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

Application of ultrasound in early prediction of delayed graft function after renal transplantation

Kidney transplantation is currently the most effective treatment for end-stage renal disease. Delayed graft function (DGF) is one of the most common complications after renal transplantation and is a significant complication affecting graft function and the survival time of transplanted kidneys. Therefore, early diagnosis of DGF is crucial for guiding post-transplant care and improving long-term patient survival. This article will summarize the pathological basis and clinical characteristics of DGF after kidney transplantation, with a focus on contrast-enhanced ultrasound. It will analyze the current application status of ultrasound technology in DGF diagnosis and provide a comprehensive review of the clinical applications of ultrasound technology in this field, serving as a reference for the further application of ultrasound technology in kidney transplantation.

Management and Outcome After Early Renal Transplant Vein Thrombosis: A French Multicentre Observational Study of Real-Life Practice Over 24 Years

Early (<14 days) renal transplant vein thrombosis posttransplant (eRVTPT) is a rare but threatening complication. We aimed to assess eRVTPT management and the rate of functional renal transplantation. Of 11,172 adult patients who had undergone transplantation between 01/1997 and 12/2020 at 6 French centres, we identified 176 patients with eRVTPT (1.6%): 16 intraoperative (Group 1, G1) and 160 postoperative (Group 2, G2). All but one patient received surgical management. Patients in group G2 had at least one imaging test for diagnostic confirmation (N = 157, 98%). During the operative management of the G2 group, transplantectomy for graft necrosis was performed immediately in 59.1% of cases. In both groups, either of two techniques was preferred, namely, thrombectomy by renal venotomy or thrombectomy + venous anastomosis repair, with no difference in the functional graft rate (FGR) at hospital discharge (p = NS). The FGR was 62.5% in G1 and 8.1% in G2 (p < 0.001). Numerous complications occurred during the initial hospitalization: 38 patients had a postoperative infection (21.6%), 5 experienced haemorrhagic shock (2.8%), 29 exhibited a haematoma (16.5%), and 97 (55.1%) received a blood transfusion. Five patients died (2.8%). Our study confirms the very poor prognosis of early renal graft venous thrombosis.

Contrast-enhanced ultrasound of transplant organs - liver and kidney - in children

Ultrasound (US) is the first-line imaging tool for evaluating liver and kidney transplants during and after the surgical procedures. In most patients after organ transplantation, gray-scale US coupled with color/power and spectral Doppler techniques is used to evaluate the transplant organs, assess the patency of vascular structures, and identify potential complications. In technically difficult or inconclusive cases, however, contrast-enhanced ultrasound (CEUS) can provide prompt and accurate diagnostic information that is essential for management decisions. CEUS is indicated to evaluate for vascular complications including vascular stenosis or thrombosis, active bleeding, pseudoaneurysms and arteriovenous fistulas. Parenchymal indications for CEUS include evaluation for perfusion defects and focal inflammatory and non-inflammatory lesions. When transplant rejection is suspected, CEUS can assist with prompt intervention by excluding potential underlying causes for organ dysfunction. Intracavitary CEUS applications can evaluate the biliary tract of a liver transplant (e.g., for biliary strictures, bile leak or intraductal stones) or the urinary tract of a renal transplant (e.g., for urinary obstruction, urine leak or vesicoureteral reflux) as well as the position and patency of hepatic, biliary and renal drains and catheters. The aim of this review is to present current experience regarding the use of CEUS to evaluate liver and renal transplants, focusing on the examination technique and interpretation of the main imaging findings, predominantly those related to vascular complications.

Advances of Contrast-Enhanced Ultrasonography and Elastography in Kidney Transplantation: From Microscopic to Microcosmic

Kidney transplantation is the best choice for patients with end-stage renal disease. To date, allograft biopsy remains the gold standard for revealing pathologic changes and predicting long-term outcomes. However, the invasive nature of transplant biopsy greatly limits its application. Ultrasound has been a first-line examination for evaluating kidney allografts for a long time. Advances in ultrasound in recent years, especially the growing number of studies in elastography and contrast-enhanced ultrasonography (CEUS), have shed new light on its application in kidney transplantation. Elastography, including strain elastography and shear wave elastography, is used mainly to assess allograft stiffness and, thus, predict renal fibrosis. CEUS has been used extensively in evaluating blood microperfusion, assessing acute kidney injury and detecting different complications after transplantation. Requiring the use of microbubbles also makes CEUS a novel method of gene transfer and drug delivery, enabling promising targeted diagnosis and therapy. In this review, we summarize the advances of elastography and CEUS in kidney transplantation and evaluate their potential efficiency in becoming a better complement to or even substitute for transplant biopsy in the future.

Doppler Ultrasonography Findings During Recovery Period of Transplanted Kidney After Infarction and Necrosis Due to Renal Vein Thrombosis: A Case Report

A 47-year-old male patient underwent living-related renal transplant. On day 3 posttransplant, without evidence of associated clinical symptoms, the patient's serum creatinine levels had increased. The patient was given immunosuppressive medication, and a followup Doppler ultrasonography revealed hypoechoic areas in the inferior pole of the renal parenchyma. Eventually, on day 25, there was no perfusion in the superior and inferior poles of the transplanted kidney. No venous flow was shown in the middle segment, and only arterial vascularization with a high resistive index and negative diastolic phase was observed. Renal biopsy showed acute humoral rejection. This was interpreted as venous thrombosis secondary to acute humoral rejection. Tissue plasminogen activator infusion, plasmapheresis, and hemodialysis were administered. After 1.5 months, arterial flow returned to its normal pattern and the renal allograft recovered by gaining back its full vascularity at the end of month 8.

Standard B presentation vs. contrast-enhanced ultrasound (US-CE). A comparison of usefulness of different ultrasonographic techniques in the evaluation of the echo structure and size of haematomas inpost-renal transplant patients: A preliminary report

Background:

During routine ultrasonographic examination in B presentation, performed as a standard diagnostic procedure during the early post-operative period, the most important problem with the interpretation of the images of perirenal haematoma is their ability to change in time. The aim of this work was to assess the echogenicity and the size of perirenal haematomas in patients after kidney transplant during routine examinations in B presentation and during examinations enhanced with a contrast medium (CE-US).

Material/Methods:

Thirty-seven patients after kidney transplant were examined using standard examination in B presentation. Sixteen patients (7 women and 9 men) with isoechogenic and hypoechogenic areas visualized within the renal parenchyma, who were suspected of perirenal haematoma, underwent a CE-US examination after intravenous administration of sculpture hexafluoride (dose: 2.4 ml/examination). Using time-intensity curves (TIC), changes in the values were analysed for two areas of interest (ROI): in the renal parenchyma and in the areas identified during standard US as haematomas. Identical examination protocols and dynamic data loops allowed the acquisition of identical kidney cross-sections and enabled measuring the echogenicity and thickness of the abnormalities at the same location.

Results:

During the routine B presentation examination, the average difference between haematoma and the renal cortex was 5 dB. When performing US-CE examination, a significantly greater difference in echogenicity was observed and reached 31 dB. In six patients, the size of haematomas was comparable using both techniques, whereas in ten patients lesions visualized in B presentation were smaller than in the US-CE examination.

Conclusions:

The US-CE examination demonstrated a greater, statistically significant, difference in the echogenicity of perirenal haematomas compared to the routine examination in B presentation. This method enabled a more detailed assessment of the size of haematomas in the perirenal space that appeared during early post-operative period.