What is the primary indicator that a patient does not have a mechanical outflow obstruction when attempting catheterization?

The primary indicator that a patient does not have a mechanical outflow obstruction during catheterization is that the catheter passes easily. When there is no obstruction, whether due to anatomical anomalies, strictures, or other physical blockages within the urinary tract, the catheter will navigate through the urethra and bladder without any significant resistance. This ease of passage suggests that the pathway for urine flow is clear, allowing for successful catheterization without encountering barriers that would indicate an obstruction.

Other factors, such as pain experienced by the patient or normal urine output, do not provide definitive insight into the presence or absence of a physical blockage. Severe pain may suggest other issues, but does not specifically indicate an obstruction. Similarly, a significant amount of resistance encountered during catheterization would point to possible obstruction, opposite to what the question is asking. Thus, the ability of the catheter to pass easily confirms an unobstructed pathway.