Effects of Massive Resection of the Distal Small Intestine on the Metabolism of Vitamin D and Bone in Dogs

Mikio Imamura, Hidemi Yamauchi

Department of Surgery, Sendai National Hospital

Experiments were performed on dogs to investigate the consequences of malnutrition after massive resection of the small intestine on the metabolism of vitamin D and bone. We further investigated the therapeutic effects of the administration of active vitamin D₃ (1α(OH)D₃) with or without ursodeoxycholic acid (UDCA). Nine adult beagle dogs underwent 75% resection of the distal small intestine, and were divided into three groups: Group A (n=3) received both 1α (OH)D₃ and UDCA, Group B (n=3) received 1α (OH)D₃ alone, and Group C (n=3) did not receive either. During the observation period of six months after surgery, body weight decreased, watery diarrhea occurred, and transit time of the whole alimentary tract shortened. The administration of both 1α (OH)D₃ and UDCA improved the maldigestive state. Plasma levels of vitamin D metabolites such as 25 (OH)D and 24·25 (OH)₂D decreased after surgery, whereas 1α·25 (OH)₂D levels were barely kept within the preoperative range. Plasma levels of calcium, phosphorus, and protein remained unchanged for six months postoperatively. Histological study of the third lumbar spine did not show any findings of osteoporosis. Bone histomorphometry using a digitizing system showed no definite decrease in bone volume, but revealed a significant decrease in osteoid volume (OV), thickness (O.Th) and surface (OS), and bone formation rate (BFR). Mineralized surface (MS) and BFR were markedly reduced in Group C. These results suggest that insufficient matrix formation caused by nutritional malabsorption is related with decreases in OV, O.Th, OS and BFR, and will lead to osteopenia after a longer period. It is probable that administration of 1α (OH)D₃ together with UDCA after massive small bowel resection is effective to lighten the disturbance of matrix formation, although further studies are needed.

Key words
massive bowel resection, beagle dogs, ursodeoxycholic acid, vitamin D metabolites, bone histomorphometry

Reprint requests
Mikio Imamura Department of Surgery, Sendai National Hospital
2-8-8 Miyagino, Miyagino-ku, Sendai, 983 JAPAN

Accepted
June 17, 1992

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