Background <p>Atypical haemolytic uraemic syndrome (aHUS) leads to acute kidney injury, necessitating dialysis in about half of patients. A certain proportion of patients treated with C5 inhibitors discontinue dialysis; however, little is known about the patient characteristics and clinical courses relating to discontinuation.</p> Methods <p>We compared the characteristics and clinical courses of patients with aHUS on dialysis at the initiation of eculizumab during post-marketing surveillance&#xa0;in Japan, stratified by those who did (Group A) and did not (Group B) discontinue dialysis within 26&#xa0;weeks of eculizumab treatment.</p> Results <p>Of 38 included patients, 21 (55.3%) and 17 (44.7%) were placed in Groups A and B, respectively. No patient re-started dialysis. Hypertension was less frequent in Group A than in Group B (6/21 [28.6%] vs. 11/17 [64.7%], <i>p</i> = 0.022). Both the duration of dialysis before eculizumab initiation (6 vs. 17&#xa0;days, <i>p</i> = 0.011) and the time from thrombotic microangiopathy onset to eculizumab initiation (9 vs. 25&#xa0;days, <i>p</i> = 0.008) were shorter in Group A. A duration of less than 15&#xa0;days from thrombotic microangiopathy onset to eculizumab initiation was associated with dialysis discontinuation. Kidney function improvement and normalisation of platelet count and lactate dehydrogenase levels were achieved earlier in Group A than in Group B (<i>p</i> = 0.050, 0.014, and &lt; 0.001, respectively). Five (29.4%) of 17 patients in Group B discontinued dialysis after 27&#xa0;weeks of eculizumab treatment, including one patient who underwent kidney transplantation.</p> Conclusions <p>Early initiation of eculizumab was significantly correlated with dialysis discontinuation.</p> Graphical Abstract <p></p>