Impact of ultrasound examination shortly after kidney transplantation

Predictive value of the renal resistive index in the immediate postoperative period after kidney transplantation on short- and long-term graft and patient outcomes

INTRODUCTION

During the postoperative stay in the intensive care unit after kidney transplantation, the renal resistive index (RI) is routinely measured. An increased RI, measured months posttransplant, is associated with a higher mortality. We wanted to investigate the value of the RI immediately posttransplant in predicting both short- and long-term outcome.

METHODS

We performed a retrospective single-center study. The RI was collected <48 h posttransplant in patients undergoing kidney transplantations between 2005 and 2014. Short-term outcome was evaluated by delayed graft function (DGF). The long-term endpoints were kidney function and mortality at 30 days, 1 year and 5 years.

RESULTS

We included 478 recipients, 91.4% of whom reached the end of the 5-year follow-up. A higher RI < 48 h posttransplant was significantly associated with DGF. This association was particularly strong in patients receiving grafts from donors after brain death and expanded criteria donors. A higher RI also correlated with mortality and death with functioning graft but not with graft failure. After adjustment for confounders, we found an association between increased RI and DGF, but not with long-term kidney function or mortality.

CONCLUSION

The RI routinely measured <48 h posttransplant is an independent predictor of short-term kidney function.

Impact of intra-abdominal pressure on early kidney transplant outcomes

Increased intra-abdominal pressure (IAP) is common among post-surgical patients and may cause organ dysfunction. However, its impact after kidney transplantation on early postoperative complications and graft recovery remains unclear. We designed a prospective, observational cohort study to describe the prevalence and determinants of IAP, as well as its effect on delayed graft function, postoperative complications, and graft recovery. IAP was measured in 205 kidney transplant recipients every 8 h during the first 72 h after surgery using the urinary bladder technique. Intra-abdominal hypertension was defined as IAP ≥ 12 mmHg. Patients were followed for 6 months or until graft failure/death. Mean IAP was 12 ± 3.3 mmHg within the first 24 h. 78% of subjects presented with intra-abdominal hypertension during the first 72 h. Increased IAP was associated with higher renal resistive index [r = 0.213; P = 0.003] and lower urine output [r =  - 0.237; P < 0.001]. 72 h mean IAP was an independent risk factor for delayed graft function [OR: 1.31; 95% CI: 1.13-1.51], postoperative complications [OR: 1.17; 95% CI: 1.03-1.33], and absence of graft function recovery [HR for graft function recovery: 0.94; 95% CI: 0.88-0.99]. Increased IAP was highly prevalent after transplantation and was independently associated with delayed graft function, postoperative complications, and absence of graft function recovery. Routine IAP monitoring should be considered post-transplantation to facilitate early recognition of relevant complications.

Current Status of Ultrasound in Acute Rejection After Renal Transplantation: A Review with a Focus on Contrast-Enhanced Ultrasound

Renal transplantation has developed into the best treatment for end-stage renal disease, but severe cases can even lead to loss of renal allograft function due to rejection and complications caused by surgical procedures. If a series of postoperative complications can be reduced or even avoided, the quality of life of recipients will be significantly improved. Acute rejection in a transplanted kidney is one of the main complications after renal transplantation. Early detection and diagnosis will significantly help the prognosis of transplanted kidney patients. As a seminal morphological and hemodynamic examination method, ultrasound can monitor the tissue structure and arteriovenous blood flow of the transplanted kidney, providing information on the transplanted kidney’s gross shape and blood perfusion. Ultrasound is a commonly used detection method after renal transplantation. At present, two-dimensional ultrasound, color Doppler ultrasound, three-dimensional ultrasound, and contrast-enhanced ultrasound have been applied in the monitoring of complications after renal transplantation. Contrast-enhanced ultrasound, as a non-invasive, radiation-free, and easy to perform examination technique, can qualitatively and quantitatively evaluate the microcirculatory blood perfusion of the transplanted kidney. It can reflect the function of the transplanted kidney more objectively and sensitively. In recent years, contrast-enhanced ultrasound has attracted attention as a new technology that can quantitatively monitor the transplanted kidney’s microcirculation perfusion. A large number of studies have shown that contrast-enhanced ultrasound has unique advantages in monitoring acute rejection after renal transplantation compared with other imaging methods, providing a reliable basis for clinical intervention. This article reviews the current status of and recent research on contrast-enhanced ultrasound in acute rejection after renal transplantation.

