Helical CT in renal transplantation: normal findings and early and late complications

Contrast Enhanced Ultrasound Compared with MRI and CT in the Evaluation of Post-Renal Transplant Complications

Renal transplantation (RT) is the treatment of choice for end-stage renal disease, significantly improving patients’ survival and quality of life. However, approximately 3–23% of patients encounter post-operative complications, and radiology plays a major role for their early detection and treatment or follow-up planning. CT and MRI are excellent imaging modalities to evaluate renal transplant post-operative course; nevertheless, they are both associated with a high cost and low accessibility, as well as some contraindications, making them not feasible for all patients. In particular, gadolinium-based contrast can lead to the rare condition of nephrogenic systemic fibrosis, and iodine-based contrast can lead to contrast-induced nephropathy (CIN). CT also exposes the patients who may require multiple examinations to ionizing radiation. Therefore, considering the overall advantages and disadvantages, contrast-enhanced ultrasound (CEUS) is presently considered an effective first-line imaging modality for post-operative early and long-term follow-up in RT, reducing the need for biopsies and providing adequate guidance for drainage procedures. Hence, this paper aims to review the updated knowledge on CEUS compared with CT and MRI for the evaluation of RT renal transplant complications; advantages, limitations, and possible recommendations are provided.

Evolving Medical Imaging Techniques for the Assessment of Delayed Graft Function: A Narrative Review

Purpose of review

Delayed graft function (DGF) is a significant complication that contributes to poorer graft function and shortened graft survival. In this review, we sought to evaluate the current and emerging role of medical imaging modalities in the assessment of DGF and how it may guide clinical management.

Sources of information

PubMed, Google Scholar, and ClinicalTrial.gov up until February 2021.

Methods

This narrative review first examined the pathophysiology of DGF and current clinical management. We then summarized relevant studies that utilized medical imaging to assess posttransplant renal complications, namely, DGF. We focused our attention on noninvasive, evolving imaging modalities with the greatest potential for clinical translation, including contrast-enhanced ultrasound (CEUS) and multiparametric magnetic resonance imaging (MRI).

Key findings

A kidney biopsy in the setting of DGF can be used to assess the degree of ischemic renal injury and to rule out acute rejection. Biopsies are accompanied by complications and may be limited by sampling bias. Early studies on CEUS and MRI have shown their potential to distinguish between the 2 most common causes of DGF (acute tubular necrosis and acute rejection), but they have generally included only small numbers of patients and have not kept pace with more recent technical advances of these imaging modalities. There remains unharnessed potential with CEUS and MRI, and more robust clinical studies are needed to better evaluate their role in the current era.

Limitations

The adaptation of emerging approaches for imaging DGF will depend on additional clinical trials to study the feasibility and diagnostic test characteristics of a given modality. This is limited by access to devices, technical competence, and the need for interdisciplinary collaborations to ensure that such studies are well designed to appropriately inform clinical decision-making.

Infiltrating Kaposi sarcoma presenting as acute kidney injury: An unexpected consequence of deliberate hepatitis C-positive organ transplantation

Kaposi sarcoma (KS) following kidney transplantation can result from recipient reactivation of latent human herpesvirus 8 (HHV-8) infection or activation of donor-acquired HHV-8 infection. Post-transplant KS typically manifests with cutaneous pathology, but rare cases of renal allograft involvement have been reported. We describe two cases of donor-derived HHV-8 infection in two hepatitis C (HCV) viremia-negative transplant recipients who each received a kidney from a donor with HCV viremia. One recipient did not develop KS while the other presented with acute kidney injury caused by extensive KS infiltration of the renal parenchyma and metastatic disease. This report reviews the literature for cases of KS involving the renal allograft and highlights an unexpected consequence of deliberate HCV-positive organ transplantation.

