² Salford Royal NHS Foundation Trust, Salford, UK

Introduction

In the United Kingdom, 109 new patients per million population (pmp) were started on renal replacement therapy (RRT) in 2009. Ninety days after starting RRT, 47.4% of these patients were on hospital haemodialysis (HD), 25.8% were on satellite HD, 0.7% were on home HD, 18.9% were on peritoneal ­dialysis (PD) and 7.2% had a functioning transplant. The median age for starting RRT was 64.8 years, and 61.7% of new patients started on RRT were male. For many years, the ‘take-on’ rate of new patients has increased – largely because improved funding allowed patients to be offered treatment who would ­previously not have been offered treatment, and partly because of an ageing population and an increased prevalence of diabetes. However, for the last few years, take-on rate appears to have stabilised, and at a rate well below that of some other developed nations, such as the USA. This is likely to be due mostly to arresting the progression of CKD in primary care in the UK, but may also be due to the increasing use of maximal conservative care.

The survival of patients with chronic kidney disease (CKD) stage 3–5 is improving over time, presumably due to improvements in care. Patients aged 18–64 who started on RRT in 2004 had a five-year survival of 67.9%, ­compared to 60.7% for the cohort starting in 1997; and patients aged over 65 starting RRT in 2004 had a five-year survival of 26.9%, compared to 16.5% for the cohort starting in 1997. However, survival still compares poorly to that for common malignant diseases: overall five-year survival for breast cancer is 83.3%, for prostate cancer 79.7%, and for colon cancer 50–52.9%.

Referral

The UK National Institute for Health and Clinical Excellence (NICE) guidelines recommend that all patients with CKD stages 4 and 5, and patients with CKD and rapidly deteriorating renal function, should be referred to, or discussed with, a nephrologist. Rapidly deteriorating renal function is defined as a fall in estimated glomerular filtration rate (eGFR) of more than 5 mL/min/1.73 m² in 12 months or a drop in eGFR of more than 10 mL/min/1.73 m² over five years. Additional referral criteria, designed to pick up patients likely to benefit from specialist management, include heavy proteinuria, proteinuria with haematuria, and resistant hypertension.

Late referral, usually defined as referral to a nephrologist less than 90 days before the start of RRT, is associated with higher risks of hospitalisation, ­complications and mortality (Chan et al. 2007). Late referral also prevents patients benefiting from interventions that can delay progression of their renal impairment and from pre-emptive transplantation. Late-referred patients are less likely to undergo PD, and are more likely to start HD without a functioning arteriovenous fistula. Late referrals are more common in the elderly, and may represent up to 60% of elderly patients presenting with stage 5 CKD. Reassuringly, there has been a steady fall in the number of late referrals, from 27% in 2004 to 19% in 2009, possibly due to improved recognition of high-risk patients in primary care as a result of the Quality and Outcomes Framework (QOF) and the availability of referral guidelines.

As recognition of progressive CKD improves, an increasing proportion of so-called late referrals are in fact unavoidable late presentations of kidney ­disease that could not reasonably have been anticipated or diagnosed earlier, for instance kidney disease caused by previously undiagnosed myeloma or systemic vasculitis. Such patients form an irreducible minimum of patients who will present as uraemic emergencies.

Variation and inequity in the use of different RRT modalities

The proportion of patients on home HD and on PD varies widely from centre to centre in the UK, and this variation cannot be explained by differences in age or comorbidity. Whether the variation is caused by supply-led demand (the economic incentive to fill HD spaces once a new satellite unit has been opened, for instance), by inadequate clinical expertise in home-based therapies, or by a genuine clinical belief (in the absence of evidence) that PD is associated with inferior clinical outcomes, is uncertain. Some variation in uptake of home-based therapies is attributable to variations in housing stock; it is much easier to establish patients on home treatment if they own their own home than if they live in multi-occupancy tenancies, for instance. Some centres have found ways to pay for carers to offer ‘assisted PD’, in which a carer is paid to help older, frail patients with PD at home. The ­numbers are currently small, but new financial arrangements may result in expansion of this modality in England.

Recent research from the UK Renal Registry has shown that social deprivation is associated with a lower chance of being put on the transplant waiting list. Once social deprivation had been taken into account, there was no association between ethnic origin and transplant listing. There is also marked centre-to-centre variation in the chances of new patients with stage 3–5 CKD being added to the transplant waiting list. The proportion of new patients under 65 years of age who are on the transplant list within two years of the start of RRT varies from less than 20% to greater than 80%. Patients looked after in non-transplanting renal centres are less likely to be placed on the transplant waiting list than those managed in transplanting renal centres. The reasons for these variations are the subject of ongoing research.

