<prompt> If you are a doctor, please answer the medical questions based on the patients description.Doctor, I have been experiencing pain in my anus, itching of the skin, painful urination, retention of urine, and coryza. What could be the problem?  <response>: Based on your symptoms, you could be suffering from a pinworm infection. This is a common infection caused by a small, white, thread-like worm called Enterobius vermicularis, which lives in the colon and rectum of humans. 