Flank pain on one side while urinating is a symptom consistent with a kidney stone, or nephrolithiasis. Kidney stones form when materials in the urine build up in the kidney. The resulting stone can block the urine flow and cause waves of pain along the path of the urinary tract.
Causes
Stones form when substances normally found in the urine, such as calcium, oxalate, cystine and uric acid, are at high levels and build up in the urinary tract. Even if the levels are normal, kidney stones may still form. Children who don't drink enough fluids and those who eat ketogenic, or low-carbohydrate diets are more prone to kidney stones. Children who have had kidney stones in the past, and those with parents and siblings who have had kidney stones, are at increased risk.
Symptoms
When a tubule in the body such as the ureter (the tube that carries urine from the kidney to the bladder) is blocked by a stone, the body tries to unblock it. This causes waves of pain when a kidney stone is being passed. Your child may feel pain that travels from the flank to the groin. Males may feel pain in their testicle. Blood in the urine, or hematuria, nausea, vomiting and frequent urination can occur.
Treatment
Your child's doctor can diagnose a kidney stone by testing the urine and ordering imaging studies such as an x-ray or CT scan of the abdomen. The urinalysis may show blood in the urine or signs of a urinary tract infection, which is a complication of kidney stones. If the stone shown in the imaging studies is less than 5 mm, it will pass on its own. Give your child plenty of fluids to flush the stone out and use acetaminophen or ibuprofen, according to the directions on the box for pain control. You will need to strain your child's urine until the stone passes. The stone can be analyzed to determine its composition, just in case your child develops another stone in the future.
Conclusion
Kidney stones are traditionally rare in children, but are becoming more common. Your child's doctor can diagnose kidney stones and treat them with hydration and pain control, if they're small enough to pass naturally. Stones that are too large to pass safely through the urinary tract require shock wave lithotripsy, a procedure that delivers high-energy shock waves to break the stone apart. Some patients may need a minor surgical procedure to remove the stone.
