Induction of urolithiasis in single comb white Leghorn pullets: effect on glomerular number

Urolithiasis was induced in an experimental group of Single Comb White Leghorn pullets by feeding them layer ration and exposing them to nephrotrophic Gray strain infectious bronchitis virus (IBV). Gray strain IBV was recovered from kidney and cloacal swabs for up to 26 days after exposure to the virus. Control pullets fed pullet grower ration and not exposed to Gray strain IBV did not develop urolithiasis. The experimental design did not allow differentiation between the roles of layer ration and IBV in triggering urolithiasis. Urolithiasis was associated with asymmetry in left vs. right kidney weight comparisons for individual pullets. Pullets from the urolithiasis group had 43,800 +/- 4,500 glomeruli/gram kidney weight, whereas control pullets had 68,770 +/- 3,500 glomeruli/gram kidney weight. This difference was significant (P less than .01). Total kidney weights did not differ significantly when the experimental and control pullets were compared. Comparisons of glomeruli size distributions indicated that the number of intermediate sized glomeruli (.15 to .22 mm in circumference) was significantly reduced in pullets from the urolithiasis treatment group. These observations indicate that a significant reduction in nephron number can be masked by compensatory hypertrophy of the remaining kidney tissue in pullets with urolithiasis.