Microsoft word - tradravelli3.ruolo nel tx . doc.doc
US sonography in renal transplant: what role?
Our experience in recent years, together with the literature of the same period, allows us to
state that, from the early seventies (1), when our radiology colleagues were the first to undertake the US study of renal transplant, to these days, the technology has undergone fascinating developments and US has, at the same time, experienced a sort of “clinical-sonographic evolution”, entering into the differential diagnosis of not only surgical complications, both urological and vascular (2-4, 11, 17, 20, 23), but medical complications as well (5-9, 12, 15, 17-19, 21, 22, 24, 26-28, 49-51). Ultrasonography has endowed transplant nephrology with unhoped-for potentialities, which have proven in time to be vital and to offer almost immediate solutions to clinical problems of great relevance for allograft follow-up. The interplay between transplant nephrology and ultrasonology has yielded striking results, which have narrowed the role of histological diagnosis, with enormous repercussions in terms of human costs and of health expenditure as well. For these reasons I think the role of allograft ultrasonography in nephrology is specific and cannot be replaced by competences that aren’t closely related to clinical practice. This contribution, though not expecting to be conclusive, aims to take stock of the role US has played (and, thanks to its acknowledged role, is still playing) in transplant diagnostics. It will subsequently consider how such role has evolved and end offering some cues for a reflection on the future of transplant ultrasonology, now more urgently than ever requested to cope with unavoidable ethical issues.
At its dawn US dealt with the differential diagnosis of surgical and medical complications,
acute rejection being among the latter. Its contribution then extended to biopsy control, post-biopsy monitoring, pre-explantation evaluation, as well as interventional management and/or US support in vascular and urological complications (10-12, 21, 24, 83-87). With the introduction of new therapeutic protocols, from the nineties on, a clinical problem arose: that of “chronic allograft nephropathy” (CAN) or “chronic allograft dysfunction” (CAD) (65, 67, 74, 75, 90), with the consequent irreversible decline in renal function, which is well-known to be linked to immunologic and non-immunologic factors, among which the toxicity of calcineurin inhibitors (CNI) is not secondary. Our studies began in December 1987 and have continued in subsequent years. To date we have about 9,300 “clinical” ultrasonographies on allograft in total, where by “clinical” we mean supported by cytohistologic, laboratory and therapeutic evidence. Already in the early nineties (29), such studies enabled us, after dealing with acute rejection diagnosis, to address the problem of calcineurin-inhibitors-induced nephrotoxicity, characterized by a specific US pattern. Hricack generically described such pattern, at the beginning of the eighties, as “nephrotoxicity” in the native kidney (34) and we confirmed it, by means of cyto-histological evidence, in the transplanted kidney. Thus, ultrasound depicted nephrotoxicity in renal transplant 12 years before the first scientific works appeared (58). On the basis of histological correlation (mainly for acute rejection) and cytological correlation (mainly for nephrotoxicity), it has since demonstrated high rates of diagnostic sensitivity and specificity (in our case series ,100% and 98% ,respectively, in acute rejection and 88% and 100%, respectively, in nephrotoxicity).
A potential corollary to this eminently clinic role of US is the study of toxicity mechanisms
of drugs even in the native kidney. Some data (30-32, 65) regarding the clinical presentation of “chronic allograft nephropathy” (“chronic allograft dysfunction”) of partially non-immunologic nephrotoxic origin (75) lead to the hypothesis of potentially ubiquitous mechanisms involving subcellular structures (57): such mechanisms, which are consistent with the US picture, offer exciting prospects for potential use of the new technologies. A second corollary concerns health expenditure. As early as 2001-2002, we calculated how much could be saved yearly reducing the dosage of immunosuppressant. The calculation was based on the costs of drugs reported by the hospital-based pharmacy of Azienda Ospedaliera di Brescia in February 2002. Merely reducing
tacrolimus by 1 mg (current mean dosage is 7-8 mg per day , about 50% of the dosage in 1996) the yearly saving amounts to about €650 for each patient.
