Katalin Kiss: Mannitol – a promising tool for measuring kidney function easy and safe
The sugar molecule mannitol is a promising and reliable option for directly measuring kidney function - both in critically ill patients and those with stable chronic kidney disease. That’s the conclusion of research presented in Katalin Kiss’s doctoral thesis. But before the method can be widely adopted in clinical practice, more studies involving larger patient groups are needed.
KATALIN KISS
Dissertation defense: 11 June 2025 (click for details)
Doctoral thesis:
Research area: Anesthesiology and Intensive Care
Sahlgrenska Academy, The Institute of Clinical 91̽s
NOTE: It is possible to follow the public defense via Teams:
The kidneys play a key role in regulating the body’s fluid and electrolyte balance, removing waste products, and producing hormones that affect blood pressure, red blood cell production, and vitamin D activation.
The gold standard for assessing kidney function is to measure what’s known as the glomerular filtration rate (GFR). While direct measurement is the most accurate method, the accessibility is limited. That’s why estimated GFR (eGFR) is often used instead. These estimates work well for stable patients—but can be very unreliable in critically ill individuals, especially those in intensive care units.
“In my thesis, I investigated mannitol, a sugar molecule that is freely filtered by the kidneys and can be used to directly measure kidney function,” says Katalin Kiss, specialist in anesthesiology, intensive care, and pulmonary medicine. She works at the Department of Anesthesiology at Sahlgrenska University Hospital and a doctoral student at the Institute of Clinical 91̽s.
The method was tested on both critically ill ICU patients and outpatients with chronic kidney disease, and the results were compared to established reference methods.
Simplified figure that resembles a more complex figure from the thesis: The glomerular filtration rate (GFR) tells us how well the kidneys are working. It shows how much blood the kidneys clean every minute. Measured and estimated GFR can differ a lot in different clinical situations, highlighting the need for wider implementation and accessibility of the measurements in routine clinical practice.
Mannitol is easy to use and has no side effects
Measurements using mannitol closely matched current reference methods in both patient groups—those treated in outpatient care and those in the ICU. The technique is simple to use and safe, since mannitol doesn’t cause any side effects.
“We also demonstrated that relying solely on estimates can lead to misleading results—especially in ICU patients. This highlights the importance of direct measurement when accurate results are essential. The method has also been tested by another research group on premature babies.”
What’s been the most rewarding and most challenging part of your PhD project?
“The first study, with outpatient participants, went smoothly. But when we moved on to ICU patients, we ran into problems—the results were odd. It took a while to figure out that a commonly used medication actually contains mannitol, which interfered with the measurements. Once we adjusted the inclusion criteria to exclude patients receiving that medication, the data lined up perfectly with standard methods.”
Text: Susanne Lj Westergren