Brain scans reveal metabolic shifts in kidney disease patients with thinking problems

People with advanced chronic kidney disease frequently struggle with memory, attention, and problem-solving, yet the biological reasons behind these deficits have remained stubbornly unclear. A new systematic review now pulls together the scattered evidence from brain chemistry scans and finds a recurring pattern: patients on dialysis or in late-stage kidney disease show consistent drops in creatine and N-acetylaspartate-to-creatine ratios alongside rising myo-inositol-to-creatine ratios in specific brain regions. But the review also delivers a sobering caveat—these metabolic shifts do not reliably track with cognitive test scores, and the strongest reported correlation comes from a single pediatric study that no one has replicated.

The review, published in the Egyptian Journal of Radiology and Nuclear Medicine, screened 671 articles and identified just five observational studies involving 231 patients that measured brain metabolites with proton magnetic resonance spectroscopy while also administering standardized cognitive tests. That small evidence base, the authors conclude, is too limited to support using these scans as clinical screening tools, though the recurring metabolic signatures offer researchers a starting point for understanding how kidney failure reshapes the brain.

Proton magnetic resonance spectroscopy works by detecting the chemical fingerprints of molecules inside living brain tissue without radiation or biopsy. It quantifies N-acetylaspartate, a marker of neuronal health; creatine, which reflects energy metabolism; choline, tied to membrane turnover; and myo-inositol, associated with osmotic stress. In chronic kidney disease, where waste products accumulate and blood vessels stiffen, this window into brain chemistry seemed promising for explaining why so many patients develop thinking problems.

The five included studies covered strikingly different populations. One pediatric cohort from Egypt contributed roughly 61 percent of all participants, while the remaining adult studies focused on hemodialysis patients, non-dialyzed stage 4–5 kidney disease, and kidney-pancreas transplant recipients with type 1 diabetes. Cognitive assessments ranged from full intelligence quotient batteries in children to Montreal Cognitive Assessment scores and Trail Making Test performance in adults. Despite these differences, cognitive impairment appeared in every study, with deficits spanning memory, attention, executive function, and processing speed, and generally worsening as kidney function declined.

The metabolic findings showed the most consistency in dialyzed and advanced disease. Creatine concentrations in parieto-occipital white matter dropped from 5.26 millimolar in controls to 3.46 millimolar in dialyzed adults in one study, and a pediatric study documented a stepwise decline from 5.2 in controls to 4.40 in stage 5 dialysis patients. N-acetylaspartate-to-creatine ratios fell from 1.99 in controls to 1.43 in stage 5 dialysis children. Myo-inositol-to-creatine ratios climbed in a dose-dependent fashion, from 0.66 in controls to 0.80 in stage 5 dialysis. Yet absolute myo-inositol concentrations did not differ significantly, suggesting the ratio elevation partly reflects the shrinking creatine denominator rather than genuine accumulation of that molecule.

The correlation between myo-inositol-to-creatine and performance intelligence quotient in the pediatric cohort was strikingly strong, reaching a coefficient of negative 0.895, meaning the ratio statistically explained about 80 percent of the variance in that cognitive domain. The review authors emphasize this finding originated from a single Egyptian pediatric study, has never been independently replicated, and cannot be verified for multiple-comparison correction, outlier influence, or adjustment for confounders like age and disease stage. They classify it as hypothesis-generating rather than evidence of a validated biomarker.

Equally telling are the null results. In non-dialyzed stage 4–5 patients, creatine was reduced and learning was impaired, yet no metabolite correlated with any cognitive measure. Adult dialysis cohorts showed metabolic changes without corresponding correlations in most domains. This dissociation between brain chemistry and test performance suggests that metabolic abnormalities alone cannot explain cognitive decline, and that vascular disease, anemia, inflammation, and uremic toxin accumulation likely contribute through pathways spectroscopy cannot detect.

Methodological quality varied considerably. Two studies earned good ratings on the Newcastle-Ottawa Scale, one was fair, and two were rated poor, with common weaknesses including absent control groups, no adjustment for confounding factors, and no blinded outcome assessment. Certainty of evidence was low for the recurring creatine, N-acetylaspartate-to-creatine, and myo-inositol-to-creatine abnormalities, and very low for direct metabolite-cognition associations. The heterogeneity in brain regions, scanner protocols, quantification methods, and cognitive batteries prevented any meta-analysis, forcing a narrative synthesis instead.

The review also highlights intradialytic brain changes captured by advanced imaging. During dialysis sessions, one study measured a 2.8 percent increase in fractional anisotropy and a 16.9 milliliter expansion in white matter volume, consistent with cytotoxic edema, while another documented a 21 percent rise in prefrontal cortex glucose. These acute shifts suggest the dialysis procedure itself perturbs brain physiology, though whether such changes accumulate into lasting damage remains unknown.

For now, the authors conclude that proton magnetic resonance spectroscopy in chronic kidney disease remains an investigational research tool. Establishing clinical utility would require standardized acquisition protocols, multicenter reproducibility, normative reference ranges adjusted for age and dialysis status, and longitudinal studies tracking whether metabolic abnormalities predict cognitive deterioration. Until such evidence exists, the recurring metabolic signatures serve as clues for mechanistic research rather than as diagnostic markers, and the current evidence does not support routine clinical use of MRS-based biomarkers in chronic kidney disease.

Subject of Research: Cerebral metabolite alterations and cognitive dysfunction in chronic kidney disease assessed by proton magnetic resonance spectroscopy

Article Title: Cerebral metabolite alterations and cognitive dysfunction in chronic kidney disease: a systematic review of proton magnetic resonance spectroscopy studies

Article References: Koesbandono, Aman, M., Murtala, B., & Octavius, G. S. (2026). Cerebral metabolite alterations and cognitive dysfunction in chronic kidney disease: a systematic review of proton magnetic resonance spectroscopy studies. Egyptian Journal of Radiology and Nuclear Medicine, 57(1), Article 228. https://doi.org/10.1186/s43055-026-01890-1

Image Credits: AI Generated

DOI: 10.1186/s43055-026-01890-1

Keywords: chronic kidney disease, magnetic resonance spectroscopy, cognitive impairment, dialysis, myo-inositol, creatine, N-acetylaspartate, systematic review, brain metabolism, uremic toxins, Newcastle-Ottawa Scale, GRADE certainty