HK1125873B - Method and apparatus for home dialysis - Google Patents

Description

Method and apparatus for home dialysis

Technical Field

The present invention relates to dialysis, in particular to haemodialysis or peritoneal dialysis performed in the home of a patient.

Background

Patients with low or lost kidney function rely heavily on regular hemodialysis or peritoneal dialysis. Dialysis may be done in a dialysis room of a hospital, an outpatient department remote from a hospital, a self-service center (with some assistance from staff), or at home. For self-service or home dialysis, special training is required.

While some home dialysis patients follow a standard schedule of 4 to 5 hours per day for 3 days per week, there are also some patients who use nighttime home dialysis, who have 4 to 6 nights per week and who have 6 to 8 hours per night while sleeping for dialysis. Home dialysis greatly enhances the removal of waste products from the human body and has been found to improve health to allow a more liberal diet and reduce the need for medications. This is mainly due to the increase in dialysis time allowed for dialysis performed in the patient's daily environment.

Existing home haemodialysers (see 2 in figure 1) and peritoneal dialysers have some disadvantages. The design of existing instruments is based on dialyzers for clinical applications, which optimize the speed (typical dialysis duration is 2-4 hours), which means large artificial kidneys, high blood flow rate and similar high dialysate flow rates. The operation and user interface of these dialyzers is often designed for professional clinical personnel and is too complex for untrained home users. Furthermore, the dialyser relies on large water purification devices, which are typically available in the clinic.

This means that existing home dialyzers have the following drawbacks:

1. too complex to handle.

2. Too large to be installed only in very wide environments and difficult to install in smaller private apartments.

3. Too heavy to be moved around in the home by a weakened person (as is the case with many patients or what these patients are about to be) is closely related to whether day and night dialysis is available. The weight and size of existing dialyzers do not allow to routinely carry the dialyzer out of the house, for example on vacation.

4. It is not suitable for use in dialysis of longer duration, e.g. 6-8 hours.

5. Depending on the large flow rate of the dialysis fluid and thus on the excessive volume of purified water used for preparing the dialysis fluid. Purified water may be provided by micro-purification devices installed in the home or integrated in the hemodialyzer, thereby presenting another operational problem to the patient. Alternatively, previously manufactured dialysate or purified water can be supplied to the home in containers, which again presents handling problems for weak people due to the large volume.

Disclosure of Invention

It is an object of the present invention to provide a dialyzer suitable for use in a patient's home and for operation by the patient, which dialyzer has a low dialysate consumption and is suitable for performing dialysis for a long duration.

A first embodiment of the present invention is a hemodialysis system particularly suited for home hemodialysis. The system includes a hemodialyzer and two or more dialysate containers connected to control dialysate flow to the hemodialyzer, and is characterized by:

the dialysate container is filled with dialysate;

the system further comprises at least one empty or partially filled flexible dialysate container;

the volume of the dialysate container does not exceed 10L;

the dialysate containers are connected between the outlet and the inlet of the hemodialyzer so that dialysate flowing from the outlet of the hemodialyzer will be recirculated to the inlet of the hemodialyzer.

In one form of dialysis, peritoneal dialysis, the dialysate solution flows through a catheter into the peritoneal cavity where it absorbs waste products. The fluid may stay in the peritoneal cavity for a specified period of time and be replaced later, or the fluid may be replaced continuously (requiring two tubes or a dual lumen tube) by verifying that flow exists. In another form of dialysis, hemodialysis, involves diffusion of a solution across a semi-permeable membrane in an extracorporeal circuit in which dialysate flows in a direction opposite to the flow of blood on opposite sides of the membrane. The present invention may be used in both peritoneal dialysis and hemodialysis, collectively referred to herein as dialysis. Similarly, the equipment used to perform these forms of dialysis is called a dialyzer. Examples and embodiments relating to hemodialysis are given primarily.

Preferably, the dialyzer includes a pump arrangement and a dialysate flow path configured to facilitate recirculation of dialysate from a dialysate outlet of the dialyzer to a dialysate inlet of the dialyzer through a dialysate container between the dialysate outlet and the dialysate inlet of the dialyzer.

