Renal transplant complications

Early and late assessment of renal allograft dysfunction using intravoxel incoherent motion (IVIM) and diffusion-weighted imaging (DWI): a prospective study

PURPOSE

To evaluate the ability of the Intravoxel Incoherent Motion (IVIM) and monoexponentially ADC in renal allograft function in the early and late phases of transplantation, and to predict their effectiveness in discrimination of the graft pathology.

METHODS

This is a prospective study included participants scanned with quantitative diffusion and perfusion sequences on a 3-T MR scanner (Philips, Ingenia); the ADC and IVIM parameters; were calculated. Correlations and regression analysis with the eGFR, transplantation periods, and pathology were assessed.

RESULTS

This study included 105 renal allograft recipients (85 males, and 20 females with mean age = 32.4 ± 11.9 years and age range = 22-61 years). There was a significant positive correlation between the whole parameters of the ADC and IVIM with eGFR however, the cortical parameters showed higher significant correlation coefficients (p < 0.001). Regression analysis revealed the most significant model can predict eGFR groups included cortical pseudo diffusion (D*) and cortical ADC (p < 0.001). In graft dysfunction eGFR was 61.5 ml/min and normal graft was 64 ml/min. This model demonstrates a high performance of an AUC 96% [0.93-0.97]. In the late transplantation, there is a higher correlation with D* compared to ADC, p-values = 0.001.

CONCLUSION

IVIM and ADC Values are significant biomarkers for renal allograft function assessment, cortical ADC, and D* had the highest performance even in situations with mild impairment that is not affect the eGFR yet as cases of proteinuria with normal eGFR. Furthermore, D* is superior to ADC in the late assessment of the renal transplant.

Iliac artery dissection - A rare complication of renal transplantation: A case report and literature review

External iliac artery dissection is a rare and under-reported vascular complication after renal transplantation. The etiology is yet to be fully understood. The presentation, investigation and management of this condition are highly variable. Here we report a 52-year-old man successfully treated by endovascular stenting with nitinol stents for an external iliac artery dissection proximal to the anastomosis.

Detecting impaired function of renal allografts at the early stage after transplantation using intravoxel incoherent motion imaging

Background

Detecting renal allografts with impaired function early after renal transplantation and timely intervention are important to ensure a successful outcome.

Purpose

To detect impaired function of renal allografts at the early stage after renal transplantation using intravoxel incoherent motion imaging (IVIM).

Material and Methods

Forty-six recipients with good allograft function and 32 recipients with impaired function were included in this study. All participants were scanned with IVIM using 11 b-values on a 3-T magnetic resonance (MR) scanner; the apparent diffusion coefficient (ADC), ADC of slow diffusion (ADCslow), pseudo-diffusion (ADCfast), and perfusion fraction (f) values were calculated using a full bi-exponential model. Correlations between estimated glomerular filtration rate (eGFR) and the IVIM parameters were assessed by using Spearman correlation analysis. Receiver operating characteristics were used to assess the diagnostic utilities for detecting allografts with impaired function.

Results

The ADC, ADCslow, ADCfast, and f values of the renal cortex and the ADC and ADCslow values of the renal medulla were significantly higher in allografts with good function compared to those with impaired function (all P < 0.05). There was a significant corticomedullary difference in ADCslow, ADC, and f in all allografts. ADCfast values were higher in the cortex than in the medulla for allografts with good function but no differences were seen in allografts with impaired function ( P > 0.05). Combined use of all cortical IVIM parameters has higher efficacy in detecting renal allograft dysfunction than any single parameter (sensitivity = 90.62%; specificity = 78.26%).

Conclusion

IVIM technique may be useful for detecting renal allograft dysfunction, especially combined use of cortical parameters.

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.

Detection of transplant renal artery stenosis: determining normal velocities at the renal artery anastomosis

PURPOSE

Renal artery anastomosis peak systolic velocity (RAA PSV) exceeding 250 cm/s and a ratio of the renal artery to the adjacent external iliac artery (RAA:EIA) exceeding 1.8 historically suggest significant transplant renal artery stenosis (TRAS). However, the range of RAA PSV in transplants without TRAS has not been established.

METHODS

A retrospective review of renal transplants at a single institution over 5 years was performed identifying patients without graft dysfunction, failure, or refractory hypertension. RAA PSV obtained during interval postoperative sonograms was recorded.

RESULTS

Of 1141 patients, 844 met the inclusion criteria. Mean RAA PSV for 377 patients evaluated within 2 days of transplant measured 195 cm/s; RAA PSV exceeded 250 cm/s in 97 patients (26%). Mean RAA PSV for 820 patients evaluated 1-month post-transplant measured 206 cm/s; RAA PSV exceeded 250 cm/s in 224 patients (27%). Mean RAA PSV for 785 patients evaluated 4-month post-transplant measured 203 cm/s; RAA PSV exceeded 250 cm/s in 201 patients (26%). Mean RAA PSV for 766 patients evaluated 1-year post-transplant measured 189 cm/s; RAA PSV exceeded 250 cm/s in 141 patients (18%). At each of the given time points, 24%-34% of normal patients had RAA-to-EIA ratios greater than 1.8.

CONCLUSION

Approximately, 26% of patients without TRAS have RAA PSV > 250 cm/s in the first 9 months, and 18% do at 1 year. Similar findings also occurred with regards to the RAA-to-EIA ratio threshold of 1.8. In isolation, a PSV over 250 cm/s or 1.8 ratio threshold for suspicion of TRAS will lead to a large number of false-positive assessments.

External Iliac Arterial Obstruction Caused by Satinsky Atrauma Forceps in Renal Transplantation

External iliac arterial obstruction is relatively rare in renal transplantation, and may cause surgical failure and ipsilateral leg ischaemia. Prompt diagnosis and management of this kind of complication is essential to rescue the patient and allograft. Four patients with external iliac arterial obstruction caused by Satinsky atrauma forceps in renal transplantation were analysed and summarized. In case one, the obstruction of the external iliac artery distal to the renal allograft caused ipsilateral leg ischaemia. After surgical fixation of the endarterium, the patient recovered from the lower limb ischaemia. In case two, the obstruction of the external iliac artery was located proximal to the renal allograft. Since the endarterial rupture was not found and fixed in time, the renal allograft was lost. The third case was similar to the second. Based on the previous experience, we fixed the endarterium promptly and transplanted the kidney back successfully. In case four, there was endarterial rupture with atherosclerosis located around the anastomosis stoma. After taking out the atherosclerotic plaque and fixing the endarterium, the blood supply of kidney and lower limb was good. External iliac arterial rupture and obstruction caused by Satinsky atrauma forceps in renal transplantation is rare, but may cause severe and depressing outcome. The critical step is to find and fix the impaired endarterium as early as possible.