The role of imaging techniques in renal transplantation

Preoperative evaluation of iliac blood vessels for first kidney transplant recipients: Combination of conventional and contrast-enhanced ultrasonography

OBJECTIVE

To assess iliac blood vessels using conventional ultrasound (US) and contrast-enhanced ultrasonography (CEUS) before kidney transplantation (KT) and determine whether US findings related to post-transplant outcomes.

METHODS

A total of 119 patients received US and CEUS before KT waiting-list acceptance. The preoperative iliac blood hemodynamics and vascular conditions were evaluated. The operative strategy and follow-up outcomes were recorded. Logistic regression and correlation analysis were used. The accuracy in determining the patency of iliac blood vessels was calculated before and after the injection of contrast materials.

RESULTS

CEUS can help to significantly improve the visualization of the internal iliac artery, but there was no significant correlation with post-transplant outcomes. In terms of accuracy, there were significant differences in determining the patency of internal iliac arteries between conventional US and CEUS (60.5% and 100%, p < 0.001). The surgical strategy of one patient was regulated and two patients were excluded from KT according to US findings.

CONCLUSIONS

Compared with conventional US, CEUS helps to improve the visualization of the internal iliac artery. Conventional US and CEUS have the potential to serve as effective methods to evaluate anatomy and hemodynamics of iliac vessels and have a potential value while defining clinical algorithms in surgery decision-making.

B-Flow Sonography vs. Color Doppler Sonography for the Assessment of Vascularity in Pediatric Kidney Transplantation

OBJECTIVE

 To compare B-flow sonography (BFS) with color Doppler sonography (CDS) for imaging of kidney transplant vascularization in children.

PATIENTS AND METHODS

 All children receiving a kidney transplantation who underwent a protocol-based ultrasound examination (Loqiq 9, GE Medical Systems, Milwaukee, WI, USA) using the BFS and CDS technique with equal settings and probe position between January 2013 and January 2016 were retrospectively assessed (n = 40). The obtained datasets were visually graded according to the following criteria: (I) delineation of the renal vascular tree (Grade 1 - clear demarcation of interlobar, together with arcuate and interlobular vessels; Grade 2 - clear demarcation of interlobar and cortical vessels, but no distinction of interlobular from arcuate vessels; Grade 3 - only clear demarcation of interlobar vessels, Grade 4 - insufficient demarcation) (II) delineation of cortical vessel density in ventral, lateral, and dorsal part of the transplant, (III) smallest vessel-capsule distance, and (IV) maximum cortical vessel count. Comparison between methods was performed using Fisher's exact and paired sample t-tests.

RESULTS

 Applying a curved transducer (C1-6), BFS showed superior delineation of the renal vascular tree (p < 0.001), a lower vessel-capsule distance (p < 0.001), a higher cortical vessel count (p < 0.001), and a higher cortical vessel density in the superficial cortex (p = 0.01) than CDS. In the dorsal and lateral aspects of the transplant, cortical vessel density was lower with BFS (both p < 0.001). Using a linear high-resolution transducer (ML 6-15), no significant differences between the methods were found.

CONCLUSION

 Improved imaging of kidney transplant vascularization can be achieved in children by adding BFS to a standard protocol. The BFS technique is especially beneficial for overall assessment of the renal vascular tree together with the extent of cortical vascularization on curved array images.

KEY POINTS

  · Depiction of vascular tree and ventral cortical vessels is improved by BFS.. · The dorso-lateral cortex was better represented with CDS because of higher penetration.. · Additional monitoring with BFS improves the monitoring of transplant viability..

CITATION FORMAT

· Dammann E, Groth M, Schild R et al. B-Flow Sonography vs. Color Doppler Sonography for the Assessment of Vascularity in Pediatric Kidney Transplantation. Fortschr Röntgenstr 2021; 193: 49 - 60.

