Abdominal distension may be generalised or may be localised to a discrete mass or enlargement of an organ. The main causes of generalised abdominal distension are easily remembered by the five Fs:

• Fat (obesity)
• Faeces (constipation)
• Fetus (pregnancy)
• Flatus (gastrointestinal)
• Fluid (ascites)

The most common causes are obesity, pregnancy, irritable bowel syndrome,¹ constipation, fibroids and an enlarged bladder.

Causes of gastrointestinal abdominal distension

Non-obstructive causes

• Obesity.
• Pregnancy.
• Gas, e.g. irritable bowel syndrome.
• Ascites, e.g. congestive cardiac failure, cirrhosis, nephrotic syndrome, peritoneal carcinomatosis, peritoneal tuberculosis.
• Lymphadenopathy.
• Intra-abdominal bleeding, e.g. ruptured aortic aneurysm.

Mechanical bowel obstruction

• Neoplasms: intraluminal, extraluminal.
• Infections: diverticulitis, intra-abdominal abscess, parasitic infections.
• Foreign bodies: bezoar, ingested foreign body.
• Miscellaneous: adhesions, endometriosis, pregnancy, strangulated hernia, volvulus, intussusception, gallstones, faecalith/meconium ileus, haematoma, pneumatosis intestinalis (pneumatosis coli), superior mesenteric artery syndrome, annular pancreas, Hirschsprung's disease, stenosis (radiation, surgical anastomosis site, Crohn's disease, tuberculous).

Nonmechanical bowel obstruction

• Vascular insufficiency: thrombosis, embolism.
• Retroperitoneal irritation: renal colic, neoplasm, infection.
• Extra-abdominal infection: sepsis, pneumonia, empyema, spinal osteomyelitis.
• Metabolic/toxic: hypokalaemia, uraemia, lead poisoning.
• Chemical irritation: perforated peptic ulcer, pancreatitis, biliary peritonitis.
• Miscellaneous: excessive intraluminal gas, intra-abdominal infection, trauma, mechanical ventilation, other causes of peritoneal inflammation, severe pain and non-steroidal anti-inflammatory drugs (NSAIDs).

Localised causes of abdominal distension

Right upper quadrant

• Hepatomegaly, hepatoma, liver cancer.
• Gall bladder, e.g. mucocele, empyema, secondary to carcinoma of pancreas.
• Right colon, e.g. colonic carcinoma, faeces, caecal volvulus, intussusception.
• Right kidney, e.g. polycystic kidney, hydronephrosis, cyst, renal tumour, tuberculosis.

Left upper quadrant

• Splenomegaly
• Stomach: stomach cancer, gastric distension (e.g. pyloric stenosis).
• Pancreas, e.g. pseudocyst, carcinoma.
• Left kidney, e.g. polycystic kidney, hydronephrosis, cyst, tumour, tuberculosis.
• Colon, e.g. carcinoma, faeces, diverticular mass.

Epigastrium

• Abdominal wall, e.g. lipoma, hernia.
• Stomach, e.g. carcinoma, distension due to pyloric stenosis.
• Pancreas, e.g. pseudocyst, carcinoma.
• Transverse colon, e.g. carcinoma, faeces, diverticular mass.
• Hepatomegaly.
• Retroperitoneum, e.g. aortic aneurysm, lymphadenopathy.
• Omentum, e.g. secondaries from stomach or ovary.

Umbilical

• Hernia, paraumbilical or umbilical.
• Stomach, e.g. carcinoma.
• Transverse colon, e.g. carcinoma, faeces, diverticular mass.
• Small bowel, e.g. Crohn's disease.
• Omentum, e.g. secondaries from stomach or ovary.
• Retroperitoneum, e.g. aortic aneurysm, lymphadenopathy.

Right and left lower quadrants

• Abdominal wall, e.g. lipoma, hernia.
• Colon, e.g. carcinoma, faeces, volvulus, intussusception (right lower quadrant), appendix mass (right lower quadrant).
• Small bowel, e.g. Crohn's disease, lymphoma.
• Gynaecological, e.g. ovarian cyst, ovarian tumour, ectopic pregnancy, fibroid.
• Kidney, e.g. polycystic kidney, hydronephrosis, cyst, tumour, tuberculosis.

Suprapubic

• Enlarged bladder, e.g. acute or chronic retention, bladder cancer.
• Uterus, e.g. pregnancy, fibroids, cancer of uterus.
• Bowel, e.g. Crohn's disease, colorectal carcinoma.

Presentation

• Careful history taking and abdominal examination are essential. Clinical assessment will usually indicate the nature of abdominal distension (i.e. whether ascites, gastrointestinal gas, pregnancy, etc.) but further investigations are often required to determine the precise aetiology.
• Resonance on percussion may be misleading because there may be bowel overlying a solid tumour or enlarged organ.
• Weight loss associated with abdominal distension suggests malignancy.
• Constipation needs to be fully evaluated to establish any underlying cause.
• Obesity may make examination very difficult to provide a clear assessment and an ultrasound may then be required, irrespective of the likely cause of distension.

Investigations

• Urinalysis: may show haematuria in patients with tumours of kidney or bladder.
• Pregnancy test.
• Abdominal ultrasound.
• Full blood count: raised white cell count in infection or malignancy, anaemia with abnormal vaginal bleeding associated with fibroids, or as a consequence of malignancy.
• Urea and electrolytes: renal dysfunction; hypokalaemia or uraemia may cause nonmechanical bowel obstruction.
• Liver function tests: liver failure, cholestatic hyperbilirubinaemia with carcinoma of pancreas, hypoalbuminaemia associated with ascites.
• Abdominal X-ray, barium enema: constipation, large bowel pathology, bowel obstruction.
• Sigmoidoscopy, colonoscopy.
• Further investigations may include CT scan and paracentesis.

Referral

• Any patient who presents with abdominal distension without a clear diagnosis requires referral.
• Referral will also be required for any patient with a serious underlying cause but for many patients the cause is benign.

Document references

1. Chang L, Lee OY, Naliboff B, et al; Sensation of bloating and visible abdominal distension in patients with irritable bowel syndrome. Am J Gastroenterol. 2001 Dec;96(12):3341-7. [abstract]

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