Normally, urine (pee) is made in the kidneys and flows downward in tubes called ureters to the bladder. It's stored in the bladder until we urinate (pee). The ureteropelvic (yeh-ree-tuh-roh-PEL-vik) junction (UPJ) is where the ureter meets the kidney. In UPJ obstruction, pee can't pass out of the kidney as easily as it should because of a blockage.

In some kids who have the condition, it causes no problems. But in others, it can make the kidney swell with urine, leading to damage over the long term.

UPJ obstruction might cause no symptoms, or it may cause pain, an area of fullness in the belly, nausea, vomiting, blood in the urine, a urinary tract infection (UTI), or poor growth. Even without symptoms, many children with UPJ obstruction will need surgery to protect their kidneys from damage.

Health care providers might recommend surgery soon after diagnosing UPJ obstruction, or they might watch to see if it's needed later or if the obstruction will go away on its own. Ultrasounds help them see how a child's kidneys are doing. They might recommend antibiotics to help prevent infections.

• Ask the health care provider if your child should avoid any sports or activities.
• Give your child any recommended antibiotics as directed by the health care provider.
• Follow up with the health care provider and go to all recommended care visits and ultrasounds.

Your child:

• has blood in their pee for the first time
• has pee that looks redder than before
• gets a fever
• develops a lump in the abdomen (belly)
• has pain
• is vomiting

Your child:

• has severe pain
• appears dehydrated; signs include dizziness, drowsiness, a dry or sticky mouth, sunken eyes, increased thirst, peeing less than usual, or crying with little or no tears
• is not peeing

What causes UPJ obstruction? Most children with UPJ obstructions are born with them. Sometimes, UPJ obstruction develops in older kids or adults because of scar tissue, inflammation, or a kidney stone. An obstruction can happen in one kidney or both.