Overactive bladder (OAB) occurs when the bladder works beyond its normal capacity. This heightened activity arises when the detrusor muscle—the muscle layer of the bladder—contracts excessively, creating a constant sensation of needing to urinate. Typically, the bladder contracts before reaching its age-appropriate capacity, causing urgent urges but only small volumes of urine each time. The causes of OAB are diverse; the most common include underlying constipation, neurological disorders, incomplete bladder emptying during toileting, behavioral toilet issues, consumption of bladder-irritating foods and beverages, and developmental problems. Once the cause is identified, a pediatric urologist should begin appropriate treatment promptly and address any concurrent constipation.

The bladder and intestines lie close together in the abdomen. When the bowels are full, they can press on the bladder and trigger increased urinary frequency. Research shows that a mass of retained stool can press on the detrusor muscle, causing it to become overactive. In addition to increased detrusor activity, this pressure can reduce bladder capacity, leading to extreme urgency with only small volumes of urine voided. When constipation underlies OAB, treating the constipation is essential to restore normal bladder function.

Functional bladder capacity in children is estimated using the formula (age + 2) × 30 ml up to around age 12. For example, a 6-year-old would be expected to hold about 240 ml at maximum urgency. If a child routinely voids less than the expected volume for their age, reduced bladder capacity may be present. However, because the bladder is a muscular organ, it can grow in volume. In cases of OAB, capacity may not increase without treatment, so early intervention by a pediatric urologist is important. If left untreated, small bladder capacity and symptoms may persist, and the child may develop coping behaviors that still impact daily life.

The key symptoms of overactive bladder (OAB) include increased frequency of urination, a strong urgency to void, inability to suppress the urge, and often accompanying daytime and/or nighttime incontinence.

Normally, a healthy child voids about 4–7 times per day with age-appropriate fluid intake. Children with OAB often urinate more than 7 times a day, even when they try to limit fluids. To suppress urgency, they may cross their legs, press or squeeze the genital area, rock or dance, squat, or, in boys, pinch the tip of the penis.

Vesicoureteral reflux (VUR), or kidney reflux, occurs when urine flows backward from the bladder into the ureters and kidneys and is often seen with urinary tract infections. Excessive bladder muscle activity can raise bladder pressure, causing urine to backflow into the ureters. In such cases, it is valuable to begin medical treatments to reduce bladder pressure and start pelvic floor rehabilitation promptly.

Evaluation should start with a detailed history and physical exam by a pediatric urologist. Important history points include past medical treatments, voiding and bowel habits, diet and fluid intake, toilet-training history, and any psychological issues. The physical exam should assess genital anatomy and the lumbar region for neural involvement; an MRI may be ordered if indicated.

• Urinalysis and urine culture if a urinary infection is suspected; blood tests to assess kidney function, infections, metabolic disorders, and hormonal balance.
• Renal and bladder ultrasound to detect hydronephrosis, anatomical abnormalities, post-void residual urine, bladder wall thickness, and rectal stool masses.
• Voiding test (uroflowmetry) to measure urine flow rate and pattern; the child urinates into a sensor-equipped toilet in a painless, child-friendly test.
• Bladder diary (2-day voiding diary) recording frequency, volume (ml), incontinence episodes, and fluid intake; parents assist younger children. Access the diary here.
• Bowel diary (7-day stool diary) tracking times and stool form for one week; note any soiling episodes. Access the diary here.
• Urodynamics for storage and voiding function, measuring bladder capacity and pressure via catheter over about 20 minutes.

These tests, chosen based on the child’s age, symptoms, and clinical findings, help plan the most effective treatment.

If constipation underlies OAB, relieving constipation should be the first step.

• Urotherapy education (Healthy Bladder & Bowel Training) delivered by specialized physiotherapists covering toileting posture, healthy diet and fluids, bladder and bowel emptying techniques, and scheduled voiding, tailored to each child.
• Medication therapies may include anticholinergics to reduce bladder contractions and, for recurrent infections, prophylactic antibiotics, all prescribed and monitored by a pediatric urologist.
• Pelvic floor muscle rehabilitation with massage, breathing exercises, biofeedback-assisted muscle training, stabilization exercises, and neuromodulation to improve pelvic floor control.

Overactive bladder is a urological condition that can significantly impair quality of life for the child and family. Frequent voiding or social holding maneuvers can lead to social difficulties, and daytime or nighttime incontinence may cause psychological and social issues. Early diagnosis by a pediatric urology specialist and prompt treatment planning are essential.