The role of fine needle aspiration cytology in the management of renal allograft dysfunction.BV Mittal
Dept. of Pathology, Seth GS Medical College and KEM Hospital, Parel, Bombay, India., India
Keywords: Biopsy, Needle, Graft Rejection, pathology,Human, Kidney Failure, Chronic, surgery,Kidney Transplantation, pathology,Sensitivity and Specificity,
Renal transplantation has become the preferred treatment for many patients with end stage renal diseases Despite HLA matching, repeated episodes of rejection are not uncommon in the post transplant period, and the survival of the graft depends on early detection and prompt treatment of rejection. During the early transplant period, there exists a dilemma when confronted by graft dysfunction. Acute tubular degeneration following prolonged ischaemia time, cyclosporin toxicity, infection and surgical complications could be other causes of graft dysfunction and these have to be differentiated from rejection as the treatment modalities are different for all these conditions.
Clinical diagnosis of rejection is based on the presence of fever, graft tenderness, recent onset hypertension, elevation of BUN/Creatinine by 25% over the last value and oliguria. However, all of these are not seen simultaneously in a given patient. Needle biopsy is accepted as a 'gold standard' for the diagnosis of rejection. However, there is limitation due to the risk of bleeding which could jeopardise the graft and patient's life. Hence the FNAC has become a safe, reliable and reproducible tool for monitoring renal allograft dysfunction. It has an added advantage of providing a quick result (within three hours).
In acute cellular rejection, a needle biopsy specimen shows an interstitial infiltrate of lymphoblasts, large activated lymphocytes and plasma cells. Each of these cells can be identified and quantitated in FNAC. The diagnosis of rejection is based on the principle that after subtraction of blood background the method enables a numerical evaluation of the composition of the inflammatory infiltrate primarily due to rejection. This when multiplied by the relative risk factor and partial scores added, gives the total score.
The diagnosis of acute cellular rejection (ACR) is based on the findings of a total score more than 3 and has to be accompanied by large activated lymphocytes and/or lymphoblasts. Presence of monocytes, macrophages and plasmablasts is indicative of acute vascular rejection (AVR) or irreversible rejection. Both these types of rejection are accompanied by moderate tubular degenerative changes. When such tubular changes are seen with scores below 3 and in the absence of lymphoblasts or large lymphocytes, a diagnosis of acute tubular necrosis (ATN) is offered. Cyclosporin A toxicity has been associated with isometric vacuolation in the early stages and marked vacuolar degeneration in later stages,.
At our centre, we followed the procedure of von Willebrand and Hayry, for the FNACs. Initially, we followed a protocol of performing the FNACs on the 4th day, every week for 4 weeks, every month for 3 months, as well as whenever there was graft dysfunction. Now we carry out a baseline FNAC in the first week and later whenever there is graft dysfunction, as a follow up after treatment of rejection or in asymptomatic patients with only rise in creatinine.
A total of 1238 FNACs were carried out since 1987 till 1993. In the initial period of one year only one nephrology resident was performing the FNAC and sending the samples and with experience, the adequacy rate was 87%. Subsequently it has been incorporated in the residency programme and any resident posted in the transplant unit, carries out the FNAC in rotation and hence with every new batch of residents initially the adequacy rate is low. Despite this, the overall adequacy rate was 82.6%. This still compares with other centres like Reeve et al (83%) and Heldermann et al (85%).
To assess the efficacy of any new procedure, its comparison with a 'gold standard' is essential. At our centre, 152 needle biopsies were carded out simultaneously with the FNACs. All other FNACs were compared with either the clinical diagnosis, biochemical parameters, DTPA scan or Doppler studies to confirm the FNAC diagnosis. 251 of the 1096 adequate FNACs showed evidence of rejection while 635 were negative for rejection.
The analysis of 153 FNACs wherein the concomitant needle biopsies (NB) were available for comparison is presented. Acute cellular rejection was diagnosed in 55 cases and AVR in 19 cases on needle biopsy. In 39 of these cases, ACR and 12 AVR FNAC diagnosis concurred with the NB diagnosis. One case of ACR was diagnosed as AVR and in 4 cases of AVR a diagnosis of ACR was offered. FNAC was found to be inadequate in one case each of ACR and AVR. In 16 cases of rejection, a false negative diagnosis was given, one of these showed evidence of ATN. In two of the three cases of borderline rejection, the FNAC scores were also borderline (2.9) while in one case, there was no evidence of rejection seen.