Multimodality imaging of pancreas-kidney transplants

Simultaneous pancreas-kidney transplant remains a treatment option for patients with insulin-dependent diabetes mellitus type 1, aimed at restoring normoglycemia, alleviating insulin dependency, avoiding diabetic nephropathy, and thereby improving the quality of life. Imaging remains critical in the assessment of these transplant grafts. Ultrasound with Doppler remains the primary imaging modality for establishing baseline assessment of the graft as well as for evaluating vascular, parenchymal, and perigraft complications. Noncontrast MR imaging is preferred over non-contrast CT for evaluation of parenchymal or perigraft complications in patients with decreased renal function, although contrast-enhanced CT/MR imaging may be obtained following multidisciplinary consultation in cases with high clinical and laboratory suspicion for graft dysfunction. Catheter angiography is reserved primarily for therapeutic intervention in suspected or confirmed vascular complications. An understanding of the surgical techniques and imaging appearance of a normal graft is crucial to identify potential complications and direct timely management. This article provides an overview of surgical techniques, normal imaging appearance, as well as the spectrum of imaging findings and potential complications in pancreas-kidney transplants.

A Novel CNN-Based CAD System for Early Assessment of Transplanted Kidney Dysfunction

This paper introduces a deep-learning based computer-aided diagnostic (CAD) system for the early detection of acute renal transplant rejection. For noninvasive detection of kidney rejection at an early stage, the proposed CAD system is based on the fusion of both imaging markers and clinical biomarkers. The former are derived from diffusion-weighted magnetic resonance imaging (DW-MRI) by estimating the apparent diffusion coefficients (ADC) representing the perfusion of the blood and the diffusion of the water inside the transplanted kidney. The clinical biomarkers, namely: creatinine clearance (CrCl) and serum plasma creatinine (SPCr), are integrated into the proposed CAD system as kidney functionality indexes to enhance its diagnostic performance. The ADC maps are estimated for a user-defined region of interest (ROI) that encompasses the whole kidney. The estimated ADCs are fused with the clinical biomarkers and the fused data is then used as an input to train and test a convolutional neural network (CNN) based classifier. The CAD system is tested on DW-MRI scans collected from 56 subjects from geographically diverse populations and different scanner types/image collection protocols. The overall accuracy of the proposed system is 92.9% with 93.3% sensitivity and 92.3% specificity in distinguishing non-rejected kidney transplants from rejected ones. These results demonstrate the potential of the proposed system for a reliable non-invasive diagnosis of renal transplant status for any DW-MRI scans, regardless of the geographical differences and/or imaging protocol.

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.

CT evaluation of the renal donor and recipient

Proper pre- and post-transplant diagnostic imaging work-up is fundamental in ensuring a successful outcome for renal transplantation. Despite exposure to ionizing radiation, CT has high spatial resolution and is a widely available and fast imaging technique. CT is performed routinely to delineate the anatomy of the kidney, relevant vasculature, and urinary collecting system in the living donor, to assess the iliac vessels in potential recipients prior to surgery, and to assess early and late-term post-transplant complications. The purpose of this article is to outline the optimal CT protocol and the main reportable findings for both the donor and the recipient diagnostic imaging work-up as well as to point out the main issues regarding ionizing radiation exposure and contrast medium injection in these subjects.

A Giant Primary Retroperitoneal Serous Cystadenoma: Case Report and Review of Retroperitoneal Cysts

Primary retroperitoneal serous cystadenomas (PRSCs) are rare cystic lesions whose pathogenesis is currently not well understood. Although the vast majority of tumors are benign, early recognition and resection is necessary to avoid malignant transformation, rupture, and secondary infection. Here we present the case of a 79-year-old woman who presented with confusion, visual hallucinations, and a history of fall. As part of the work-up for abdominal distension, computed tomography scan of the abdomen and pelvis was performed, which revealed a right-sided retroperitoneal cystic lesion measuring 26.6 × 16.7 cm in size. The lesion was resected laparoscopically, and the surgical specimen measured 28 × 17 cm. Histology revealed a serous cystadenoma. The postsurgical course was uneventful, and no radiological recurrence was noted on 3 months follow-up. Very few primary retroperitoneal cystic lesions have been reported in the literature. Most lesions are benign and predominantly occur in females. They may remain asymptomatic for long periods of time and are usually discovered when they reach very large in size. In rare cases, these lesions may have malignant potential. Diagnosis of PRSC should be considered in the differential diagnosis of all retroperitoneal cysts.

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.

