Use of copeptin in interpretation of the water deprivation test.

INTRODUCTION: Currently, the water deprivation test remains the standard method for distinguishing primary polydipsia (PP) from cranial diabetes insipidus (cDI) and nephrogenic diabetes insipidus (nDI). There is increasing interest in a direct estimate of antidiuretic hormone using plasma copeptin as a stable and reliable surrogate marker. We present our experience of measuring copeptin during the water deprivation test. METHODS: Forty-seven people (17 men) underwent a standard water deprivation test between 2013 and 2021. Plasma copeptin was measured at the start of the test and at the end of the period of water deprivation (maximum osmotic stimulation). Results were classified using prespecified diagnostic criteria. As it is known that a significant proportion of tests will reveal indeterminate results, a final diagnosis was obtained by including relevant pre- and post-test clinical criteria. This diagnosis was then used to plan individual treatment. RESULTS: Basal and stimulated copeptin were significantly higher in the nephrogenic DI group than other categories (p < .001). There was no significant difference in basal or stimulated copeptin between PP, cDI or partial DI. Nine results were indeterminate where the serum and urine osmolality did not give a unified diagnosis. Stimulated copeptin was helpful in reclassifying these patients into the final diagnostic groups. CONCLUSION: Plasma copeptin has additional clinical utility in interpretation of the water deprivation test and may continue to have a place alongside newer stimulation tests.

Extensive Primary Male Genital Tuberculosis.

Genital tuberculosis (GTB) is uncommon, and the most common genital sites of tuberculous infection are epididymis and prostate; isolated testicular TB is extremely rare, comprising only 3% of GTB. The usual modes of genital involvement include descending infection from the kidneys, intracanalicular or direct extension from neighboring foci in the genital tract, and hematogenous dissemination. Ultrasonography (USG) and USG-guided fine-needle aspiration cytology of testicular swelling may confirm the diagnosis of GTB. Anti-TB chemotherapy is the mainstay of treatment to ensure the complete resolution of the lesion. Infertility in GTB is a result of obstruction at the terminal portion of the ejaculatory duct, resulting in dilatation of the proximal ductal system including the vas deferens preventing seminal vesicle secretions from reaching the ejaculate. Seminal vesicle secretions make up the bulk of the ejaculate, contain fructose, and alkalinize the ejaculate, and with obstruction, patients present with azoospermia or aspermia. Here, we present a rare case of extensive primary GTB in a 36-year-old male.