| Abstract|| |
Background: Renal dysfunction in allograft transplant is common and its assessment is done using Revised Banff '97 working classification, which is the accepted formulation for the evaluation of histological appearance of renal allograft biopsies. The nonrejection category under the Banff working classification of renal allograft pathology forms a large group resulting in allograft dysfunction. Aim: To evaluate the spectrum of histopathological changes seen in renal allograft dysfunction. Materials and Methods: A total of 119 renal biopsies were studied over 10 years presenting with renal allograft dysfunction from a tertiary center in North India. Results: Majority of the biopsies were in the nonrejection category (47.1%), which included few cases of acute tubular necrosis (25.2%), cyclosporine nephrotoxicity (16%), infections (10.9%), and thrombotic microangiopathy (3.4%). The second largest category in our study was acute/active cellular rejection group (31.9%), which displayed moderate to severe tubulitis, mononuclear cell infiltrate in the interstitium, and vasculitis. Antibody-mediated rejection cases were seen in 28.6% of the renal biopsies followed by chronic allograft nephropathy cases (12.6%) showing features of tubular atrophy and interstitial fibrosis. Borderline changes with features of mild tubulitis contributed to 7.6% of the biopsies. The smallest group comprised of only 4.2%, which were within normal histological limits. Conclusion: Timely accurate diagnosis of renal allograft dysfunction is essential for prompt, effective management of renal transplant patients. Thus, nonrejection pathology forms a significant cause of renal dysfunction in patients with renal allograft transplantation.
Keywords: Acute tubular necrosis, cyclosporine nephrotoxicity, infections, nonrejection
|How to cite this article:|
Philip KJ, Calton N, Pawar B. Nonrejection pathology of renal allograft biopsies: 10 years experience from a tertiary care center in north India. Indian J Pathol Microbiol 2011;54:700-5
|How to cite this URL:|
Philip KJ, Calton N, Pawar B. Nonrejection pathology of renal allograft biopsies: 10 years experience from a tertiary care center in north India. Indian J Pathol Microbiol [serial online] 2011 [cited 2020 Aug 13];54:700-5. Available from: http://www.ijpmonline.org/text.asp?2011/54/4/700/91498
| Introduction|| |
Renal dysfunction in transplant patients is assessed by renal biopsy. Banff working classification for renal allograft pathology is the standard classification and widely used for evaluation of renal allograft dysfunction since its formulation in August 1991.  The nonrejection category forms a large group comprising of causes resulting in allograft dysfunction such as acute tubular necrosis (ATN), drug toxicity secondary to calcineurin inhibitors (cyclosporine, tacrolimus), infections such as viral, bacterial, and fungal etiology, de novo glomerulonephritis, and recurrent renal diseases. The aim of this study was to evaluate every renal allograft biopsy indicated for clinically deteriorating renal function in a tertiary care centre conducted over 10 years to understand various nonrejection causes of renal allograft dysfunction.
| Materials and Methods|| |
All the renal allograft biopsies that were received in our tertiary centre in the department of Pathology were included in this 10 years study period.
Routine hematoxylin and eosin (H and E), periodic acid Schiff (PAS), and silver methenamine stains were used. Immunofluorescence (IF) examinations of the biopsies were done as required. Diagnosis was made according to the criteria as per the Revised Banff '07 classification. ,
| Results|| |
This study is a histopathology review of 119 renal allograft biopsies carried out on patients that underwent renal transplant at this hospital. According to the latest Revised Banff '97 schema, a large group of nonrejection causes were identified, which were causes of renal dysfunction in transplant recipients. The details of the various categories under the Revised Banff '97 schema are mentioned in [Table 1]. We found that 41.4% of the renal biopsies showed histological features involving more than one group.
|Table 1: Renal biopsy findings according to the revised Banff '97 diagnostic criteria|
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There were 56 patients (47.1%) who had changes in the kidney biopsy that were nonrejection related; the average age in the transplant patients was 40.8 years (ranging from 18 to 62 years).The majority of the transplant patients were males (82.0%) with a male: female sex ratio of 4.6:1. The renal biopsy was done as early as few hours after engraftment to 15 years post transplant. Majority of the renal allograft biopsies were done within few months following transplantation (26.2%), mainly within 1 month.
Renal dysfunction with serum creatinine levels ranging from 1.7 to 8.2 mg/dl with a mean of 4.5 mg/dl was seen in all the cases. The blood urea levels ranged from 40.6 to 271 mg/dl with a mean of 129.8 mg/dl. All our transplant patients were on immunosuppressant drugs mainly cyclosporine based, the levels of which were monitored.
The details of the various entities under the nonrejection category of renal allograft biopsies are mentioned in [Table 2].
