Left lower abdominal pain: causes, red flags and when to get it checked

The sigmoid colon is the narrowest and most muscular part of the large bowel, so pressure builds there when stool is hard or when small pouches form in the wall. It is also close to pelvic organs and the left urinary tract, so several systems can produce pain here.

• Constipation and trapped wind: crampy pain, relieved by passing stool or wind.

• Irritable bowel syndrome: recurrent abdominal pain related to bowel movements with bloating and altered stool pattern over months.

• Diverticular disease and diverticulitis: pouches in the bowel wall that can become inflamed, causing constant pain, fever and tenderness, more common over 40.

• Gastroenteritis and food-related upset.

• Urinary tract infection or a kidney stone passing down the left ureter.

• In women: ovarian cyst, endometriosis, pelvic inflammatory disease, period pain or ectopic pregnancy.

• Inflammatory bowel disease (ulcerative colitis, Crohn disease) with diarrhoea, blood, weight loss and tiredness.

• Hernia, bowel obstruction, ischaemic colitis and bowel cancer, which are less common but important.

Constant severe pain, fever, vomiting, a hard swollen abdomen, blood or mucus in the stool, a change in bowel habit lasting over six weeks, unintentional weight loss, iron deficiency anaemia, and pain in a woman who could be pregnant need prompt assessment.

• Call 999: severe abdominal pain with collapse, a rigid abdomen, heavy rectal bleeding or severe one-sided pain with vaginal bleeding and dizziness.

• Same-day GP or A&E: constant lower-left pain with fever or vomiting, or an inability to pass wind or stool with distension.

• Urgent GP referral: bowel habit change with rectal bleeding, weight loss or anaemia, particularly over 50.

• Routine GP: recurrent cramping linked to bowel habits.

Doctors ask about onset, character, relation to eating and bowel movements, stool changes, blood, fever, urinary symptoms, periods, sexual history, medicines and family history of bowel disease or cancer. They examine the abdomen for tenderness, masses and guarding, and may do a rectal examination.

• Blood tests: full blood count, CRP, ferritin, coeliac screen and kidney function.

• Faecal immunochemical test (FIT) and faecal calprotectin: to look for bowel cancer risk and inflammation.

• CT abdomen and pelvis: the main test for acute diverticulitis and complications.

• Colonoscopy: after recovery from diverticulitis, or for blood, weight loss or bowel habit change.

• Pelvic ultrasound: for ovarian and pelvic causes in women.

For constipation or IBS, increase fibre and fluids gradually, stay active and keep a food and symptom diary. Mild diverticulitis may be treated at home with rest and, in some cases, antibiotics under medical direction. Avoid regular use of strong painkillers such as codeine, which worsen constipation.

The NHS route is a GP, with surgical or gastroenterology referral for complicated or persistent disease. Private colorectal and gastroenterology consultations offer direct access to CT and colonoscopy.