Unmasking hidden shapes: unusual red cell morphologies in urine sediment

Schistocytes are fragmented red blood cells (RBCs) classically restricted to peripheral blood smears, where they serve as a hallmark of microangiopathic haemolytic anemia (MAHA) and thrombotic microangiopathy (TMA). Their presence in urine has been rarely documented. We report a 30-year-old postpartum woman who developed severe anemia, thrombocytopenia, acute kidney injury, and biochemical evidence of intravascular haemolysis following massive transfusion after caesarean delivery. Urinalysis revealed haematuria and proteinuria, and manual phase-contrast microscopy demonstrated atypical RBC morphology. Parallel blood smear examination corroborated systemic schistocytosis. ADAMTS13 activity of 35 % with absent anti-ADAMTS13 antibodies excluded thrombotic thrombocytopenic purpura (TTP), and the clinical course favoured a diagnosis of atypical haemolytic uremic syndrome (aHUS). Initiation of complement blockade with eculizumab led to rapid haematological and renal recovery. This case provides the first report linking the detection of schistocytes in voided urine to aHUS, a mechanistically plausible phenomenon in renal microangiopathy with disruption of the glomerular filtration barrier (GFB). Beyond its novelty, it underscores the enduring diagnostic value of urine sediment microscopy in revealing clinically meaningful features of TMA.