Background: Hyperparathyroidism is common in patients with chronic kidney disease with reduced renal function and has been observed after kidney transplantation. The optimal treatment for cases in which hyperparathyroidism persists after kidney transplantation has not been determined. Methods: This retrospective study included 83 patients with tertiary hyperparathyroidism who underwent kidney transplantation between 2000 and 2018 at a single tertiary center in Korea. Sixty-four patients underwent parathyroidectomy and 19 patients were treated with cinacalcet following renal transplantation. Biochemical parameters and clinical outcomes were compared between the two groups. Results: Serum calcium and parathyroid hormone (PTH) levels improved in both the parathyroidectomy and cinacalcet groups. One year after treatment, parathyroidectomy resulted in a lower mean serum calcium level than cinacalcet (9.7 ± 0.7 mg/dL vs. 10.5 ± 0.7 mg/dL, p = 0.001). Regarding serum PTH, the parathyroidectomy group showed a significantly lower PTH level than the cinacalcet group at 6 months (129.1 ± 80.3 pg/mL vs. 219.2 ± 92.5 pg/mL, p = 0.002) and 1 year (118.8 ± 75.5 pg/mL vs. 250.6 ± 94.5 pg/ mL, p < 0.001). There was no statistically significant difference in the incidence of kidney transplant rejection, graft failure, cardiovascular events, fracture risk, or bone mineral density changes between the two groups. Conclusion: Parathyroidectomy appears to reduce PTH and calcium levels effectively in tertiary hyperparathyroidism. However, creatinine level and allograft rejection should be monitored closely.

Nutcracker syndrome is caused by external compression of the left renal vein and is characterized by various symptoms, such as hematuria and left flank pain. However, long-standing gross hematuria is uncommon. We report the case of a 23-year-old woman who had had painless gross hematuria for several months. Kidney biopsy revealed thin basement membrane disease, but this did not explain the gross hematuria with proteinuria. Renal venography and Doppler ultrasonography showed increased diameter and velocity ratios between the left renal vein and inferior vena cava. Cystoscopy revealed that the hematuria originated from the left ureteral orifice. These results indicate coexisting Nutcracker syndrome. Nutcracker syndrome with thin basement membrane disease should be considered in the differential diagnosis of a patient who has long-standing gross hematuria.