Isolated hematuria with ureterolithiasis in an infant with late-onset vitamin K deficiency bleeding.

Late-onset vitamin K deficiency bleeding (VKDB) usually manifests as intracranial or gastrointestinal hemorrhage, and hematuria is rarely reported. We describe a 2-month-old, exclusively breastfed male infant who had received vitamin K prophylaxis at birth and developed gross hematuria on hospital day 9 while recovering from rotavirus gastroenteritis and cefotaxime-treated aspiration pneumonia. His prothrombin time was 136.9 s (INR 12.6), and activated partial thromboplastin time was 71.1 s. Factors II, VII, IX, and X were each <10%. Urine culture was sterile, and computed tomography demonstrated a right vesicoureteric calculus. A single 1-mg dose of parenteral vitamin K normalized coagulation parameters and resolved the hematuria within four hours. Rotavirus gastroenteritis and prolonged antibiotic use collectively depleted vitamin K stores in this infant despite prophylaxis. VKDB should be considered, particularly when potential risk factors for vitamin K depletion are recognized despite an atypical presentation, and vitamin K administration can be life-saving.