Current dosages of cyclosporine (presenting an intraindividual variability in blood level
judged unacceptable by experts) have been reduced, too, by 10-30% after the introduction of blood level evaluation at baseline and 2 hours after administration. A reduction by 25mg per day saves €216 yearly for each patient. Because of many variables, some of which are imponderable, haematic levels assessment is imprecise, both for cyclosporin and for other immunosuppressants, which makes the method not very reliable as a tool for therapy monitoring.
Another, collateral but not secondary, problem is that hospital-based pharmacies have
extremely expensive stocks, which are not usually bought back by pharmaceutical companies and accumulate as a consequence of continual changes in therapeutic protocols.
On the other hand, the kind of approach to therapy monitoring “alternative” to US suggested
by Rush in the early nineties, namely sequential protocol biopsy (protocol biopsy) (59), elicited, and still elicits, some perplexities. Notwithstanding recent publications (89-94), it is still controversial, and rightly so. On this subject we wish to mention that our 13-year retrospective case analysis on post-biopsy complications in tx (39) made clear that, although thin needles (18g) were used, the incidence of major complications (FAV) is 4 times higher in allograft (0.8%) than in the native kidney: 3 cases resulted in emergency explantation owing to the rupture of the pseudoaneurysm that had formed on the renal artery; 3 cases (0,4%) lead to embolization. Moreover our data seem to suggest that embolization inevitably leads to dialysis, owing to possible and, indeed, likely alterations in intrarenal circulation with consequent overwork for residual nephrons. Earlier US monitoring (starting 24-48 hours after transplant, but, if necessary, even possible while the patient is still in the operating room) would instead allow an accurate and careful transplant management and also a reduction in health care expenditure. More on this later.
In the field of differential diagnosis of medical complications, US also enabled us to
describe two kinds of rejection (predominantly “vascular” and/or predominantly “interstitial”) (37) and also, as early as the year 2000, the pattern of subclinical rejection (38), defined on the basis of alterations in Doppler and Colour Doppler parameters occurring in temporal sequence. We managed to identify subclinical rejection comparing the succession of such alterations with the outcome of the considered patients’ clinical course in histologically proven rejection, since a comparison with the histological picture of subclinical rejection, which can still only be defined on the basis of protocol biopsies (88-95), is not possible.
Let’s turn to the future. The abovementioned results have been achieved resorting to minimal (and easily available)
technology, yet combined with a precise and rigorous method, so as to avoid the sort of operator-dependence that has always been a burden to US diagnostics and will certainly be minimized by contrast agents (UCA). However the problem of training a good sonographer remains and the experts claim this accounts for the most considerable item of expenditure in ultrasonology.
What stated above shows that, while new extremely potent drugs are shifting the focus from
acute rejection to irreversible CAN-related loss of the renal function, with cyclosporine-induced damage, already at year 10, making such drug unacceptable for long-term immunosuppression (68, 69, 72, 76), the current, and in some respects potential, role of ultrasound is mainly clinical, or as was authoritatively stated back in 2002, “sophisticated”. In this context the challenges ultrasonology intends to face nowadays are method standardization on one hand and, definitely, therapy optimization/personalisation on the other. However, it is now already clearly evident that no other diagnostic method can guide clinical practice with the same reliability, non-invasiveness, repeatability , combined with an obvious cost containment.