Traditionally, the measurement of dialysis efficiency is based on the removal of molecules such as urea and creatinine from the blood. These molecules are small and have a molecular weight of typically about 60 au. It has been found that other heavier substances, which have molecular weights in the range of 1,000-2,000au and even up to 10,000au, also have a greater effect in poisoning caused by kidney disease. Such macromolecules move around in the organism at a much slower rate than small molecules, which diffuse from the tissue into the blood at a much slower rate.

The slow diffusion of important substances means that short duration hemodialysis has less effect on the removal of these important substances. Therefore, it is beneficial to use hemodialysis that has a smaller blood flow rate and dialysate flow rate, but is performed for a longer period of time. Also, since the removal of important substances takes place at a slow rate, the concentration of these important substances in the used dialysis fluid is relatively small.

Thus, an essential element of the invention is that the dialysis fluid is recirculated, which means that the dialysis fluid that has passed through the artificial kidney is collected and led to the inlet of the haemodialyser for another passage. Similar considerations apply to peritoneal dialysis. The recirculation of the dialysis fluid provides the advantage of a significant reduction of the total volume of dialysis fluid consumed, since the same volume of dialysis fluid is used several times. The reduced consumption and the resulting smaller demand for dialysate volume provide a number of additional advantages:

the costs and effort involved in obtaining the dialysis fluid are reduced, since a smaller dialysis fluid volume is required. It becomes simple to provide centrally prepared dialysate, manufactured at a professional dialysate preparation device or site, to the home and thereby also to work in connection with the patient or a relative preparing dialysate from tap water;

the smaller volume of dialysate also allows the use of higher quality dialysate at competitive prices. Since the quality of the dialysis fluid is one of the other parameters that depends on the purity of the water provided, and since very pure water is not readily available, one advantage is that the reduced consumption of dialysis fluid allows the use of smaller amounts of this water;

a smaller volume of dialysate means less dialysate is handled by the patient. By handling relatively little dialysate and easily handling the containers, even weak patients can set up a dialysis operation without assistance. Long duration hemodialysis using prior art hemodialyzers typically requires the handling of 70-120L of dialysate, which is a large volume for the vast majority of patients who need to be operated daily. The system according to the invention comprises a container that can be manipulated by the patient, preferably a container containing a volume of not more than 10L of dialysis liquid, for example not more than 8L of dialysis liquid. For more debilitating patients, it may be preferable to use a container containing a volume of dialysate not exceeding 6L, for example not exceeding 5L in the system;

the feature that the dialysis fluid is recirculated is such that only a quantity that can be managed is required, which means that the dialysis fluid is circulated in a closed system. This has the advantage that no validation of the discharge of used dialysis fluid is required, resulting in a higher transportability and more flexibility of the system.

An important advantage of low dialysate consumption is that it allows dialysis even for very long durations to be performed using relatively cheap and manageable volumes of dialysate. As mentioned previously, it has been demonstrated that continuous dialysis is one of the most important factors in determining the health of a patient, and that long-duration dialysis is preferred. In hospitals and clinics, efficiency and speed must be weighed when assessing dialysis duration, whereas in home dialysis the daily life of the patient can be adapted to dialysis. Long term dialysis can be particularly important for bedridden patients.

Due to the recirculation of the dialysis fluid, the total volume increases when fluid is extracted from the patient through the artificial kidney of the hemodialyzer. To provide for preservation of this fluid, the empty or partially filled container is preferably capable of receiving at least 1L of fluid accumulated by the hemodialyzer.

In one embodiment, the dialysate containers are filled with centrally prepared dialysate. The dialysate is preferably on standby without any pre-treatment of the patient. Supplying professional centrally prepared dialysis fluid offers the advantage of reduced manufacturing costs and improved quality using high-end large manufacturing equipment. A further advantage is that this eliminates the need for the patient to store and operate the water purification system and this increases the transportability of the system. The centrally prepared dialysis fluid therefore preferably comprises a physiological grade electrolyte. The applicable physiological levels cover a range of concentrations that can be adjusted to specific circumstances, but which are also personal preferences and opinions of the responsible physician. Typical values for a typical electrolyte are:

Na 130-145mmol/l

K 0-3mmol/l

Ca 1.0-1.75mmol/l

Mg 0.2-0.6mmol/l

Cl 90-110mmol/l

the centrally prepared dialysate preferably comprises water with an endotoxin content of less than 0.05 iu/ml. Preferably, the water is ultrapure water or reverse osmosis water (biowater) that is sterilized, pyrogen-free, has a total solids content of less than 1ppm and a maximum of 0.1 Colony Forming Units (CFU).

