Pain in the left side of your lower stomach usually involves one of a handful of organs clustered in that area: the descending and sigmoid colon, portions of the small intestine, the left ureter and kidney, and in women, the left ovary and fallopian tube. The most common cause in adults over 50 is diverticulitis, while younger adults are more likely dealing with a muscle strain, trapped gas, constipation, or a reproductive or urinary issue. What the pain feels like, how fast it came on, and what other symptoms tag along with it all help narrow down the cause.
Diverticulitis: The Most Common Culprit Over 50
Diverticulitis happens when small pouches that form in the colon wall become inflamed or infected. It is the single most recognized cause of left lower abdominal pain in middle-aged and older adults because those pouches develop most often in the sigmoid colon, which sits right in that area. The pain is typically sudden and intense, though it can also start mild and build over hours or days. Alongside the pain, you may notice fever, nausea, tenderness when you press on the spot, and a sudden change in bowel habits, either diarrhea or constipation.
Mild episodes sometimes resolve with a liquid diet and rest, while more severe cases need antibiotics or, rarely, surgery. A CT scan with contrast is the preferred way to confirm the diagnosis. If you’ve had one flare, you’re at higher risk for another, so dietary changes (particularly increasing fiber gradually) become important afterward.
Constipation and Gas
Before jumping to a serious diagnosis, it’s worth considering the most mundane explanation. Stool and gas tend to accumulate in the descending and sigmoid colon on your left side, so that’s exactly where you feel the cramping, bloating, and pressure when things aren’t moving. The pain often comes in waves, feels better after a bowel movement or passing gas, and worsens after meals. If you haven’t had a good bowel movement in a couple of days and the pain is more of a dull ache or pressure than a sharp, constant stab, constipation is a strong possibility.
Irritable Bowel Syndrome
IBS is a disorder of gut-brain interaction, meaning the nerves connecting your brain and digestive tract are overly sensitive, causing the muscles in your bowel to contract abnormally. There’s no visible damage to the intestine itself, which is what separates IBS from inflammatory bowel disease (IBD). The hallmark is repeated abdominal pain tied to changes in your bowel movements: diarrhea, constipation, or an alternating mix of both. Pain tends to be crampy, comes and goes over weeks or months, and often eases after a bowel movement. Bloating is almost always part of the picture. If your left-sided pain keeps returning, especially in connection with stress or certain foods, IBS is worth exploring with your doctor.
Inflammatory Bowel Disease
Unlike IBS, IBD involves actual inflammation you can see on imaging or a scope. Ulcerative colitis, in particular, starts in the rectum and can extend through the sigmoid and descending colon on the left side. The key differences from IBS are bloody stools, unintentional weight loss, persistent diarrhea (often more than four or five times a day), and fatigue. Crohn’s disease can affect the left colon too, though it more commonly involves the end of the small intestine. Both conditions tend to flare and remit, so the pain and symptoms come in cycles that last days to weeks.
Kidney Stones Passing Through the Left Ureter
A stone that drops out of the left kidney into the ureter, the narrow tube leading to the bladder, can cause pain that radiates from your back and side down into your lower left abdomen and groin. The pain is famously severe and comes in waves as the ureter spasms around the stone. You’ll usually notice urinary symptoms alongside the pain: a burning sensation when you pee, blood in your urine (which may look pink, red, or brown), frequent urges to go, and producing only small amounts each time. If the pain is colicky and your urine looks off, a stone is a strong possibility.
Causes Specific to Women
Several gynecologic conditions cause pain that localizes to one side of the lower abdomen. An ovarian cyst on the left ovary can produce a dull ache or sudden sharp pain if it ruptures or twists. Ovulation itself sometimes causes a brief, one-sided pain (called mittelschmerz) around the middle of your cycle. Endometriosis, where tissue similar to the uterine lining grows outside the uterus, often causes chronic pelvic pain that worsens with periods. Pelvic inflammatory disease, usually from an untreated sexually transmitted infection, brings pain along with fever, unusual discharge, and pain during sex.
An ectopic pregnancy, where a fertilized egg implants in the left fallopian tube instead of the uterus, is a true emergency. The pain tends to be sharp and one-sided, sometimes with vaginal bleeding and dizziness. If there’s any chance you could be pregnant and you’re experiencing left-sided pelvic pain, this needs immediate evaluation. For premenopausal women with unclear left lower abdominal pain, a pelvic ultrasound is often the recommended first imaging step to sort out gynecologic causes from digestive ones.
Causes Specific to Men
Inguinal hernias occur when tissue pushes through a weak spot in the abdominal wall near the groin. You may notice a visible bulge in the groin or scrotum along with a feeling of heaviness, discomfort, or burning. Symptoms typically worsen when you strain, lift, cough, or stand for long periods, and improve when you lie down. Hernias develop on one side at a time, and while the right side is slightly more common, left-sided hernias are not unusual. A hernia that becomes “stuck” or loses its blood supply (strangulated) causes sudden, severe pain and needs emergency treatment.
Testicular problems, including infection or torsion, can also refer pain upward into the lower left abdomen, even when the primary issue is in the scrotum.
Epiploic Appendagitis: A Mimicker Worth Knowing
This is a lesser-known condition where a small, fat-filled pouch on the outside of the colon loses its blood supply and becomes inflamed. About 5% of people initially diagnosed with diverticulitis actually have epiploic appendagitis instead. Three out of four people with the condition report lower abdominal pain, and more than half say it’s on the left side. The pain comes on suddenly, feels sharp and localized to one spot, and can last several weeks. The important distinction is that epiploic appendagitis resolves on its own. The inflamed tissue eventually calcifies and detaches, ending the pain without antibiotics or surgery. It’s diagnosed on CT, and the main value in identifying it is avoiding unnecessary treatment for diverticulitis.
Warning Signs That Need Urgent Attention
Most left lower abdominal pain turns out to be something manageable, but certain features signal that you should get to an emergency room rather than waiting for a scheduled appointment:
- Pain so severe it interrupts your ability to function, especially if it came on suddenly
- Inability to keep liquids down because of persistent vomiting
- Complete inability to pass stool or gas, combined with worsening pain and abdominal swelling
- Fever with a rapid pulse alongside abdominal pain
- Pain that worsens with movement, coughing, or deep breaths, which can indicate peritoneal irritation
- Signs of internal bleeding, including dizziness, lightheadedness, or fainting along with abdominal pain
If you’ve had previous abdominal surgery and develop new pain that feels different from anything you’ve experienced before, that also warrants prompt evaluation. Prior surgeries create adhesions that can cause bowel obstructions, sometimes years later.
What to Expect at the Doctor’s Office
Your doctor will press on different areas of your abdomen to locate the tenderness, ask about your bowel and urinary habits, and in many cases order a CT scan of your abdomen and pelvis with contrast dye. This is the single most informative test for sorting out the various causes. Women of reproductive age will often get a pelvic ultrasound as well, particularly if a gynecologic cause is suspected. Blood work and a urine sample help check for infection, inflammation, kidney stones, and pregnancy. In many cases, particularly with gas, constipation, or mild muscle strain, no imaging is needed at all, and your doctor can guide you based on your symptoms and a physical exam alone.