Renal Allograft Torsion: US and CT Imaging Findings of a Rare Posttransplant Complication

Vascular torsion is a rare renal transplant complication which requires prompt diagnosis and surgery to salvage allograft function. We report here a case of renal allograft torsion with interesting imaging findings on unenhanced CT and color Doppler ultrasound. A 60-year-old woman with a history of pancreas and kidney transplant presented to the emergency room with nausea, vomiting, abdominal pain, and minimal urine output. Unenhanced CT of the abdomen demonstrated an enlarged and malrotated renal allograft with moderate hydronephrosis. Color Doppler ultrasound demonstrated lack of vascularity within the allograft. The patient was taken urgently to the operating room where the renal allograft was found twisted 360 degrees around the vascular pedicle. After the allograft was detorsed, the color of the kidney returned and the Doppler signals for arterial flow improved. Intraoperative biopsy showed no evidence of infarct or acute cellular rejection. The detorsed kidney was surgically fixed in position in its upper and lower poles. Follow-up ultrasound 1 day later demonstrated normal blood flow to the renal allograft and the serum level of creatinine returned to normal.

Transplant renal artery stenosis: clinical manifestations, diagnosis and therapy

Transplant renal artery stenosis (TRAS) is a well-recognized vascular complication after kidney transplant. It occurs most frequently in the first 6 months after kidney transplant, and is one of the major causes of graft loss and premature death in transplant recipients. Renal hypoperfusion occurring in TRAS results in activation of the renin–angiotensin–aldosterone system; patients usually present with worsening or refractory hypertension, fluid retention and often allograft dysfunction. Flash pulmonary edema can develop in patients with critical bilateral renal artery stenosis or renal artery stenosis in a solitary kidney, and this unique clinical entity has been named Pickering Syndrome. Prompt diagnosis and treatment of TRAS can prevent allograft damage and systemic sequelae. Duplex sonography is the most commonly used screening tool, whereas angiography provides the definitive diagnosis. Percutaneous transluminal angioplasty with stent placement can be performed during angiography if a lesion is identified, and it is generally the first-line therapy for TRAS. However, there is no randomized controlled trial examining the efficacy and safety of percutaneous transluminal angioplasty compared with medical therapy alone or surgical intervention.

Mimickers of neoplasm on abdominal and pelvic CT

PURPOSE

The radiologist can encounter benign significant imaging findings on computed tomography that can be incorrectly interpreted as neoplasm. The authors review several benign findings and demonstrate several methods to differentiate these findings from more sinister pathology.

CONCLUSION

It is imperative for the radiologist to be cognizant of and how to correctly identify mimickers of pathology so that unnecessary interventions and surgeries are avoided.

Renal Transplant Complications: Diagnostic and Therapeutic Role of Radiology

Kidney was the first and is the most frequently transplanted organ. Despite improved surgical techniques and transplantation technology, complications do occur and, if left untreated, may lead to catastrophic consequences. Renal transplantation complications may be vascular (eg, renal artery and vein stenosis and thrombosis, arteriovenous fistula, and pseudoaneurysms); urologic (eg, urinary obstruction and leak, and peritransplantation fluid collections, including hematoma, seroma, lymphocele, and abscess formation); and nephrogenic, including acute tubular necrosis, graft rejection, chronic allograft nephropathy, and neoplasm. Early diagnosis and treatment of these complications are paramount to prevent graft failure and other significant morbidities to the patients. Radiology plays a pivotal role in the diagnosis and treatment of these complications, with minimally invasive percutaneous techniques. In this article, we reviewed renal transplantation anatomy, a wide range of complications that may occur after renal transplantation surgery, typical imaging appearances of the complications on varies imaging modalities, and percutaneous interventional techniques that are used in their treatment.

Depiction of transplant renal vascular anatomy and complications: unenhanced MR angiography by using spatial labeling with multiple inversion pulses

PURPOSE

To evaluate the ability to depict anatomy and complications of renal vascular transplant with unenhanced magnetic resonance (MR) angiography with spatial labeling with multiple inversion pulses (SLEEK) and to compare the results with color Doppler (CD) ultrasonography (US), digital subtraction angiography (DSA), and intraoperative findings.