Early urological complications after kidney transplantation: An overview

Urological complications, especially urine leaks, remain the most common type of surgical complication in the early post-transplant period. Despite major advances in the field of transplantation, a small minority of kidney transplants are still being lost due to urological problems. Many of these complications can be traced back to the time of retrieval and implantation. Serial ultrasound examination of the transplanted graft in the early post-operative period is of key importance for early detection. The prognosis is generally excellent if recognized and managed in a timely fashion. The purpose of this narrative review is to discuss the different presentations, compare various ureterovesical anastomosis techniques and provide a basic overview for the management of post-transplant urological complications.

Outcomes of pancreas retransplantation in patients with pancreas graft failure

Background

Pancreas retransplantation is still a controversial option after loss of a pancreatic graft. This article describes the experience of pancreas retransplantation at a high‐volume centre.

Methods

This was a retrospective observational study of all pancreas retransplantations performed in a single centre between 1997 and 2013. Pancreatic graft loss was defined by the return to insulin dependence. Risk factors for graft loss as well as patient and graft survival were analysed using logistic and time‐to‐event regression models.

Results

Of 409 pancreas transplantations undertaken, 52 (12·7 per cent) were identified as pancreas retransplantations. After a median follow‐up of 65·0 (range 0·8–174·3) months, 1‐ and 5‐year graft survival rates were 79 and 69 per cent respectively, and 1‐ and 5‐year patient survival rates were 96 and 89 per cent. During the entire follow‐up, 22 grafts (42 per cent) were lost. Patient survival was not associated with any of the donor‐ or recipient‐related factors investigated. Five‐year graft survival was better after simultaneous kidney–pancreas retransplantation than pancreas retransplantation alone: 80 per cent (16 of 20) versus 63 per cent (20 of 32) (P = 0·226). Acute rejection (odds ratio 4·49, 95 per cent c.i. 1·59 to 12·68; P = 0·005) and early surgical complications (OR 3·29, 1·09 to 9·99, P = 0·035) were identified as factors with an independent negative effect on graft survival.

Conclusion

Pancreas retransplantation may be considered for patients whose previous graft has failed.

Good outcome in selected patients

Vascular rejection in renal transplant: Diagnostic value of contrast-enhanced ultrasound (CEUS) compared to biopsy

BACKGROUND

Despite of the more potent immunosuppressive medication, vascular rejection is still a major issue after renal transplantation. Renal biopsy is the gold standard diagnostic to evaluate acute and chronic allograft rejection. As it is an invasive diagnostic there is the risk of complications like haematoma, arteriovenous fistulas, active bleeding or infection. Contrast-enhanced ultrasound is a non-invasive imaging modality that allows visualising renal transplant perfusion.

OBJECTIVE

To analyse the sensitivity and specificity of contrast-enhanced ultrasound (CEUS) compared to biopsy as gold standard in diagnosing vascular rejection in renal transplant patients.

METHODS

A total of 57 renal transplant recipients with poor renal allograft function with initial diagnostic imaging between 2006 and 2017 were included in the study. Clinical data and imaging studies were analysed retrospectively. The diagnostic accuracy of CEUS in diagnosing vascular rejection of the renal transplant was compared to renal biopsy as gold standard. Out of 57 patients 7 patients showed signs of vascular rejection in biopsy. In 6 out of these 7 patients CEUS described irregularities in renal perfusion suspicious of vascular rejection.