Once patients are on the transplant waiting list, the chance of receiving a transplant depends on how active the local centre is in facilitating living donor transplantation, and, at present, on the number of organs retrieved from donors after cardiac death. For the majority of patients for whom no living donor can be found, there is a national organ allocation scheme for kidneys from donors after brainstem death, described in detail below. This is designed to maximise the overall benefit from transplantation.

Empowering patients to make an informed choice: shared decision making

‘Shared decision making’ describes a process in which a patient chooses ­between different treatment options, based on a full understanding of the advantages and disadvantages of the options and on his or her own preferences and attitudes. Patients who feel that they have been part of the decision about a particular treatment are more likely to adhere to that treatment in the long term. Facilitating this type of decision making involves multidisciplinary education and the use of patient decision aids for each ‘preference-sensitive decision’. Although some patients appear to prefer the team looking after them to make decisions for them, it remains important to establish the preferences of the patient when making preference-sensitive decisions, rather than imposing the preferences of the medical team (Ubel et al. 2011). Decision aids to support patients choosing whether or not to undergo dialysis, or choosing dialysis modality, are under development in the UK.

There is wide variation among UK centres in the quality of written information, the availability of dedicated education nurses, and the provision of structured education programmes for patients deciding on RRT modality. This variation persists despite good evidence that patients who undergo a structured education programme are more likely to choose a self-care modality (especially PD), and have better compliance and improved survival (Wingard et al. 2007).

Choice of RRT modality

Decisions and preparation for RRT take a long time. CKD is often an incidental finding, and remains asymptomatic until a late stage, so patients with CKD often have difficulty in accepting that they have a potentially fatal disease for which advance planning is beneficial. Delayed decisions regarding treatment modalities can result in the patient requiring emergency dialysis (due to hyperkalaemia, pulmonary oedema or pericarditis), by which time it is often too late for any real choice. These patients are likely to start HD with a temporary central venous catheter, the use of which is associated with an increased risk of infection, thrombosis, and poor flow resulting in inadequate dialysis dose. Emergency insertion of a Tenckhoff catheter for PD can be performed in such patients, but in many centres this is seldom considered.

For these reasons and others, many patients on HD report feeling that they were not given a choice of treatment. The extent to which genuine choice is offered to patients at the start of RRT has not been systematically studied in the UK. In Canada, many patients with stage 3–5 CKD report having no information about their options, whereas in Australia 84% of patients reported being presented with information about their options prior to starting dialysis. Throughout their lives, many patients with stage 5 CKD will experience several different treatment options depending on changes in their personal circumstances, while waiting for transplantation, or when one type of treatment modality fails. Instead of RRT being a choice, it can be thought of as an integrated treatment pathway. In addition, the best modality will vary from one individual to another.

Factors influencing decision making

There are several factors which influence patients when deciding on which modality they would prefer (Morton et al. 2010). Some patients prefer to take control of their treatment and will choose a self-care therapy. Other patients feel safer when someone medically trained carries out their treatment. Patients are sometime influenced by both the negative and positive experiences of other patients. For example, patients may decide on transplantation because they have seen another patient looking well following transplantation, or they may decide against haemodialysis when they see patients with a swollen arm following an access-related complication. (Similar considerations apply to the use of ‘expert patients’ in education programmes: patients are often expert in their own experiences, but do not always have sufficient knowledge of other patients’ experiences, and may bring their own biases to the discussion, thus offsetting some of the benefits of being able to describe the experience of RRT first-hand.) Some patients will give more weight to survival, and others to medium-term quality of life and the effects of a treatment strategy on their current lifestyle. Some elderly patients are concerned about the burden that their treatment will place on their family members. Some patients with familial disease, for instance polycystic kidney disease, will be influenced by the experiences of other family members who have undergone RRT, often decades earlier, and it is important to explore these in detail, as the results and complications of treatment may have changed considerably since.

Cognitive impairment and lack of mental capacity

The prevalence of cognitive impairment in patients with CKD stage 3–5 is 16–38%, much higher than in the general population. Cognitive impairment is likely to affect a patient’s ability to make informed decisions about whether or not to start RRT, the choice of modality, and the outcome of RRT, but is under-recognised by nephrologists. HD may accelerate the progression of vascular dementia. There is a strong case for the routine use of screening tools for cognitive impairment in pre-dialysis clinics, and an urgent need for guidelines on RRT for patients who lack capacity. Nephrologists should also encourage patients with CKD who retain mental capacity to record advance directives stating their wishes should they lose capacity.

