My son developed a urachal cyst when he was 10 years old. The first signs that something was wrong was slight discomfort in his abdomen followed by blood in his urine. When taken to the ER, the culture showed urinary tract infection and he was treated with antibiotics. A few weeks later the same thing occurred. Same diagnosis. When it happened a third time, we were referred to a pediatric urologist, who believed it was kidney stones by the elevated calcium level in his urine. We changed his diet and watched for a passing kidney stone. Meanwhile, my son's pain level was increasing, and the recurrence of blood in the urine was increasing.
Ultrasounds and a CT scan showed nothing. Three cystoscopies were preformed, each with no result. He was put on morphine for the pain, which could become excruciating, and he was scheduled for exploratory abdominal surgery. That surgery found a "remnant" of what was believed could have been a urachal cyst, and so that tissue was removed, along with some surrounding tissue "just to be sure". A few weeks passed and the same symptoms as before continued.
I rushed him to the emergency when he was in excruciating pain and they did an MRI and found a cyst the size of a golf ball on the dome of his bladder. He had surgery to remove it. What had been happening was the cyst would fill and then expel inside the bladder, causing the pain, and then the blood from the fluid inside the cyst would be present in his urine. It was all timing. When the previous procedures had been preformed, the cyst had already expelled and was lying flat on the bladder wall, undetectable by imaging or surgical view. I had searched the web endlessly for some idea what it could be prior to it being resolved. I post this here to maybe help anyone else who is looking for answers to unconventional symptoms.