Background

Renal allograft recipients (RAR) may develop tertiary hyperparathyroidism despite adequate renal function. Secondary hyperparathyroidism is a common metabolic complication after bariatric surgery (BS) with a prevalence of 35.4% at 1-year mark. However, the long-term effect on calcium metabolism in RAR undergoing BS is not completely clear. In this study, we evaluate the changes to calcium and parathyroid hormone (PTH) homeostasis following BS in RAR.

Methods

A retrospective, multi-institutional study was conducted using the TriNetX database. There were 69 RAR who underwent BS compared to a control group of 27,593 RAR alone. These groups were propensity matched, including a BMI of over 35 kg/m2.

Results

There were no significant differences in normocalcemia and hypercalcemia in RAR with or without BS up to 2-years. However, there was significantly lower incidence of hypocalcemia in RAR after BS (p<0.05). Significantly fewer RAR after BS took calcium supplements up to 1-year mark (p<0.02). Cinacalcet intake was not significantly different between the two groups (P>0.05) at 2-years. Significantly more RAR after BS had low PTH levels (P<0.001), while normal and high PTH levels were not significant (p>0.05) at 2-years. None of the RAR underwent parathyroidectomy within 2-years with or without BS. No RAR had Vitamin-D deficiency, osteoporosis, or stress-fractures up to 2-years following BS. Osteopenia in RAR following BS was insignificant (p=0.695).

Conclusions

Bariatric surgery in renal allograft recipients does not increase hypocalcemia, Vitamin D deficiency, stress fractures, and osteoporosis up to 2 years. Further studies are needed to confirm these findings.