Gastric patch pyeloplasty: development of an animal model to produce upper tract urinary acidification for treating struvite urinary calculi.
OBJECTIVE
Struvite calculi form in an alkaline environment created by urease producing uropathogens. We developed a viable upper tract urinary acidification model by performing gastric patch pyeloplasty in the rabbit. This model produces urinary acidification sufficient for the treatment and prevention of struvite renal calculi. We evaluated the physiological, metabolic and surgical outcomes.


METHODS
gastric segment was harvested based on branches of the left gastro-epiploic artery. The flap was folded along the transverse axis and the adjacent edges were closed. The mouth of this reconfigured pouch provided optimal dimensions for anastomosis with the diminutive renal pelvis. Half of the rabbits were treated with internal stenting and H-2 blockade. Urinary pH was assessed by weekly cage collection and direct collection from the cannulated ureters. Urine culture was done, and serum gastrin and electrolytes were assessed at regular intervals. The rabbits were sacrificed at 3 to 26 weeks. Histological examination was routinely performed.


RESULTS
A total of 15 rabbits were available for complete assessment. Sustained urinary acidification was produced in 7 animals (47%) with a mean pH decrease of 2.27. In another 2 rabbits (13%) the urine was initially acidic but subsequently became alkaline due to ureteral obstruction. Electrolytes and gastrin were unchanged in these rabbits and urine culture was positive in 2. Histological testing revealed nonspecific inflammatory changes of the renal pelvis. Anastomotic complications were the most common surgical complication and the most common cause of failed acidification. The cohort treated without stents and H-2 blockade was at significantly greater risk for anastomotic leakage.


CONCLUSIONS
Gastric patch pyeloplasty may significantly increase urinary acidity in the rabbit model without altering the serum electrolyte balance or gastrin level. The procedure utilizes common techniques of reconstructive urology and may be possible with laparoscopy. Further study is required to assess the in vivo effect of this procedure for treating and preventing upper tract struvite calculi.
Donnellan
S M
SM
Departments of Urology and Surgery, Austin and Repatriation Medical Centre, Melbourne, Victoria, Australia.
Ryan
A J
AJ
Bolton
D M
DM
D000818:Animals; D004573:Electrolytes / Q000097:blood; D005755:Gastrins / Q000097:blood; D006863:Hydrogen-Ion Concentration; D007682:Kidney Pelvis / Q000601:surgery*; D017616:Magnesium Compounds / Q000378:metabolism*; D023421:Models, Animal; D010710:Phosphates / Q000378:metabolism*; D011817:Rabbits; D013270:Stomach; D000069877:Struvite; D013524:Surgical Flaps; D014545:Urinary Calculi / Q000378:metabolism / Q000517:prevention & control / Q000628:therapy*; D014556:Urine
D004573:Electrolytes; D005755:Gastrins; D017616:Magnesium Compounds; D010710:Phosphates; D000069877:Struvite