Acute hypocalcemia following kidney transplantation may depend on the type of remote parathyroidectomy: a retrospective cohort study .

BACKGROUND

Secondary hyperparathyroidism is a common complication of chronic kidney disease. When medical management fails, parathyroidectomy (PTX) is a treatment option. The two most common types are subtotal PTX and total PTX with autotransplantation (AT). To date, there is no consensus as to which procedure is preferable, especially in patients who are candidates for future kidney transplantation. The aim of this study was to identify if the type of PTX is a risk factor for acute postrenal transplant (postRTX) hypocalcemia and a concern for problems with long-term calcium homeostasis.

METHODS

Renal transplant recipients at Rhode Island Hospital from 2005 to 2014 were screened for prior PTX. Out of 297 participants, 11 patients met the criteria. They were further divided into subtotal PTX (n = 5) vs. total PTX+AT (n = 6). Immediate postoperative (14 days) and long-term (1 year) calcium levels were followed and analyzed. Linear growth models were used to determine the effects of type of parathyroidectomy (subtotal PTX, total PTX+AT) alone on hypocalcemia over time. In these models, pretransplant levels of calcium and PTH were included as covariates.

RESULTS

Baseline characteristics showed that prerenal transplant (preRTX) parathyroid hormone (PTH) levels were lower in total PTX+AT vs. subtotal PTX (3.5 vs. 247.2 mg/dL, p < 0.005). PreRTX calcium levels were slightly lower in subtotal PTX (9.5 vs. 8.25 mg/dL, p < 0.01), but were within normal limits for both groups. No significant differences were noted between total vitamin D levels and time between PTX and RTX. Within 14 days postRTX, the total PTX+AT group had lower average calcium levels (5.8 vs 8.8 mg/dL, p < 0.001); however, both groups had normal and stable calcium levels from 1 month to 1 year after transplant. This was further supported after adjusting for preRTX levels of calcium and PTH, showing a significant interaction between treatment and time such that patients had lower calcium levels if they underwent total PTX+AT vs. subtotal PTX within 14 days postRTX (β = -0.204, SE = 0.039, p < 0.001) (Figure 1) but not at 1 year postRTX (β = 0.035, SE = 0.075, p = 0.640).

CONCLUSION: This study suggests that total PTX+AT increases the risk for acute postRTX hypocalcemia but has no effect on long-term calcium homeostasis. We speculate that the acuity of the hypocalcemia may be compounded by high-dose glucocorticoids required for induction, in addition to the preoperative undetectable PTH. Thus, prior to RTX, physicians should take into account the type of remote PTX. If a patient had a total PTX+AT, then postRTX hypocalcemia is likely to occur.
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