Over the years clinical practice has provided ultrasonology with research grounds, which
were unexpected in its beginning and ultrasonology has learnt from clinical practice to focus on more and more precise goals, using sophisticated and always evolving technologies: 3D
ultrasonography (40), harmonic imaging and other imaging sequences, matrix probes, B-flow, elastosonography, contrast agents (UCA) (35-38). Especially second generation non-toxic UCA used with low mechanical index and in association with particular imaging sequences (pulse inversion, harmonic imaging, stimulated acoustic emission), have the advantage over other innovations to allow a numerical definition of some parameters, thus reducing operator-dependence, which has always hindered the standardization of US examinations. Renal perfusion can thus be adequately assessed, even in the peripheral parenchyma, on the arcuate arteries, and defined through numeric parameters, thus obtaining functional evaluation (52, 53, 79-81). The role has changed from strictly morphologic to morphologic-functional but even the more and more realistic possibility of a therapeutic role is approaching, through the use of contrast agents as “vehicles” for active pharmaceutical ingredients (48-50, 54, 55). It goes without saying that the first application of such agents, having vascular distribution, is the treatment of vascular complications and a more precise definition of any mass (41, 45). The opportunity of defining numeric indices will however allow methodologic standardization, even in the field of the differential diagnosis of medical complications, with enormous repercussions on clinical practice (as well as on training, as sonographers will have to be trained to perform correct contrastographic examinations, combined with new imaging sequences). All these potentialities, however, need to be weighed up, now already, against the cost-benefit ratio, so as to avoid an indiscriminate use, which may have a negative spillover effect on health care expenditures. Indications should instead be specified.
As for their potential therapeutic use (48-50, 55), even in renal transplant, I think an exciting
future is in store for us. Yet, at the same time, the new technologies urgently require Guidelines to be established, a grid and diagnostic paths to be defined, the cost-benefit ratio to be determined, dedicated operators for transplant Centres to be trained and, lastly, centres of excellence to be identified. All this has two aims: on one hand, to restrain pharmaceutical expenditure and, on the other, to limit the risks for the patient and for the allograft: this is the last facet I would like to deal with.
In recent years the focus in nephrology has undoubtedly shifted from acute rejection to slow
and irreversible decline in renal function, defined “chronic transplant nephropathy” or “chronic allograft dysfunction”; back in 2002 the two major experts, P.Halloran and B.Kahan, were wondering what the best immunosuppressive option might be.
The most authoritative transplant surgeons claim that histology doesn’t always succeed in
glomerulonephritis and transplant glomerulopathy; moreover it only detects damage when it is already at an advanced and irreparable stage; lastly, in our experience, it fails to distinguish the relative importance of the two components when acute and chronic lesions occur together. In our case series, sonography has shown better correlation with clinical diagnosis (92%) than histological investigation has (88%). This achievement on the part of ultrasound confirms its unchallenged role, not to be replaced, at this moment, by any other imaging technique, and certainly not by (cyto)-histologic investigation.
With regard to the literature, we reported, on the basis of ultrasound, calcineurin-inhibitors-
induced nephrotoxicity as early as 1991, whereas the first work on the subject and on the negative effects of excessive immunodepression (with an increase, particularly, of lymphoproliferative disorders) was published in 2001 (58). Subsequently other works (59-60) pointed out an improved renal function in patients who, because of a histological diagnose for CAN, or for other reasons, had reduced or discontinued CNI, introducing, or continuing, the assumption of mycophenolate, either with or without steroid at low dosage.
More recently other works (64, 68, 69, 71) have pointed out that pathologies, of probable
iatrogenic origin, have cleared up by reducing immunosuppressive therapy, without any decline in renal function.
Such observations have inspired research to seek for non-nephrotoxic drugs, some of which,
though, are burdened with other side effects, probably not entirely known yet (introduction of new
protocols dates back ten years). The authors conclude that the only acceptable therapeutic option is, at the moment, the reduction of immunosuppressive therapy (68, 69, 72, 76), with a view both to preserve renal function and to improve patient survival. However, the following questions still remain to be answered: “ To what extent?”, “How?”, “On the basis of which parameters?”.
