Abstract 81: A rare case of central diabetes insipidus unmasked after renal transplantation in a young male

Background: The diagnosis of central Diabetes insipidus (DI) requires intact renal function to manifest polyuria. Therefore, it may not become evident in patients with oliguric or anuric renal failure such as in chronic kidney disease (CKD) or end stage renal disease (ESRD). This might get manifested after renal transplantation, however there are only 5 cases reported so far of Central DI post renal transplantation. Here we report a case of central DI that was unmasked in a patient with CKD after kidney transplantation leading to polyuria. Case Report: RV, 26-year-old male had one episode of febrile illness with hematuria at age of 20 years and was diagnosed IgA nephropathy by renal biopsy following which he recovered completely. Hypertension was detected in Feb 2021, and he has been on Cilnidipine 10 mg OD, Clonidine 0.1 mg TDS, Metoprolol XL 40 mg OD. At age of 25 years, he had covid illness and his kidney function deteriorated to ESRD for which he was started on twice weekly hemodialysis for 8 months and then underwent live donor renal transplantation in October 2021. Two months later, he was admitted for polyuria, polydipsia, and nocturia. After renal transplantation, his urine volume increased to 9-10 L/ d, while it had been less than 500 mL/day before the transplantation. His serum creatinine level improved from 3.2 mg/dL prior to transplant to 0.8 mg/dL after transplant. He had not been diagnosed with diabetes before, and his blood glucose levels were within the normal range. He showed no symptoms of polyuria or polydipsia before transplantation and had no history of head trauma or neurosurgery. Diagnosed to have primary hypothyroidism in Feb 2021 during pre-transplant workup, for which he was started on levothyroxine 50 ug and was euthyroid. The patient received prednisolone, tacrolimus, mycophenolate mofetil, and sulfamethoxazole/trimethoprim after the transplantation. During evaluation for polyuria, urine volume was >100 ml/kg in 24 Hour. Serum osmolality of 295 mOsm/kg, urine osmolality of 101 mOsm/kg, and serum sodium of 138 mEq/L, RBS 86 mg/dl, Urea 24 mg/dl. Anterior pituitary hormone profile workup was normal. To evaluate the cause of polyuria, water deprivation test was performed which confirmed complete central diabetes insipidus. He was started on oral desmopressin 120 ug in divided doses. His urine output subsequently decreased to about 2.5 L/d with resolution of excessive thirst and nocturia. MRI sella revealed normal anterior pituitary, infundibulum and diminished posterior pituitary bright spot in the T1-weighted image. Patient is continued on desmopressin therapy at 6 months with marked improvement in symptoms. Conclusion: In this case, the water deprivation test and diminished posterior pituitary bright spot-on MRI and the responsiveness to desmopressin therapy confirm the diagnosis of central DI. Hence, any case of polyuria after renal transplantation must be evaluated for Central Diabetes Insipidus.