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[Conditions](https://durgical.com/en/conditions/) · [Nephrology and urology](https://durgical.com/en/conditions/)

# Vesicoureteral reflux

Urine flows backward from the bladder up the [ureters](https://durgical.com/en/anatomy/ureter/) toward the kidneys. In children it raises the risk of kidney infections and scarring.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Ureters](https://durgical.com/en/anatomy/ureter/)
- [Urinary bladder](https://durgical.com/en/anatomy/urinary-bladder/)
- [Kidneys](https://durgical.com/en/anatomy/kidney/)
- [Trigone of bladder](https://durgical.com/en/anatomy/trigone-of-bladder/)
- [Renal pelvis](https://durgical.com/en/anatomy/renal-pelvis/)

## In embryology

- [Kidney: pronephros, mesonephros, metanephros and ascent](https://durgical.com/en/embryology/kidney-pronephros-mesonephros-metanephros-and-ascent/)
- [Bladder, urachus and urethra](https://durgical.com/en/embryology/bladder-urachus-and-urethra/)
- [Horseshoe kidney and renal ectopia](https://durgical.com/en/embryology/horseshoe-kidney-and-renal-ectopia/)
- [Duplicated ureter, UPJ obstruction and posterior urethral valves](https://durgical.com/en/embryology/duplicated-ureter-upj-obstruction-and-posterior-urethral-valves/)
- [Bladder exstrophy](https://durgical.com/en/embryology/bladder-exstrophy/)

## Why it happens

- [Micturition and the bladder reflex](https://durgical.com/en/physiology/micturition-and-the-bladder-reflex/)
- [Ureter, bladder and urethra: urothelium](https://durgical.com/en/histology/ureter-bladder-and-urethra-urothelium/)

## What it is

Retrograde flow of urine from the bladder into one or both ureters and sometimes the kidneys, usually because the valve-like junction where the ureter enters the bladder does not close properly. It is mainly a disease of infants and young children.

## Who gets it

Found in a large share of young children investigated after a febrile urinary infection, and in some siblings and children of affected people. Many cases are detected after a first febrile urinary infection or because of hydronephrosis on prenatal ultrasound.

## Causes

- Primary: a short intramural (submucosal) ureter segment at the ureterovesical junction, which tends to lengthen with growth
- Secondary: high bladder pressure from posterior urethral valves, neurogenic bladder or bladder–bowel dysfunction
- Familial tendency

## Risk factors

- Sibling or parent with reflux
- Infancy and young age
- Hydronephrosis detected before birth
- Bladder–bowel dysfunction (holding urine, constipation)
- Posterior urethral valves or neurogenic bladder

## Pathophysiology

The ureter normally tunnels obliquely through the bladder wall, so bladder filling compresses it shut. A short or laterally placed tunnel lets urine flow back during filling or voiding. Bacteria in the bladder then reach the kidney, causing pyelonephritis, and repeated infection in a growing kidney leads to scarring (reflux nephropathy).

## Classification

- International grading I–V on voiding cystourethrography: I = ureter only; II = up to the [pelvis](https://durgical.com/en/anatomy/region/pelvis/) without dilatation; III–IV = increasing dilatation of ureter and calyces; V = severe tortuous dilatation with loss of papillary impressions
- Primary or secondary
- Unilateral or bilateral

## Symptoms and signs

- Often none until a urinary infection occurs
- Febrile urinary tract infection in infants: fever, irritability, poor feeding, vomiting
- In older children: painful or frequent urination, flank or abdominal pain
- Daytime wetting or constipation (bladder–bowel dysfunction)
- Hydronephrosis found on prenatal ultrasound

## Red flags

- High fever, vomiting or a toxic appearance in an infant (pyelonephritis, urosepsis)
- Recurrent febrile urinary infections
- Raised blood pressure in a child
- Poor growth, rising creatinine or protein in the urine (reflux nephropathy)
- Weak or dribbling stream in a boy (posterior urethral valves)

## Diagnosis

**Clinical**
Suspect it in infants and children with febrile urinary infection, a family history or prenatal hydronephrosis; ask about voiding and bowel habits and check blood pressure and growth.

**Tests**
Urinalysis and urine culture from a properly collected sample; creatinine and urine protein when there is scarring.

**Imaging**
[Kidney](https://durgical.com/en/anatomy/kidney/) and bladder ultrasound first. Voiding cystourethrography (VCUG) is the reference test to diagnose and grade reflux; DMSA scan detects kidney scarring.

## Differential diagnosis

- Ureteropelvic junction obstruction
- Posterior urethral valves
- Primary megaureter or ureterocele
- Neurogenic bladder
- Recurrent cystitis without reflux

## Goal of treatment

Prevent febrile urinary infections and kidney scarring while waiting for spontaneous resolution, and correct reflux when it persists or causes harm.

## Treatment

**Follow-up**
Watchful waiting with prompt urine testing and treatment of every febrile illness; low grades often resolve with growth.

**Medical**
Prompt antibiotic treatment of infections; continuous low-dose antibiotic prophylaxis in selected children, especially higher grades or recurrent infections.

**Lifestyle**
Treating bladder–bowel dysfunction: regular voiding, good fluid intake and correcting constipation; circumcision may be discussed in boys with high-grade reflux.

**Procedure**
Endoscopic injection of a bulking agent at the ureteral opening.

**Surgical**
Ureteral reimplantation (open, laparoscopic or robotic) for breakthrough infections, new scarring or persistent high-grade reflux; secondary reflux is treated at its cause.

## Complications

- Recurrent pyelonephritis and urosepsis
- Kidney scarring (reflux nephropathy)
- Hypertension
- Chronic kidney disease and, rarely, kidney failure
- Pregnancy complications in women with scarring

## Prognosis

Most low-grade primary reflux resolves within a few years as the child grows. High-grade and bilateral reflux resolves less often and carries the highest risk of scarring, hypertension and kidney disease.

## Prevention

- Early diagnosis and treatment of febrile urinary infections in infants
- Screening of siblings in selected families

## Test yourself

Think of the answer, then tap the question to see it.

## What is the reference imaging test to diagnose and grade vesicoureteral reflux?

Voiding cystourethrography (VCUG).

## What causes primary vesicoureteral reflux?

A short intravesical (submucosal) ureteral tunnel at the ureterovesical junction, so the valve does not close.

## Which test detects kidney scarring?

A DMSA renal scan.

## What is the main long-term risk of high-grade reflux?

Reflux nephropathy: kidney scarring leading to hypertension and chronic kidney disease.

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## Related conditions

- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)
- [Acute pyelonephritis](https://durgical.com/en/conditions/acute-pyelonephritis/)
- [Hydronephrosis and obstructive uropathy](https://durgical.com/en/conditions/hydronephrosis-and-obstructive-uropathy/)
- [Posterior urethral valves](https://durgical.com/en/conditions/posterior-urethral-valves/)
- [Neurogenic bladder](https://durgical.com/en/conditions/neurogenic-bladder/)
- [Chronic kidney disease](https://durgical.com/en/conditions/chronic-kidney-disease/)
- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)
- [Spina bifida (myelomeningocele)](https://durgical.com/en/conditions/spina-bifida/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Vesicoureteral Reflux (VUR)](https://www.niddk.nih.gov/health-information/urologic-diseases/hydronephrosis-newborns/vesicoureteral-reflux) (NIDDK (National Institutes of Health), 2024); [Bilateral hydronephrosis: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000474.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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Source: https://durgical.com/en/conditions/vesicoureteral-reflux/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/vesicoureteral-reflux/