The Meaning of the Blood Urea Nitrogen/creatinine Ratio in Acute Kidney Injury

Methods: We conducted a retrospective study using a large hospital database. Patients were divided into three groups: 'low BCR' (if BCR when acute kidney injury (AKI) developed was ≤20), 'high BCR' (if BCR when AKI developed was >20) and 'no AKI' if patients did not satisfy any of the Risk, Injury, Failure, Loss and End-stage kidney disease criteria for AKI during hospitalization.

Results: Among 20 126 study patients, 3641 (18.1%) had AKI. Among these patients, 1704 (46.8%) had a BCR <20 at AKI diagnosis ('low BCR') and 1937 (53.2%) had a BCR >20 ('high BCR'). The average BCR for the two groups was 15.8 versus 26.1 (P < 0.001). Hospital mortality was significantly less in the 'low-BCR' group (18.4 versus 29.9%, P < 0.001). Multivariable logistic regression analysis for hospital mortality ('no AKI' as a reference) showed that the odds ratio of 'high BCR' (5.73) was higher than that of 'low BCR' (3.32).

Conclusions: Approximately half of the patients with AKI have a BCR >20, the traditional threshold of diagnosing PRA. Unlike PRA patients who have a lower mortality than ATN patients, high BCR patients had higher hospital mortality compared with low BCR patients, which was confirmed with multivariable analysis. These findings do not support BCR as a marker of PRA.

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References

Singri N, Ahya S, Levin M . Acute renal failure. JAMA. 2003; 289(6):747-51. DOI: 10.1001/jama.289.6.747. View

Dossetor J . Creatininemia versus uremia. The relative significance of blood urea nitrogen and serum creatinine concentrations in azotemia. Ann Intern Med. 1966; 65(6):1287-99. DOI: 10.7326/0003-4819-65-6-1287. View

Marshall S . UREA-CREATININE RATIO IN OBSTRUCTIVE UROPATHY AND RENAL HYPERTENSION. JAMA. 1964; 190:719-20. DOI: 10.1001/jama.1964.03070210025004. View

. K/DOQI clinical practice guidelines for chronic kidney disease: evaluation, classification, and stratification. Am J Kidney Dis. 2002; 39(2 Suppl 1):S1-266. View

Macedo E, Mehta R . Prerenal failure: from old concepts to new paradigms. Curr Opin Crit Care. 2009; 15(6):467-73. PMC: 3895370. DOI: 10.1097/MCC.0b013e328332f6e3. View

Uchino S, Bellomo R, Goldsmith D, Bates S, Ronco C . An assessment of the RIFLE criteria for acute renal failure in hospitalized patients. Crit Care Med. 2006; 34(7):1913-7. DOI: 10.1097/01.CCM.0000224227.70642.4F. View

Beier K, Eppanapally S, Bazick H, Chang D, Mahadevappa K, Gibbons F . Elevation of blood urea nitrogen is predictive of long-term mortality in critically ill patients independent of "normal" creatinine. Crit Care Med. 2010; 39(2):305-13. PMC: 3448784. DOI: 10.1097/CCM.0b013e3181ffe22a. View

Fonarow G, Adams Jr K, Abraham W, Yancy C, Boscardin W . Risk stratification for in-hospital mortality in acutely decompensated heart failure: classification and regression tree analysis. JAMA. 2005; 293(5):572-80. DOI: 10.1001/jama.293.5.572. View

Hartz A, Kuhn E, KAYSER K, Johnson W . BUN as a risk factor for mortality after coronary artery bypass grafting. Ann Thorac Surg. 1995; 60(2):398-404. DOI: 10.1016/0003-4975(95)00358-r. View

10.

Liano F, Pascual J . Epidemiology of acute renal failure: a prospective, multicenter, community-based study. Madrid Acute Renal Failure Study Group. Kidney Int. 1996; 50(3):811-8. DOI: 10.1038/ki.1996.380. View

11.

Bagshaw S, Langenberg C, Bellomo R . Urinary biochemistry and microscopy in septic acute renal failure: a systematic review. Am J Kidney Dis. 2006; 48(5):695-705. DOI: 10.1053/j.ajkd.2006.07.017. View

12.

Agrawal M, SWARTZ R . Acute renal failure. Am Fam Physician. 2000; 61(7):2077-88. View

13.

Tian J, Barrantes F, Amoateng-Adjepong Y, Manthous C . Rapid reversal of acute kidney injury and hospital outcomes: a retrospective cohort study. Am J Kidney Dis. 2009; 53(6):974-81. DOI: 10.1053/j.ajkd.2009.02.007. View

14.

Wu B, Bakker O, Papachristou G, Besselink M, Repas K, van Santvoort H . Blood urea nitrogen in the early assessment of acute pancreatitis: an international validation study. Arch Intern Med. 2011; 171(7):669-76. DOI: 10.1001/archinternmed.2011.126. View

15.

Lameire N, Van Biesen W, Vanholder R . Acute renal failure. Lancet. 2005; 365(9457):417-30. DOI: 10.1016/S0140-6736(05)17831-3. View

16.

Feinfeld D, Bargouthi H, Niaz Q, P Carvounis C . Massive and disproportionate elevation of blood urea nitrogen in acute azotemia. Int Urol Nephrol. 2003; 34(1):143-5. DOI: 10.1023/a:1021346401701. View

17.

Bellomo R, Ronco C, Kellum J, Mehta R, Palevsky P . Acute renal failure - definition, outcome measures, animal models, fluid therapy and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) Group. Crit Care. 2004; 8(4):R204-12. PMC: 522841. DOI: 10.1186/cc2872. View

18.

Uchino S, Bellomo R, Bagshaw S, Goldsmith D . Transient azotaemia is associated with a high risk of death in hospitalized patients. Nephrol Dial Transplant. 2010; 25(6):1833-9. DOI: 10.1093/ndt/gfp624. View

19.

Le Gall J, Lemeshow S, Saulnier F . A new Simplified Acute Physiology Score (SAPS II) based on a European/North American multicenter study. JAMA. 1993; 270(24):2957-63. DOI: 10.1001/jama.270.24.2957. View

20.

Tariq M, Memon M, Jafferani A, Shoukat S, Gowani S, Nusrat R . Massive fluid requirements and an unusual BUN/creatinine ratio for pre-renal failure in patients with cholera. PLoS One. 2009; 4(10):e7552. PMC: 2763218. DOI: 10.1371/journal.pone.0007552. View