A small child with a posterior urethral flap may present with varying degrees of urinary obstruction. The valve is usually located at the distal end of the prostatic urethra and is formed by mucosal folds that resemble a very thin membrane. The flap can cause varying degrees of obstruction during urination. What are the examination items of the urethral flap? 1, cystoscopy: generally by the above examination can identify the fistula site, size, bladder capacity, mucosal condition, etc.. Those who are high can be located with the help of cystoscopy and the relationship between the fistula hole and the ureteral orifice can be clarified as a reference when repairing. In units where available, it is advisable to use cystoscopy to examine the fistula in the bladder even if the fistula is found in the vagina. 2. Intravenous pyelogram: It helps to clarify the side and location of ureteral injury and renal function, as well as whether there is narrowing, dilatation or obstruction of the ureter on the injured side. The method is to inject intravenous sodium pantothenate, perform X-ray of kidney, ureter and bladder, and make a diagnosis according to the imaging situation. Before the intravenous pyelogram, the patient should have an ultrasound examination to understand the general condition of both kidneys, renal pelvis, ureter and bladder. In individual cases, retrograde cystography is sometimes used. 3. Renogram: The purpose is to understand the renal function and the patency of the upper urinary tract. If there is stenosis or obstruction due to ureteral fistula, it may lead to hyperalgesia or renal atrophy and loss of renal function on the affected side.