In Press, 1995, Transplantation Proceedings copyright by Appleton and Lange.

Diagnosis of Chronic Rejection Using Peritubular and Glomerular Capillary Lesions

Kunio Morozumi, Tadashi Oikawa, Michio Fukuda, Kenji Sugito, Oki Takeuchi, Akiyoshi Oda, Takao Fujinami, Asami Takeda* and Kazuharu Uchida**

Nagoya City University School of Medicine, Department of Medicine III, Nagoya Daini Red Cross Hospital, Division of Nephrology* and Transplantation**

 

Address for Correspondence:	Kunio Morozumi, M.D.
				c/o Nagoya City University School of Medicine
				Department of Medicine III
				1 Kawasumi Mizuho Nagoya Aichi
				467 Japan

				Tel:  +81-52-853-8660
				Fax:  +81-52-852-3796
			

Chronic graft failure is one of the most important renal allograft topics in the cyclosporine A(CyA) era. Graft survival rate after the second year of transplantation has not improved with the advent of the potent immunosuppressive agent CyA and other newer agents. The causes of chronic graft failure can be divided into two major categories, i.e., immunologic and nonimmunologic graft injury. We are well aware of the importance of the nonimmunologic causes of late renal graft loss, however, chronic rejection due to presumed immunologic causes seems to be the most important cause of chronic graft failure. CyA has tremendously changed clinico-pathological characteristics of both acute and chronic rejection. Morphological changes in renal allografts with chronic rejection using CyA were usually milder and less specific than those in the steroid azathioprine era. Furthermore, concomitant lesions of glomerulonephritis, chronic CyA nephrotoxicity and acute rejection frequently accompany chronic rejection. Therefore, two questions distress many pathologists and nephrologists: Which lesion, e.g., chronic rejection, chronic CyA nephrotoxicity or glomerulonephritis, is a key determinant of the long-outcome of the graft? Which changes are specific for the diagnosis of chronic rejection? This study was carried out to identify and determine the significance of lesions specific for chronic rejection in the CyA era.

 

Materials and Methods

From 1982 to December 1994, 173 biopsies from 119 patients (77 living donors; 42 cadaveric donors) were performed to evaluate the cause of deterioration of the grafts and/or proteinuria after the sixth month of transplantation using CyA or FK506 (tacrolimus) as a main immunosuppressive agent. The total number of graft biopsies was 547 from 373 patients (225 living donor, 148 cadaveric donor) during the same period. The basic strategy for immunosuppression has been double therapy using steroids and CyA of FK506 with strict blood level monitoring. So-called triple therapy using azathioprine or mizoribine in addition to the standard double therapy was adopted for the patients with frequent acute rejections of glomerulonephritis. Pathological diagnosis of each biopsy was confirmed by two pathologists using light, immunofluorescence and electron microscopy. The diagnostic criteria of chronic rejection was based on Banff classification [1] and that of glomerulonephritis on the World Health Organization classification. The diagnosis of chronic CyA nephrotoxicity was made by the criteria of Mihatsch et al. [2]. A total number of biopsies which contained more than 6 glomeruli and was suitable for chronic rejection study was 69 among 173 biopsies after the sixth month. Clinicopathologic study was carried out to clarify the long-outcome of chronic rejection under CyA treatment. The distribution of chronic rejection and a concomitant diagnosis and the outcome of the patients were also analyzed. A multi-splitting lesion of peritubular capillary basement membrane which was observed only by electron microscopy was focused upon as a sensitive and reliable indicator of chronic rejection. Glomerular capillary wall lesions showing duplication of basement membrane and subendothelial expansion without subendothelial deposits were also taken into account as a sensitive indicator of chronic rejection. Chronic rejection was divided to three subgroups, i.e. 1) Interstitial type, 2) Vascular type with transplant glomerulopathy (TPG) and 3) Vascular type without TPG by the light microscopic findings. The prevalence of peritubular and glomerular lesions in each subgroup chronic rejection was studied to find a new and more sensitive diagnostic indicator for chronic rejection from the view point of morphology.

 

Results

Clinico-pathologic characteristics of chronic rejection under cyclosporine A treatment.

