RENAL DAMAGE WITH INTESTINAL-BYPASS

Renal function and biopsies were studied in 18 patients, 7 to 108 mth after intestinal bypass. Enteropathy was found in 12 and hyperoxaluria in 16. Every biopsy showed a type of focal interstitial nephritis, tubular atrophy, fibrosis, and glomerular hyalinization. Damage ranged from minimal to extensive and renal function from normal to end-stage failure. Tubular injury had resulted partly from oxalate deposits. However, in 10 patients no oxalate crystals were seen. In 8 others, most of the damaged areas were remote from crystal deposits. Immunoglobulin M and C3 deposits, found in glomerular capillaries and the mesangium in 6 of 11 specimens, and the presence of circulating immune complexes in 5 of 10 patients, in addition to the extraintestinal organ involvement, suggested immune complex mesangial injury as one factor in bypass nephropathy. With progressive impairment of renal function, a biopsy appears justified. If damage is significant, the bypass should be dismantled.