Bacteraemic urinary tract infections may mimic respiratory infections: a nested case–control study

Daily practice suggests that respiratory signs may be observed in bacteraemic urinary infections (BUI). Our objective was to search for an association between the presence of respiratory symptoms and the bacteraemic nature of urinary tract infections (UTI). A nested case–control study was carried out based on our computerised dashboard from January 2011 to June 2015. Cases were defined as patients with a BUI due to Enterobacteriaceae species, identified in blood and urine cultures. Controls had fever and a positive urinary sample but sterile blood cultures (NBUI) and a final diagnosis of urinary infection. Patients from the BUI group were 1:1 matched to the NBUI group according to four parameters: age, gender, cardiovascular and pulmonary comorbid conditions. Subjects with cognitive impairment limiting clinical accuracy and those with healthcare-associated infections were excluded. We compared systematically recorded respiratory and urinary symptoms between groups: signs on auscultation, dyspnoea, chest pain, cough and sputum, dysuria with burning, pollakiuria, flank or costovertebral angle tenderness and ischuria. One hundred BUI were compared to 100 NBUI, both groups exhibiting a similar rate for all considered comorbid conditions. In the BUI group, 58 % showed at least one respiratory sign vs. 20 % in the NBUI group, p < 0.001, while urinary signs were less frequent: 54 % vs. 71 %, p = 0.013. In the multivariate analysis, BUI was associated with the presence of abnormal pulmonary auscultation [adjusted odds ratio (AOR), 5.91; p < 0.001] and a trend towards less urinary symptoms (AOR, 1.58; p = 0.058). Patients with BUI presented with significantly more respiratory signs, which overshadowed urinary symptoms, compared to those with non-bacteraemic UTI. Such observations impact clinical decision-making.