MATERIALS AND METHODS

This study was approved by the institutional review board, and written informed consent was received before examination. Seventy-five patients who underwent renal transplantation were examined with unenhanced MR angiography with SLEEK and CD US. DSA was performed in 15 patients. Surgery was performed in eight patients. The ability of SLEEK to show transplant renal vascular anatomy and complications was evaluated by two experienced radiologists who compared the results with CD US, DSA, and intraoperative findings.

RESULTS

Patients successfully underwent SLEEK MR angiography. Transplant renal vascular anatomy was assessed in 87 arteries and 78 veins. Renal vascular complications from transplantation were diagnosed in 23 patients, which included 14 with arterial stenosis, three with arterial kinking, two with arteriovenous fistulas, two with venous stenosis, one with pseudoaneurysms, and one with fibromuscular dysplasia. Three patients had two renal transplants and nine patients had nine accessory renal arteries. More accessory renal arteries were detected with SLEEK than with CD US. Correlation was excellent between the stenosis degree with SLEEK and DSA (r = 0.96; P < .05). For those with significant artery stenosis (>50% narrowing) proved with DSA (n = 7) or surgery (n = 3), positive predictive value was 91% (10 of 11).

CONCLUSION

Unenhanced MR angiography with SLEEK preliminarily proved to be a reliable diagnostic method for depiction of anatomy and complications of renal vascular transplant. It may be used for evaluation of patients with renal transplant, and in particular for those with renal insufficiency.

Imaging of vascular complications and their consequences following transplantation in the abdomen

Transplantation is the surgical treatment of choice for end-stage organ failure. Transplantation procedures performed in the abdomen include liver, renal, pancreas, islet, intestinal, and multivisceral transplantations. Imaging plays a pivotal role in the posttransplantation setting for monitoring the transplant allograft and screening for complications. Knowledge of the surgical techniques employed in abdominal transplantation is essential because it facilitates radiologic understanding and interpretation of the posttransplantation anatomy. This article includes a basic description of the standard surgical techniques performed in the abdomen, with emphasis on the relevant vascular anastomotic reconstructions used. Posttransplantation complications can be broadly classified as vascular or nonvascular in origin. Many of these complications can be accurately depicted and characterized at imaging and dealt with definitively by using interventional radiology techniques, which can be graft- and life-saving and can obviate further complex surgical intervention. The article discusses imaging appearances of vascular complications and their consequences after transplantation in the abdomen. These vascular complications include arterial thrombosis, arterial stenosis, venous thrombosis and stenosis, arteriovenous fistula formation, and pseudoaneurysm formation. The relevant predisposing factors, clinical features, imaging appearances, and potential treatment options for vascular complications of various types of transplantation are presented in a logical and integrated fashion. Knowledge and imaging recognition of the posttransplantation vascular complications discussed in this article will aid radiologists in accurate imaging characterization and thereby facilitate appropriate clinical management and therapy.

Imaging evaluation of kidney transplant recipients

Renal transplantation is nowadays accepted as the treatment of choice for patients with end-stage renal disease. However, despite progress in immunosuppression and surgical techniques, various complications still can occur. Complications vary from vascular disorders and urologic diseases to parenchymal and immunologically related complications. The clinician evaluating the recipient with graft dysfunction has the option of choosing among a variety of imaging modalities including ultrasonography, nuclear medicine, computed tomography, and magnetic resonance imaging to start or continue the diagnostic work-up. In this article, we discuss the evaluation of the kidney transplant recipient using these imaging procedures, emphasizing the clinical diagnostic utility and role of each modality.

Magnetic resonance with diffusion-weighted imaging in the evaluation of transplanted kidneys: preliminary findings

BACKGROUND

The aim of this study was to compare values of apparent diffusion coefficient (ADC) and diffusion (D) with renal function indexes, in a population of kidney transplant recipients who underwent magnetic resonance with diffusion-weighted imaging (DWI) of the transplanted graft.

MATERIALS AND METHODS

We studied 21 patients using a 1.5-Tesla magnetic resonance; DWI sequences were acquired with several b-values. Patients were divided into 3 groups by their creatinine clearance values: group A, clearance >60 mL/min; group B, clearance >30 and ≤60 mL/min; and group C, clearance ≤30 mL/min. ADCs values between groups were compared using the Mann-Whitney U test. Receiver operating characteristic (ROC) curves were created for prediction of normal renal function (group A) and renal failure (group C).