A vital future role for ultrasound will definitely be to shed light on possible toxicity
mechanisms underlying the US picture, which will also have a potential and important impact on the problem of nephrotoxicity in the native kidney, and, maybe, to cope with the problem of irreversible functional loss (where’s the point of no return?) throwing light, in a non-invasive way, on the damage as it arises. Only thus can the proposal of protocol biopsies be handled (56, 88-95), with an honestly critical attitude. Such diagnostic technique should of course be preliminary to the search for therapeutic options which, as shown, could issue from ultrasonology itself, through the use of microbubbles contrast agents as vectors for targeted localized release, with adequate rupture frequencies of active pharmaceutical ingredients (48-50)
Considering these clinical demands the renewed role for ultrasound is going to be,
preliminarily, a better definition (and therefore standardization) of the pattern of kidney in functional balance (that, besides, we have already described) through a focused and standardized use of technologic innovations, followed by the definition of numeric indices. Whichever the kind of therapeutic protocol in use (be it nephrotoxic or non nephrotoxic) the abovementioned tasks are preliminary to the achievement of the therapy optimization and personalization already asked of US in cardiology and oncology.
Furthermore, there is the organizational and managerial problem of identifying centres of
excellence, already provided for at ministerial level, among those already being referred to as teaching hospitals and supposed to provide training in new US technologies.
In conclusion, I believe that, considering the results achieved so far, US monitoring, when in
the hands of clinicians or of skilled physicians is, already now, proving to be able to help contain health care expenditure, thanks to: 1) reduced hospitalizations due to surgical complications, acute rejection and/or iatrogenic pathologies (hospitalizations in the first 24 months after transplantation, including the first 6, are now mostly linked to infectious complications deriving from excessive immunodepression) (76); 2) decrease in problems related to post-biopsy FAV ( the occurrence of major complications is 4 times higher in allograft than in the native kidney, their outcome being either explantation or irreversible loss of renal function) (39).
In the future US could lead to further savings, reducing dosages and/or stocks in hospital
pharmacies, as a consequence of establishing the appropriate therapeutic protocol for each patient.
I think what stated above shows that the role of ultrasound in transplant management also
has an intrinsically bioethical value, as it is a non-invasive method with high humanizing diagnostic-(therapeutic) potential.
Enabling the allograft to live longer entails reducing the number of patients that might
potentially resume dialysis and register again on the waiting list, thus contributing to reducing organ demand, always far exceeding supply. The data from the Istituo Superiore di Sanità give an idea of such discrepancy: of the 7,451 patients on the renal transplant waiting list in 2001, only 18.6% received an organ in the following year. In January 2004 more than 40,000 people were listed in Europe for renal transplant. In this context any effort to improve transplant management, in the direction of prolonging the life of the allograft (and of the patient, in the first place) is bound to contribute positively to reducing such disproportion and, indirectly, also to facing an issue Prof. Girolamo Sirchia mentioned at the conference “Medicine and Human Dignity”, held in Bari in November 2004. Prof. Sirchia, at the time Health Minister, called it “ the most urgent bioethical issue today’s medicine has to face besides stem cells: the organ trade”.
Back in 2003 the anthropologists at Berkeley University reported organ trade (79). It seemed
to be a problem with no relevance to the Italian context, but in June 2005 headlines in national newspapers made one suspect its existence also in Italy. The same topic appeared also in the electronic issue of the journal Kidney International in February 2006, together with the proposal
from overseas to legalize the trade; moreover, the topic came to the fore again on the cover of the March issue of the same journal; the media have recently talked about it; the problem can’t be eluded any longer, yet it requires mindful and honest critical analysis of all its facets and of possible clinical, anthropological, psychological and social implications.
Considering what has been stated above, I believe that, because of the direct or indirect role
of US in transplantation problems, the definition “clinical-sonographic evolution”, which may have seemed a challenge at first, is actually a fact, though certainly still evolving. I also think that, owing to some of its potential uses, US “are showing the way to outlining more extensive studies in the future”, an expression I allow myself to borrow from an esteemed colleague, much more illustrious than I am.
I think US diagnostics well represents what, from a bioethical perspective, has been
described as the aim of a science serving mankind: “to suggest some instruments to find again the ways of human and spiritual wisdom and inspire research to engage in the pursuit of new processes of real humanization” (78).
Considering the reasons stated above and acting in the primary interest of transplanted
patients, who can’t any longer be denied an US examination , competently performed by, possibly, dedicated physicians, I believe any difficulty , unrelated to the search for a better quality of life for each patient, must be overcome. REFERENCES
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