Most common cause of acute retention of urine in a child of 2 years age:

c. Meatal ulceration with scabbing(Ref: Nelson's 20/e p 2562-2567, Ghai 8/e p 485-486)Meatal ulceration with scabbing can cause acute retention of urine.Dont get confused by option 'a'- Though posterior urethral valve is the most common cause of obstructive uropathy in children, it does not cause acute retention.Posterior urethral valve usually presents with chronic obstructive symptoms like weak urinary stream, distended bladder, uremia or sepsis caused by infection in the obstructed urinary tract.Urethral stone may cause obstruction, but the most common presentation is hematuria with or without pain.