Persistent proteinuria as a prognostic factor for determining long-term graft survival in renal transplant recipients

Immune monitoring of allograft status in kidney transplant recipients

Kidney transplant patients require careful management of immunosuppression to avoid rejection while minimizing the risk of infection and malignancy for the best long-term outcome. The gold standard for monitoring allograft status and immunosuppression adequacy is a kidney biopsy, but this is invasive and costly. Conventional methods of allograft monitoring, such as serum creatinine level, are non-specific. Although they alert physicians to the need to evaluate graft dysfunction, by the time there is a clinical abnormality, allograft damage may have already occurred. The development of novel and non-invasive methods of evaluating allograft status are important to improving graft outcomes. This review summarizes the available conventional and novel methods for monitoring allograft status after kidney transplant. Novel and less invasive methods include gene expression, cell-free DNA, urinary biomarkers, and the use of artificial intelligence. The optimal method to manage patients after kidney transplant is still being investigated. The development of less invasive methods to assess allograft function has the potential to improve patient outcomes and allow for a more personalized approach to immunosuppression management.

Membranous Nephropathy Posttransplantation: An Update of the Pathophysiology and Management

Membranous nephropathy (MN) is a common cause of nephrotic syndrome after transplantation and is associated with an increased risk of allograft loss. MN may occur either as a recurrent or as a de novo disease. As in native kidneys, the pathophysiology of the MN recurrence is in most cases associated with antiphospholipid A2 receptor antibodies. However, the posttransplant course has some distinct features when compared with primary MN, including a lower chance of spontaneous remission and a greater requirement for adjuvant immunosuppressive therapy to induce complete remission. Although the efficacy of rituximab in primary MN is now well established, no randomized studies have assessed its effectiveness in MN after transplant, and there are no specific recommendations for the management of these patients. This review aims to synthesize and update the pathophysiology of posttransplant MN, as well as to address unsolved issues specific to transplantation, including the prognostic value of antiphospholipid A2 receptor, the risk of living-related donation, the link between de novo MN and rejection, and different therapeutic strategies so far deployed in posttransplant MN. Lastly, we propose a management algorithm for patients with MN who are planning to receive a kidney transplant, including pretransplant considerations, posttransplant monitoring, and the clinical approach after the diagnosis of recurrence.

High-grade proteinuria as a cardiovascular risk factor in renal transplant recipients

BACKGROUND

Proteinuria is a marker of graft damage and is closely associated with a higher risk of morbidity, mortality, and cardiovascular disease in kidney transplant recipients (KTRs). Arterial stiffness is a well-known predictor of vascular calcification and systemic arteriosclerosis. In our study, we aimed to investigate the association between proteinuria and graft/patient survival and to determine whether proteinuria may be a predictor for cardiovascular disease in our KTR population.

METHODS

Ninety KTRs (31 women; age, 38.7 ± 11 years, with 45.9 ± 9.6 months post-transplantation period) with normal graft functions in the 3 to 5 years of the post-transplantation period were enrolled. All patients were evaluated for their standard clinical (age, sex, and duration of hemodialysis) parameters. High-grade proteinuria was defined as proteinuria >500 mg/day in the 24-hour urine collection. All patients were evaluated by means of pulse-wave velocity (PWV) measurement at the initiation of the study.

RESULTS

Patients were divided into 2 groups: group 1 (high-grade proteinuria) patients with ≥500 mg/24 hours (n = 30) and group 2 (low-grade proteinuria) patients with <500 mg/24 hours (n = 60). High-grade proteinuria was correlated with higher PWV measurements and lower estimated glomerular filtration levels. Proteinuria appears to precede the elevation of serum creatinine and thus may be a useful marker of renal injury and may also be a contributing factor on deterioration of the graft.

CONCLUSIONS

High-grade (>500 mg/day) proteinuria in KTRs is strongly associated with poor graft survival and increased risk of cardiovascular events. In our study, we proved the significant difference between high-grade and low-grade proteinuric patients, and we suggest 500 mg/day as the threshold of proteinuria in KTR population.

Proteinuria 1 year after renal transplantation is associated with impaired graft survival in children

BACKGROUND

Proteinuria is a common manifestation of chronic kidney disease (CKD), and there is a high incidence of CDK and its complications following renal transplantation. However, little data are available on the association between proteinuria and graft/patient survival in the paediatric transplant population. The primary aim of this study was to investigate the associations between posttransplant proteinuria and graft/patient survival in children after renal transplantation.

METHODS

In this retrospective study, we screened all 91 children receiving renal allografts at a single institution between 1997 and 2007. The inclusion criteria were a functioning graft at 1 year posttransplant, data availability and no recurrence of focal-segmental glomerulosclerosis. The final cohort included 75 patients. Proteinuria was considered to be pathologic if the urinary protein/creatinine ratio was >30 mg/mmol. Donor and recipient characteristics, data on proteinuria, estimated glomerular filtration rate (eGFR) and rejection episodes were analysed. The most recent of the biopsies performed during the follow-up after 1 year posttransplant were analysed separately in the proteinuric group and the non-proteinuric group.

