Three-year-old baby peeing penis bulging a small bag may be circumcision, eczema caused by the patient should consult a doctor in time, clear cause for treatment. 1. circumcision: men in the natural state, the head of the penis can not be exposed or only partially exposed, childhood can be manifested as the penis bulging a small bag when peeing, the patient will also have difficulty urinating, circumcision, and other symptoms, secondary infections will be localized redness and swelling and purulent secretions. 2. eczema: three-year-old baby peeing penis bulging a small bag, may also be caused by eczema, which will be accompanied by localized obvious itching, oozing and erosion. Three-year-old baby peeing penis bulging a small bag may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.