The mean interval from operation to graft biopsy revealing chronic rejection was 1070 905 (SD) days. The mean value of serum creatinine and daily proteinuria at the time of graft biopsy were 2.8 1.2mg/dl and 1.8 2.4gram/day, receptively. The majority of the recipients with high serum creatinine over 3mg/dl lost graft function and half of the patients with lower serum creatinine than 2mg/dl also lost graft function until the recent follow-up point. The outcome of the recipients who developed profuse proteinuria exceeding 3.5 gram/day was worse than that of those with mild proteinuria. However, the graft function of the patients without proteinuria showed slowly deterioration of graft function.

Distribution of histologic diagnosis and the outcome of each group is shown in Table 1. Only 13 among 69 biopsies (19%) showed isolated chronic rejection without concomitant lesions. A concomitant chronic rejection and CyA associated arteriolopathy was the most common finding and occurred in 27 biopsies (39%). The incidence of a combined chronic and acute rejection (so-called acute on chronic rejection) was 33% and this was the second most frequent diagnosis. A combination of three or more diagnoses was not rare. The prognosis of the patients with a concomitant acute on chronic rejection was worse than that of the concomitant CyA arteriolopathy group.

Electron microscopic diagnosis of chronic rejection

1) multi-splitting of peritubular capillary wall
Figure 1 shows the typical circumferential multi-splitting of capillary basement membrane and infiltration of lymphocytes under the endothelium. The prevalence of peritubular capillary splitting was studied in each type of chronic rejection; 1) Interstitial type, 2) Vascular type with transplant glomerulopathy (TPG) and 3) Vascular type without TPG. Typical vascular chronic rejection and/or well developed chronic transplant glomerular lesions is easy to make a diagnosis, however, interstitial type is very difficult especially in patients with CyA nephrotoxicity. Table 2 shows the prevalence of peritubular and glomerular capillary wall lesions in each chronic rejection group. Seven (58%) out of 12 biopsies of interstitial type showed a typical peritubular capillary lesion but only 2 of 12 (17%) developed glomerular capillary lesion. In patients showing chronic vascular rejection without TPG by light microscopy glomerular capillary basement membrane splitting was found in 64% whereas peritubular capillary lesions were found in 43%. In the patients showing chronic vascular rejection with TPG, the incidence of both glomerular (80%) and peritubular (69%) capillary lesion were high. Table 3 shows the relationship between glomerular and peritubular capillary lesions in each type of chronic rejection. Only one patient showed both peritubular and glomerular capillary lesions out of 5 patients with typical peritubular lesion in chronic interstitial group. On the contrary, 4 patients out of 5 with no peritubular capillary lesions also revealed no glomerular lesions.

 

Discussion

Chronic graft failure has become a much more important entity with the introduction of the potent immunosuppressive agents CyA and tacrolimus. The graft loss rate after the second year of the transplantation is approximately 3% both in living and cadaveric recipients. The long-outcome of renal allograft was not significantly improved in cyclosporine era which acute rejection has significantly decreased and changed to mild. Many risk factors are known to participate in late graft failure. The cause of chronic graft failure was divided to two major categories, i.e. immunologic and non-immunologic factors [3]. Of course, the most important cause is chronic rejection, however, a concomitant glomerulonephritis, cyclosporine nephrotoxicity, hypertension and/or other metabolic factors interact with each other and play a key role. Furthermore, there is no specific clinical feature for chronic rejection and laboratory finding of chronic rejection became less specific under immunosuppression of cyclosporine. Therefore, graft biopsy is requested to make a definite diagnosis.