RESULTS

Comparing mean values of ADC between groups A and C, we observed a difference (P=0.0012), with higher values in group A. Regarding mean values of D, we observed a difference between groups A and C (P=0.022). In the comparison between contiguous groups, we observed no difference for ADC and D values. In the prediction of normal clearance values (group A), ROC curve showed an area under curve (AUC) of 0.861, with a sensitivity of 88.89% and specificity of 75% using a threshold ADC value ≥2.1 × 10(-3) mm(2)/sec. For prediction of normal clearance values (group A), ROC curve showed an AUC of 0.787, with a sensitivity of 77.8% and specificity of 83.3% using a threshold D value ≥2.3 × 10(-3) mm(2)/sec.

CONCLUSION

Although studies with a larger number of patients are needed, DWI represents a promising tool for noninvasive assessment of renal function. An ADC ≥ 2.1 × 10(-3) mm(2)/sec and a D ≥ 2.3 × 10(-3) mm(2)/sec may be used as a threshold for predicting normal clearance.

In vitro renal cortex elasticity and viscosity measurements with Shearwave Dispersion Ultrasound Vibrometry (SDUV) on swine kidney

Renal fibrosis threatens kidney viability and fibrosis has been associated with altered tissue structure affecting the biomechanical properties of the kidney, quantifiable as elasticity and viscosity. Importantly, early detection of renal fibrosis may guide therapy and eliminate invasive biopsy procedures. The ability to detect fibrosis early and monitor it regularly with sufficient sensitivity and specificity is an active area of research. A newly emerging method called Shearwave Dispersion Ultrasound Vibrometry (SDUV), that quantifies both elasticity and viscosity by evaluating dispersion of shear wave propagation speed versus its frequency, offers a potential tool to determine renal elasticity and viscosity in vivo. The purpose of this study was to evaluate the feasibility of SDUV for in vitro measurements of renal cortex elasticity and viscosity in the kidney.

Vascular complications in renal transplantation: a single-center experience in 1367 renal transplantations and review of the literature

Renal transplantation is the treatment of choice for end-stage renal disease. Vascular complications in renal transplantation are not uncommon and may often lead to allograft loss. The most common vascular complications are transplant renal artery stenosis, transplant renal artery thrombosis, transplant renal vein thrombosis, biopsy-induced vascular injuries, pseudoaneurysm formation, and hematomas. Transplant renal artery and vein thrombosis have an early onset and a dramatic clinical manifestation and usually lead to allograft loss. In contrast, transplant renal artery stenosis has better treatment possibilities, whereas the rest do not occur so often. In our institution, 1367 renal transplantations were performed from September 1980 to April 2005. During this period, we encountered 38 major vascular complications leading to graft loss and 19 transplant renal artery stenoses with successful treatment in the majority of cases. According to these data, we can conclude that renal transplantation is a safe therapeutic procedure for renal failure.

Multidetector computed tomography findings of spontaneous renal allograft ruptures

AIM

To describe the characteristics of spontaneous renal allograft rupture using multidetector computed tomography (MDCT).

METHOD

Five patients with spontaneous renal allograft rupture, as confirmed by pathologic examination, were referred to our institution between 1985 and 2008. The clinical records and preoperative MDCT findings of the patients were studied retrospectively.

RESULTS

Clinical and/or histological findings were consistent with acute rejection in all cases. Using MDCT, disruption of the capsular integrity and parenchymal rupture was seen in four patients. Four of the five patients showed decreased enhancement and swollen grafts. Perirenal (n=4), subcapsular (n=1), and intraparenchymal (n=1) haematomas were also seen. In the patient with an intraparenchymal haematoma there was no disruption of capsular integrity, but capsular irregularities were seen near the haematoma.

CONCLUSION

MDCT is a useful investigative tool for the evaluation of suspected spontaneous renal allograft rupture. As well as a swollen graft, disruption of the capsule, parenchyma, and/or haematoma should prompt the radiologist to consider this diagnosis.