The centrally prepared dialysate preferably has a pH value of physiological grade, for example in the range of [5.50-7.45 ]. Bicarbonate, acetate or lactate based pH buffer systems are widely used and can be used to ensure that the centrally prepared dialysate has the proper pH. Bicarbonate-based solutions are not completely stable over time at once, but are generally provided in two capsules, the pH being ensured for at least 24 hours after rupture of the semi-permeable membrane. Acetate or lactate based systems are stable over time, but are less common because of the difficulty some patients have in metabolizing large amounts of lactate. This last problem is alleviated by the present invention. Since the total amount of dialysate is significantly reduced, the total amount of buffer will also be significantly reduced. During recirculation, the buffer concentration and thus the absorption rate are slowly reduced as equilibrium is approached. Thus, with the system of the present invention, the amount of buffer absorbed by the patient is considerably smaller.

In another embodiment, the dialysate container is filled with dialysate typically prepared from tap water in the patient's home. In this embodiment, the dialysis system may include a filter for filtering tap water to increase purity. Furthermore, the system may comprise connectors, adapters for filling the dialysate containers with purified tap water. The system may further comprise means for mixing a previously mixed mixture of buffer and electrolyte (e.g. salts and solutions) with purified tap water to obtain a dialysate with similar properties as the above centrally prepared dialysate.

When reference is made in the rest of the application to a previously manufactured or supplied dialysis fluid, this means that the dialysis fluid supplied to the dialyzer in the dialysis container is at least partly manufactured in advance, and it is understood that the dialysis fluid may be prepared centrally or at the home of the user on the basis of filtration and treatment of tap water.

Some dialyzers can adjust the electrolyte concentration and pH of the supplied dialysate, which means additional complexity in operation and maintenance and increased price. Thus, according to a preferred embodiment, the system according to the invention does not add substances for the purpose of adjusting the electrolyte level or pH of the dialysate from the dialysate containers, nor does it include options for this purpose, and the system of the invention applies to the previously manufactured dialysate directly supplied from said containers without prior modification. However, for long term storage of containers filled with dialysate, the system may provide a container with two or more chambers separated by a semi-permeable membrane, which when ruptured before use, the solutions are mixed to produce a dialysate with physiological electrolyte levels and pH.

When using the present system, the number of times a given volume of electrolyte is cycled is determined by operating parameters including: the flow rate F of the dialysate flowing through the hemodialyzer; duration t of hemodialysis_D(ii) a Total volume V of previously produced dialysis fluid in the container_total(ii) a And the amount of fluid accumulated from the patient during dialysis. Since the accumulated volume is typically less than 5% of the total volume, it is ignored below for simplicity. To quantify the recirculation, the degree of recirculation RD is defined as the number of times an arbitrary volume of dialysate passes through the artificial kidney of the hemodialyzer during dialysis; RD is F × t_D/V_total。

Recycling the dialysate only once or twice means that only a small fraction of the large molecules will diffuse into the dialysate, which means a low degree of use of the dialysate (and a larger required volume for a given flow rate and duration). Recirculating the dialysate too many times results in high concentrations of macromolecules and other extracts, which will result in very poor and inefficient performance during the final cycle. The dialyzer preferably applied in the present invention further comprises means for calculating and adjusting a first operating parameter (e.g. dialysate flow rate), the calculation being based on the set values of other operating parameters (e.g. desired dialysis duration and total volume of dialysate in the connected dialysis container) to provide a flow rate in the range of [ 3.5; 6] degree of recirculation within the interval of. Any of the flow rate, duration, or total volume may be input into the dialyzer by the patient or operator.

