An abdominal mass is a localized swelling or enlargement in one area of the abdomen.

An abdominal mass is usually detected on routine physical examination. It may not have been detected by the affected person because most abdominal masses develop slowly.

An abdominal mass can be a sign of an abscess, a problem with a blood vessel (such as an aneurysm), an enlarged organ (such as the liver, spleen, or kidney), a tumor, or an accumulation of feces.

The abdomen is usually divided into 4 quadrants: right-upper quadrant, left-upper quadrant, right-lower quadrant, and left-lower quadrant. Other terms used to localize masses (or pain) in the abdomen include periumbilical, which describes the area around the navel, and epigastric, which describes the area in the center of the abdomen just below the ribcage. The location of the mass, and its firmness, texture, and other qualities can provide clues as to the cause of an abdominal mass.

• Abdominal aortic aneurysm can cause a pulsating mass around the navel.
• Bladder distention (urinary bladder over-filled with fluid) can cause a firm mass in the center of the lower abdomen above the pelvic bones, and in extreme cases can extend as far up as the navel.
• Cholecystitis can cause a very tender mass that is felt below the liver in the right-upper quadrant (occasionally).
• Colon cancer can cause a mass almost anywhere in the abdomen.
• Crohn's disease or bowel obstruction can cause multiple tender, sausage-shaped masses anywhere in the abdomen.
• Diverticulitis can cause a mass that is usually located in the left-lower quadrant.
• Gallbladder tumor can cause a moderately tender, irregularly shaped right-upper quadrant mass.
• Hydronephrosis (fluid-filled kidney) can cause a smooth, spongy-feeling mass in one or both sides or toward the back (flank area).
• Kidney cancer can sometimes cause a mass in the abdomen.
• Liver cancer can cause a firm, lumpy mass in the right upper quadrant.
• Liver enlargement (hepatomegaly) can cause a firm, irregular mass below the right rib cage (right costal margin), or on the left side in the stomach area (epigastric).
• Neuroblastoma, a malignant tumor often found in the lower abdomen, that primarily occurs in children and infants.
• Ovarian cyst can cause a smooth, rounded, rubbery mass above the pelvis in the lower abdomen.
• Pancreatic abscess can cause a mass in the upper abdomen in the epigastric area.
• Pancreatic pseudocyst can cause a lumpy mass in the upper abdomen in the epigastric area.
• Renal cell carcinoma can cause a smooth, firm, nontender mass near the kidney (usually only affects one kidney).
• Spleen enlargement (splenomegaly) -- the edge of an enlarged spleen may sometimes be felt in the left-upper quadrant.
• Stomach cancer can cause a mass in the left-upper abdomen in the stomach area (epigastric) if the cancer is large.
• Uterine leiomyoma (fibroids) can cause a round, lumpy mass above the pelvis in the lower abdomen (occasionally can be felt if the fibroids are large).
• Volvulus can cause a mass anywhere in the abdomen.
• Ureteropelvic junction obstruction can cause a mass in the lower abdomen.