Hyponatremia After Colonoscopy Bowel Preparation: Challenges in Managing Syndrome of Inappropriate Antidiuretic Hormone Without Established Guidelines.

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition that leads to free water retention and solute excretion, predisposing patients to hyponatremia. We present the case of a 79-year-old female with a history of SIADH well-controlled with fluid restriction and sodium chloride tablets who presented with hyponatremia after bowel preparation. Her medication regimen was not adjusted before she took the bowel preparation. Her SIADH diagnosis was unknown when she presented but was exemplified by her sodium levels dropping while on a normal saline drip on her third day in the hospital. She was able to successfully take the bowel preparation without hyponatremia after oral urea was added to her regimen. There are currently no clinical guidelines for SIADH patients receiving bowel preparation for colonoscopies and no case reports describing this situation. We discuss the pathophysiology behind the patient's fluctuating sodium levels when on various maintenance fluids and when on fluid restriction. This case concludes that it is imperative to either increase solute intake or increase free water excretion for SIADH patients receiving bowel preparation to prevent potentially deadly hyponatremia.