Maintenance peritoneal dialysis and hemodialysis sustain the lives of approximately 250,000 uremic patients in industrialized nations worldwide. The cost of uremia therapy, however, exceeds health care budgets in developing countries. As a consequence, most of those alive today have no chance of effective treatment should their kidneys fail. Extraction, modification, or recycling of nitrogenous wastes by the gastrointestinal tract is a potentially low-cost means of substituting for missing renal function. Multiple approaches to the bowel as a substitute kidney have been attempted. Direct removal of nitrogen-containing compounds by an external gut fistula, gastric, ileal, or colonic gavage (dialysis) or induced diarrhea extract water and urea but only minimal amounts of larger molecules such as creatinine. Binding of nitrogen compounds to inert orally administered sorbents such as charcoal or oxystarch has been pursued in advanced uremia. Modification of nitrogen compounds by ingesting enzymes derived from soil bacteria or packaged in artificial cells is an approach that, although exciting, is incompletely evaluated. Evidence indicates that strains of bacteria can be induced to synthesize enzymes that recycle urea and other nitrogen compounds retained by uremic individuals. Clinical trials to substantiate uncontrolled trials of bowel substitution in renal failure will, if positive, accelerate development of a practical regimen to extend life where no other means are possible.