Multi-layering of better peritubular capillary basement membrane seen by electron microscopy was first suggested by Monga [4, 5] as a diagnostic indicator for chronic rejection. Monga reported the diagnostic possibilities of peritubular lesions and the morphologic similarities between glomerular and peritubular capillary lesions. The immunosuppressive regimen used in Monga's study was conventional in 45% and CyA in 55%. The present study also revealed the diagnostic utility of the peritubular capillary lesion. However, the relevant similarities between peritubular and glomerular capillary lesions were confirmed only in the chronic vascular rejection with TPG in our study. Typical chronic vascular rejection and typical well developed glomerular lesions required no new and expensive and/or complicated diagnostic criteria for chronic rejection. The peritubular capillary lesion and the glomerular lesion seem to be independent at least in the chronic interstitial rejection group in the CyA era. Using CyA as the main immunosuppressive agent approximately 60% of chronically failing grafts developed the peritubular capillary lesion. In acute cellular rejection without glomerular change, an infiltration of activated lymphocytes into the peritubular capillary subendothelial layer is often observed. The direct injury of endothelial cell owing to transplant immunity plays an important role in the pathogenesis of peritubular capillary lesions in chronic rejection. Therefore, the peritubular capillary lesion is a worthwhile addition as a new criterion for chronic rejection. Non specific laboratory data, mild and non-specific morphological findings and a presence of concomitant lesions result in a difficult diagnosis of chronic rejection in cyclosporine era. A negative result of peritubular capillary lesion in interstitial group is found mainly in the recipients with a concomitant severe CyA arteriolopathy. Diffuse fibrosis leads to the diagnosis of chronic transplant nephropathy using Banff diagnostic criteria, but no evidence for chronic rejection was observed by electron microscopy in this group.

To make an effective therapeutic plan for chronic graft failure, the timing of graft biopsy should be carefully considered. Graft biopsy performed too late does not lead to a successful treatment, therefore early graft biopsy should be contemplated.

Finally we try to summarize the morphologic diagnostic criteria of chronic rejection in the CyA era. New diagnostic criteria for chronic rejection are urgently needed to improve the long-term outcome of renal allografts. Classical vascular and glomerular lesions corresponding to chronic rejection are still useful. Multi-splitting of peritubular capillary basement membrane is specific and valuable as a criterion for chronic rejection, especially in patients with a light microscopic pattern of the interstitial type. A new approach using immuno-histochemical analysis will be a great help to improve the diagnostic specificity and sensitivity of chronic rejection in the future.

 

Literature

  1. Solez K, et al: Kidney Int 44, 411. 1993

     

  2. Mihatsch MJ, Thiel G, Ryffel B: Prog Allergy 38; 447, 1986

     

  3. Bia MJ: Kidney Int 47; 1470, 1995

     

  4. Monga G, et al: Ultrastructural Path 14; 201, 1990

     

  5. Monga G, et al: Modern Path 5; 125, 1992

     


Tables

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Table 1:

 
      outcome  
    surviving graft loss or
sCr >5.0mg/dl
unknown
a) CR n=13 7 6  
b) CR + CAA n=21 8 13  
c) CR + CAA + AR n=2 0 2  
d) CR + CAA + GN n=3 3 0  
e) CR + CAA + AR + GN n=1 1 0  
f) CR + AR n=16 3 12 1
g) CR + AR + GN n=5 0 4 1
h) CR + GN n=8 3 5  
total n=69   AR: acute rejection
CAA: CsA associated arteriolopathy
GN: glomerulonephritis
 

Table 2: Light microscopy vs. Electron microscopy of chronic rejection in CsA era

 
1. Interstitial type   (+) (-)
  MSPTC (n=12) 7 5*
  GBM lesion (n=12) 2 10
  *Severe CAA with a concomitant mild interstitial CR has no MSPTC.  
2a. Vascular type   (+) (-)
TPG (-) MSPTC (n=14) 6 8
  GBM lesion (n=15) 9 5
2b. Vascular type   (+) (-)
TPG (+) MSPTC (n=13) 9 4
  GBM lesion (n=15) 12 3
___________________________________________________________________________________________
MSPTC: multi-splitting of peritubular capillary basement membrane
TPG: transplant glomerulopathy

Table 3: Light microscopy vs. Electron microscopy of chronic rejection in CsA era GBM lesion vs MSPTC

 
1. Interstitial type     MSPTC (+) (-)
  GBM lesion (+)
(-)
  1
4
1
4*
2a. Vascular type
TPG (-)
    MSPTC (+) (-)
  GBM lesion (+)
(-)
  2
4
5
2
2b. Vascular type
TPG (+)
    MSPTC (+) (-)
  GBM lesion (+)
(-)
  7
1
3
1
___________________________________________________________________________________________
MSPTC: multi-splitting of peritubular capillary basement membrane
TPG: transplant glomerulopathy

 


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Last Modified: April 03, 1996 11:38:41 AM