According to MedlinePlus, a swollen lymph node in the pelvic area, also referred to as the groin, can indicate urethritis, a urinary tract infection that causes inflammation and swelling of the urethra. Urethritis is caused by bacteria or viruses, and symptoms include blood in the urine, pelvic pain, swollen lymph nodes in the groin area and discharge.
According to WebMD, swollen lymph nodes in the groin area often occur with sexually transmitted infections, foot or leg injuries and genital infections. In rare instances, swollen lymph nodes of the groin indicate testicular cancer, melanoma or lymphoma.
The Mayo Clinic explains that the most common cause of swollen lymph nodes is infection. The lymph nodes located in the pelvic area tend to swell in response to viruses and infections that are located in or around the groin. Lymph nodes are also located in the neck, under the chin and in the armpits. Lymph nodes produce protein particles and macrophages that work together to capture and break down viruses and other immune invaders. The lymphocytes and macrophages filter the fluid in the lymph nodes as it flows through the body and protect the body by destroying viruses and invaders that cause infection and illness.