Hello! Thanks for putting your query in HCM. I am a Gastroenterologist (DM).
Pain in left side lower part radiating to back may be due to:
1. Colonic disease like malignancy, diverticulitis
2. Urinary tract
disease like stone in tract
3.Pelvic organ disease.
So I will advise you to get yourself examined by a Doctor who may advise for ultrasound
abdomen, urine examination and may be sigmoidoscopy
for confirming the diagnosis
I hope I have answered your query and this will help you. If you have any further query I will be happy to answer that too. Remain in touch and get-well soon.