RADIOLOGICAL IMAGING IN RENAL TRANSPLANTATION

SUMMARY – Radiological diagnostic methods have a significant role in the preoperative and postoperative care of patients after kidney transplantation. Improvement and innovations in technology, but also the growing experience of the radiologists who deal with kidney transplant patients as part of the transplant team lead to earlier detection of complications in the postoperative period, which are the leading cause of transplant failure. In this article, we describe, through diagnostic imaging examples, detailed evaluation of all possible complications that can occur after kidney transplantation, with evaluation of different possible diagnostic methods that can be used in the preoperative assessment and postoperative follow up and care of the transplanted patient. The goal of this article is to demonstrate and summarize in detail the possible complications of renal transplantation and how to best diagnostically approach them, with special reference to ultrasound which is the main imaging method for this group of conditions.

Non-invasive approaches in the diagnosis of acute rejection in kidney transplant recipients. Part I. In vivo imaging methods

Kidney transplantation (KTx) represents the best available treatment for patients with end-stage renal disease. Still, full benefits of KTx are undermined by acute rejection (AR). The diagnosis of AR ultimately relies on transplant needle biopsy. However, such an invasive procedure is associated with a significant risk of complications and is limited by sampling error and interobserver variability. In the present review, we summarize the current literature about non-invasive approaches for the diagnosis of AR in kidney transplant recipients (KTRs), including in vivo imaging, gene expression profiling and omics analyses of blood and urine samples. Most imaging techniques, like contrast-enhanced ultrasound and magnetic resonance, exploit the fact that blood flow is significantly lowered in case of AR-induced inflammation. In addition, AR-associated recruitment of activated leukocytes may be detectable by ¹⁸F-fluoro-deoxy-glucose positron emission tomography. In parallel, urine biomarkers, including CXCL9/CXCL10 or a three-gene signature of CD3ε, IP-10 and 18S RNA levels, have been identified. None of these approaches has been adopted yet in the clinical follow-up of KTRs, but standardization of procedures may help assess reproducibility and compare diagnostic yields in large prospective multicentric trials.

Preoperative planning of renal transplantation: a comparison of non-contrast-enhanced ultrasonography, computed tomography, and magnetic resonance angiography with observations from surgery

BACKGROUND

Many candidates for kidney transplantation need to undergo vessel examination before the transplantation procedure.

PURPOSE

To identify the optimal preoperative modality for the examination of vessel status without the use of contrast agents in kidney transplant candidates.

MATERIAL AND METHODS

Fifty-three consecutive patients were examined and 31 patients were transplanted. Ultrasonography (US), non-contrast-enhanced computed tomography (NCCT), and non-contrast-enhanced magnetic resonance angiography (NCMRA) were compared using inspection during kidney transplantation (TX) as a reference standard. The sensitivity and specificity to severe arteriosclerotic changes and the accuracy were calculated. Kappa statistics were used to assess the agreement between TX and the different examination modalities, and McNemar's test was used to test for significant differences.

RESULTS

US had higher sensitivity (1.0) and better agreement with observations from surgery (k = 0.89) than both NCCT (sensitivity = 0.60; k = 0.72) and NCMRA (sensitivity = 0.20; k = 0.30). No significant difference was found between TX and US (P = 0.3173) or TX and NCCT (P = 0.1573), but there was a significant difference between TX and NCMRA (P = 0.0455). US was inconclusive in 20% of cases, and the internal iliac artery could not be visualized in 69% of cases.

CONCLUSION

Either US or NCCT can be used as the preferred preoperative imaging modality to examine vessel status before kidney transplantation, but a combination of the two is preferable. NCMRA should not be used as the sole imaging modality for preoperative imaging before kidney transplantation because of its low sensitivity in detecting severe arteriosclerotic disease without the presence of stenosis.

Magnetic resonance imaging in the complications of kidney transplantation

Kidney transplantation is currently the treatment of choice in most patients with end-stage chronic renal failure owing to the excellent results in terms of both graft and patient survival. However, surgical complications are still very frequent. Although urological (stricture, urinary fistulas, vesico-ureteral reflux) and lymphatic complications (lymphocoele) have a high incidence, they only rarely lead to graft loss. By contrast, vascular complications (stenosis, arterial and venous thrombosis, arterio-venous fistulas, pseudoaneurysms) are relatively rare, but potentially serious and may affect graft survival. Finally, medical complications such as acute tubular necrosis (ATN), rejection and de novo neoplasms may also arise in kidney transplantation. The purpose of this pictorial review is to illustrate the increasingly significant contribution of magnetic resonance angiography (MRA) in the management of complications of kidney transplantation, and emphasise how this method should now be considered a mandatory step in the diagnostic workup of selected cases. Moreover, the application and role in this setting of new magnetic resonance imaging (MRI) techniques, such as diffusion-weighted and blood oxygen level-dependent (BOLD) MRI, are also discussed.

