The impact of body mass index on mortality in patients with acute kidney injury: a systematic review protocol.

BACKGROUND Acute kidney injury (AKI) refers to a broad spectrum of kidney damage and is attributed a high morbidity and mortality rate at all degrees of severity. Obesity increases the risk for developing AKI. However, some studies have shown that obesity at onset of AKI is paradoxically associated with greater survival. The aim of this review is to explore the relationship between body mass index and survival in patients with AKI. METHODS An electronic search will be conducted using MEDLINE, EMBASE, CINAHL and CENTRAL using predefined search strategies. The cited and citing references of selected key studies will also be searched for relevant articles. Risk of bias will be assessed using a modified Quality in Prognosis Studies (QUIPS) tool. The primary outcome will be an exploration of the association between BMI and mortality in patients presenting with AKI. Two authors will independently select, data extract, and risk of bias assess articles. Any discrepancies will be resolved by consensus or by consulting a third author. A narrative synthesis of the findings from the included studies will be presented. Meta-analyses will be conducted where the data is available from clinically and methodologically similar studies and in the same format. Heterogeneity in such analyses, beyond that expected by chance, will be quantified using the I statistic. Sub-group analyses will be performed to determine the influence of gender, AKI duration, underlying aetiology, and intervening treatments, on pooled results. DISCUSSION Body mass index may be an important modifiable risk factor for mortality in patients presenting with AKI. The proposed systematic review will help to elucidate the association between all categories of BMI and survival in this patient group. SYSTEMATIC REVIEW REGISTRATION PROSPERO CRD42017071124