Artificial kidney is often a synonym for hemodialysis, but may also, more generally, refer to renal replacement therapies (with exclusion of renal transplantation) that are in use and/or in development. This article deals with bioengineered kidneys/bioartificial kidneys that are grown from renal cell lines/renal tissue.
Hemodialysis is a method for removing waste products such as creatinine and urea, as well as free water from the blood when the kidneys are in renal failure. The mechanical device used to clean the patients blood is called a dialyser, also known as an artificial kidney. Modern dialysers typically consist of a cylindrical rigid casing enclosing hollow fibers cast or extruded from a polymer or copolymer, which is usually a proprietary formulation. The combined area of the hollow fibers is typically between 1-2 square meters. Intensive research has been conducted by many groups to optimize blood and dialysate flows within the dialyser, in order to achieve efficient transfer of wastes from blood to dialysate.
Bioengineered kidneys
Currently, no viable bioengineered kidneys exist. Although a great deal of research is underway, numerous barriers exist to their creation.[5][6][7]
However, manufacturing a membrane that mimics the kidney’s ability to filter blood and subsequently excrete toxins while reabsorbing water and salt would allow for a wearable and/or implantable artificial kidney. Developing a membrane using microelectromechanical systems (MEMS) technology is a limiting step in creating an implantable, bioartificial kidney.
The BioMEMS and Renal Nanotechnology Laboratories at the Cleveland Clinic’s Lerner Research Institute have focused on advancing membrane technology to develop an implantable or wearable therapy for end-stage renal disease (ESRD). Current dialysis cartridges are too large and require superphysiologic pressures for blood circulation, and pores in current polymer membranes have too broad of a size distribution and irregular features. Manufacturing a silicon, nanoporous membrane with narrow pore size distributions improves the membrane’s ability to discriminate between filtered and retained molecules. It also increases hydraulic permeability by allowing the mean pore size to approach the desired cutoff of the membrane. Using a batch-fabrication process allows for strict control over pore size distribution and geometry. [8]
In recent studies, human kidney cells were harvested from donated organs unsuitable for transplatation, and grown on these membranes. The cultured cells covered the membranes and appear to retain features of adult kidney cells. The differentiated growth of renal epithelial cells on MEMS materials suggests that a miniaturized device suitable for implantation may be feasible.
Indications for Dialysis: Excerpt from A Pocket Manual of Differential Diagnosis
* Biochemical Criteria
1. Volume overload
2. Serum K+ >6 mEq/L (despite medical management)
3. Serum HCO3– <10 mEq/L, pH <7.20
4. Blood urea nitrogen >80–100 mg/dL
5. Serum creatinine >8–10 mg/dL
6. Creatinine clearance <10–15 mL/min
* Symptomatic Criteria
1. Central nervous system symptoms (e.g., lethargy, confusion, seizures, asterixis)
2. Gastrointestinal symptoms (e.g., nausea, vomiting)
3. Pericarditis
4. Bleeding diathesis
* Miscellaneous Indications (Conditions Not Necessarily Associated with Renal Failure)
1. Hypercalcemia
2. Hypermagnesemia
3. Hyperuricemia
4. Hypernatremia
5. Hypothermia
6. Drug overdose, toxin ingestion
