Abdominal Distension and Bloating

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.
• Constipation.
• Fibroids.
• Enlarged bladder.

Causes of generalised abdominal distension

Non-obstructive causes

• Obesity.
• Pregnancy.
• Gas - eg, irritable bowel syndrome and other functional gut conditions.
• Ascites - eg, congestive cardiac failure, cirrhosis, nephrotic syndrome, peritoneal carcinomatosis, peritoneal tuberculosis.
• Lymphadenopathy.
• Intra-abdominal bleeding - eg, ruptured aortic aneurysm.

Mechanical bowel obstruction

• Neoplasms: intraluminal, extraluminal.
• Infections: diverticular disease, 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).

Non-mechanical 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.
• Gallbladder - eg, mucocele, empyema, secondary to carcinoma of pancreas.
• Right colon - eg, colonic carcinoma, faeces, caecal volvulus, intussusception.
• Right kidney - eg, polycystic kidney, hydronephrosis, cyst, renal tumour, tuberculosis.

Left upper quadrant

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

See the separate Left Upper Quadrant Pain article for further detail.

Epigastrium

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

Umbilical

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

Right and left lower quadrants

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

Suprapubic

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

Abdominal distension symptoms (presentation)

• Careful history taking and abdominal examination are essential. Clinical assessment will usually indicate the nature of abdominal distension (ie 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 scan or cross-sectional imaging may then be required, irrespective of the likely cause of distension.

Investigations

These should be directed by history and examination and tailored to each patient. Possible investigations include:

• FBC: raised white cell count in infection or malignancy, anaemia with abnormal vaginal bleeding associated with fibroids, or as a consequence of malignancy.
• U&Es: renal dysfunction; hypokalaemia or uraemia may cause non-mechanical bowel obstruction.
• LFTs: liver failure, cholestatic hyperbilirubinaemia with carcinoma of pancreas, hypoalbuminaemia associated with ascites.
• Coeliac serology.
• CA 125: in women, particularly postmenopausal women, to look for evidence of ovarian cancer. (Note though that CA 125 is nonspecific - it is physiologically elevated during menstruation, the first trimester of pregnancy, and postpartum, and can also increase due to endometriosis, uterine fibroids, and non-malignant ascites, amongst other things.)
• C-reactive protein, if inflammation/infection is suspected.
• Faecal calprotectin.
• Urinalysis: may show haematuria in patients with tumours of kidney or bladder.
• Pregnancy test.
• Quantitative faecal immunochemical (qFIT) testing: colorectal cancer.
• Abdominal X-ray, barium enema: constipation, large bowel pathology, bowel obstruction.
• Abdominal ultrasound.
• Transvaginal ultrasound.
• Oesophagogastroduodenoscopy (OGD).
• Sigmoidoscopy, colonoscopy.
• Further investigations might include CT scans and paracentesis.

Referral

• Referral decisions depend upon the underlying cause; many causes can be managed, at least initially, in primary care (such as IBS).
• In general, referral is recommended if there is abdominal distension without any clear diagnosis.

Bloating

Bloating is a very common and subjective ailment which can affect patients of all ages. It can be associated with any of the causes of abdominal distension but it is most commonly associated with irritable bowel syndrome. Bloating can have a major impact both socially and psychologically. It is incompletely understood and often inadequately treated.

Interventions include:^[1]

• Keeping a food and symptom diary to identify and avoid triggers.
• Avoiding artificial sweeteners containing poorly-absorbed sugar alcohols (eg, sorbitol, mannitol and xylitol).
• Following a low FODMAP diet.
• Probiotics (although evidence is limited).
• Antispasmodics, such as mebeverine, peppermint oil, and hyoscine butylbromide.
• Secretagogues, such as linaclotide.
• Neuromodulatory drugs, such as amitriptyline and some SSRIs.
• Biofeedback therapy.
• Gut-directed hypnotherapy.

For further information see the related separate Irritable Bowel Syndrome article.