Acute Tubular Necrosis
Thirty cases of ATN (25.2%) were identified forming the largest group in the nonrejection category. The period from engraftment to renal biopsy ranged from 4 days to 14 years. Fourteen of the cases were within the first 3 months following transplantation (11.8%). Histologically, the renal biopsy showed frank coagulative type of tubular necrosis with desquamation of the cells in to the tubular lumen. There was dense mononuclear cell infiltrate in the interstitium, and few dilated tubules.
ATN was associated with seven cases of acute cellular rejection (ACR), five cases of antibody-mediated rejection (AbMR) (of which three were of acute AbMR and two were of chronic AbMR), two cases of polyoma viral infection, two cases of cyclosporine toxicity, two cases of borderline changes, and one case of chronic allograft nephropathy (CAN).
Cyclosporine toxicity was seen in 19 cases (16%) forming the second largest group. The period between the engraftment and the time of biopsy was ranging from 2 months to 7 years. Out of 19 patients diagnosed with cyclosporine toxicity, 10 of the patients had cyclosporine levels within the therapeutic range. Cyclosporine was continued in these 10 patients, but with lower doses after confirmation on biopsy. Four of the patients had high cyclosporine levels; hence, cyclosporine was stopped and started them on sirolimus. Five of the patients were lost on follow-up; hence, change of immunosuppressant could not be implemented. There were no follow-up renal biopsies performed to see for change in cyclosporine toxicity related renal morphology after stoppage of CSA/lowering the drug levels of CSA.
The diagnosis was based on the morphological features of mesangial expansion of the glomeruli, isometric tubular vacuolation, and arteriolar hyalinosis (ah). Arteriolar hyalinosis is an important manifestation, which was graded based on the degree of PAS positivity. Mild to moderate PAS positive hyaline arteriolar thickening (ah1) was seen in 6.7% of the cases, while 1.7% of the cases showed severe PAS positive hyaline thickening (ah3) in many arterioles. Only 0.8% of the cases showed moderate PAS positive hyaline thickening in more than one arteriole (ah2). Among the other features of cyclosporine toxicity, tubular atrophy (ct) was seen in six cases (5%), three of which had coexisting features of CAN. Stripped interstitial fibrosis (ct) was seen in 12 cases of cyclosporine toxicity out of which 5 cases had coexisting features of CAN. Two of the cases of cyclosporine toxicity showed features of fibrointimal thickening (cv). There was one case of nodular hyalinosis of the glomeruli.
There was evidence of infection in 13 of the allograft biopsies (10.9%), polyoma viral infection forming the largest infective group in the nonrejection category. There are nine cases of polyoma viral infection with an age spectrum ranging from 31 to 55 years (mean of 47.3 years) and M:F ratio of 8:1. The post transplant period from engraftment to time of biopsy varied from 2 weeks to 6 years. Histologically, all the nine renal biopsies showed basophilic homogenous intranuclear inclusions in the nuclei of the renal tubular epithelial cells [Figure 1], associated interstitial mononuclear cell infiltrate was seen in areas where tubular cells were infected by the polyoma virus.
|Figure 1: Section shows intranuclear basophilic polyoma viral inclusions within the tubular epithelium (H and E, ×400)|
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The patients diagnosed with polyoma viral infection had associated type III ACR (one case), grade I acute AbMR (one case), chronic AbMR (two case), ATN (two cases), CAN (one case), and thrombotic microangiopathy (TMA) (one case).
There were three cases of tubercular infection of which one was a 25-year-old female patient with a 15-year-old renal allograft presenting with deranged renal parameters. The microscopic examination of the urine showed marked sterile pyuria. Renal biopsy revealed presences of small necrotic areas with epithelioid cell collection forming granulomas surrounded by lymphocytic infiltrate. The urine TB PCR was positive for tuberculosis. She was started on standard anti tubercular drugs thereafter, and her condition and renal functions improved along with renal parameters. Two of our patients diagnosed with tubercular infection had associated type IB and type IIB ACR, respectively.
