A diverticulitis attack typically feels like a persistent, cramping pain in the lower left side of your abdomen that builds over several hours or even a couple of days. The pain can range from a dull ache to a sharp, stabbing sensation, and it often worsens when you move, cough, or press on the area. Most people also notice changes in their bowel habits, and many develop a low-grade fever.
Where the Pain Shows Up
The hallmark of a diverticulitis attack is tenderness in the lower left abdomen. This is because the sigmoid colon, the S-shaped section of your large intestine just above the rectum, is where diverticula (small pouches in the intestinal wall) most commonly form and become inflamed. Tenderness isolated to the lower left quadrant is the single most reliable physical sign of diverticulitis. When doctors find it during an exam, it raises the likelihood of diverticulitis roughly tenfold compared to other possible causes of abdominal pain.
That said, not everyone feels it on the left. In Asian populations, right-sided diverticulitis is far more common, accounting for up to 76% of diverticular disease cases compared to just 1 to 5% in Western countries. If you’re of Asian descent and experiencing persistent pain in the lower right abdomen, diverticulitis is a real possibility, even though it’s often mistaken for appendicitis in that location.
How the Pain Develops
Unlike something like a kidney stone, which hits suddenly and intensely, diverticulitis pain usually creeps in. You might notice a vague soreness after eating that gradually sharpens over a day or two. Some people describe the sensation as a constant pressure or fullness, almost like something is swollen inside. Others compare it to severe menstrual cramps that don’t let up.
The pain tends to get worse after meals and may ease slightly after passing gas or having a bowel movement, though not always. Lying still on your back or on your left side sometimes provides a bit of relief, while bending, walking, or straining makes it worse. In a mild attack, the discomfort might stay at a manageable level for days. In a more severe flare, it can escalate to the point where any movement of your abdomen is painful.
Beyond the Pain: Other Symptoms
Diverticulitis rarely shows up as pain alone. Most attacks come with a constellation of other symptoms that can make you feel generally unwell:
- Fever and chills: A low-grade fever (around 100 to 101°F) is common. Higher fevers can signal a more serious complication like an abscess or perforation.
- Nausea and loss of appetite: Many people feel queasy and have no desire to eat, which can worsen fatigue.
- Bloating and gas: The inflamed section of colon can trap gas, leaving your abdomen feeling distended and tight.
- Urinary symptoms: Because the inflamed colon sits near the bladder, some people notice pain during urination or an increased urge to urinate.
Rectal bleeding can also occur, though it’s less common during an acute inflammatory attack. When bleeding does happen, it’s usually mild. Heavy rectal bleeding with diverticular disease tends to come from a different process (a blood vessel eroding inside a pouch) rather than from the infection itself.
Changes in Bowel Habits
Your bowel routine will likely shift during an attack, though the direction is unpredictable. Some people become constipated, passing fewer than three stools per week or straining significantly. Others swing toward diarrhea, with frequent loose or watery stools. A large prospective study of over 870 patients with diverticular disease found that both constipation and diarrhea independently increase the risk of an acute flare. Each point increase in constipation severity raised the risk of an acute attack by about 15%, and each point increase in diarrhea severity raised it by about 14%.
Some people alternate between the two within the same episode, experiencing a day or two of constipation followed by loose stools once the blockage clears. You might also notice that your stools are narrower than usual, because the swelling in the colon narrows the passageway.
Mild Versus Severe Attacks
Not all diverticulitis attacks feel the same. A mild, uncomplicated flare might feel like a persistent stomachache with some tenderness when you press on your lower left belly. You can usually still walk around, eat small amounts, and manage the discomfort at home. These episodes often improve within a week or so with rest, a temporary shift to low-fiber or liquid foods, and sometimes antibiotics.
A complicated attack is a different experience. If an abscess forms (a pocket of infected pus near the inflamed pouch), the pain intensifies and becomes more localized. You may develop a higher fever and feel increasingly sick. The area might feel firm or swollen when you touch it. If the inflamed pouch actually tears, intestinal bacteria can spill into your abdominal cavity, causing peritonitis. At that point, the pain often becomes sudden, severe, and widespread across the entire abdomen. Your belly may feel rigid and board-like, and pressing on it causes sharp pain when you release the pressure. This is a medical emergency.
How It Differs From Similar Conditions
Diverticulitis pain can overlap with several other conditions, and knowing the differences helps you describe your symptoms more accurately.
Irritable bowel syndrome (IBS) can cause cramping in a similar location, but IBS pain is typically intermittent and closely tied to bowel movements. It rarely causes fever, and pressing on the abdomen doesn’t usually produce the kind of sharp, localized tenderness that diverticulitis does. IBS also doesn’t cause the general sense of being sick (fever, chills, elevated inflammation) that accompanies an infected diverticulum.
Appendicitis pain starts around the belly button and migrates to the lower right side, usually over 12 to 24 hours. It tends to come on faster than diverticulitis and escalates more quickly. The classic age for appendicitis is 10 to 19, while diverticulitis more commonly strikes after age 40. Right-sided diverticulitis can closely mimic appendicitis, but it tends to produce less nausea (roughly 16% of cases versus 33% for appendicitis), less rebound tenderness, and a longer duration of symptoms before people seek care.
Signs That Need Immediate Attention
Most diverticulitis attacks are uncomfortable but manageable. Certain symptoms, however, suggest the situation has become dangerous. Constant abdominal pain that suddenly worsens or spreads across your entire belly can indicate perforation. A high fever (above 102°F), rapid heart rate, dizziness, or an abdomen that feels rigid and extremely painful to touch all point toward possible peritonitis or sepsis. Significant rectal bleeding, where you’re passing large amounts of blood or feel faint, also warrants emergency evaluation.
If your pain has been steady for more than a day or two and you’re running a fever with noticeable changes in your bowel habits, that combination alone is worth getting checked. A CT scan can confirm whether diverticula are inflamed and whether any complications have developed, giving you and your doctor a clear picture of what’s happening and how aggressively it needs to be treated.