The dialyser and the dialysate containers according to the invention are preferably designed for use by persons who are hardly or not trained at all. Thus, preferably all connections of the end parts, e.g. the inlet/outlet of the dialyzer and the input/output of the container and any conduits or pipes connecting these inlets/outlets and inputs/outputs, are designed to have physical limitations which only allow a correct fitting and connection and/or which are designed to be connectable in a plurality of correct ways. Also, preferably, the dialyzer requires as little input from the patient or operator as possible to initiate dialysis. Thus, in a preferred embodiment, the total volume of dialysate is automatically detected when the patient is connected to the container. Here, the system may comprise a scale for weighing the connected dialysate containers and estimating the total dialysate volume, and the system may further comprise means for providing the estimated volume to the means for calculating the flow rate. The amount of accumulated fluid to be ignored during dialysis is preferably also specified by the patient. This can be done by entering a volume value that is expected to be ignored, e.g. 0.75L, or by indicating the current weight of the patient, wherein the dialyzer is able to compare the current weight of the patient with a predetermined optimal weight. Thus, the operator only needs to specify the desired dialysis duration and fluid eligibility values in order to start dialysis.

To improve transportability, the dialyzer is preferably designed with a dry weight of less than 15Kg, preferably less than 10 Kg. Alternatively, the dialyzer may be made up of two or more easily separable parts, for example one part with a balance and an electronic processing unit and one part with a pump, conduits and connectors for both blood and dialysate lines, and an artificial kidney.

Preferably, the present invention provides a disposable dialysate container having a volume of no more than 10L and having sealed dialysate input and output ends adapted to provide fluid connections with other dialysate containers and the inlet/outlet of a dialyzer. The dialysate container may have the features described in relation to the dialysate container and dialysate in the first embodiment.

Furthermore, it may be beneficial that the dialysate container comprises a passage for continuously administering or extracting fluid or additives to or from the dialysate container, e.g. by dripping or as required. Dialysate samples can be extracted by the patient and sent to a central laboratory for analysis to determine the removal of toxic substances such as urea, sodium and phosphate. Furthermore, the passage gives rise to the possibility of continuously analyzing the waste removal rate. Alternatively, the pathway may be provided to administer a drug or nutrient (e.g., glucose, vitamins, or minerals) to the dialysate and thereby to the patient.

A second embodiment of the invention is a method of administering dialysate to a dialyzer, the method comprising:

-providing a dialyzer having a dialysate inlet and a dialysate outlet and pump means for circulating dialysate in the dialyzer and the container;

-providing a flexible dialysate container having an input end opening and an output end opening to provide a fluid connection;

-connecting a dialysate container to an inlet of a dialyzer;

the method is characterized in that:

the step of providing a dialysate container comprises providing a dialysate container containing dialysate and at least one of these containers is empty or a partially filled flexible dialysate container;

-each dialysate container has a volume of no more than 10L;

-the step of connecting the dialysate containers to the dialyzer comprises the step of connecting the dialysate containers between an inlet and an outlet of the dialyzer;

the method further comprises the step of recirculating the dialysate from the outlet of the dialyzer to the inlet of the dialyzer via the connected dialysate containers by activation of the pump means.

The method of administering dialysate to a dialyzer is a technical step and not a treatment. The step of providing a dialysate container with dialysate can be achieved by providing a container with centrally prepared dialysate or by an operator filling said container with purified tap water with additives and connecting the provided filled container to a dialyzer.

A third embodiment of the present invention is a method for performing dialysis, the method comprising:

-providing a dialyzer having a dialysate inlet and a dialysate outlet and providing pump means for circulating the dialysate in the dialyzer and the container;

-providing two or more flexible dialysate containers containing dialysate, each flexible dialysate container having a volume of no more than 10L and input and output ends for providing fluid connections with other dialysate containers and the inlet/outlet of the dialyzer;

-providing at least one empty or partially filled flexible dialysate container;

-connecting the provided dialysate containers in series and/or in parallel between the inlet and the outlet of the dialyzer;

-connecting the dialyzer to a recipient and performing dialysis; and

-circulating the dialysate from the outlet of the dialyzer to the inlet of the dialyzer through the connected dialysate containers.

Preferably, the method further comprises the steps of: adjusting the dialysate flow rate of the dialyzer to provide a flow rate in the interval [ 3.5; 6] degree of recirculation. Also, preferably, the desired dialysis duration is the only parameter directly specified by the operator to the dialyzer, e.g. by typing on a keyboard or equivalent.

