Objective  To explore the clinical characteristics and the prognosis of diabetic foot ulcers (DFU) inpatients of different renal function statuses.

  Methods  A retrospective analysis of 962 inpatients with DFU was conducted. The patients were divided into three groups according to their renal function statuses, and the clinical characteristics of the three groups were compared to identify differences. In addition, the patients were followed up in outpatient clinics or by telephone and their prognostic status and risk factors for death were analyzed.

  Results  Analysis of the clinical characteristics showed that, compared with diabetic patients with normal renal function or mild renal function impairment, diabetic patients with moderate and severe renal function impairment had a longer course of disease (P<0.001). Patients with foot ulcers of Wagner grade 4 predominates the moderate and severe renal function impairment groups (P<0.05). Patients in the moderate and severe renal function impairment groups had a relatively higher proportion of comorbidities, including hypertension, coronary heart disease, and peripheral arterial disease (P<0.05). These patients had relatively lower levels of glycosylated hemoglobin and hemoglobin (all P<0.05) and relatively higher levels of neutrophil ratio and procalcitonin (all P<0.05). Of the two groups, patients in the moderate renal function impairment group were older (P<0.001) and had lower ankle-brachial index (P<0.001). The severe renal function impairment group had a higher proportion of patients with foot ulcers of Wagner grades 3 and 5 (all P<0.05). For the purpose of conducting prognostic analysis, 748 patients were followed up in outpatient clinics or by telephone for a median length of 41 months. Among them, 239 died. The all-cause mortality was 31.9%, and the mortality in the three groups was 25.8%, 46.2% (P<0.001), and 59.4% (P<0.001), respectively. The survival rate of patients in the moderate and severe renal function impairment groups was significantly lower than those in the normal renal function and mild renal function impairment groups (P<0.001). Univariate Cox regression analysis showed that age, concomitant coronary heart disease and peripheral arterial disease, degree of renal function impairment, and foot ulcers of Wagner grade 4 and 5 were associated with all-cause deaths. Furthermore, multivariate Cox regression analysis showed that moderate and severe renal function impairment was an independent risk factor for all-cause deaths in DFU patients (P<0.001).

  Conclusions  As renal function impairment worsens, patients with DFU present clinical characteristics of greater complexity, higher risks of cardiovascular events, and higher mortality. It is essential to prevent kidney damage and foot ulcers, to pay attention to the cardiovascular risks of DFU patients with moderate and severe renal function impairment, and to reduce mortality.