Kawasaki disease (KD) is a systemic vasculitis that can present various manifestations in children, including neural, gastrointestinal, hepatobiliary involvement, and so on. With the development of abdominal ultrasound, complications of hydrops with or without cholestasis in KD are being recognized more frequently. However, this is rarely reported in China. Case Presentation A 6-year-old boy previously well was admitted to the hospital with a history of fever for 4 days, rash, and stiff neck for 2 days; he also complained of a diffuse abdominal pain, fatigue, and acholic stool. At admission, physical examination was significant for icterus, bilateral conjunctivitis, red cracked lips, a "strawberry tongue", tenderness, bilateral cervical lymphadenopathy, normal cardiac and respiratory patterns, abdominal dilatation and diffuse pain without guarding, and no palpable mass; on the second day of admission, he developed a desquamation around anus. The rash faded away after 2 days in hospital, and on the eighth day of hospitalization, desquamation of the fingertips was noted. Laboratory results on admission showed an elevation of inflammatory indices: a white blood cell count of 19.2 × 10 9 /L with 75% neutrophil; platelet count of 288 × 10 9 /L, which then rose to 633 × 10 9 /L on the ninth day of admission; erythrocyte sedimentation rate 60 mm/h; and C-reactive protein >90 mg/L; liver function test showed a total serum bilirubin of 164.9 µmol/L with a direction fraction of 65.9%, accompanied by an elevated alkaline phosphatase and γ-glutamly transferase. Hypoproteinmia and hyponatremia were noted, renal function was normal, and blood culture was sterile. The diagnosis of KD was made at admission. Chest X-ray showed blunted costophrenic angles; ultrasound of abdomen revealed hydrops of the gallbladder (GB) measuring 9.7 cm in longitudinal and 5.4 cm in anteroposterior diameter, with no calculi, no thickness of the walls or evidence of sludge, and a spleen enlargement and mesenteric nodes enlargement; ascites was also found (Figure 1). A differential diagnosis of hematologic malignancies disease was considered and further