Diagnostic value of the urea-to-creatinine ratio for gastrointestinal bleeding source: influence of renal function
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Springer Nature
Abstract
Background: Gastrointestinal (GI) bleeding is frequent and clinically critical, especially in patients with renal
dysfunction. Localization of the source is relevant for treatment and outcomes. The urea-to-creatinine ratio (UCR) has
been proposed as a tool to differentiate between upper and lower GI bleeding. However, its diagnostic utility across
varying degrees of renal impairment remains unclear.
Methods: From January 2021 to October 2023, all patients with suspected GI bleeding who underwent endoscopy
were retrospectively analyzed in a single center. Patients without confirmed bleeding were excluded. Patients were
stratified by renal function: normal renal function, chronic kidney disease (CKD), acute kidney injury (AKI), and AKI with
pre-existing CKD (acute-on-chronic). We assessed the discriminatory power of the UCR to distinguish upper from
lower GI bleeding within each group.
Results: A total of 849 patients (mean age 66.9 ± 18.2 years) were included. Approximately two-thirds of the patients
(n = 544; 64.1%) were male. CKD was present in 321 (37.8%) and AKI in 354 (41.7%) patients; 199 (56.2%) of those
with AKI had pre-existing CKD. Upper GI bleeding occurred more frequently in patients with AKI (75.1%) and CKD
(72.9%) than in those with normal renal function (p < 0.0001 and p = 0.0003, respectively); both groups also required
transfusions more frequently (p < 0.0001 for both). UCR values were significantly higher in upper vs. lower GI bleeding
in patients with normal renal function (67.5 vs. 42.5; p < 0.0001), but this difference was reduced in CKD (49.3 vs. 41.0;
p = 0.0103) and not significant in AKI (53.1 vs. 47.7; p = 0.09). The diagnostic performance of UCR was best in patients
with normal renal function (AUROC 0.69) and markedly impaired in CKD (AUROC 0.56) and AKI (AUROC 0.54).
Conclusion: The diagnostic value of UCR to localize GI bleeding depends strongly on renal function. While the UCR
may help to identify the bleeding site in patients with normal kidney function, impaired renal function hampers the
reliability of the UCR, especially in patients with AKI. As renal dysfunction is common in patients with GI bleeding,
kidney function must be taken into account when interpreting UCR values.
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