A young 20-year-old individual diagnosed to have fungal infection presented 3 months postrenal transplant period with high grade fever and hematuria showing signs of acute rejection with declining renal functions. Nephrectomy was done. The allograft kidney was markedly enlarged and edematous. The external surface showed dark brown hemorrhagic areas and tiny grayish-white pyaemic areas. Cut section showed yellowish necrotic areas. Normal cortex and medulla could not be identified. Histologically, there was extensive cortical necrosis, interstitial inflammation with microabscesses. There were numerous broad, aseptate branching fungal hyphae in the large areas of necrosis within the walls and lumen of blood vessels [Figure 2]. The urine culture and wound culture grew Mucor fungal species. The patient succumbed to infection.
|Figure 2: Section shows few black broad, short, aseptate, nonbranching hyphae with features of angioinvasion (silver methenamine, ×400)|
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Five cases of TMA were diagnosed. The time between engraftment and time of renal biopsy was ranging from 1 week to 6 months. Two of the renal biopsies showed double contouring of the glomerular capillaries with platelet thrombi in few of them [Figure 3]. In addition, mesangial widening, tuft necrosis of the glomeruli, and splitting of the internal elastic lamina of the vessel with vasculitis were seen in one of the cases. The arterioles also showed platelet thrombi. Other three cases, in addition, also had histological features of polyoma viral infection, cyclosporine toxicity, and moderate atherosclerosis. TMA was associated with type II ACR (one case), acute AbMR (one case), and chronic AbMR (one case).
|Figure 3: Section shows a glomerulus with platelet microthrombi and double contouring of the capillary basement membrane (H and E, ×400)|
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A single case of recurrent IgA nephropathy was detected in a 50-year-old male, also a known case of hepatitis B and C infection. The time interval between the renal engraftment and that of the biopsy was 12 years.
The renal biopsy showed mild mesangial widening (mm1) in the glomeruli and severe tubular atrophy (ct3). IF studies showed IgA deposits (3+) granular capillary wall and IgM mesangial deposits (2+).
De novo Glomerulonephritis
In our study, there was a single case of de novo glomerulonephritis related to focal segmental glomerulosclerosis of a 38-year-old male patient with a 1-year-old renal allograft, evaluated for deranged renal allograft function. The renal biopsy showed segmental sclerosis of the glomeruli characterized by localized hypertrophy and hyperplasia of the epithelial cells overlying the area of sclerosis. There was interstitial stripped fibrosis (ci2). In addition, polyoma viral infection and cyclosporine toxicity related changes were also seen.
| Discussion|| |
Renal allograft dysfunction among transplant recipients is common and its evaluation is done using renal biopsy to understand the various morphological changes using Revised Banff '97 working classification, which is the widely accepted classification for categorizing various rejection and nonrejection causes of allograft dysfunction. 
In our study, nonrejection category formed the largest group (47.1%) of which ATN (26.1%) comprised the main group. Jain et al. and Mazzali et al. found smaller groups (27.5% and 19.5% respectively) of ATN cases in their study. We found that 11.8% of the patients had undergone renal biopsy within 3 months of post transplant period, which was almost comparable to the findings of Kon et al. (14.1%).  Mazzali et al. found that most of the renal biopsies were performed within 2 months post transplant period. In our study, there was associated cyclosporine toxicity in two cases of ATN, while Solez et al. identified cyclosporine toxicity associated changes in 5 of the 12 cases of ATN.
The second largest group in the nonrejection category in our study was cyclosporine toxicity (16%). Unlike our study, Solez et al. and Randhawa et al. found a larger group of cyclosporine nephrotoxicity (42.9% and 88%, respectively) owing to their study population, which comprised largely of cyclosporine toxicity related transplant recipients. Our study showed an age spectrum of 23-52 years among those with cyclosporine toxicity which was similar to findings of Randhawa et al. (23-57 years). Arteriolar hyalinosis and stripped interstitial fibrosis formed important histological findings in the diagnosis of cyclosporine toxicity, which was similar to the morphological findings shown by Solez et al. and Randhawa et al.
Infection-related renal allograft biopsies formed the third largest in the nonrejection category (10.9%). Polyoma viral infection formed the largest among the infection (7.6%). Hirsch et al. and Singh et al. identified similar findings in their studies (6.4% and 7.3%, respectively). There was an associated feature of ATN in two cases as was found by Nickeleit et al. in their study.
We found three cases of renal allograft tuberculosis (2.5%). All three patients showed epithelioid cell collection forming granulomas with areas of necrosis. They improved on antitubercular therapy. Sakhuja et al. found incidence of tuberculosis in 36 out of 305 patients followed up over 8 years (11.8%), while Meehan et al. in his study on 1574 renal allograft biopsies identified three cases of granulomatous tubulointerstitial nephritis in the renal allograft (0.6%). Al Soub et al. presented a case report of a 50-year-old male individual with a 10 months old renal allograft who developed progressive declining renal functions with septicemia leading to nephrectomy. The allograft nephrectomy specimen showed features of caseating granulomatous inflammation with chronic rejection. Patient expired 3 months later following disseminated tuberculosis to the bone marrow, pleura, lung, and heart. 
