We report a 15-year-old boy who presented with painful gross hematuria and tenderness in the left loin. Urological examinations showed idiopathic, abacterial posterior urethritis extending into the bladder trigone including the ureteral orifice, which led to vesico-ureteric reflux and hydronephrosis. The patient failed to respond to conventional medications for a long time, and finally improved with the administration of oral prednisolone.The 15-year-old boy had painful frank hematuria, left loin pain and difficulty weight bearing on the left side for 2 days. Examination showed a tender left loin. Urine cultures, and hematological, biochemical and microbiological investigations, and plain X-ray were normal. Ultrasound scan showed bilateral hydronephrosis with an antero-posterior diameter of 1.2 cm on the right side and 2.7 cm on the left side (Fig. 1a). Mercaptoacetyltriglycine renogram showed a non-obstructive curve.Cystoscopy showed severe posterior urethritis extending into the bladder with dilated and inflamed ureteric orifices (Fig. 1b). Voiding cystourethrogram showed left vesicoureteral reflux (Fig. 1c). Triamcinolone 40 mg was instilled intravesically. Intravenous urogram showed no evidence of obstruction. Magnetic resonance angiogram and magnetic resonance urogram failed to show a crossing vessel. A repeat cystoscopy and further dose of 80 mg triamcinolone was instilled.The patient had several admissions, repeat investigations, and full analgesia and courses of antibiotics without any improvement. A second opinion was sought, and intermittent pelvi-ureteric junction obstruction was suspected, and insertion of a double J stent was advised to see if the pain could be relieved. Insertion of a double J stent was attempted through the left ureteric orifice, but was abandoned as a result of contact bleeding.We treated the patient with a short course of oral prednisolone 50 mg daily for 1 week followed by alternate days for another 2 weeks. After starting steroids, he underwent cystourethroscopy and insertion of a double J stent (4.7, 22-32 size).Two months later, the double J stent was removed. On repeat cystoscopy at 4 months, there was no urethritis or bladder inflammation and both ureteric orifices were normal. Micturating cystourethrogram was normal. At 3 years, the patient is asymptomatic with normal ultrasound.Eradi and Ninan reported the use of intravesical topical instillation of steroids in idiopathic urethritis with complete reversal of symptoms and local inflammation. 1 We have reported successful treatment of recurrent epididymitis secondary to idiopathic urethritis with steroid instillation.2 We failed to reproduce this effect in the present case. We hypothesise that the inflammation was so severe that the vesicoureteric reflux of the steroids into the upper tracts was inadequate to treat the upper renal tract areas leaving a persistent reservoir of inflammation.The patient's symptoms continued unabated for several months, and required several admissions, investigations and interventions, and wer...