Seromuscular colocystoplasty lined with urothelium protects dogs from acidosis during ammonium chloride loading

We compared the metabolism of intravesical ammonium chloride in dogs in which the bladder had been enlarged by seromuscular colocystoplasty lined with urothelium, dogs that had undergone conventional colocystoplasty and control dogs.

Eight adult female mongrel dogs were divided into control (2), colocystoplasty (3) and seromuscular colocystoplasty (3) groups. Serum creatinine, bicarbonate, sodium, chloride, and potassium levels were measured every 2 weeks during the 6-week recovery period. Six weeks after augmentation the dogs were placed under general anesthesia, the bladder was instilled with a hyperosmolar solution of 400 mmol/l. ammonium chloride, the femoral artery and portal vein were cannulated to obtain blood samples and the ureters were divided with the proximal ends diverted to allow serial urine measurements. Blood and urine electrolyte analysis was performed at 0, 60, 120, 180 and 240 minutes after the intravesical instillation of ammonium chloride.

During acid loading dogs that had undergone conventional colocystoplasty had a progressive decrease in serum carbon dioxide and arterial pH as well as increased levels of serum chloride and a significant increase in plasma ammonia concentration in the portal vein compared to controls and dogs that had undergone seromuscular colocystoplasty. In contrast, there were no differences in seromuscular colocystoplasty compared to control animals.

Increased ammonia in the portal vein and hyperchloremic acidosis in dogs that underwent conventional colocystoplasty suggest intravesical absorption of ammonium chloride. Dogs that underwent augmentation with seromuscular colocystoplasty lined with urothelium seemed to respond to acute intravesical ammonium in a way similar to that of control dogs and they are protected from these metabolic anomalies.