RESULTS

Proteinuria at 1-year posttransplant was pathologic in 35 % of patients. The 5-year graft survival rate was significantly lower in the proteinuric group than in the non-proteinuric group (77 vs. 100 %; p < 0.001). Proteinuria at 1 year posttransplant was associated with reduced long-term graft survival independent of other risk factors, including decreased eGFR or episodes of acute corticosensitive and corticoresistant rejection. The most frequent histologic finding in the proteinuric group was chronic rejection. There was no significant difference in the 5-year patient survival rate between the proteinuric group and the non-proteinuric group.

CONCLUSION

This study emphasizes the importance of proteinuria as a prognostic factor of renal allograft survival in children.

Posttransplantation proteinuria: an approach to diagnosis and management

Proteinuria is a common problem encountered in the treatment of renal transplant recipients, occurring in up to 45% of patients. Proteinuria from native kidneys falls rapidly after renal transplantation, and persistent or worsening proteinuria is usually indicative of allograft pathology. Biopsy studies of transplant patients with proteinuria have confirmed that transplant-specific diagnoses (transplant glomerulopathy, interstitial fibrosis and tubular atrophy, and acute rejection) are more commonly found than other proteinuric conditions, such as glomerulonephritis. As in the nontransplant setting, proteinuria is associated with worse clinical outcomes, including an increased risk for death, cardiovascular events, and graft loss. Blockade of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers will reduce proteinuria, but the long-term effect of these medications on patient and graft survival remains unknown.

Advanced glycation end products in kidney transplant patients: a putative role in the development of chronic renal transplant dysfunction

Chronic renal transplant dysfunction is one of the leading causes of graft failure in kidney transplantation. A complex interplay of both alloantigen-related and alloantigen-unrelated risk factors is believed to underlie its development. We propose that advanced glycation end products (AGEs) are involved in the development of chronic renal transplant dysfunction. AGE formation is associated with different alloantigen-unrelated risk factors for chronic renal transplant dysfunction, such as recipient age, diabetes, proteinuria, hypertension, and hyperlipidemia. In vitro studies have shown that AGEs induce the expression of various mediators associated with chronic renal transplant dysfunction. Furthermore, AGE-induced renal damage has been found in multiple experimental studies. This renal damage shows similarity to the damage found in chronic renal transplant dysfunction. Together, several lines of evidence support a role of AGEs in the development of chronic renal transplant dysfunction and suggest that preventive therapy with AGE inhibitors may be helpful in preserving renal function in transplant recipients.

Effect of mycophenolate mofetil on kidney graft function and body weight in patients with chronic allograft nephropathy

BACKGROUND

Chronic allograft nephropathy (CAN) is the most common cause of late graft loss. A beneficial effect of mycophenolate mofetil (MMF) on CAN was observed, although, due to the loss of body weight (BW) under MMF, serum creatinine (sCr) and reciprocal sCr may be unsuitable markers of graft function.

METHODS

In 17 kidney transplant patients with CAN, azathioprine (Aza) was replaced by MMF. The remaining therapy was not changed; specifically, the cyclosporine (CsA) dose was not decreased. The mean values and regression coefficients of reciprocal sCr, CCr, urinary creatinine excretion (uCr x V), proteinuria, BW, blood pressure (BP), serum cholesterol (sChol), and serum triglycerides (sTG) versus time were analyzed 12 months before and after institution of MMF by a paired-comparison t test.

RESULTS

The mean regression coefficient of reciprocal sCr differed significantly before and after conversion to MMF (mean -0.01 +/- 0.01 vs +0.012 +/- 0.029 mg/dL per month), suggesting improved graft function. However, the mean values of BW (74 +/- 15 vs 71 +/- 15 kg, P <.001) and uCr x V (1152 +/- 321 vs 1065 +/- 266 mg per 24 hours, P=.0897) decreased, making the increase in CCr less significant (mean -1.16 +/- 2.69 vs 0.40 +/- 1.79 mL/min per month, P <.05). BP, sChol, sTG, and proteinuria before and after conversion did not differ significantly. Among patients with long-term stable graft function at 36.5 +/- 16.9 months after conversion to MMF there was an almost significant improvement in renal protein excretion.

CONCLUSIONS

MMF improved graft function, although this effect was overestimated using reciprocal sCr. Other risk factors, such as BP, sChol, and sTG, showed no significant differences, suggesting that MMF accounted for the improvement in CAN. The course of proteinuria under MMF seems to be of prognostic significance.

Post-transplant nephrotic syndrome: A comprehensive clinicopathologic study

BACKGROUND

Post-transplant (Tx) nephrotic syndrome (NS) is not well defined.

METHODS

Seventy-four renal transplant recipients with NS were studied.

