<b><i>Background:</i></b> Cerebral microbleeds (CMBs) detected on susceptibility-weighted imaging (SWI) are associated with cerebral small vessel disease. Chronic kidney disease and microalbuminuria have been associated with the presence of CMBs in stroke patients. Urinary immunoglobulin G (IgG) is measured to document glomerular injury; however, the relationship between urinary IgG and CMBs is unknown. <b><i>Methods:</i></b> We retrospectively enrolled consecutive patients who had been admitted with transient ischemic attack (TIA) or ischemic stroke and identified those who had undergone SWI and a spot urine test. The location of CMBs was classified on magnetic resonance imaging as strictly lobar, deep/infratentorial (D/I), or mixed areas. We analyzed the association between urinary IgG and the presence and location of CMBs. <b><i>Results:</i></b> We included 298 patients (86 female, median age 70 years, median eGFR 65.8 mL/min/1.73 m²). Positive urinary IgG and CMB results were found in 58 (19%) and 160 patients (54%), respectively. Urinary IgG positivity was significantly associated with CMBs compared with non-CMBs (28% vs. 9%, <i>p</i> &#x3c; 0.001), and with D/I or mixed CMBs compared with non-D/I or mixed CMBs (34% vs. 10%, <i>p</i> &#x3c; 0.001). Multivariate analysis revealed that urinary IgG and hypertension positivity were strongly associated with D/I or mixed CMBs (OR 3.479, 95% CI: 1.776–6.818, <i>p</i> &#x3c; 0.001; OR 3.415, 95% CI: 1.863–6.258, <i>p</i> &#x3c; 0.001). <b><i>Conclusions:</i></b> Urinary IgG was associated with the prevalence of D/I or mixed location CMBs in TIA or ischemic stroke patients. Our findings provide new insights into the association between urinary IgG and the distribution of CMBs.

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