I have it a few times during urodynamics. Before urethral catheterization nurse lube my anal sphincter and insert a small catheter with a sort of rubber cylinder on the tip, it felt intrusive and slightly stretching, which triggered an immediate reflex to tighten. That initial moment was the most uncomfortable, more because of the instinctive reaction than actual pain.
Once in place, there was a persistent feeling of fullness, like a constant mild pressure inside the rectum. It wasn’t painful, but it was impossible to ignore. At times, there was a faint tickling or “foreign object” sensation, almost like an internal sort of dilatation rather than something sharp. That odd mix of pressure and tickle made it difficult to relax fully at first.
When the balloon was inflated during the test, the sensation shifted. It created a gradual, increasing urge similar to needing to defecate. The feeling built slowly and became quite strong diffusing a mild pain on my entire belly. At peak inflation, it felt very urgent, but still under control.
Emotionally, this part was the most challenging because it forced attention onto very private bodily sensations. However, the discomfort eased quickly once the pressure was released at the end of the examination. Having my sphincter and penis completely exposed while having my bladder filled with saline and asked to squeeze added a lot to the embarassement.