RESULTS

Biopsies showed chronic allograft nephropathy (CAN) in 31 patients; recurrent glomerular disease (GN) in 15, de novo GN in 18, and undetermined GN in 9. NS developed 0.25 to 384 months post-Tx and was treated with angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB) in 18 patients; calcium channel blockers in 25; or both drugs in 31. NS remitted in 24% of cases 2 to 28 months after onset, and this persisted in all except 3 patients. The remission rate was lowest (9%) for CAN and highest (47%) for de novo GN. Compared with persistent NS, those with remission showed higher prevalence of de novo GN (53% vs. 17%), lower prevalence of CAN (18% vs. 50%), earlier onset of NS (39 vs. 59 months), lower serum SCr at onset (2.3 vs. 2.9 mg/dL), and higher incidence of treatment with ACE or ARB. The 5-year graft loss rates for CAN, recurrent and de novo GN were 57%, 36%, and 23%, respectively. Compared with the functioning grafts, the failed grafts showed higher prevalence of CAN (60% vs. 16%), lower prevalence of de novo GN (12% vs. 46%), earlier onset of NS (47 vs 65 months post-Tx), higher serum SCr at onset (3.3 vs. 2.0 mg/dL), lower prevalence of remission of NS (5% vs. 48%), and higher proteinuria at follow-up (5.1 vs. 2.5 g/day). Graft survival improved with NS remission (88% vs. 18%).

CONCLUSION

Post-Tx NS displays distinctive clinicopathologic features with pathogenetic and therapeutic implications.

The remission of post-transplant nephrotic syndrome clinicopathologic characterization

Among 67 renal transplant recipients with nephrotic syndrome (NS), nine episodes were reversible in eight patients. Biopsies showed minimal-change disease, focal segmental membranous glomerulonephritis and acute glomerulitis, IgA nephropathy and acute glomerulitis or thrombotic microangiopathy, and chronic transplant nephropathy with or without acute glomerulitis. NS developed 1-4 months post transplant in the four patients with minimal-change disease, but later (33-151 months) in the others. At onset, serum creatinine was normal or elevated. Treatment included calcium-channel blockers, angiotensin-converting enzyme inhibitors, or both, together with routine antirejection therapy. Remission was achieved 4-12 months after onset, when renal function remained normal in four, improved in four, and worsened in one. At last follow-up, six patients still had remission and functional grafts. One lost graft to chronic transplant nephropathy while NS remained in remission. In the remaining patient, proteinuria, which was due to chronic transplant glomerulopathy unrelated to the initial minimal-change disease-associated NS, recurred 50 months post transplant. Remission of post-transplant NS is possible. It is often associated with minimal-change diseases and less frequently with other glomerular lesions, including acute glomerulitis. Reversible post-transplant NS does not have an adverse effect on the renal allografts.

De novo minimal change disease associated with reversible post-transplant nephrotic syndrome. A report of five cases and review of literature

Nephrotic syndrome (NS) is frequent in renal transplant recipients and may be related to a large variety of glomerular lesions. In some of these cases, the transplant biopsy showed no significant glomerular changes and the NS was reversible, but the primary renal disease was not minimal change disease (MCD), suggesting that MCD may develop de novo in renal transplant setting. Knowledge of this entity, however, is limited. Among 67 cases of post-transplant NS encountered in a 12-yr period, five were found to be associated with de novo MCD. A critical review of the literature revealed nine additional cases of de novo MCD. The data from these 14 cases show that patients with de novo MCD had a large variety of primary renal diseases but MCD or focal segmental glomerulosclerosis was not among them. Eight of the 14 transplanted kidneys (60%) were from living related donors, suggesting this as a risk factor. Nephrotic range proteinuria (3-76 g/d) developed immediately or shortly after transplantation (within 4 months for all reported cases, except for one at 24 months). The serum creatinine when NS was first diagnosed was normal or mildly elevated, but acute renal failure occurred in three patients. On biopsy, the glomeruli were normal or, more frequently, displayed mild, focal segmental mesangial sclerosis, hypercellularity, deposition of IgM/C3, or accumulation of mononuclear inflammatory cells in some glomerular capillaries. The tubulointerstitial compartment was normal in cases with normal renal function; displayed mild acute and/or chronic rejection that correlated with a mildly elevated serum creatinine; or showed acute changes including acute rejection, acute tubular necrosis, or acute cyclosporin A toxicity, which accounted for both acute renal failure at presentation and its subsequent reversibility. Under various treatments, including increased steroids, angiotensin converting enzyme inhibitors, calcium channel blockers and angiotensin receptor blockers, sustained remission of NS was achieved in 13 cases, within a year (0.5-12 months) in 10 and later (24, 34 and 98 months, respectively) in three. In the remaining case, the patient died of septic shock 2 months after transplantation. After remission of the NS, the grafts functioned well without or with minimal proteinuria for several years. De novo MCD has characteristic clinical and pathologic features. It represents an important but hitherto underemphasized cause of post-transplant NS, which is potentially reversible and does not adversely affect the renal transplants.