Routine transplant Doppler ultrasonography following pediatric kidney transplant

The utility and cost-effectiveness of routine transplant renal DU as a screening test in the immediate postoperative period following pediatric renal transplantation has not been systematically evaluated. Our center's transplant protocol includes a routine DU on postoperative day 3, unless an earlier DU was obtained for a specific indication. We retrospectively evaluated 113 consecutive pediatric renal transplant recipients. Indication for DU (routine vs. non-routine), timing, results, and graft outcome data were collected. We determined whether the DU result affected patient management. Eighty routine DU examinations were evaluated. Thirty (37.5%) of the 80 routine DUs had abnormalities. Most abnormalities were minor and did not require intervention. One patient with a dysfunctional bladder had mild hydronephrosis; this led to a decision to increase the frequency of bladder catheterization. This was the only intervention based upon the routine DUs. Twenty percent of routine DUs revealed abnormalities that led to a follow-up study, but none of these studies led to an intervention. The incremental cost of each DU exceeded $1080 and the incremental cost-effectiveness ratio for a documented change in management exceeded $86, 400. Our results suggest that routine post-transplant DU is not cost-effective in pediatric renal allograft recipients.

Extraperitoneal urine leak after renal transplantation: the role of radionuclide imaging and the value of accompanying SPECT/CT - a case report

BACKGROUND

The differentiation of the nature of a fluid collection as a complication of kidney transplantation is important for management and treatment planning. Early and delayed radionuclide renography can play an important role in the evaluation of a urine leak. However, it is sometimes limited in the evaluation of the exact location and extent of a urine leak.

CASE PRESENTATION

A 71-year-old male who had sudden anuria, scrotal swelling and elevated creatinine level after cadaveric renal transplantation performed Tc-99 m MAG3 renography to evaluate the renal function, followed by an ultrasound which was unremarkable. An extensive urine leak was evident on the planar images. However, an exact location of the urine leak was unknown. Accompanying SPECT/CT images confirmed a urine leak extending from the lower aspect of the transplant kidney to the floor of the pelvic cavity, presacral region and the scrotum via right inguinal canal as well as to the right abdominal wall.

CONCLUSIONS

Renal scintigraphy is very useful to detect a urine leak after renal transplantation. However, planar imaging is sometimes limited in evaluating the anatomical location and extent of a urine leak accurately. In that case accompanying SPECT/CT images are very helpful and valuable to evaluate the anatomical relationships exactly.

KDOQI US commentary on the 2009 KDIGO clinical practice guideline for the care of kidney transplant recipients

In response to recently published KDIGO (Kidney Disease: Improving Global Outcomes) guidelines for the care of kidney transplant recipients (KTRs), the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) organized a working group of transplant nephrologists and surgeons to review these guidelines and comment on their relevance and applicability for US KTRs. The following commentaries on the KDIGO guidelines represent the consensus of our work group. The KDIGO transplant guidelines concentrated on aspects of transplant care most important to this population in the posttransplant period, such as immunosuppression, infection, malignancy, and cardiovascular care. Our KDOQI work group concurred with many of the KDIGO recommendations except in some important areas related to immunosuppression, in which decisions in the United States are largely made by transplant centers and are dependent in part on the specific patient population served. Most, but not all, KDIGO guidelines are relevant to US patients. However, implementation of many may remain a major challenge because of issues of limitation in resources needed to assist in the tasks of educating, counseling, and implementing and maintaining lifestyle changes. Although very few of the guidelines are based on evidence that is strong enough to justify their being used as the basis of policy or performance measures, they offer an excellent road map to navigate the complex care of KTRs.

