Sonographic Evaluation of Clinically Significant Perigraft Hematomas in Kidney Transplant Recipients. AJR Am J Roentgenol. 2015;205:802-806. [PMID: 26397328 DOI: 10.2214/ajr.15.14426]

Renal Transplantation: Immediate and Late Complications

Kidney grafts are the most common transplanted solid organ. To optimize graft survival, radiologists should be familiar with the anatomy and potential complications unique to transplanted kidneys. In addition to being able to recognize the imaging characteristics to diagnose etiologies of kidney graft dysfunction, an understanding of the pathophysiology is a key to narrowing the differential diagnosis. This article provides a summary of the most common complications based on broad categories of type of complication and posttransplant timing.

Role for contrast-enhanced ultrasound in assessing complications after kidney transplant

Kidney transplantation (KT) is an effective treatment for end-stage renal disease. Despite their rate has reduced over time, post-transplant complications still represent a major clinical problem because of the associated risk of graft failure and loss. Thus, post-KT complications should be diagnosed and treated promptly. Imaging plays a pivotal role in this setting. Grayscale ultrasound (US) with color Doppler analysis is the first-line imaging modality for assessing complications, although many findings lack specificity. When performed by experienced operators, contrast-enhanced US (CEUS) has been advocated as a safe and fast tool to improve the accuracy of US. Also, when performing CEUS there is potentially no need for further imaging, such as contrast-enhanced computed tomography or magnetic resonance imaging, which are often contraindicated in recipients with impaired renal function. This technique is also portable to patients' bedside, thus having the potential of maximizing the cost-effectiveness of the whole diagnostic process. Finally, the use of blood-pool contrast agents allows translating information on graft microvasculature into time-intensity curves, and in turn quantitative perfusion indexes. Quantitative analysis is under evaluation as a tool to diagnose rejection or other causes of graft dysfunction. In this paper, we review and illustrate the indications to CEUS in the post-KT setting, as well as the main CEUS findings that can help establishing the diagnosis and planning the most adequate treatment.

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.

Imaging of Renal Transplant Complications throughout the Life of the Allograft: Comprehensive Multimodality Review

The kidney is the most commonly transplanted solid organ. Advances in surgical techniques, immunosuppression regimens, surveillance imaging, and histopathologic diagnosis of rejection have allowed prolonged graft survival times. However, the demand for kidneys continues to outgrow the available supply, and there are efforts to increase use of donor kidneys with moderate- or high-risk profiles. This highlights the importance of evaluating the renal transplant patient in the context of both donor and recipient risk factors. Radiologists play an integral role within the multidisciplinary team in care of the transplant patient at every stage of the transplant process. In the immediate postoperative period, duplex US is the modality of choice for evaluating the renal allograft. It is useful for establishing a baseline examination for comparison at future surveillance imaging. In the setting of allograft dysfunction, advanced imaging techniques including MRI or contrast-enhanced US may be useful for providing a more specific diagnosis and excluding nonrejection causes of renal dysfunction. When a pathologic diagnosis is deemed necessary to guide therapy, US-guided biopsy is a relatively low-risk, safe procedure. The range of complications of renal transplantation can be organized temporally in relation to the time since surgery and/or according to disease categories, including immunologic (rejection), surgical or iatrogenic, vascular, urinary, infectious, and neoplastic complications. The unique heterotopic location of the renal allograft in the iliac fossa predisposes it to a specific set of complications. As imaging features of infection or malignancy may be nonspecific, awareness of the patient's risk profile and time since transplantation can be used to assign the probability of a certain diagnosis and thus guide more specific diagnostic workup. It is critical to understand variations in vascular anatomy, surgical technique, and independent donor and recipient risk factors to make an accurate diagnosis and initiate appropriate treatment.^©RSNA, 2019.

Evaluation of the Renal Transplant Recipient in the Emergency Department

Renal transplants are becoming more and more frequent in the United States and worldwide. Studies demonstrate that these patients inevitably end up visiting an emergency department. In addition to typical medical and surgical problems encountered in the general population, this group of patients has unique problems arising from their immunocompromised state and also due to side effects of the medications required. This article discusses these risks and management decisions that the emergency department physician should be aware of in order to prevent adverse outcomes for the patient and transplanted kidney.

Optimizing renal transplant Doppler ultrasound

Doppler ultrasound is routinely used for the post-operative evaluation of renal transplant patients. Knowledge of the surgical anatomy and application of a robust technique are important for appropriate evaluation of a transplanted kidney. In this review article, we discuss the surgical anatomy of renal transplantation, techniques to optimize image acquisition, as well as commonly associated pitfalls with Doppler ultrasound evaluation of renal grafts.

Imaging non-vascular complications of renal transplantation

In patients with end-stage renal disease, the treatment of choice for most patients is renal transplantation. Complications that occur after kidney transplant can be broadly divided into vascular and non-vascular categories. Non-vascular complications can further be divided into surgical and medical categories. When evaluating renal transplant imaging, it is helpful to consider the occurrence of complications in a timeline from time of surgery. Ultrasound is often the first modality used for evaluation of renal transplants particularly in the early postoperative period. Contrast-enhanced ultrasound can be a helpful adjunct in evaluating certain complications such as hematoma, rejection, and infection. Computed tomography (CT) is also helpful in accurately diagnosing complications. Surgical complications include perinephric fluid collections (hematoma, urinoma from urine leak, abscess, and lymphocele), urinary obstruction, and incisional fluid collections and hernias. One major category of medical complications that affect the renal parenchyma includes rejection (hyperacute, acute, and chronic), delayed graft function, acute tubular necrosis (ATN), and nephrotoxicity. Infection, renal calculi, and neoplasms such as post-transplant lymphoproliferative disease are medical complications that occur after renal transplantation. It is important for radiologists to be aware of the ultrasound and CT findings of the surgical and medical complications after renal transplant for prompt identification and treatment.

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.