Recirculation of dialysate is involved in the prior art, see "Dialysis equivalent and dialysate, past, present and the future" published by John C van Stone at the workshop of crystallography (1999, vol 11, p 3 214-; and "Critical adaptation of therefor and the above-mentioned reduction of therefor, which was published by Cambi et al in Journal of analysis (volume 2, page 143-154 in 1978).

The van Stone article is a historical review that describes how to mix a tank containing 100L of tap water, most often made of glass or steel, with dry chemicals and use large volumes of dialysate. This technique is abandoned because these buckets are difficult to handle. However, van Stone speculates on future development (1997) and he wants the dialysis machine to develop in the future, so that it can be used daily at home, and during each dialysis treatment the amount of dialysis fluid received by the patient will be measured and recorded. The Cambi article describes a system for research. The authors used a system described as "batch transport system filled with 20L or 40L of conventional dialysis solution", i.e. a one-chamber bucket system. Patients were treated only 3 times a week for only 2 hours each time. The system is not able to keep the pH of the patient within acceptable limits and therefore the patient needs a continuous intravenous infusion of baking soda during the dialysis session. The instillation rate is 50-80 mils per hour. Because of the excessively short treatment times in each stage, the authors themselves predicted that the system was insufficient to remove medium-sized molecules (and larger molecules). Data are given after "several weeks of treatment" and the trial is cancelled after 4 months. None of these references describe a system that can be used for home hemodialysis.

An important problem solved by the present invention is how to make home dialysis easier for renal patients. The idea underlying the present invention relates to a system based on recirculation of dialysate, which allows very little consumption of dialysate, which in turn allows a series of advantageous features not present in the prior art, as previously mentioned. These features provide a system for home dialysis that is easy to use, has improved portability, provides high quality dialysate, and allows for long duration dialysis.

Drawings

Figure 1 is a diagram of a typical hemodialyzer according to the prior art;

figure 2 is a perspective view of a dialyzer for use in the present invention;

figure 3 is a cross-sectional view of a dialyzer for use in the present invention;

FIGS. 4-7 illustrate various layouts of a dialysate flow system;

figure 8 shows a system for filling a dialysate container with purified tap water;

figure 9 is a diagram of a dialyzer according to an embodiment of the present invention.

Detailed Description

Figure 2 shows a possible layout of a dialyzer 2 for use in a system according to an embodiment of the invention. The dotted lines represent features inside the dialyzer. Some features that are normally included in the dialyzer but are not relevant to the present invention are omitted. Although the appearance and the external design of the shown dialyser are different from known dialysers, most technical components (pumps, artificial kidneys, sensors, valves, etc.) are similar and perform similar functions. The main difference is that the flow path of the dialysate is designed so that it is recirculated after passing through the artificial kidney, which requires some changes in the tubing and pump arrangement. However, the ability of a person of ordinary skill in the art to construct dialyzers will enable these changes to be made upon review of the present specification.

The dialyzer 2 is a hemodialyzer having a blood inlet 4 and a blood outlet 5 connected to the patient's blood system, as well as a blood pump (not shown) and a blood flow indicator 6. Commercially available catheters, injection needles and artificial kidneys may be used for this purpose. The blood circulates through one side of an artificial kidney (not shown) of the hemodialyzer while the dialysate circulates through the other side of the artificial kidney. For this purpose, the dialyzer has a dialysate circulation system comprising one or more inlets 7 for receiving dialysate and one or more outlets 10 for leading used dialysate out of the dialyzer. The inlet and outlet are fluidly connected to inlet/outlet lines 8 and 11, respectively, to direct dialysate into or out of the artificial kidney. One pump 9 connected to the inlet line 8 regulates the inflow of dialysate from the connected reservoir to the artificial kidney, while the other pump 12 connected to the outlet line 11 regulates the flow of dialysate from the artificial kidney back to the connected reservoir 25 for recirculation. The inlet 7, outlet 10, tubing 8 and 11, pumps 9 and 12, and connected dialysate containers are collectively referred to as a dialysate flow system.

The hemodialyzer 2 has a keypad 15 for the patient to enter, for example, desired dialysis duration and fluid stagnation override values, and the hemodialyzer 2 also has a display 16, the display 16 being used to provide feedback, status and confirmation to the patient. For ease of transport, the dialyzer may have a transport belt 30 or handle (not shown).

