Complex catheter placement is performed when a standard urinary catheter cannot be inserted safely or easily. Difficulty may occur because of an enlarged prostate, urethral narrowing, scar tissue, previous surgery, altered anatomy, or another obstruction. The urologist may use specialized catheter types, guidewires, a cystoscope, or other techniques to carefully navigate the urinary passage and reach the bladder while minimizing trauma. Once the catheter is correctly positioned, it allows urine to drain and relieves bladder pressure. Depending on the reason for the difficulty, additional evaluation may be recommended to identify and treat the underlying cause of the obstruction or catheterization problem.