Options

The purpose of all forms of RRT is to improve symptoms, quality of life and survival amongst patients with advanced CKD, by replacing the excretory functions of the kidney. Additional treatments are required to replace the endocrine functions of the kidney (e.g. erythropoiesis-stimulating agents to correct anaemia, hydroxylated vitamin D derivatives to correct hyperparathyroidism and osteomalacia). Adjunctive treatments are also often required – for instance, phosphate binders are prescribed to reduce phosphate absorption from food, because removal of phosphate by most forms of dialysis is inadequate. Antihypertensive drug treatments are often required, because RRT does not fully correct all of the factors that contribute to hypertension in CKD.

The decisions facing patients with CKD, and the professionals responsible for their care, vary over time, and include:

• whether or not to undergo RRT
  
• timing of the start of RRT
  
• whether or not to have a kidney transplant
  
• whether to have treatment at home, in a satellite unit or in a hospital setting
  
• whether to have PD or HD
  
• whether to withdraw from RRT

Making an informed decision requires a full understanding of the various options and their interactions with the patient’s preferences, lifestyle and comorbidities – which may themselves change over time.

Timing of start

Internationally, there has been a trend towards initiating dialysis with a higher eGFR, driven partly by the recognition that clearance of small molecules is poorer in patients with advanced CKD than it is in those receiving doses of dialysis shown to confer optimal survival. In the UK, the mean eGFR at initiation of dialysis in 1999 was 6.9 mL/min/1.73 m² for both HD and PD, compared with more recent figures of 8.5 and 9.2 for HD and PD respectively. The Renal Association guidelines recommend that renal replacement therapy should commence when a patient has an eGFR < 15 mL/min/1.73 m² and has symptoms or signs of uraemia, fluid overload or malnutrition in spite of medical therapy; or before eGFR has fallen below 6 mL/min/1.73 m² in an asymptomatic patient.

Early observational studies showed that earlier initiation was associated with improved survival. However, these studies failed to distinguish adequately between late presentation and late start. Later observational and registry studies have shown that there is no mortality benefit from initiating dialysis early, and many recent studies have shown higher mortality in patients starting RRT with more residual renal function than in those starting with more advanced disease. While these findings are mostly explained by the fact that patients with comorbidity often start with higher residual function than those without, it is impossible to exclude the possibility that dialysis itself might cause harm – for instance as a result of infection associated with peritoneal or vascular access, the effects of fistula formation on cardiovascular function, or the haemodynamic instability caused by dialysis treatment.

A recent randomised controlled trial which compared early start (eGFR 10–14) with late start (eGFR 5–7) showed no difference in mortality or quality of life. However, a large proportion of the patients who were assigned to the late-start group were started on dialysis earlier because of symptoms, and many in the early-start group were actually started with an eGFR < 10 (Cooper et al. 2010).

Peritoneal dialysis

Peritoneal dialysis (PD) is the primary form of treatment used at home and for self-dialysis. The purpose of peritoneal dialysis is to remove solutes and maintain acid–base and fluid balance. Peritoneal dialysis therapy involves draining dialysis solution into the peritoneal cavity via a catheter inserted through the abdominal wall. The solution contains electrolytes and an osmotic agent – usually glucose. The peritoneal membrane is semipermeable, permitting solutes to diffuse across the membrane from the blood into the dialysis solution in the peritoneal cavity, so that draining the fluid out results in removal of these ­solutes, including uraemic toxins and water.

Peritoneal membrane

The peritoneal membrane is a thin, translucent, porous layer of tissue with numerous blood vessels. It consists of two layers, the parietal layer, which lines the inner surface of the abdominal wall, and the visceral layer, which covers the abdominal organs in the peritoneal cavity. The visceral peritoneum accounts for about 80% of the total peritoneal surface area. The space ­between the parietal and visceral peritoneum is called the peritoneal cavity. It normally contains less than 10 mL of fluid, but can accommodate several litres without patient discomfort. The osmotic gradient between plasma and dialysate also generates convective loss of water and solutes, enabling control of fluid balance.

