Swollen Abdomen: Causes and When to Worry

Bloating vs true swelling

Bloating is a feeling of fullness or tightness, often with a visibly swollen belly that is flat in the morning and grows through the day. It usually comes from gas or sensitive bowels. True distension that persists day and night, or keeps increasing, is more likely to mean fluid, an enlarged organ or a growth. For day-to-day bloating, see stomach bloating.

The six main causes

1. Gas (flatus)

Swallowed air, fizzy drinks and fermentation of food by gut bacteria produce gas. Beans, onions, cabbage, wheat, artificial sweeteners and dairy (in lactose intolerance) are common triggers. Irritable bowel syndrome makes the gut more sensitive and the belly wall relaxes outward, so swelling is visible even with normal amounts of gas. Small intestinal bacterial overgrowth, celiac disease and gastroparesis are other causes.

2. Stool (feces)

Constipation causes a full, hard belly, especially in the lower left side, with infrequent or hard stools. In older adults, severe constipation can cause marked swelling and loss of appetite.

3. Fat

Gradual weight gain around the waist (central obesity) enlarges the belly evenly. The belly is soft, and the navel sinks inward. After menopause, fat tends to shift toward the abdomen.

4. Fluid (ascites)

Ascites is fluid collecting inside the abdominal cavity. The belly bulges at the sides (flanks), the navel may flatten or poke out, and the swelling increases over weeks. Ankle swelling and weight gain are common. Causes include:

• Cirrhosis of the liver, the most common cause, from alcohol, fatty liver disease or hepatitis
• Cancer in the abdomen, especially ovarian, bowel, stomach and pancreatic cancer
• Heart failure and kidney disease
• Tuberculosis and pancreatitis, less often

5. Pregnancy (fetus)

Pregnancy is the most common cause of a growing belly in women of reproductive age. Take a pregnancy test if pregnancy is possible.

6. Growths and enlarged organs

• Uterine fibroids: benign growths that can make the lower belly swell, often with heavy periods.
• Ovarian cysts and ovarian cancer.
• Enlarged liver or spleen.
• Abdominal aortic aneurysm: a pulsating swelling in the upper belly.
• Bladder distension from urinary retention: a swollen lower belly with difficulty urinating.
• Hernias: a bulge in the belly wall or groin that gets bigger when standing or coughing.

Bowel obstruction

A blockage from adhesions after surgery, a hernia or a tumor causes rapid swelling with cramping pain, vomiting and inability to pass gas or stool. It is an emergency.

Swollen abdomen in women

Women have additional causes: menstrual bloating, pregnancy, fibroids, ovarian cysts, endometriosis and ovarian cancer. Ovarian cancer is easy to miss because its early symptoms are vague. See a doctor if you have persistent bloating on most days for 3 weeks or more, feel full quickly, have pelvic or belly pain, or need to urinate more often, especially over age 50. A blood test (CA-125) and pelvic ultrasound are the usual first tests.

Clues to the cause

How doctors find the cause

The doctor will ask how quickly the swelling developed, whether it changes through the day, and about bowel habits, periods, alcohol, weight change and appetite. Examination checks for gas (a drum-like sound), fluid (a shifting dull sound when you roll over), masses and organ enlargement. Tests may include:

• blood tests: liver and kidney function, blood count, albumin, and CA-125 in women
• pregnancy test
• abdominal and pelvic ultrasound
• CT scan
• celiac antibodies and stool tests for bloating
• drawing off a sample of ascitic fluid for analysis (paracentesis)

Treatment

Treatment depends on the cause:

• Gas and IBS: smaller meals, eating slowly, limiting fizzy drinks and gas-producing foods, a low-FODMAP diet with a dietitian, peppermint oil and regular exercise
• Constipation: more fiber and fluids, physical activity and laxatives, following the label dose
• Ascites: a low-salt diet, diuretics, draining fluid and treating the underlying liver, heart or cancer disease
• Fibroids, cysts and tumors: medicines, procedures or surgery
• Bowel obstruction: hospital care with bowel rest, a drainage tube and sometimes surgery

Frequently asked questions

Why is my abdomen swollen and hard?

A hard, swollen belly is most often from trapped gas or constipation. If it is persistent, getting bigger, or comes with pain, vomiting, weight loss or yellow skin, it may be fluid (ascites), an enlarged organ, a growth or a bowel blockage, and needs medical assessment.

When should I worry about a swollen abdomen?

Get emergency care for a swollen belly with severe pain, vomiting, and no passing of gas or stool. See a doctor promptly if swelling keeps growing, lasts more than 3 weeks, or comes with weight loss, early fullness, jaundice, breathlessness or a lump.

How do I know if my swollen belly is fluid or fat?

Fat accumulates gradually with overall weight gain and feels soft. Fluid (ascites) builds up over weeks, bulges the sides of the belly, may push the navel out, and often comes with ankle swelling. A doctor can tell the difference by examination and ultrasound.

Can stress cause a swollen abdomen?

Stress does not cause true fluid swelling, but it can worsen bloating by affecting gut movement and sensitivity, especially in IBS. People under stress may also swallow more air and eat irregularly. Persistent swelling should still be checked for other causes.