Urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function
Abstract Ammonium excretion is often estimated using urinary anion gap (UAG) and osmolality gap (UOG) when direct measurement is unavailable, particularly in patients with impaired kidney function. We aimed to examine how UAG and UOG vary across different levels of kidney function and their relation...
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Nature Portfolio
2025-07-01
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| Online Access: | https://doi.org/10.1038/s41598-025-05249-w |
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| author | Saeko Hatanaka Ito Go Kanzaki Hideaki Kuno Takahito Niikura Kosuke Honda Yasuyuki Nakada Nobuo Tsuboi Takashi Hasegawa Takashi Yokoo |
| author_facet | Saeko Hatanaka Ito Go Kanzaki Hideaki Kuno Takahito Niikura Kosuke Honda Yasuyuki Nakada Nobuo Tsuboi Takashi Hasegawa Takashi Yokoo |
| author_sort | Saeko Hatanaka Ito |
| collection | DOAJ |
| description | Abstract Ammonium excretion is often estimated using urinary anion gap (UAG) and osmolality gap (UOG) when direct measurement is unavailable, particularly in patients with impaired kidney function. We aimed to examine how UAG and UOG vary across different levels of kidney function and their relationships with acid–base parameters. This retrospective cohort study included 531 outpatients categorized by estimated glomerular filtration rate (eGFR: ≥ 90, 60–89, 45–59, 30–44, and < 30 mL/min/1.73 m2). UAG values increased significantly with declining eGFR (p = 0.002), whereas UOG showed no clear trend (p = 0.303). UAG correlated positively with serum pH (ρ = 0.135, p = 0.002) and urinary pH (ρ = 0.333, p < 0.001). UOG was strongly inversely correlated with urinary pH (ρ = -0.512, p < 0.001). Sensitivity analyses stratified by serum anion gap and bicarbonate substantiated UAG’s relationship with eGFR. Multivariate analyses confirmed UAG’s association with eGFR, serum pH, and urinary pH, whereas UOG was predominantly influenced by urinary pH and minimally by eGFR. Although UOG has traditionally been considered superior, our findings suggest that UAG demonstrated more consistent associations with kidney function parameters. However, direct NH₄⁺ measurements remain necessary for definitive clinical assessment. |
| format | Article |
| id | doaj-art-7fbb1fc6744440f4874054a123c1ff83 |
| institution | Kabale University |
| issn | 2045-2322 |
| language | English |
| publishDate | 2025-07-01 |
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| spelling | doaj-art-7fbb1fc6744440f4874054a123c1ff832025-08-20T03:38:15ZengNature PortfolioScientific Reports2045-23222025-07-011511910.1038/s41598-025-05249-wUrine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney functionSaeko Hatanaka Ito0Go Kanzaki1Hideaki Kuno2Takahito Niikura3Kosuke Honda4Yasuyuki Nakada5Nobuo Tsuboi6Takashi Hasegawa7Takashi Yokoo8Division of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineDivision of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineDivision of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineDivision of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineDivision of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineDivision of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineDivision of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineDepartment of Internal Medicine, Atsugi City HospitalDivision of Nephrology and Hypertension Department of Internal Medicine, The Jikei University School of MedicineAbstract Ammonium excretion is often estimated using urinary anion gap (UAG) and osmolality gap (UOG) when direct measurement is unavailable, particularly in patients with impaired kidney function. We aimed to examine how UAG and UOG vary across different levels of kidney function and their relationships with acid–base parameters. This retrospective cohort study included 531 outpatients categorized by estimated glomerular filtration rate (eGFR: ≥ 90, 60–89, 45–59, 30–44, and < 30 mL/min/1.73 m2). UAG values increased significantly with declining eGFR (p = 0.002), whereas UOG showed no clear trend (p = 0.303). UAG correlated positively with serum pH (ρ = 0.135, p = 0.002) and urinary pH (ρ = 0.333, p < 0.001). UOG was strongly inversely correlated with urinary pH (ρ = -0.512, p < 0.001). Sensitivity analyses stratified by serum anion gap and bicarbonate substantiated UAG’s relationship with eGFR. Multivariate analyses confirmed UAG’s association with eGFR, serum pH, and urinary pH, whereas UOG was predominantly influenced by urinary pH and minimally by eGFR. Although UOG has traditionally been considered superior, our findings suggest that UAG demonstrated more consistent associations with kidney function parameters. However, direct NH₄⁺ measurements remain necessary for definitive clinical assessment.https://doi.org/10.1038/s41598-025-05249-wUrine anion gapUrine osmolality gapAcid–base balanceChronic kidney disease |
| spellingShingle | Saeko Hatanaka Ito Go Kanzaki Hideaki Kuno Takahito Niikura Kosuke Honda Yasuyuki Nakada Nobuo Tsuboi Takashi Hasegawa Takashi Yokoo Urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function Scientific Reports Urine anion gap Urine osmolality gap Acid–base balance Chronic kidney disease |
| title | Urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function |
| title_full | Urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function |
| title_fullStr | Urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function |
| title_full_unstemmed | Urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function |
| title_short | Urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function |
| title_sort | urine anion and osmolality gaps in the comprehensive evaluation of acid base balance across different levels of kidney function |
| topic | Urine anion gap Urine osmolality gap Acid–base balance Chronic kidney disease |
| url | https://doi.org/10.1038/s41598-025-05249-w |
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