Renal transplant: nonenhanced renal MR angiography with magnetization-prepared steady-state free precession

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to investigate nonenhanced magnetic resonance (MR) angiography with steady-state free precession (SSFP) with inversion recovery for assessing renal arteries in patients with renal transplants. Thirteen recipients of renal transplants underwent SSFP MR angiography before contrast material-enhanced MR angiography. Three stenoses (two mild, one severe) were identified at SSFP MR angiography in agreement with findings at contrast-enhanced MR angiography. There was no significant difference in image quality between the two methods. Results suggest SSFP MR angiography permits image quality of renal transplant arteries and detection of arterial stenosis comparable with those at contrast-enhanced MR angiography.

Diagnosis of common iliac artery thrombosis and renal artery thrombosis in a kidney transplant by radionuclide renography

In a 58-year-old woman, the external iliac artery was accidentally dissected during the arterial anastomosis of a kidney transplant. An immediate CT angiogram showed an almost total occlusion of the common iliac artery. After the transplantation, radionuclide renography with Tc-99m MAG3 showed no flow across the right common iliac artery and no graft vascularization. Sequential images showed a photopenic area corresponding to the renal graft. These findings were interpreted as common iliac artery thrombosis and renal artery thrombosis associated with renal graft infarct. Excision of the transplant and iliofemoral bypass were performed. Pathologic examination of the graft showed massive acute renal infarct and renal artery thrombosis.

Abdominal computed tomography findings of malignant tumors in patients with solid organ transplants

AIMS

Incidence of malignancy in solid organ transplant recipients is higher compared to the general population. The aim of this study was to characterize distribution and appearance of abdominal malignant tumors detected with spiral computed tomography (CT) examination in patients with solid organ transplantation.

MATERIALS AND METHODS

Between July 1994 and April 2006, 198 patients underwent liver transplantation and 568 patients underwent renal transplantation in our center. The abdominal CT studies were reviewed to determine the presence or absence of abdominal malignancy. All abdominal CT examinations were performed prior to immunomodulation or chemotherapy.

RESULTS

Eleven renal and one liver transplantation patient developed an abdominal malignancy. Among 11 renal transplantation patients eight were diagnosed as abdominal Kaposi's sarcoma (KS) and three as posttransplantation lymphoproliferative disorder (PTLD) upon spiral CT examination. In two patients the transplanted organ itself had malignant tumors: one patient had PTLD with Burkitt lymphoma in the transplanted liver and the other a renal cell carcinoma in the transplanted kidney. Abdominal PTLD and KS showed imaging findings and the site of organ involvement somewhat different from nontransplant patients. The most common pathologies in KS were liver lesions (n=6) and lymphadenopathy (n=6). But in abdominal PTLD, the spleen (n=3) was the most involved organ.

CONCLUSIONS

The early diagnosis of abdominal malignancies after solid organ transplantation is crucial for the patient's prognosis, especially under immunosuppression. The abdominal spiral CT examination was an effective modality to depict a malignancy among patients with solid organ transplantation.

Renal transplant imaging and complications

The management of end stage renal disease has been revolutionised with the advent of renal transplantation, which offers good quality of life with low morbidity. Imaging plays an important role in the diagnosis and management of complications arising in renal transplant recipients. Ultrasound, Doppler and nuclear medicine are the main imaging modalities. CT scan, MRI and angiography are used in indeterminate cases. Interventional radiology plays a vital role in the management of complications. The aim of this pictorial review is to illustrate the role and limitations of imaging in renal transplant. The normal appearances, the spectrum of pathological conditions affecting the transplant and the complications of immunosuppression are discussed and illustrated.

Contrast-enhanced MR angiography (CE-MRA) in the evaluation of vascular complications of renal transplantation

Vascular complications associated with renal transplantation merit urgent investigation since they are often correctable, and timely intervention can help salvage the graft kidney. Contrast-enhanced MR angiography (CE-MRA) is a promising non-invasive technique, uses relatively non-nephrotoxic contrast agents and can rapidly demonstrate the underlying lesion in most instances. In this pictorial review we present the spectrum of abnormalities, as well as the pitfalls of interpretation of CE-MRA, that we encountered in 41 cases where there was clinical suspicion of vascular complications of renal transplantation. We believe that CE-MRA is a valuable, non-invasive screening technique in these cases, and further investigation and management of these patients can be confidently tailored to the results of the CE-MRA study.