KDIGO clinical practice guideline for the care of kidney transplant recipients

The 2009 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline on the monitoring, management, and treatment of kidney transplant recipients is intended to assist the practitioner caring for adults and children after kidney transplantation. The guideline development process followed an evidence-based approach, and management recommendations are based on systematic reviews of relevant treatment trials. Critical appraisal of the quality of the evidence and the strength of recommendations followed the Grades of Recommendation Assessment, Development, and Evaluation (GRADE) approach. The guideline makes recommendations for immunosuppression, graft monitoring, as well as prevention and treatment of infection, cardiovascular disease, malignancy, and other complications that are common in kidney transplant recipients, including hematological and bone disorders. Limitations of the evidence, especially on the lack of definitive clinical outcome trials, are discussed and suggestions are provided for future research.

What is the relevance of systematic aorto-femoral Doppler ultrasound in the preoperative assessment of patients awaiting first kidney transplantation: a monocentric prospective study

BACKGROUND

The purpose of our study was to study the relevance of a systematic aorto-femoral colour Doppler ultrasound (DUS) in the evaluation of first renal transplant receivers.

METHODS

We prospectively studied 100 consecutive first renal transplant (RT) receivers. All patients had a preoperative physical examination with a careful vascular system evaluation including assessment of risk factors and colour DUS of aortic, iliac and femoral arteries. Renal transplantation was planned in the right iliac fossa with end-to-lateral vascular anastomoses. Clinical parameters, DUS results, operative and post-operative parameters at 3 months were compared according to the vascular assessment.

RESULTS

Among the 84 patients presenting with a normal preoperative physical arterial examination, 12 patients (14.3%) had an abnormal DUS, revealing atherosclerotic arteries, but no case of arterial stenosis. Among the 16 patients with abnormal physical arterial examination, 10 patients (62.5%) had abnormal DUS, including 4 cases of iliac stenosis. In 3 of the 16 patients (18.8%), DUS revealed right iliac artery stenosis requiring a modification in the surgical procedure. No additional vascular procedure was reported in the case of normal preoperative vascular examination. No technical problems during arterial anastomosis and no post-transplantation arterial complications were reported. In multivariate analysis, abnormal physical examination was the most significant risk factor of atherosclerotic infiltration in DUS.

CONCLUSION

The abnormality of arterial physical examination is the best clinical predictor of abnormal DUS in preoperative assessment of renal transplant receivers. However, the low sensitivity and positive predictive value of the physical examination do not support the conclusion that DUS can be avoided in patients with normal arterial physical examination. Nevertheless, in the case of arterial physical abnormality, 'for case' DUS is critical and helps in the surgical strategy in approximately 20% of cases.

Simple provocative maneuvers in renal transplant scintigraphy for detecting urine leak

Urine leak in the early postoperative period following renal transplantation is a serious complication requiring early identification and aggressive intervention, which significantly reduces the morbidity and mortality. Renal transplant scintigraphy is a noninvasive method to evaluate the perfusion and function of a transplanted kidney and urinary drainage including urine leak. Here, we reported two cases in which the standard transplant renogram failed to demonstrate urine leak. The cases were referred for a diethylenetriaminepentaacetic acid renogram following the transplantation to evaluate the cause of symptoms or elevated serum creatinine level. In both the cases, urine leak was successfully detected following simple maneuvers such as diuretic administration or Foley catheter irrigation. Renal transplant scintigraphy is an effective and safe technique and the use of these simple maneuvers can enhance the diagnostic sensitivity of the transplant renogram in the detection of urine leak.

Pertinent issues in pretransplant recipient workup

Renal transplantation is recognized as the treatment of choice in most patients with end-stage renal disease. The evaluation of the candidate for kidney transplantation has been the recent subject of clinical practice guidelines published by the European Renal Association- European Dialysis Transplant Association and the American Society of Transplantation. The purpose of this article is to review the current literature for urological evaluation and treatment of patients prior to renal transplantation. In India, urologists are involved in evaluating not only the genitourinary problems but also vascular access and, vascular anatomy and pathology especially related to major pelvic vessels. Hence, evaluation of the transplant recipient should include assessment of vascular access for hemodialysis, access for peritoneal dialysis, assessment of pelvic vessels to which renal allograft vessels need to be anastomosed and genitourinary system. In addition, review of the serological tests for infective viral diseases like hepatitis and human immunodeficiency viruses should always be done before starting clinical evaluation. A note of the evaluation performed by other specialists like nephrologist, cardiologist, endocrinologist, pulmonologist, anesthetist etc. should always be reviewed.

