graft failure is an important postoperative complication and most commonly occurs as a result of pancreatitis, graft thrombosis or rejection. Distinguishing between these causes is necessary to determine timely, appropriate management and thereby potentially minimising graft loss. Multi-detector CT imaging may be used to identify the cause of pancreatic graft dysfunction when renal function is not markedly impaired.

Disturbances of kidney graft perfusion as indicators of acute renal vein thrombosis in contrast-enhanced ultrasonography.

INTRODUCTION: The aim of this study was to evaluate the usefulness of contrast-enhanced ultrasound (US-CE) to diagnose acute renal vein thrombosis (ARVT), acute rejection episodes (ARE), or acute tubular necrosis (ATN) in kidney grafts. MATERIALS AND METHODS: We analyzed 171 US-CE among kidney transplantation patients in the early postoperative period. Patients underwent US-CE following a standard diagnostic protocol including real-time ultrasound (B-mode) and color Doppler ultrasound with spectral flow analysis. Tissue perfusion was analyzed based upon time-intensity curves for two regions: the renal cortex and the renal pyramids. RESULTS: Of 14 patients, in whom standard ultrasound showed high resistance parameters in the renal artery, three showed ARVT and 11 had ATN or ARE, which were confirmed by biopsy. Among patients with ARVT, the US-CE showed a lack of contrast perfusion into the cortex and renal pyramids. Patients with ARE/ATN showed slower contrast inflow into the parenchyma with reduced but still present perfusion. The differences in mean signal intensity values were significant for both the cortex and the renal pyramids: cortex: -53.8±5.4 dB versus -35.0±3.5 dB (P<.05) and pyramids: -54.8±5.4 dB versus -37.0±3.5 dB (P<.05). CONCLUSION: US-CE is a noninvasive method that provides easy, reliable differentiation of ARVT from ARE/ATN.

[Clinical application of digitized three-dimensional image reconstruction for surgical simulation in living-related kidney transplantation].

OBJECTIVE: To study the application of digitized three-dimensional (3D) image reconstruction in living-related kidney transplantation. METHODS: The image data of 16-slice spiral CT in 5 cases of living-related kidney transplantation were collected to reconstruct the 3D model of the donor and recipient, which were then imported in the FreeForm Modeling System. The optimal surgical approach for each individual case was planned and simulated for verification. During the actual surgeries, the surgical findings were compared against the reconstructed model and the results of simulated surgery. RESULTS: The 3D model clearly displayed the anatomy of the kidney and the variation of the related vessels. The optimal surgical approaches were planned through the simulated surgery. The anatomy of the kidney and the related vessels found in the actual surgeries were consistent with that displayed by the reconstructed 3D model. All the operations were completed successfully according to the surgical plan, and the patients recovered uneventfully without obvious complications. CONCLUSION: Three-dimensional reconstruction and simulated surgery allow optimization of the surgical approaches of living-related kidney transplantation to ensure successful operation and minimize the surgical risks.