The rapidity with which small solutes (e.g. glucose, urea) are transported across the peritoneal membrane varies markedly from patient to patient, and cannot be predicted, but has to be measured, usually six weeks after the start of PD and annually thereafter, by the peritoneal equilibration test. Fast transport results in rapid equilibration between dialysate and plasma. This results in rapid removal of urea, but also rapid loss of osmotic gradient, and eventually – if the ‘dwell time’ is too long – net absorption of fluid from the peritoneal cavity, resulting in low drain volumes, and thus low net removal of uraemic toxins. Slow transport allows sustained ultrafiltration, but results in slower removal of uraemic toxins. Fast transporters benefit from rapid cycles; slow transporters need fewer, longer cycles.

Additional complications are caused by the complex nature of the peritoneal membrane. Water (but not solutes) can pass through aquaporins (small pores) in the cell membrane of the peritoneal cells, whereas solutes can only pass by convection through medium and large pores between cells. Early in the cycle, particularly in slow transporters, water transport from the body into the dia­lysate causes hypernatraemia and a reduction of the dialysate sodium concentration, which, later in the cycle, drives convective transfer of sodium through medium pores. Using short cycles in slow transporters can thus cause hypernatraemia, resulting in thirst and compounding problems with salt and water overload (Van Biesen et al. 2010).

Peritoneal dialysis access: the Tenckhoff catheter

In 1968, Tenckhoff and Schechter revolutionised the field of PD when they introduced a permanent catheter and a method of implantation that for the first time allowed relatively long periods of usage with a significant reduction in exit-site infections. Tenckhoff recommended using a curved tunnel, downward-directed exit to reduce a potential accumulation of debris at the exit site and to reduce infection. These innovations became the basis for PD catheters still used today. Most catheters used in modern practice are silastic coiled catheters with a radiopaque marker.

Catheter insertion should be undertaken by an experienced operator, under operating-room sterile conditions. The operator can be a surgeon, specialist nurse or physician, who has specific training and expertise in peritoneal ­dialysis access creation. This can be done on either an inpatient or an outpatient basis. About two-thirds of catheter insertions in the UK are performed using the open surgical technique, with the majority of the others using the medical percutaneous technique, and a small number using peritoneoscopy. Catheters can be inserted under local anaesthetic, with or without sedation, or general anaesthetic. The type of anaesthetic used will depend on the method of insertion and patient comorbidities. The anaesthetic requirement for the procedure depends on the technique selected, which is influenced by the ­characteristics of the patient (Figueiredo et al. 2010).

Preoperative preparation

The Renal Association guidelines recommend that patients have their PD access surgery approximately two weeks before commencing dialysis (Woodrow & Davies 2011). Prior to surgery it is important to identify and repair any hernias. It is also important to determine where the exit site should be, this should be done with discussion with the patient so that the exit site does not sit on the belt line and the patient can see the exit site. Patients should have laxatives/bowel preparations as per local guidance. Measures should be taken to reduce the risk of infection, such as skin washing and perioperative antibiotic prophylaxis (See Chapter 7).

Once the catheter is placed, and until healing is completed, the dressing changes should be done by a dialysis nurse using an aseptic non-touch technique (Figueiredo et al. 2010). The area should be kept dry until it is well healed, usually for 10–14 days to permit healing and reduce the frequency of early peri-catheter leakage of dialysate. Catheters inserted percutaneously can often be used earlier than this.

On discharge home, the patient should be given laxatives with instructions to avoid constipation, and advice on recognition of potential complications.

Types of PD

Peritoneal dialysis can be performed in a number of ways, and these are described below.

Continuous ambulatory peritoneal dialysis (CAPD)

This is the most common form of PD. The process of draining and filling is called an exchange, and it takes about 30–40 minutes to complete. The period the dialysis solution is in the abdomen is called the dwell time. A typical schedule consists of approximately four two-litre dialysis exchanges a day, each with a dwell time of 4–6 hours. The last exchange of the day is usually left in overnight and exchanged the following morning. It is a simple procedure that most patients are able to perform, and there are assisted devices available for patients with visual or dexterity problems. No machines are necessary, and this procedure can be performed in many locations outside of the home, making travelling and holidays easy to organise. It is less suitable for fast transporters without residual renal function.

Automated peritoneal dialysis (APD)

Related posts:

Managing Chronic Conditions: The Policy Context Acute Kidney Injury in Hospitalised Patients Optimising Nutrition in People with Chronic Kidney Disease Supportive and Palliative Care for Patients with Advanced Kidney Disease Medication Management and Chronic Kidney Disease A Practical Approach to Chronic Kidney Disease in Primary Care

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