It has been shown that excretion of sodium and water through the skin in the form of sweat represents a regulatory mechanism of electrolyte- and fluid balance. Since patients with chronic kidney disease (CKD) exhibit increased skin sodium content, we investigated the feasibility of sweat testing as a novel experimental tool to a more complete assessment of fluid- and sodium homeostasis.

In this cross-sectional feasibility study, we applied pilocarpine iontophoresis to induce sweat testing in 58 patients across various stages of CKD including patients after kidney transplantation as well as a healthy control cohort (n=6) to investigate possible effects of CKD and transplantation status on sweat rate and sodium concentration. Due to non-linear relationships, we modeled our data using polynomial regression.

Decline of kidney function showed a significant association with lower sweat rates: adj R²= 0.2278, F(2, 61) = 10.29, p = 0.000141. Sweat sodium concentrations were increased in moderate CKD, however this effect was lost in end stage renal disease: adj R² = 0.3701, F(4, 59) = 10.26, p = 2.261e-06. We observed higher sweat weight in males compared to females.

Diagnostic sweat analysis represents an innovative and promising noninvasive option for more thorough investigation of sodium- and fluid homeostasis in CKD patients. Lower sweat rates and higher sweat sodium concentrations represent a unique feature of CKD patients with potential therapeutic implications.

Inclusion Criteria:

Completed 18th year of life and the ability and willingness to provide informed consent

Exclusion Criteria:

General exclusion criteria were signs of acute infection, clinical signs of kidney graft rejection or pregnancy. Exclusion criteria for the healthy controls were pregnancy or the presence of chronic metabolic, renal, cardiovascular, or rheumatologic conditions, hypertension, chronic or recent intake (8 weeks prior to testing) of psychiatric or antihypertensive medication.

Healthy controls older than 18 years old. Patients older than 18 years old with all grades of Chronic Kidney Disease (also patients receiving hemodialysis)