Kidney Disease: Hidden Acid Imbalance Often Missed in Routine Care

A concerning blind spot in the care of chronic kidney disease (CKD) patients has been identified: a lack of routine monitoring for metabolic acidosis. A recent Japanese registry study reveals that serum bicarbonate levels – a key indicator of acid-base balance – are infrequently measured, leading to potentially widespread underdiagnosis and undertreatment of this common complication.

Metabolic acidosis, where the body accumulates too much acid, isn’t a rare occurrence in those with CKD. It’s linked to a range of adverse health outcomes, including muscle wasting, weakened bones, insulin resistance, a faster decline in kidney function, and even increased mortality. Clinical guidelines recommend intervention when serum bicarbonate dips below 22 mEq/L, but real-world adherence, particularly in Asia, hasn’t been well understood – until now.

Assessing the Gap in Care

Researchers led by Mai Tanaka at Niigata University extracted data from over 21 university hospitals participating in the Japan Chronic Kidney Disease Database Extension (J-CKD-DB-Ex). Their analysis, published in Scientific Reports, focused on adults with CKD stages 3a-4 between 2014 and 2021. The study aimed to determine how often bicarbonate levels were measured, and, among those tested, how frequently metabolic acidosis was diagnosed and treated.

The findings were striking. The annual rate of serum bicarbonate measurement remained consistently below 10% throughout the study period. As Tanaka explains, “The annual measurement rate of serum bicarbonate levels in Japanese patients with CKD stages 3a to 4 was consistently below 10%, suggesting that metabolic acidosis itself may be underassessed.” This low testing rate skews the overall picture of metabolic acidosis prevalence within the broader CKD population.

However, when researchers looked specifically at patients who did have their bicarbonate levels measured, the prevalence of metabolic acidosis was surprisingly high – nearly 44.2%. This figure increased as CKD progressed to more advanced stages. Even among those with bicarbonate levels below 22 mEq/L, diagnosis rates were only 8.6%, and treatment rates lagged even further behind at 7.5%.

A Global Pattern of Under-Recognition

This isn’t solely a Japanese issue. Research from North America, led by Abramowitz and Whitlock, has revealed a similar pattern of underdiagnosis in CKD patients. Their large-scale analysis showed that fewer than 20% of patients received sodium bicarbonate therapy, and many cases went unrecorded in administrative data. This suggests a broader global trend of overlooking metabolic acidosis in CKD management.

The consequences of untreated metabolic acidosis extend beyond immediate discomfort. Acid retention can accelerate kidney damage through mechanisms that promote inflammation and scarring within the kidneys. Dietary acid load further complicates the situation. The J-CKD-DB-Ex database, as highlighted on its website, is actively contributing to research on these complex interactions within CKD.

Understanding Metabolic Acidosis and its Implications

Metabolic acidosis occurs when the body’s ability to eliminate acids or replenish bicarbonate is impaired. In CKD, the kidneys lose their capacity to effectively excrete acids, leading to a buildup. This imbalance can disrupt various bodily functions. While the study doesn’t establish a direct causal link, it reinforces the association between untreated metabolic acidosis and poorer outcomes in CKD patients.

Current clinical guidelines, including those from the Japanese Society of Nephrology, emphasize the importance of monitoring and correcting metabolic acidosis in CKD to maintain bicarbonate levels at or above 22 mEq/L. However, the Tanaka study demonstrates that these recommendations aren’t consistently implemented in routine clinical practice.

The good news is that measuring serum bicarbonate is a relatively inexpensive and readily available test. The primary barrier appears to be a lack of awareness and a failure to incorporate it into standard CKD monitoring protocols.

Improving Detection and Treatment

The study underscores a clear opportunity for quality improvement within CKD care. Systematically assessing bicarbonate levels in CKD patients could significantly enhance the detection of metabolic acidosis. Early identification could then facilitate timely initiation of alkali therapy (such as sodium bicarbonate) or dietary interventions, both of which show promise in slowing kidney function decline. A related study, published last year, explored the potential survival benefits of sodium bicarbonate in CKD patients.

For clinicians and healthcare systems, incorporating bicarbonate testing into standard CKD monitoring panels represents an actionable step. Given the rising global prevalence of CKD, particularly in aging populations, addressing this assessment gap could be a practical and scalable strategy to improve patient outcomes. The core message is simple yet powerful: metabolic acidosis in CKD is often hidden, not because it’s uncommon, but because it’s not consistently measured.

Publication details: Mai Tanaka et al, Assessment and treatment of metabolic acidosis in CKD: a registry-based study, Scientific Reports (2026). DOI: 10.1038/s41598-026-35335-6

Journal information: Scientific Reports