Dialysis
Figure 1: Surveillance to Detect Early Signs of Encapsulating Peritoneal Sclerosis
Patient on PD Stable on PD Peritonitis Ultrafiltration failure Transplant Immediate Surveillance Switch to HD Immediate
around the use of gadolinium in dialysis patents. Developments in image analysis have pioneered a diagnostic tool using cine MRI that shows promise in the detection of EPS. The technique does not require a gadolinium contrast agent, but rests on motion analysis of abdominal organs to infer the absence/presence of EPS. It produces a vector map of pixel displacement that relates to anatomical structures between sequential images. Analysis using vector calculus is effective in highlighting alterations due to anatomical movement. The smooth normal inter-organ sliding is disrupted in the presence of EPS, providing an altered movement ‘signature’ from which EPS can be diagnosed. MRI data have been obtained from a small cohort of reference patients and separate receiver operating characteristic analysis has demonstrated the value of the technique.
GI symptoms Mild Severe
There is an urgent need for laboratory-based tests that can be applied routinely to indicate the degree of peritoneal fibrosis in order to assist with the clinical management of the patient and, perhaps more importantly, to identify the risk of EPS onset before symptoms develop.20
Despite evidence from experimental models CT scan Surgical assessment
Pre-operative nutritional support
Surgical intervention
CT = computed tomography; EPS = encapsulating peritoneal sclerosis; GI = gastrointestinal; HD = haemodialysis; PD = peritoneal dialysis.
Early Detection
Currently, we have no reliable methods of detecting which ones of our PD patients are likely to develop EPS. The only method we have is monitoring the length of time on PD. In a retrospective qualitative study in which patients were being asked about their experience of EPS, a large percentage reported that the delay in diagnosis caused a high level of distress.15
tomography (CT) is unreliable in the detection of early EPS.16,17
We and others have shown that computed We
attempted to use CT scans to assess ongoing peritoneal damage, and maybe predict developing EPS, but unfortunately this has not yielded informative results. Some have suggested that patients should not remain on PD for more than four years, but this is complicated, as we still do not know whether switching modality can be a trigger of EPS. Clearly, this is a dilemma for clinicians as well as for patients. Quite often, in our experience, when patients are stable on PD with a good quality of life and no apparent complications, changing modality is difficult to justify; the decision can vary according to individual circumstances.18
In an attempt to find more reliable and sensitive imaging techniques, we have recently reported the potential of cine magnetic resonance imaging (MRI).16,19
MRI is used routinely in
abdominal and GI investigations and resolution is improving with advances in technology and image processing. However, it has not so far been useful for diagnosing EPS, partly because of concerns
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In another retrospective study, Lambie et al. have demonstrated that there was a change in the osmotic conductance of the peritoneal membrane prior to EPS.22
and clinical research, there has been no validation of the usefulness of early biomarkers of membrane damage, due to the chronicity of the pathology. Also, the low incidence of EPS (in single centres) in the total PD population has made the validation of EPS markers difficult. This is compounded by the lack of suitable bio-banks and insufficient confidence in tentative biomarkers to perform large-scale studies. Two preliminary studies have highlighted interleukin 6 and Ca 125 as potential biomarkers in a small cohort.21
The metabolic and
proteomic study of PD effluent has not been previously described. Using samples from the Global Fluid Study, we have developed and validated a methodology to analyse metabolomic profiles in PD fluid. To date, these metabolomic data have enabled us to identify several potential candidate biomarkers. We now seek to extend this pilot work by further refining the methodology and applying it to a much larger number of patients in order to investigate markers of peritoneal fibrosis (which could precede ultrafiltration failure), including in patients developing EPS.23
Surveillance and Referral
In the absence of validated methodologies or biomarkers to predict early signs that patients are at risk of developing EPS, and until research provides some answers, the only way to detect those early signs is by a close programme of clinical surveillance, as summarised in Figure 1. Targeted groups should be patients on long-term PD and patients who have been switched to either HD or transplant. The latter should be closely monitored for GI symptoms starting at the time of modality change. In our experience, patients are typically referred with a history of often protracted GI symptoms over long periods of time, substantial weight loss and nutritional deficiency with raised inflammatory markers. Frequently, these patients have endured months of vomiting and diarrhoea and considerable abdominal discomfort and have been investigated for a variety of abdominal conditions before a diagnosis of EPS was entertained. It is essential that clinicians and healthcare professionals are empowered with the necessary knowledge to enable them to diagnose patients before these are too decompensated and major surgery is the only management option
EUROPEAN NEPHROLOGY
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