Metabolic Bone Disease After Intestinal Bypass for Treatment of Obesity

Abstract

We studied the bone status in 52 patients 1 to 14 years after intestinal shunt surgery. Before operation, bone mass measured by photon absorptiometry and radiographic morphometry was normal by two criteria and slightly reduced by a third. After jejunocolostomy both cross-sectional and longitudinal data showed accelerated loss of bone due to increased net endosteal resorption. Similar but less significant changes occurred after jejunoileostomy. The severity of bone loss correlated better with hypoproteinemia than with any other biochemical measurement. Bone biopsy after tetracycline labeling in 10 patients with bone pain showed osteomalacia in two and significant impairment of osteoblast function in seven. Plasma 25-hydroxycholecalciferol levels were normal or low despite prescription of 1.25 mg of vitamin D2 daily. Plasma parathyroid hormone levels were raised in only three of the patients with abnormal bone histology. We conclude that intestinal shunt surgery has an adverse effect on the bones. There is persistent intestinal malabsorption of vitamin D and calcium, doses of which ordinarily given to these patients may be too small, but it is likely that other nutritional deficiencies are also important.