The dialyzer 2 is adapted to carry a provided dialysate container 25, e.g. such that the dialysate container 25 is located on the surface 22. The surface 22 is also connected to a balance for weighing the dialysate containers and their contents. The hemodialyzer 2 can thus automatically assess the volume of dialysate in the connected containers before and after dialysis.

The dialysate container 25 is preferably flexible and has an input 26 and an output 27. In order to ensure that the dialysate flows through the container, the dialysate container 25 is oriented with the input 26 connected to the outlet 10 of the hemodialyzer and the output 27 connected to the inlet 7. By making the surface 22 slightly inclined it is ensured that the dialysis fluid in the dialysis fluid container is always collected on the output 27.

Figure 3 is a cross-sectional illustration of a hemodialyzer 30 similar to the hemodialyzer 2 of figure 2 but having a different dialysate flow system layout. Here, the input 26 and the output 27 of the dialysate container 25 are formed at the same lower end, at which the input 9 and the output 11 lines are also formed.

In peritoneal dialyzers, the dialysis fluid traditionally left in the peritoneal cavity is completely and automatically replaced several times by the dialyzer. Modern peritoneal dialyzers allow for the flow of dialysate through the use of dual lumen tubing that enters the peritoneal cavity. In the latter form, the dialysate can be recirculated and has the same advantages as the hemodialyzer. Here, the replacement dialysate is recirculated to the artificial kidney, and the dialysate is recirculated to the peritoneal cavity through the dual lumen tubing.

Figures 4-7 show different layouts of the dialysate flow system. In fig. 4, the dialysate containers 25 are connected in parallel to the input 26 and output 27 on opposite ends, which ensures correct mixing of the dialysate. In fig. 5, the dialysate containers 25 are connected in series with an intermediate conduit 28 interconnecting the containers.

Fig. 6 shows another possible layout of a dialysate flow system with dialysate containers 25 connected in series. Here, the input 26 and the output 27 of each dialysate container 25 are located at the same end of the dialysate container, which makes the flow path of the dialysate flow system simpler. In fig. 7, the input and output of each dialysate container is provided by an opening, which has the advantage of making the handling of the interconnected dialysate containers simpler.

In all arrangements it is important that there is space for loading the liquid extracted from the patient. This may be achieved by providing an empty or partially filled container in the flow system.

The dialysate containers can be made of a material such as PVC which makes them inexpensive and disposable, and appear to withstand autoclaving (autoclaving), and does not require additional cleaning operations.

As mentioned before, the dialysate containers can be filled with centrally prepared dialysate or with dialysate prepared from tap water at the patient's home. Figure 8 shows an installation with a dialysate container 25 filled with water from a tap 45 via a filter 44 and a connector 43. An adapter (not shown) for connecting the filter to the faucet may be included. The apparatus may also include means for supplying additives (e.g. buffers and electrolytes) to the filtered water, for example by adding the additives through the opening 42 before filling the container through the connector 43. Filters or purifiers suitable for preparing dialysate from tap water have been described in, for example, US6719745, which describes a filtration device for producing water of a quality suitable for injection into the human body.

In another embodiment, the filter is manufactured in two parts, which can be separated and transported independently. Each part is much lighter than the entire apparatus and this provides improved handling and increased transportability. An embodiment of such a dialyzer is shown in figure 9. In this embodiment, the dialyzer has two parts 32 and 34, wherein the lower part 34 comprises the balance 22, the electronic processing unit 36 and a contact surface port 38, which contact surface port 38 has a counterpart (not shown) in the upper part 32. The upper part 32 carries the pumps (9, 12 and blood pumps), conduits and connectors for both the dialysate and blood lines, while the upper part 32 also comprises a keypad 15 and a display 16 for convenient placement. The electronic processing unit 36 may also be loaded in the upper part. A transport handle may be provided on both parts and a set of wheels 40 may facilitate transport of the assembled dialyzer.

Since the balance is loaded from the lower portion 34, the entire upper portion can be weighed. This has the advantage that the dialysate can be weighed whether it is in the container or in the tubing of the dialyzer. When the weight of the empty upper portion 32 is programmed into the dialyzer, the total amount of dialysate can be determined. Since the residual dialysate in the catheter is also included in the weighing, a more accurate difference between the starting weight and the final weight can also be calculated to determine the amount of liquid to be ignored.

