A Mathematical Approach to the Evaluation of Sediment Transport Capacity in the Human Urinary Tract

Abstract

Background It is not yet clear whether forced diuresis is useful for flushing out of the urinary tract, especially in cases of renal calculi or infections. A series of experiments conducted initially in vitro and then in vivo in rabbits, using sand and small glass spheres, showed that sediments can be eliminated from the urinary tract by forced diuresis. When distilled water was used, the effect was greater, both as weight of sand and as number of spheres eliminated, than when normal saline was used. The different characteristics of the two liquids gave rise to different intrapelvic pressures for a given flow. Materials and Methods Intrapelvic pressures, and liquid and solid discharges in vitro and in rabbits were used in a fluid mechanics analysis of the phenomenon to obtain non-dimensional formulae so that the results in rabbits could be extended to humans. Results The results made it possible to evaluate solid transport capacity induced in a healthy human of given weight by drinking a given quantity of water in an hour. Conclusions The mathematical model makes it possible to determine the quantity of water a patient must drink to induce a transport force sufficient for urinary tract wash-out.