A 9-year-old boy in India had a 7-millimeter stone lodged low in the ureter, the tube that carries urine from his left kidney to his bladder. Twelve days later, an X-ray showed the stone was no longer there. It had not been passed. It had moved back up, against the normal flow of urine, to the region of his kidney.
Urologists at MGM Medical College and Hospital in the Mumbai area reported the case in Urology Case Reports, published online Sept. 7, 2026. "To our knowledge, this is the first reported paediatric case of spontaneous retrograde migration of a ureteric calculus in world literature," they write. Earlier reports of stones moving backward involved only adults.
Then, six weeks after the surgery that followed, the stone slid back down.
Blood in the Urine and a Swollen Kidney
The boy had pain in his left flank for a week. Over the previous month, he had three episodes of "gross, painless haematuria," meaning blood he could see in his urine. His physical exam and blood tests were normal.
An ultrasound showed an enlarged left kidney that was moderately swollen with backed-up urine, a condition called hydronephrosis, and its tissue had thinned. The entire left ureter was dilated, and a 7-mm stone sat in its lower portion. A plain abdominal X-ray confirmed a single stone in the same spot.
When doctors performed an intravenous urogram 12 days later, the first X-ray, taken before contrast dye, showed the stone "in the renal region rather than in the distal ureter where it had been documented 12 days earlier."
A Wide Ureter With a Narrow Exit
Further tests found an underlying problem. A bladder X-ray study showed no reflux of urine back toward the kidney. A nuclear kidney scan showed "an obstructive drainage pattern" on the left, although that kidney still provided 45% of his total kidney function.
The diagnosis was primary non-refluxing obstructive megaureter, in which the ureter becomes very wide above a narrow segment near the bladder. The authors note that it accounts for 5% to 10% of hydronephrosis detected before birth. According to the Pediatric Urology Book, megaureter is about twice as common in boys and occurs more often on the left. A ureter wider than 7 mm is considered abnormal in children, and in one series about a third of primary megaureters resolved on their own over an average of about three years.
The authors' hypothesis is that the shape and behavior of his ureter let the stone move both ways. They suggest that "uncoordinated or frankly reverse ureteric peristalsis," along with weak muscle tone in the lower ureter and altered pressure, allowed "to-and-fro movement of urine," carrying the small stone with it. They acknowledge that "as a single case, the proposed mechanism remains speculative."
The Stone Came Back Down
Because the ureter was obstructed, surgeons performed an open reimplantation of the left ureter into the bladder, using a technique called the Politano-Leadbetter procedure. During the operation they found a greatly dilated upper ureter with a narrow lower segment, but "no calculus could be palpated along the course of the ureter." They placed a temporary stent, and recovery went smoothly.
Six weeks later, an X-ray showed that "the calculus had returned to the left lower ureter." This time the boy took tamsulosin, a drug that relaxes the ureter, at bedtime. He passed the stone in his urine, and the stent was removed.
The authors say this second move "underscores the dynamic, bidirectional mobility of a calculus within such a dilated, dysfunctional system."
Why a Vanishing Stone Is Not Always Good News
The main lesson is practical. When a stone no longer appears where it was, doctors may assume it has passed. In this case, the authors warn, a disappearing stone "does not necessarily indicate stone passage." They write that "repeat imaging immediately prior to surgery and meticulous follow-up are essential."
Backward stone movement is rarely reported even in adults. A 2016 report in Urology Annals described an adult case as the first in the English medical literature. In a 2025 case in Annals of Medicine and Surgery, a 23-year-old woman's 9-by-7-mm stone drifted back into her kidney over about two weeks and was later broken up with shock waves.
Most stones simply pass or are removed. An archived AUA/EAU ureteral stone guideline, drawn from studies that largely did not separate children from adults, estimated that about 68% of stones 5 mm or smaller pass on their own, compared with about 47% of stones between 5 and 10 mm.
The case also comes as kidney stones become more common in young people. A South Carolina study published in 2016 found that stone incidence rose 16% between 1997 and 2012, with the steepest increases among teenagers, women and Black patients. The risk of developing a stone during childhood doubled for both boys and girls, although the absolute risk remained low.
According to the NIDDK, children with stones may have sharp pain in the back, side, lower abdomen, or groin, or blood in the urine. Parents who notice these signs should have their child evaluated by a doctor.
Key Questions Answered
What happened?
A 7-mm stone in a 9-year-old's lower left ureter moved back up to the region of his kidney within 12 days. Six weeks after surgery, it moved back down, and he passed it.
Why could the stone move backward?
He had an obstructive megaureter, a very wide ureter with a narrow end. The authors suspect that abnormal or reversed muscle contractions and pressure changes moved urine and the stone back and forth.
Is this the first case in a child?
The authors say that, to their knowledge, it is the first reported pediatric case of spontaneous retrograde ureteral stone migration. Earlier reports involved adults.
How was he treated?
He had surgery to reattach the ureter to the bladder, with a temporary stent. No stone was found during the operation. He later took tamsulosin and passed the stone.
Does a stone disappearing on a scan mean it passed?
Not always. The authors recommend repeat imaging right before surgery and close follow-up.
What symptoms suggest a kidney stone in a child?
Sharp pain in the back, side, lower abdomen, or groin, or blood in the urine, according to NIDDK.
Published by Medicaldaily.com
