1991 Volume 82 Issue 3 Pages 439-446
To clarify the mechanism of metabolic changes after using intestinal segments as a urinary tract, absorption of urinary constituents from the ileum was studied in dogs.
An isolated distal ileum (30cm in length) was anastomosed to the urinary bladder in each dog. Although these animals maintained the normal renal function throughout the experimental period, mild acidosis was noticed one month after anastomosis and it became severe after six months.
Stagnation of a urine-like solution (artificial urine: AU) in the isolated ileum resulted in an absorption of 66% of the instilled solvent on average during 60 minutes. The average absorption rates of each AU constituent were as follows: sodium 63%, potassium 80%, chloride 83%, phosphorus 68%, magnesium 34%, urea nitrogen 93% creatinine 56%, and ammonia 97%. On the contrary, calcium increased in the stagnated fluid by 21%.
In spite of the severe histologic changes in the villi of the ileal mucosa, which became atrophic and flat, no deterioration in the absorptive capacity of the AU constituents was noticed during the six month experimental period.
Furosemide administration suppressed the absorption of urinary constituents, especially water and sodium. On the other hand, the absorption of urea nitrogen and ammonia was scarcely affected.
Perfusion of the isolated ileum with AU (0.5ml/min) for 60 minutes resulted in an absorption of 59% of the solvent and 50 to 86% of each constituent. The rate of absorption was reduced after increment of the perfusion rate.
In conclusion, the absorption of urinary constituents occurs rapidly and significantly. The absorptive capacity remains longer regardless the severity of histological changes of the ileal mucosa. These results indicate that an increase in frequency of micturition, an increase in urine volume, and reducing the time of urinary stagnation in the ileum are important to prevent metabolic acidosis after utilizing the ileum as a urinary tract.