In this study, a 20-year-old male presented with mucormycosis-related allograft rejection who underwent nephrectomy, which revealed large fungal hyphae scattered all over the parenchyma (forming abscesses) with evidence of angioinvasion. Ahmadpour et al. found a total of 22 patients who had post transplant renal complication with mucormycosis out of 7132 renal transplant recipients. Most of the cases were identified within 1 year after renal transplantation (n = 13). Radha et al. reported a case of mucormycosis that underwent nephrectomy for worsening renal functions with uneventful recovery on antifungal therapy. The allograft nephrectomy showed dense neutrophilic infiltrate with focal giant cell reaction, broad nonseptate branching fungal hyphae suggestive of mucor, which was confirmed on culture.
Our patient had exclusive renal involvement of fungal infection. Ahmadpour et al. found that the major forms of the disease were rhinocerebral, pulmonary, cutaneous, and disseminated. Overall mortality was 59%, particularly in those with pulmonary infection (100%).
In the present study, TMA formed the fourth largest group (4.2%) among nonrejection category. Liapis  and Zarifian et al. also identified TMA-related allograft rejection (0.7%-14%, respectively). This study showed association with CAN (Grade I), one case each with chronic AbMR, with polyoma viral infection, cyclosporine toxicity, moderate atherosclerosis, and acute AbMR, respectively. Liapis  found nine cases of TMA secondary to CsA toxicity, two had CMV infection proved by positive blood CMV PCR, one had residual diffuse intravascular coagulation from donor, one had acute vascular rejection associated with thrombosis, one was on sirolimus therapy, one had coincidental renal artery thrombosis, and one had recurrent hemolytic uremic syndrome (HUS). Zarifian et al found four biopsies of TMA secondary to acute CsA toxicity.
All five cases in this study showed enlarged glomeruli with presence of platelet thrombi in the arterioles and capillaries with associated mononuclear cell interstitial inflammation. These findings were consistent with those shown by Liapis and Zarifian et al..,
Qutube et al. presented a 48-year-old female patient with deteriorating renal function having a 1-week-old renal allograft. She was positive for lupus anticoagulant test with high titres of anticardiolipin antibodies and was diagnosed with antiphospholipid antibody syndrome of unknown etiology. Her renal biopsy showed features of TMA in glomerular capillary with no evidence of ACR. Among the autoimmune mechanisms, SLE is a well-known cause for TMA in allograft kidneys, which could have further worsened with CsA administration as in this case. 
This study had one case of de novo glomerulonephritis (0.8%) related to focal segmental glomerulonephritis (FSGS). Meehan et al., Gough et al., and Hariharan et al. also found similar results on de novo glomerulonephritis ranging from 0.6% to 2.5%. In this study, the period between the engraftment period and time of biopsy was 1 year and similar observations were shown by Gough et al. and Hariharan et al. However, Meehan et al. showed a longer period of 6-25 months after transplantation.
This study showed focal segmental glomerulosclerosis in five of the glomeruli out of total number of 18 glomeruli (27.8%) but Meehan et al. demonstrated segmental sclerosis of the glomeruli ranging from 14% and even going up to 100% at the time of biopsy. The focal segmental sclerosis is a progressive disease and it advances to involve more glomeruli before reaching end stage renal disease. Since the present study had only one case of de novo glomerulonephritis, no statistical significance could be drawn.
In this study, a single case of recurrent IgA nephropathy (IgAN) was identified (0.8%) who presented clinically as nephrotic syndrome in the post transplant period (12 years). Bumgardner et al., Kim et al., Ohmacht et al., Wang et al., Gough et al., and Odum et al. demonstrated few cases of recurrent renal disease (0.7%, 1.2%, 2.0%, 5.8%, 5.9%, 58.6%, respectively). Gough et al., Bumgardner et al., and Kim et al. showed the mean post transplant graft period to range from 12 to 60 months, although the period was as high as 164 months. Bumgardner et al. and Kim et al. also found similar clinical features among the recurrent IgAN cases ranging from 29 to 44%.
In our study, serum creatinine levels were elevated, which was similar to the biochemical recordings (2.9 mg/dl) by Bumgardner et al. Ohmacht et al. and Wang et al. showed lower levels of serum creatinine [1.4 mg/dl (124μmol/L) and 1.93 mg/dl] as compared to our study. We found mesangial IgA deposits (3+) in the IF studies, which was comparable to IF findings shown by Kim et al and Odum et al.
In conclusion, making accurate diagnosis of various nonrejection-related causes of renal allograft dysfunction such as ATN, infections, drug-induced nephrotoxicity, and TMA is pertinent for better management of transplant individuals to improve the graft survival period.
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Kandathil Joseph Philip
Department of Pathology, Christian Medical College and Hospital, Punjab, Ludhiana - 141 008
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]