Evaluation of Renal Transplant Donors with 16-Section Multidetector CT Angiography: Comparison of Contrast Media with Low and High Iodine Concentrations

PURPOSE

To compare the degree of contrast enhancement, image quality, and accuracy of renal computed tomographic (CT) angiography performed with a 16-detector row CT unit and equal iodine doses of low- and high-iodine-concentration contrast medium in the evaluation of renal transplant donors.

MATERIALS AND METHODS

Eighty donors scheduled to undergo renal CT angiography with 16-detector row CT were administered nonionic contrast media with two iodine concentrations. The first group (group A, n=40) received a contrast medium with 300 mg of iodine per milliliter, and the second group (group B, n=40) received a contrast medium with 370 mg of iodine per milliliter. An equal iodine dose of 550 mg per kilogram body weight was given to both groups. Contrast enhancement was quantified by measuring attenuation in the abdominal aorta and in both renal arteries. Subjective assessment of contrast enhancement, quality of reformatted images, and visualization of branch order of renal arteries were rated with a 5-point scale. The number of renal arteries and veins seen at CT was correlated with the results at surgery.

RESULTS

The mean enhancement values in group B were significantly greater (P<.001) than those in group A. The mean HU (+/-standard deviation) in groups A and B were 298+/-76 and 344+/-75, respectively, in the aorta, 284+/-74 and 331+/-71 in the right renal artery, and 285+/-72 and 329+/-73 in the left renal artery. The mean enhancement, image quality, and branch orders visualized were rated better in group B than in group A (P<.01). The accuracies for correctly identifying renal arteries and veins, respectively, were 91% and 95% for group A and 96% and 96% for group B.

CONCLUSION

Renal donor CT angiography with a contrast medium of 370 mg of iodine per milliliter provides greater enhancement and image quality compared with a contrast medium of 300 mg of iodine per milliliter. The diagnostic accuracies were similar.

Improved Detection of Renal Vascular Anatomy Using Multidetector CT Angiography: Is 100% Detection Possible?

BACKGROUND AND PURPOSE

Multidetector CT angiography (MDCTA) is being used increasingly to evaluate vascular anatomy prior to donor nephrectomy. To improve the ability of MDCTA to predict donor renal anatomy, a novel protocol including four-phase imaging with three-dimensional reconstruction and maximum intensity projections (MIPs) was incorporated into the standard donor evaluation. The purpose of this study was to determine the results of this protocol.

PATIENTS AND METHODS

Seventy consecutive patients who underwent hand-assisted laparoscopic donor nephrectomy between January 2003 and September 2004 were reviewed. All MDCTA studies were examined initially by a radiologist alone, after which, a second preoperative reading was performed by a radiologist and the operating surgeon together. The two reviews were compared with the operative findings.

RESULTS

Using this protocol to detect the total number of renal arteries, veins, and ureters, the sensitivity of the initial radiologist was 97%, 100%, and 96%, respectively. These values increased to 100%, 100%, and 99% when the films were reviewed by a radiologist together with the surgeon who would operate on the donor. The sensitivity, specificity, and accuracy in predicting supernumerary arteries, including early (< or =1-cm) arterial branching was 89%, 100%, and 97%, respectively after the single reading but increased to 100%, 100%, and 100% with the combined reading.

CONCLUSIONS

An MDCTA study with this protocol provides excellent anatomic detail prior to donor nephrectomy. Its ability to predict renal-arterial and ureteral anatomy is enhanced when the films are reviewed simultaneously by a radiologist and the operating surgeon.

