Your protrusion and pain could be due to several things. Here's a link to abdominal masses in general: http://www.nlm.nih.gov/medlineplus/ency/article/003274.htm
It sounds like you have a right lower quadrant external bowel herniation. http://www.nlm.nih.gov/medlineplus/ency/imagepages/1090.htm An external bowel herniation wouldn't show up on a scan because during the scan you're lying down and the scan is a static picture not a dynamic one. Most hernias produce no symptoms. They are noticed as a protrusion (lump) which goes away when you lay down. The concern with hernias is incarceration. A hernia can be examined and treated using a laparascope. It's too soon to know if you will need a hysterectomy. First, you need a surgeon to use a laparascope to see what the protrusion is caused by.
If you have a question please ask me.
Dr. Hanson
Doctor (MD)
Diplomate, American Board of Quality Assurance & Utilization Review Physicians
Hello. Yes, you can still have an "external" bowel herniation even without any bowel problems. In fact, most people with external bowel herniations are asymptomatic (don't have any symptoms) except that they can feel or see a lump over their intestine. The problem is that there is no telling when or if the herniated bowel will become "incarcerated" (squeezed and the circulation to the bowel becomes cut-off).
Here's a link to an article where a gentleman had a similar case to yours: http://www.liebertonline.com/doi/abs/10.1089/109264204322973907
A surgeon should perform exploratory laparascopic surgery to find out specifically what is causing your painful lump.