Multidetector CT Angiography of the Abdomen

Multidetector CT angiography (MDCTA) is redefining traditional imaging strategies of the vascular structures of the abdomen. Angiographic depiction of normal and variant anatomy is becoming the standard for evaluation and has a significant impact in transplant and oncologic surgery. MDCTA is increasingly being used for assessing diseases affecting the vasculature of the abdominal organs, including the abdominal aorta for treatment planning and post therapy follow-up.

Acoustic radiation force impulse imaging of the abdomen: demonstration of feasibility and utility

The feasibility of utilizing acoustic radiation force impulse (ARFI) imaging to assess the mechanical properties of abdominal tissues was investigated. The thermal safety of the technique was also evaluated through the use of finite element method models. ARFI imaging was shown to be capable of imaging abdominal tissues at clinically realistic depths. Correspondence between anatomical structures in B-mode and ARFI images was observed. ARFI images showed similar tumor contrast when compared with B-mode images of ex vivo abdominal cancers. Finite element method models and in vitro measurements confirmed the thermal safety of ARFI imaging at depth. ARFI imaging is inexpensive, safe and convenient and is a promising modality for use in abdominal imaging.

The role of interventional radiology in management of patients with end-stage renal disease

The aim of the paper is to review the role of interventional radiology in the management of hemodialysis vascular access and complications in renal transplantation. The evaluation of patients with hemodialysis vascular access is complex. It includes the radiology/ultrasound (US) evaluation of the peripheral veins of the upper extremities with venous mapping and the evaluation of the central vein prior to the access placement and radiological detection and treatment of the stenosis and thrombosis in misfunctional dialysis fistulas. Preoperative screening enables the identification of a suitable vessel to create a hemodynamically-sound dialysis fistula. Clinical and radiological detection of the hemodynamically significant stenosis or occlusion demands fistulography and endovascular treatment. Endovascular prophylactic dilatation of stenosis greater than 50% with associated clinical abnormalities such as flow-rate reduction is warranted to prolong access patency. The technical success rates are over 90% for dilatation. One-year primary patency rate in forearm fistula is 51%, versus graft 40%. Stents are placed only in selected cases; routinely in central vein after dilatation, in ruptured vein and elastic recoil. Thrombosed fistula and grafts can be declotted by purely mechanical methods or in combination with a lytic drug. The success rate of the technique is 89-90%. Primary patency rate is 8-26% per year and secondary 75% per year. The most frequently radiologically evaluated and treated complications in renal transplantation are perirenal and renal fluid collection and abnormalities of the vasculature and collecting system. US is often the method of choice for the diagnostic evaluation and management of the percutaneous therapeutic procedures in early and late transplantation complications. Computed tomography and magnetic resonance are valuable alternatives when US is inconclusive. Renal and perirenal fluid collection are usually treated successfully with percutaneous drainage. Doppler US, magnetic resonance angiography and digital subtraction angiography have a principle role in the evaluation of vascular complications of renal transplantation and management of the endovascular therapy. Stenosis, the most common vascular complication, occurs in 1-12% of transplanted renal arteries and represents a potentially curable cause of hypertension following transplantation and/or renal dysfunction. Treatment with percutaneous transluminal renal angioplasty (PTRA) or PTRA with stent has been technically successful in 82-92% of the cases, and graft salvage rate has ranged from 80 to 100%. Restenosis occurs in up to 20% of cases, but are usually amenable to repeated PTRA. Complications such as arterial and vein thrombosis are uncommon. Intrarenal A/V fistulas and pseudoaneurysms are occasionally seen after biopsy, the treatment requires superselective embolisation. Urologic complications are relatively uncommon, predominantly they consist of the urinary leaks and urethral obstruction. Interventional treatment consists of percutaneous nephrostomy, balloon dilation, insertion of the double J stents, metallic stent placement and external drainage of the extrarenal collections.

The role of computed tomography in modern paediatric uroradiology

Computed tomography (CT) has developed a well-recognised role within paediatric uroradiology, especially in imaging of trauma, malignancy (in particular Wilms' tumour), atypical infection, and congenital urogenital abnormalities. CT can also be used for problem solving in nephrolithiasis and renal transplant assessment. These applications are illustrated and discussed, with an emphasis on particular information that can be gained from the CT study.