### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
Last night I was at a party with no available restroom. I had been drinking, so I had to go really bad, but I held it until I got home. I ran straight to bathroom, sat down and started to go, I went a lot at first, then suddenly without warning it completely stopped midstream. I still had the urge to urinate, and my bladder still felt very full, and I was experiencing some burning. I tried pushing but could not get a single drop out. When I wiped with the tissue I felt something hard, I was mortified to feel a kidney stone lodged in my urethra! Part of it was sticking out, I could grab it with my fingernails, but I couldn t pull it out. I spent nearly 2 hours wiggling it, pulling it, pushing it, trying to turn it but it was stuck. Finally it came out, and I was able to void my bladder, and I m feeling fine. I had no warning, I m familiar with kidney stones, I ve passed many before, the biggest bring 8mm. Those always caused me excruciating pain, but this one did not. All day I was wearing a tight corset as part of my Halloween costume, maybe I was compressed so tight I didn t feel it? I don t know. I measured my stone and it it 18mm. I always was told a stone that large would be unable to pass, so I m wondering if stones that large are common, and if people pass them without medical intervention, or am I unique??

### output:

HelloThanks for query. You are known to pass urinary stones through urethra frequently But you had retention of urine due to impacted stone of a size of 18 mm in urethra which finally passed out giving you excruciating pain. The reasons for not feeling the pain due to such a large stone are 1)With history of passing stones repeatedly your ureters are dilated and capacious enough to accommodate this stone without pain .2) The shape of the stone may be oval like a peanut without spikes helping it to pass down through dilated ureter without any obstruction and pain . We do get patients with passing large sized stone without pain. This is very common in patients who have history of repeated and recurrence of stone disease. Chat Doctor. 