Pain in the left lower side of your stomach usually comes from one of several structures packed into that area: the lower portion of the large intestine, parts of the small intestine, the left ureter, or (in women) the left ovary and fallopian tube. The most common cause in adults over 40 is diverticulitis, while in younger adults, constipation, trapped gas, muscle strain, or a reproductive issue is more likely. What’s causing your pain depends on how it started, how severe it is, and what other symptoms came with it.
What’s Actually in Your Left Lower Abdomen
The left lower quadrant sits below your belly button and to the left. The main resident is the descending colon, which runs down the left side of your abdomen and curves into the sigmoid colon, an S-shaped segment that connects to the rectum. Because this is where stool slows down and firms up before a bowel movement, it’s a common site for pressure-related problems. Loops of the small intestine also occupy this space, and the left ureter (the tube connecting your left kidney to your bladder) passes through it on its way down.
In women, the left ovary and fallopian tube sit in this quadrant too, which is why gynecological causes need to be considered alongside digestive ones.
Diverticulitis: The Most Common Culprit Over 40
Diverticulitis is the single most frequent diagnosis for left lower abdominal pain in older adults. It happens when small pouches that form in the wall of the colon (diverticulosis) become inflamed or infected. Over 50% of people older than 60 have these pouches, and the number climbs to 70% after age 80. Most people never know the pouches are there until one flares up.
The pain is typically crampy and focused on the left lower side, which is the presenting symptom in about 70% of cases. You may also notice fever, bloating, nausea, constipation, or a change in how often you go to the bathroom. The pain often builds over a day or two rather than hitting all at once.
For uncomplicated cases (no abscess, no perforation), current treatment guidelines recommend observation and pain control rather than jumping straight to antibiotics. That usually means a clear liquid diet, rest, and over-the-counter pain relief. Antibiotics are reserved for people with persistent fever, signs of infection spreading, advanced age (over 80), pregnancy, or weakened immune systems.
Constipation and Trapped Gas
Before assuming something serious, consider the simplest explanation. The sigmoid colon is a common place for stool to back up, and when it does, you feel cramping and pressure on the left lower side. Gas that gets trapped in the same area produces sharp, sometimes surprisingly intense pain that shifts around and eventually passes. If you haven’t had a bowel movement in a couple of days, feel bloated, or recently changed your diet, constipation is a strong possibility. The pain usually eases after a bowel movement or passing gas.
Irritable Bowel Syndrome
IBS can cause recurring pain in the left lower abdomen, though it rarely stays in just one spot. Most people with IBS report pain in three or more areas of the abdomen on average, and the constipation-predominant type (IBS-C) tends to affect more regions than the diarrhea-predominant type. Over half of people with IBS-C describe their pain as diffuse or spread across the whole abdomen. The key feature of IBS pain is its relationship to bowel movements: it typically improves after you go and worsens during periods of irregular stool patterns. If your left-sided pain keeps coming back over months without a clear trigger, IBS is worth discussing with your doctor.
Kidney Stones in the Left Ureter
A stone traveling down the left ureter can cause pain that starts in your flank (the side of your back below the ribs) and radiates into the lower abdomen, groin, or even the testicle or labia. This pain is distinctive: it comes on suddenly, peaks within 90 to 120 minutes, and is often described as the worst pain a person has experienced. You’ll typically feel restless and unable to find a comfortable position, and you may notice blood in your urine, nausea, or an urgent need to urinate. If this matches what you’re feeling, it’s not the kind of pain you sit at home with.
Ovarian Cysts and Torsion
In women, the left ovary can produce pain for several reasons. A ruptured or growing ovarian cyst causes a dull ache or sudden sharp pain on the affected side. More serious is ovarian torsion, where the ovary twists on its supporting ligament, cutting off blood flow. This produces sudden, severe lower abdominal pain, usually accompanied by nausea and vomiting. The pain is most often sharp and stabbing, though it can be dull and crampy. It may radiate to the thigh, flank, or lower back. A large cyst adds weight to the ovary and increases the risk of torsion. Fever or abnormal vaginal bleeding can signal that tissue is starting to lose blood supply, which requires urgent treatment.
Left-Sided Ulcerative Colitis
Ulcerative colitis is an inflammatory bowel disease limited to the colon and rectum. When it affects the left side of the colon specifically, it causes bloody diarrhea, belly cramps, and a frustrating sensation called tenesmus: feeling like you need to have a bowel movement but being unable to go. Unlike Crohn’s disease, which can affect any part of the digestive tract and penetrate deeper layers of the bowel wall, ulcerative colitis stays on the inner lining of the colon. If you’re having multiple episodes of bloody or mucus-filled diarrhea along with left-sided pain, this is a condition your doctor will want to investigate.
Inguinal Hernia
A hernia in the groin area (inguinal hernia) can cause pain in the lower left abdomen that worsens with coughing, bending, or lifting. The telltale sign is a visible or palpable bulge near the pubic bone that becomes more obvious when you stand up or strain. You may feel a burning or aching sensation at the bulge, and in men, pain and swelling can extend into the scrotum if a loop of intestine descends into it. Hernias don’t resolve on their own, but they’re not always an emergency unless the bulge becomes trapped and can’t be pushed back in.
How Doctors Figure Out the Cause
Your doctor will start with your symptom history and a physical exam, but imaging often clinches the diagnosis. CT scans are the most accurate tool for most causes of left lower abdominal pain. For diverticulitis specifically, CT detects 81% of cases compared to 61% for ultrasound. For gynecological problems, CT catches 67% versus 37% for ultrasound. That said, ultrasound is radiation-free and works well as a first step, especially in younger patients and pregnant women. Both imaging methods reliably detect common diagnoses, but CT misses fewer cases overall.
When the Pain Needs Emergency Attention
Most left lower abdominal pain resolves on its own or with straightforward treatment, but certain patterns signal something more urgent. Seek emergency care if your pain is sudden and severe, doesn’t ease within 30 minutes, or comes with continuous vomiting. Severe abdominal pain with vaginal bleeding could indicate an ectopic pregnancy, which is a medical emergency. A rigid or board-like abdomen, high fever with chills, dizziness or fainting, or blood in your stool also warrant an immediate visit. If you’re unsure, persistent pain that steadily worsens over hours rather than fluctuating is generally a stronger reason to get checked than pain that comes and goes.