Evaluation of Living Renal Donors: Accuracy of Three-dimensional 16-Section CT

PURPOSE

To retrospectively assess the sensitivity and specificity of three-dimensional (3D) 16-section computed tomography (CT) in the evaluation of vessels, pelvicalyceal system, and ureters in living renal donors, with surgical findings as the reference standard.

MATERIALS AND METHODS

This was a HIPAA-compliant study. Institutional review board approval was obtained for the review of subjects' medical records and data analysis, with waiver of informed consent. Forty-six renal donors (18 men, 28 women; mean age, 42 years) were examined with 16-section CT. Two blinded reviewers independently studied renal vascular and urographic anatomy of each donor CT scans by fist using 3D images alone, then transverse images alone, and finally transverse and 3D data set. Image quality, degree of diagnostic confidence, and time used for review were recorded. Sensitivity and specificity were calculated.

RESULTS

For 3D images, transverse images, and transverse in conjunction with 3D data sets, the respective sensitivity and specificity of CT in evaluation of accessory arteries by reviewer 1 were 100% and 100%, 89% and 100%, and 100% and 100%, and those by reviewer 2 were 89% and 97%, 89% and 100%, and 89% and 100%; the respective sensitivity and specificity in evaluation of venous anomalies by reviewer 1 were 100% and 98%, 100% and 98%, and 100% and 98%, and those by reviewer 2 were 100% and 98%, 100% and 95%, and 100% and 98%. For focused comprehensive assessment of renal donors with 3D scans alone, a reviewer on average (average of reviewers 1 and 2) used 2.4 minutes per scan, demonstrated full confidence in 93%, and rated the quality as excellent in 76%.

CONCLUSION

For focused assessment of renal vascular and urographic anatomy, review of 3D data set alone provides high sensitivity and specificity with regard to findings seen at surgery.

Electron-beam CT as a diagnostic modality in pediatric nephrology and renal transplant surgery

Electron-beam computed tomography is an imaging technology with a variety of medical applications, primarily in cardiology due to its sub-second acquisition time enabling visualization of a beating heart. Recently, this technique has also been introduced into other fields because of lower radiation exposure compared to traditional computed tomography, as well as the strengths of post-procedural three-dimensional visualization. This report evaluates electron-beam computed tomography as a diagnostic modality in pediatric nephrology patients. Seven patients reflecting typical clinical scenarios in pediatric nephrology were reviewed with regard to the value of electron-beam computed tomography and its contribution to the diagnostic workup. Electron-beam computed tomography is noninvasive and allows three-dimensional post-processing, enabling highly accurate images while requiring less radiation and acquisition time. It is very useful for clinical questions that require a detailed description of vascular and renal anatomy.

Consequences of Iliac Arterial Atheroma on Renal Transplantation

PURPOSE

Because recipient age has significantly increased in the last 15 years, surgeons must sometimes deal with atherosclerotic lesions of the iliac arterial system. Arterial restoration during renal transplantation should now be less frequent due to better preoperative screening and the prevention of arteriosclerosis in patients on renal transplantation waiting lists but in some patients EIA atheroma may require an additional surgical vascular procedure during renal transplantation. We describe the role of iliac artery atherosclerosis and the technical aspects of arterial restoration performed in patients who have undergone renal transplantation since 1985.

MATERIALS AND METHODS

In a series of 1,110 cadaveric renal transplantations performed between 1985 and 2000, 38 patients required endarterectomy during renal transplantation and 69 were considered not to require any special procedure.

RESULTS

In the 38 patients requiring endarterectomy a total of 12 end-to-end arterial anastomoses were performed and 6 ASs (50%) were observed, while 26 side-to-end arterial anastomoses were performed with only 1 AS (4%). Patient and graft survival curves showed a significant negative correlation with the severity of atherosclerosis.

CONCLUSIONS

Preoperative assessment of the EIA is mandatory before renal transplantation. Renal transplantation can be performed in patients with an atheromatous EIA if the artery can be clamped for endarterectomy. In our experience side-to-end anastomosis using a donor patch onto the EIA provides better results by avoiding AS after endarterectomy. However, despite vascular repair graft survival is significantly lower in patients with atheromatous lesions requiring endarterectomy.