Claims (22)

1. A system comprising a dialyzer and two or more dialysate containers connected to provide dialysate to the dialyzer, the system characterized by:

the system comprises at least one empty or partially filled dialysate container;

the dialysate container has a volume of no more than 10 liters;

the dialysate container is connected between the outlet and the inlet of the dialyzer such that dialysate flowing out of the dialyzer from the outlet is recirculated to the inlet of the dialyzer.

2. The system of claim 1, wherein the empty or partially filled dialysate container is capable of receiving at least 1 liter of fluid accumulated by the dialyzer.

3. The system of any of the above claims, wherein the dialysate container is flexible and rests on an inclined substantially flat surface.

4. The system of claim 3, wherein the input and output of each dialysate container are disposed in the same end of the dialysate container.

5. The system of claim 1 or 2, wherein the input and output of each dialysate container are provided by an opening in each dialysate container.

6. The system of claim 1 or 2, wherein the input and output of each dialysate container are placed in opposite ends to ensure mixing of the recirculated dialysate.

7. The system of claim 1 or 2, wherein the connected dialysate containers are connected in series.

8. The system of claim 1 or 2, wherein the connected dialysate containers are connected in parallel.

9. The system of claim 1 or 2, wherein the dialyzer further comprises means for calculating and adjusting a dialysate flow rate F of the dialyzer, the calculation and adjustment based on a desired dialysis durationTime t_DAnd the total volume V of dialysate in the connected dialysate containers_totalThe flow rate is calculated to provide a flow rate in the interval [ 3.5; 6]Degree of internal recirculation, RD ═ F × t_D/V_total。

10. The system of claim 9, wherein the system further comprises a scale for weighing the connected dialysate containers and estimating a total dialysate volume, and means for providing the estimated volume to the means for calculating and adjusting the flow rate.

11. The system of claim 1 or 2, wherein the dialyzer does not add substances for adjusting electrolyte concentration or pH to the dialysate from the dialysate containers.

12. The system of claim 1 or 2, wherein the dialyzer has a dry weight of less than 15 kilograms.

13. The system of claim 1 or 2, wherein the dialyzer comprises a pump arrangement and a dialysate flow path configured to facilitate recirculation of dialysate from a dialysate outlet of the dialyzer to a dialysate inlet of the dialyzer through the dialysate containers between the dialysate outlet and inlet of the dialyzer.

14. The system of claim 1 or 2, wherein the dialysate container is filled with centrally prepared dialysate.

15. The system according to claim 1 or 2, further comprising a filter for preparing tap water for use in the dialysate.

16. The system of claim 15, further comprising a connector for filling the dialysate container with filtered tap water.

17. The system of claim 14, wherein the dialysate comprises a physiological grade electrolyte.

18. The system of claim 14, wherein the dialysate comprises ultrapure water.

19. The system of claim 14, wherein the dialysate comprises a dialysate provided at [ 5.50; acetate, lactate, bicarbonate buffer at a pH in the range of 7.50 ].

20. A method of providing dialysate to a dialyzer, the method comprising:

providing a dialyzer having a dialysate inlet and a dialysate outlet and pump means for circulating dialysate within the dialyzer and flexible dialysate containers;

providing the flexible dialysate container with an input end opening and an output end opening to provide a fluid connection;

connecting the dialysate container to an inlet of the dialyzer;

the method is characterized in that:

the step of providing the dialysate containers includes providing a dialysate container containing dialysate and at least one empty or partially filled flexible dialysate container;

each of the dialysate containers has a volume of no more than 10 litres;

the step of connecting the dialysate containers to the dialyzer includes the step of connecting the dialysate containers between an inlet and an outlet of the dialyzer;

the method further comprises the step of recirculating the dialysate from the outlet of the dialyzer to the inlet of the dialyzer via the connected dialysate container by activation of the pump means.

21. The method of claim 20, wherein providing a dialysate container containing dialysate comprises connecting a dialysate container containing centrally prepared dialysate to the dialyzer.

22. The method of claim 20, wherein providing a dialysate container containing dialysate comprises filling the dialysate container with dialysate prepared from purified tap water and connecting the dialysate container to the dialyzer.