RESULTS

CEUS showed a sensitivity of 85.7%, a specificity of 100%, a positive predictive value (PPV) of 100%, and a negative predictive value (NPV) of 98.0%.

CONCLUSIONS

CEUS is a safe, non-nephrotoxic imaging modality for the initial imaging of renal transplant recipients with elevated kidney function parameters suspicious of vascular rejection. Compared to renal biopsy as gold standard CEUS shows a high specificity and PPV in detecting signs of vascular rejection. Since sub-types of vascular rejection with cellular and humoral components with greater risk for allograft loss have been described renal biopsy is inevitable in these cases.

Contrast-enhanced ultrasound (CEUS) as a new technique to characterize suspected renal transplant malignancies in renal transplant patients in comparison to standard imaging modalities

BACKGROUND

Renal transplant patients have a higher risk for malignancies of the renal transplant. In most cases suspected renal malignancies will be detected during the regular ultrasound follow-up and will require cross-sectional imaging to rule out a malignant aetiology. But it is well known that contrast agents for computed tomography or magnetic resonance imaging are critical in patients with limited renal function.

OBJECTIVE

This study aims to compare the sensitivity and specificity of contrast-enhanced ultrasound (CEUS) and gold standard imaging modalities in characterizing suspected renal transplant malignancies in renal transplant patients.

METHODS

A total of 22 renal transplant patients who underwent one or more CEUS examinations and at least one standard imaging modality (CT or MRI) between 2005 and 2017 were included. Patient ages ranged from 28.2 years to 74.6 (mean age 55.7 years; SD±13.0 years). CEUS of 22 patients was correlated with a standard imaging modality, CT (15 out of 22) or MRI (7 out of 22), serving as gold standard.

RESULTS

CEUS showed a sensitivity of 100%, a specificity of 94.4%, a positive predictive value (PPV) of 80%, and a negative predictive value (NPV) of 100%.

CONCLUSIONS

CEUS is an eligible method to help characterizing suspected renal malignancies in renal transplant patients compared to the well-established imaging modalities CT and MRI. As an imaging modality with no nephrotoxic effects CEUS can be used repeatedly even in patients with limited renal function.

The diagnostic value of contrast-enhanced ultrasound (CEUS) as a new technique for imaging of vascular complications in renal transplants compared to standard imaging modalities

BACKGROUND

Vascular complications in renal transplant patients are a well-known issue in post transplant patient care. If malfunctioning of the renal transplant is suspected to be caused by vascular complications an early diagnosis and therapy is required to maintain the renal transplant. Computed tomography (CT), digital substraction angiography (DSA) and radioisotope renography are the gold standard imaging modalities to diagnose vascular complications.

OBJECTIVE

To analyse the sensitivity and specificity of contrast-enhanced ultrasound (CEUS) in comparison to the standard imaging modalities CT, DSA and radioisotope renography in the diagnosis of vascular complications in renal transplant patients.

METHODS

A total of 33 renal transplant recipients with elevated kidney function parameters with initial diagnostic imaging between 2006 and 2017 were included in the study. The imaging studies and clinical data were analysed retrospectively. The diagnostic accuracy of CEUS was compared to CT, DSA and renal scintigraphy respectively which are classified as gold standard for diagnosis of vascular complications in renal transplant patients. Out of 23 patients 15 patients showed vascular complications in CT, DSA or radioisotope renography and in 15 out of 15 patients CEUS detected the vascular complication.

RESULTS

CEUS showed a sensitivity of 100%, a specificity of 66.7%, a positive predictive value (PPV) of 71.4%, and a negative predictive value (NPV) of 100%.

CONCLUSIONS

CEUS is a non-nephrotoxic and safe method for the initial imaging of vascular complications in renal transplant recipients. Compared to the gold standard imaging modalities CT, DSA and radioisotope renography CEUS shows a high sensitivity and NPV in detecting vascular complications. In cases with suspected stenosis of the transplant renal artery additional DSA might be needed.