There were seven biopsies in cases of suspected acute on chronic rejection and in six of these, the acute component of rejection was detected on FNAC. Of the 10 biopsies in chronic stable rejection, all 10 showed no evidence of rejection. Thus, the diagnosis of chronic rejection was not possible on FNAC but all of these cases which had no acute component were diagnosed as no evidence of rejection, thus helping to separate this group from that with acute on chronic rejection.
In 12 cases, the ARF was attributable to ATN on biopsy. In 10 of these, scores were below 3 and were true negatives. In seven of these, the tubular changes of ATN were seen while in the remaining three cases, scores were below 3 but were not accompanied by ATN. FNAC was inadequate in one case while a false positive diagnosis was given in two cases, however on repeat FNAC the scores were below 3. One case of CSA toxicity on NB showed isometric vacuolation in the epithelial cells in FNAC and the scores were below 3, thus suggesting that the ARF may be attributable to CSA toxicity than ACR. However, isometric vacuolation has been observed by us in patients without any clinical evidence of CSA toxicity. Hence, just the presence of isometric vacuolation has a limitation in predicting CSA toxicity and has to be judged in association with clinical and biochemical parameters.
In 40 FNACs, the diagnosis of no rejection was confirmed on NB. In four cases, the graft dysfunction was attributed to transplant glomerulopathy on biopsy. There was one case each of tuberculous and non-specific inflammatory infiltrate observed on NB. In all these cases, FNAC was negative for rejection. The sensitivity of the procedure was found to be 97.2%, specificity 78.5 % and an accuracy of 86.5%.
When the diagnosis of rejection is given, in the reports from Western countries, the total scores are reported to be on an average around 7, with large number of lymphoblasts, plasmablasts being observed in the FNAC. In our series, no such dramatic increase in the number of blast cells was seen in majority of our cases of rejection. In fact, 30% of the rejections are blastogenic. In the remaining 70%, the diagnosis of rejection is mainly offered on the basis of increase in activated large lymphocytes responsible for scores above 3. This could be because of the fact that all our cases are LRIDT while in western countries mainly cadaver transplantation is carried out. In fact, Hayry and Von Willebrand too have observed that the inflammatory response is much milder in LRDT than in cadaver transplants in their series,. In our cases, 30% showed a blastogenic ACR and the increment of blast cells was only 1-2%. This is in contrast to Heldermann et al who found more than 6 blast cells in acute rejection.
The histological features of acute vascular rejection have been shown to correlate with poor long-term survival. In this study, presence of monocytes and macrophages showed a correlation with poor graft function and persistent rejection. If we keep in mind that the most important feature of the diagnosis of rejection is the indication of activation of immune system and the pointer to this in the FNAC is the arrival of large lymphocytes and or lymphoblasts, then even in the absence of scores above 3, it serial FNACs show a rising score accompanied by increase in large lymphocytes, it could be an indication of a rejection episode. Similarly, we came across 9 FNACs out of 1096 adequate FNACs where the scores were above 3, however, the score was predominantly constituted by small lymphocytes. These were therefore reported as 'No Rejection' despite scores more than 3. None of these patients were treated for rejection despite which there was no deterioration in the renal function and follow up FNACs showed no evidence of rejection.
One of the pitfalls of this procedure encountered was false negative FNACs. This is mainly due to the small size of the sample giving rise to a sampling error. Even in a needle biopsy in a case of mild rejection the infiltrate is found to be focal. This problem can however, be obviated by repeat FNAC, this being a relatively atraumatic procedure. Further advantage of the procedure is that with repeated FNACs one can get a picture of the changing profile within the graft after the treatment of rejection and decreasing scores indicating a better prognosis, persistent or increasing scores indicating a persistent or irreversible rejection. In fact even in von Willebrand's experience, it was not the number of blast cells or large lymphocytes but the subsequent response of reversion to small lymphocytes that was indicative of the degree of severity of rejection episode. When we analysed the inflammatory response in our cases diagnosed as mild, moderate or severe rejection on NB to see if we can categorise the rejection episode based on the type of inflammatory response in FNAC samples, the blast cell response was not found to give any definite indication. However, the activated lymphocytes showed an average increment of three large lymphocytes in mild and five in moderate cellular rejection. There was only one case of severe cellular rejection seen with three repeat FNACs and in all three, the large lymphocytes were 10 in number.
I would like to thank Dr. CV Madiwale, Dr. AF Almeida, Dr. VN Acharya and Dr. AN Sadre in this collaborative study.