John is a 3-year-old boy who is brought to his pediatrician today by his mother who is concerned because “I was giving him a bath a couple of nights ago and felt a weird lump on his belly. I thought maybe he was just constipated, but he isn’t. He’s had two normal bowel movements in the last couple of days.” His mother also reports that she “thought his urine looked a little bit strange, like it was a little bit pink the other day.” N.S. appears healthy and happy; he is playing with toys in the exam room. Select a potential diagnosis for John and describe the pathophysiology of that diagnosis. How does the pathophysiology explain John's symptoms?

John is a 3-year-old boy who is brought to his pediatrician today by his mother who is concerned because “I was giving him a bath a couple of nights ago and felt a weird lump on his belly. I thought maybe he was just constipated, but he isn’t. He’s had two normal bowel movements in the last couple of days.” His mother also reports that she “thought his urine looked a little bit strange, like it was a little bit pink the other day.” N.S. appears healthy and happy; he is playing with toys in the exam room. Select a potential diagnosis for John and describe the pathophysiology of that diagnosis. How does the pathophysiology explain John's symptoms?