Routine Bladder Scanning Reduces Postoperative Hyponatremia After Joint Replacement: Study

Hyponatraemia is a frequent complication after joint replacement surgeries, often arising from fluid and electrolyte imbalances in the postoperative period. In a new article published in BMC Nephrology, Mamdouh Hefny, Raheel Faiz, Alexander Denning, Paul Saunders, and colleagues propose that routine bladder ultrasound scanning integrated into postoperative fluid management can significantly reduce the incidence of hyponatraemia. By distinguishing urinary retention from true acute kidney injury, the authors argue that more appropriate, tailored fluid administration becomes possible, decreasing the risk of dilutional hyponatraemia.

The authors studied outcomes before and after implementing a bladder scanning protocol at a single centre. In their retrospective review, hyponatraemia was common among patients undergoing elective joint arthroplasty. After introducing routine scans to monitor bladder volume at fixed intervals and using those data to guide fluid therapy decisions, the incidence of postoperative hyponatraemia fell markedly, while the rate of acute kidney injury remained stable. The authors emphasize that urinary retention can mimic low urine output, leading clinicians to mistakenly administer excess fluid, thereby provoking dilutional hyponatraemia. By comparing bladder volumes over time, one can better distinguish whether low output is caused by retention or by true renal dysfunction, and respond accordingly.

What this really means is that incorporating bladder scanning into postoperative management offers a relatively simple, noninvasive tool to improve fluid-electrolyte balance after joint replacement. The study suggests that continuous education of clinical staff and targeted interventions based on scan results can further enhance outcomes. While limitations include the single-centre design and relatively small prospective cohort, the findings are promising. They point toward a shift in postoperative protocols for arthroplasty care—one where routine bladder assessment helps prevent iatrogenic hyponatraemia without compromising renal safety. Published in BMC Nephrology, this study adds valuable insight into optimizing electrolyte management in orthopaedic surgery.

Keywords: Hyponatraemia, Acute kidney injury, Joint replacement, Arthroplasty, Bladder scanning, Postoperative fluid management, Urinary retention, BMC Nephrology, Fluid-electrolyte balance

Reference:

Hefny, M., Faiz, R., Denning, A., Saunders, P., et al. (2025). Hyponatraemia, AKI, and urinary retention following elective joint arthroplasty. BMC Nephrology, 26, Article 552. https://doi.org/10.1186/s12882-025-04473-w