Surreal illustration representing fluid overload in chronic kidney disease.

Fluid Overload in CKD: Can We Trust Our Eyes?

Lena Voss in Health & Wellness December 2025 • 4 min read.

"Balancing Act: Comparing Edema Assessment Techniques in Chronic Kidney Disease"

In the world of chronic kidney disease (CKD), managing fluid levels is a constant battle. Even when it's not obvious, fluid overload can sneak in, leading to uncontrolled high blood pressure and a greater risk of heart problems. Accurately determining how much fluid is too much is a challenge doctors face every day.

Traditional methods rely on physical exams to spot swelling (edema), but are our eyes enough? A recent study dug deeper, comparing physical assessments with more advanced techniques like ultrasound measurements of the inferior vena cava (IVC) and bioelectrical impedance analysis (MF-BIA). The goal? To get a clearer picture of hydration status in CKD patients and uncover hidden fluid overload.

This article explores the findings of this research, shedding light on the limitations of relying solely on physical exams and highlighting the importance of using a combination of methods for accurate fluid management in CKD. We'll break down the science in an easy to understand way.

Beyond the Eye Test: Unveiling Hidden Fluid

Surreal illustration representing fluid overload in chronic kidney disease.

The study, conducted between September and December 2014, involved a close look at patients with CKD. Doctors carefully checked for edema in the lower limbs. Blood samples were also taken to measure creatinine and sodium levels. Importantly, all ultrasound measurements were performed by a single physician, separate from those evaluating edema or using the bioimpedance device, ensuring unbiased results.

Researchers used MF-BIA to estimate the ratio of extracellular water (ECW) to total body water (TBW). A ratio above 0.39 was considered indicative of an edematous state. The study revealed some surprising findings:

Overt edema (visible swelling) was present in 43.5% of patients.
Patients with more advanced CKD (stage 5) had a higher incidence of overt edema.
The diameter of the IVC was smaller in patients without overt edema, as you would expect.
MF-BIA identified fluid overload in a whopping 61.3% of patients, highlighting the prevalence of hidden fluid retention.
Interestingly, 34% of patients without overt edema were diagnosed with subclinical edema (hidden fluid overload) by MF-BIA.

The study also found a link between fluid overload and hypertension. Patients with overt edema were more likely to have high blood pressure. Furthermore, there was a correlation between blood pressure and IVC diameter, as well as ECW.

What Does It All Mean? A Call for Comprehensive Assessment

This study underscores that relying solely on physical exams to detect fluid overload in CKD is not enough. Subclinical edema is common, and advanced techniques like MF-BIA can reveal hidden fluid imbalances that might otherwise go unnoticed.

The link between fluid overload and hypertension highlights the importance of accurate assessment and management. Identifying and addressing fluid overload early can lead to better blood pressure control and potentially reduce the risk of cardiovascular complications.

An isolated systolic arterial hypertension, an IVC diameter higher than 20 mm or an ECW/TBW ratio higher than 0.39 must raise awareness regarding a possible fluid overload requiring prompt management. Healthcare providers should consider incorporating MF-BIA into their assessment of CKD patients, especially when blood pressure is difficult to control or when there is suspicion of hidden fluid overload.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

Everything You Need To Know

Why is fluid management so important in chronic kidney disease?

In chronic kidney disease, managing fluid levels is crucial because fluid overload, even when not immediately apparent, can lead to complications such as uncontrolled high blood pressure and increased risk of heart problems. Accurately assessing fluid status is essential for preventing these adverse outcomes. Traditional methods, like physical exams focusing on detecting visible swelling (edema), might not be sufficient to identify hidden fluid accumulation.

What methods were used in the study to assess fluid status in CKD patients?

The study used physical examinations to detect overt edema, measured creatinine and sodium levels from blood samples, and employed ultrasound measurements of the inferior vena cava (IVC) to assess fluid volume. Bioelectrical impedance analysis (MF-BIA) was utilized to estimate the ratio of extracellular water (ECW) to total body water (TBW), with a ratio above 0.39 indicating an edematous state. This multi-faceted approach aimed to provide a more comprehensive assessment of hydration status.

What is MF-BIA, and why is it important for detecting fluid overload?

MF-BIA is significant because it can identify subclinical edema, which is hidden fluid overload not detectable through physical examinations. In the study, MF-BIA revealed that a substantial percentage of patients without overt edema were actually experiencing fluid overload. This highlights the limitations of relying solely on physical exams and underscores the importance of advanced techniques like MF-BIA for accurate fluid management. Failing to detect subclinical edema can lead to inadequate treatment and increased risk of cardiovascular complications.

How does the diameter of the inferior vena cava (IVC) relate to fluid status, and what did the study reveal about this?

The inferior vena cava (IVC) diameter is related to fluid status because a smaller IVC diameter typically indicates lower fluid volume. The study found that patients without overt edema had smaller IVC diameters, which aligns with the expectation that less visible swelling corresponds to less overall fluid. This measurement, when combined with other assessments like MF-BIA, helps provide a more complete picture of a patient's hydration status. The correlation between IVC diameter and blood pressure further emphasizes the link between fluid volume and cardiovascular health.

What are the implications of the study's findings for how fluid overload should be assessed in chronic kidney disease?

The findings suggest that relying solely on physical exams to detect fluid overload in chronic kidney disease is inadequate. Subclinical edema is prevalent, and advanced techniques like MF-BIA are necessary to uncover hidden fluid imbalances. A comprehensive assessment approach, combining physical exams with tools like MF-BIA and IVC measurements, is crucial for accurate fluid management and for preventing hypertension and related cardiovascular complications. This comprehensive approach enables clinicians to tailor treatment strategies more effectively, improving patient outcomes.