Bloody urine after injury in children not always cause for alarm

An abdominal injury during sledding, a hit to the back during football practice, or being in a minor car accident can all bruise kidneys and cause them to spill small amounts of blood in the urine.

“Many triggers, including heavy exercise or a slightly bruised kidney from trauma, can set off a ‘red-pee’ alarm, and most cases resolve on their own with rest,” says Hopkins Children’s pediatric urologist Ming-Hsien Wang, M.D. Some children may even have tiny amounts of blood in the urine without any reason at all, she adds, noting that pediatricians should rule out common causes like urinary tract infections and kidney stones, an increasingly common problem in children.

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One scenario that warrants special attention is bloody urine after a minor fall, a slight bump to the belly or other such seemingly innocuous injury, Wang says, because it could be the first sign of a urinary tract anomaly in an otherwise healthy child. One such condition is a “pelvic” kidney or a kidney that is abnormally positioned in the lower abdomen rather than higher and toward the back. The condition, Wang explains, is quite rare and occurs during fetal development when one or both kidneys fail to ascend into the back of the abdominal cavity and instead remain in the lower abdomen, their “original home” during early fetal development.

Pelvic kidneys are more vulnerable to damage because they are not as well shielded by fat, ribs and cartilage as normally positioned kidneys. Even minor falls or bumps to the abdomen can damage them, leading to bloody urine.

In addition to being more vulnerable to physical trauma, the ureters — the “drainage pipes” carrying fluid from the kidneys to the bladder — are often misshapen and squished by surrounding organs and cannot drain fluid properly. This can cause slow but progressive kidney damage over time. Timely diagnosis and surgery to restore shape and flow can save a pelvic kidney and its function, but because the condition rarely causes symptoms in early life, all too often it is discovered only after substantial kidney damage has occurred.

“For a child with a pelvic kidney, an injury that causes blood in the urine can be a blessing in disguise,” Wang says.

Blood in the urine always requires medical attention and, at a minimum, a urine analysis and blood work to check the kidney function, Wang says.

Blood in the urine that doesn’t go away after a day or two or comes and goes -- whether visible or detected during microscopic urine analysis -- should always prompt further evaluation, including a noninvasive ultrasound of the kidneys to check their position and structure.

Provided by Johns Hopkins University