The vesicoureteral reflux (reflux) belongs to the most frequent causes of urinary tract infection. Up to 30 % of the prenatally diagnosed hydronephroses by ultrasound are due to postnatally confirmed vesicoureteral reflux.
Besides the classic reflux which occurs mainly in girls and becomes symptomatic due to an urinary tract infection, there is a fetal reflux which occurs more frequently in boys and is recognizable by ultrasound already prenatally and is confirmed postnatally by a voiding cystography.

1. Reflux is a frequent disorder.
2. Reflux is a frequent cause of a simple or a complicated urinary tract infection.
3. Fetal reflux is a possible cause of an irreversible kidney damage already present at birth.
4. Classical and fetal reflux are possible causes of a reflux nephropathy which leads to different grades of diminished renal function and renal insufficiency and/or hypertension.

The primary reflux is due to an anomaly of the vesicoureteral valve, to a delayed maturation of the valve, or to a cystitis; in case of an uni- or bilateral valve anomaly the ureteral orifice lies more laterally within the trigonum and has a golf-hole shape.
The same applies to the inferior ureter in complete ureteric duplication (regardless of whether it enters the bladder or the urethra), and to some cases in incomplete duplication.
The secondary reflux may be caused by an infravesical obstruction, a neuropathic bladder, a functional voiding disorder of the bladder, or by a bladder diverticulum and other pathologies.

Primary and secondary reflux. Classic and fetal reflux. Classification of reflux: I to V. I and II slight, IV and V severe reflux.

There are no specific signs and symptoms of reflux.
The most frequent clinical presentation is a recurrent simple or complicated urinary tract infection.
Less frequently, a delay of the bladder maturation occurs with incontinence beyond the age of 5 years, appearing as a primary or secondary enuresis.
Rarely, hematuria is observed, in certain cases due to a cystitis.

In some of the patients there is a spontaneous resolution of the reflux after some time.
It concerns patients with delay of maturation of the vesicoureteral valve or with functional voiding disorders of the bladder.
However, in a population of 15-year old children with a terminal renal insufficiency 1/4 of the patients have a urological malformation, and 1/3 of them a reflux.

The differential diagnosis in case of urinary tract infection includes the following groups of pathologies:
1. Obstructive pathologies of the upper urinary tract;
2. Complete and incomplete ureteral duplications;
3. Abnormal ascent (ectopic) and abnormal fusion (horseshoe kidney) of the kidney, and hypoplastic and aplastic kidney;
4. Cystic diseases of the kidney;
5. Diverticulum of the bladder and cystitis;
6. Neuropathic bladder, functional bladder disturbances, and obstructive pathologies of the lower urinary tract.

In addition, depending on the individual differential diagnosis, leading signs other than urinary tract infections may be observed. For instance, in the group of functional bladder disturbances, abnormal voiding patterns. Besides the already mentioned pathologies, a functional voiding disorder has to be considered in case of enuresis as the main symptom.

Ultrasound of the kidney and urinary tract, and voiding cystography (=VCUG) are the basic examinations in reflux; contrast media allow a better classification of the reflux grades than isoptopes. In addition, analysis of blood (renal parameters) and urine (cultures) are essential.
Special and complex cases call for intravenous urogaphy, renal scanning, MRI with contrast, and, for the definition of the type of reflux, cystoscopy and urodynamic work-ups.

There are different opinions concerning the best therapeutic approach, e.g. non-operative treatment with prophylactic antibiotics up to the disappearance of the reflux.
Considering the different causes of reflux, a precise work-up and evident criteria for the indication of operative treatment are superior to the above mentioned options.
In case of an infravesical obstruction with secondary reflux, surgery as a primary tool is contraindicated.
The surgical procedures include:
1. Subureteric injection techniques (Deflux);
2. Surgical reimplantation by an intravesical (Cohen, Leadbetter-Politano) or extravesical procedure.
The selection of the procedure depends on the grade and the cause of reflux and combined pathologies.

In nearly 98 % the reflux may be cured permanently by surgery; in 2 - 3 % an ureteral obstruction or a recurrence of reflux may occur.
Following surgery, 1/3 of the girls exhibit recurrent simple urinary tract infections during long term follow-ups, which are not related to the former reflux.