The urinary system consists of kidney up to the genitalia. Many problems of this system can start before birth and some develop thereafter. Kidney diseases are much more common in children. Infection anywhere in the pathway of urination (UTI) mainly but not exclusively affects female babies. It manifests as fever, refusal of breast feeding, screaming or crying during urination, frequent urination (many times more than the usual), burning sensation during urination, irritability, cloudiness of urine etc. We diagnose urine infection by urine routine and culture test to see the growth of bacteria. If bacteria is positive antibiotic therapy is needed. UTI in any child under two years of age must be evaluated by a child kidney specialist (Paediatric Nephrologist). ‘Hydronephrosis’(enlarged swollen kidney) is one of the most common problem which usually starts when a child is in its mother’s womb. It can be easily diagnosed during pregnancy by ultrasonogram(USG). Another common birth defect in male babies is ‘Posterior Uretheral Valve’. The newborn present with poor urinary stream, palpable urinary bladder, repeated urinary infection and hydronephrosis. Diagnosis can be made by USG and MCU (micturating cystourethrogram) with RGU(retrograde urethrogram). Treatment is surgery. Pinhole orifice of the foreskin of penis (Phimosis) may cause difficulties in urination and repeated UTI. If so, circumcision is the solution. If a child of 4-6 years rapidly develops swelling of whole body including genitalia, scanty urine and a curd like concentration of urine while boiling in a test tube, ‘Nephrotic Syndrome’ is the highest possibility. ‘Acute glomerulonephritis’( passage of red urine with hypertension and swollen face) is the disease of 5-15 years. In case of ‘Chronic Kidney Disease’ you may find your child is getting pale (anemia) day by day, not gaining weight, having hypertension and changes in bones. If you suspect any sign that arises question in your mind, do consult your Paediatric Nephrologist. Your timely decision can save the child’s kidney.