Which of the following is the most common cause of delayed UT obstructive symptom after TURP

Transurethral prostate surgery TURP remains the most commonly performed procedure for the surgical correction of BOO. Strips of tissue are cut from the bladder neck down to the level of the verumontanum. Cutting is performed by a high-frequency diathermy current, which is applied across a loop mounted on the hand-held trigger of the resectoscope. Coagulation of bleeding points can be accurately achieved. The 'chips' of prostate are then removed from the bladder using an Ellik evacuator. Resection proceeds at 1g/minute in experienced hands. The duration of resection for monopolar TURP is limited to 1 hour due to the risk of resorption of water if 1% glycine is used as an irrigant. The advent of bipolar TURP where normal saline is used as an irri- gant permits resection of larger prostates. Following TURP, careful haemostasis is performed, and a three-way, self-re- taining catheter irrigated with isotonic saline is introduced into the bladder to prevent any fuher bleeding from form- ing blood clots. Irrigation is continued until the outflow is pale pink, and the catheter is usually removed on the sec- ond or third postoperative day. In men with small prostates or bladder neck dyssynergia or stenosis, it is better to divide the bladder neck and prostatic urethra with a collings knife. Laser can be used to evaporate (e.g. Green light laser) or enucleate the prostate (e.g. HOLEP). The advantage of green light laser is that vaporisation is haemostatic and this procedure can be performed even while patients are antico- agulated. HOLEP involves the use of a laser to coagulate any of the small vessels crossing the relatively avascular plane between the peripheral and transitional zones of the prostate while the tip of the cystoscope is used, much like the surgeons finger at Millin's prostatectomy, to enucleate the transition zone adenoma. The enucleated adenoma is pushed into the bladder, where it is morcellated and extracted the cysto- scope. Damage to the external sphincter is avoided provided one uses the verumontanum as a guide to the most distal point of the resection/vaporisation/enucleation.