Abdominal pain is a very common medical condition that can either be acute or chronic in nature. Basically it refers to pain that is felt within the abdomen which is the region of the body bounded by the ribs superiorly and the pelvis below. The image to the right displays a lady holding her lower abdomen in an attempt to relieve her pain. Abdominal pain may be a feature of numerous medical and surgical conditions and arise from organs within or adjacent to the abdominal cavity. In most cases it will be caused by something benign (not serious) but it important that it gets evaluated by a doctor to exclude sinister conditions that require urgent medical attention. Doctors diagnose the cause based on the features of the pain (location, duration, and other symptoms), physical examination and a number of diagnostic tests. Identifying the cause is particularly challenging as signs and symptoms may be non-specific, investigations are not always abnormal, different causes can mimic each other, and characteristics of the pain may change over time.

Abdominal pain in simple terms refers to pain that is felt in the abdomen (the anatomical region bounded by the ribs superiorly and the pelvis inferiorly). Abdominal pain is a challenging complaint for physicians as there are numerous possible causes some of which are benign and some that are potentially serious and possibly life-threatening. Unfortunately it can be difficult distinguishing between the two as they can present similarly. Furthermore, abdominal pain may arise from various anatomical structures including tissues comprising the abdominal wall (such as the muscles and skin) or from the actual abdominal organs themselves (stomach, small intestine, colon, liver, gallbladder, kidneys, aorta and pancreas) making diagnosis more difficult. [Please refer toanatomy and physiology of the gastrointestinal system for more information on these organs]. Occasionally pain may be felt in the abdomen even though it originates from nearby organs outside the abdominal cavity such as the lungs in pneumonia, heart during a heart attack or pelvic structures such as the uterus and ovaries. Likewise pain originating from abdominal organs may be referred to the skin or back depending on the nerve supply of the organs.

The type of abdominal pain varies greatly depending on the underlying cause. The abdominal organs are fitted with various pain receptors that detect abnormal mechanical and chemical stimuli. These send signals to the brain which leads to the sensation of pain. The mechanisms to produce abdominal pain include:

• Inflammation: This leads to the production of special chemicals that activate the pain receptors;
• Ischaemia (lack of blood supply);
• Stretching of muscles and the capsules (coverings) of organs;
• Nerve stimulation: Sometimes tumours can invade nerves and cause pain signals.

You may hear doctors use the term 'acute abdomen.' This refers to a condition where patients are really unwell with signs and symptoms (almost always including pain) that suggest an abdominal cause. These patients required urgent hospital admission and often may need surgery.

Causes

As fore mentioned, the possible causes for abdominal pain are extensive. The majority of patients will have a benign or self-limiting condition but evaluation must be able to identify patients with serious disorders that require further treatment. In particular, patients with an acute abdomen must be referred for a surgical opinion. The most common cause of abdominal pain is in fact a functional disorder caused irritable bowel syndrome. This is best described as a 'sensitive bowel' disorder and patients will experience recurrent episodes of diarrhoea, bloating and constipation. Abdominal pain is often relieved by defecation.

Other causes of abdominal pain are listed below according to the common site of pain.

Upper abdominal pain

• Biliary disease: Cholecystitis (inflammation of the gall bladder) and gall stones typically cause pain in the right upper quadrant of the abdomen. The pain can be recurrent in nature and be related to food ingestion. Patients may complain of nausea, vomiting, and anorexia in addition to the pain;
• Acute pancreatitis: This often causes severe epigastric (upper, middle abdomen) pain at the outset that radiates (spreads) to the back. Vomiting and shock are typical associated features;
• Peptic ulcer disease;
• Gastro-oesophageal reflux disease;
• Pneumonia of the lower areas of the lung can cause abdominal pain by irritating the diaphragm (the muscular structure separating the chest from the abdomen). This can mimic gall bladder disease;
• Heart attack may present with upper abdominal pain. If you are considered a high risk cardiac patient you may be monitored with an ECG;
• Damage to the spleen: This organ is situated near the stomach and is mainly involved in filtering blood. It can be damaged by trauma or by blood clots entering its circulation, both of which cause pain in the left upper quadrant of the abdomen.

Lower abdominal pain

• Acute appendicitis: This is a common surgical condition in all age groups. Appendicitis typically causes vague central abdominal pain that localises to the right iliac fossa (down near the groin). Nausea, vomiting and diarrhoea may be associated features. Your doctor can guess this is the likely cause of pain by the site of tenderness and special signs on physical examination;
• Diverticular disease: Diverticultis occurs when abnormal out-pouchings of bowl get obstructed and inflamed by faecal matter. In western countries this usually produces pain on the left side but it varies depending on your diet;
• Inflammatory bowel disease: Crohn's disease and ulcerative colitis often cause episodes of abdominal pain;
• Kidney stones;
• Hernias: If hernias become strangulated (twisted so their blood supply is cut off) they will cause abdominal pain;
• Bladder distension: This may be secondary to bladder outlet obstruction or benign prostatic hypertrophy;
• Gastroenteritis or infection of the urinary tract are common causes of abdominal pain;
• Pelvic disease: Lower abdominal (pelvic pain) is often associated with disorders of the female reproductive tract such as pelvic inflammatory disease (ascending infection of the womb and tubes), masses in the ovaries, ectopic pregnancy (growth of a fetus outside of the womb, often in the tubes), endometriosis (chronic condition where the lining of the uterus is present at other abnormal sites causing pain) or fibroids (benign growths in the wall of the uterus).

Diffuse abdominal pain

• Bowel obstruction: Small bowel obstruction is commonly due to adhesions (scarring) from previous surgery whilst large bowel obstruction is often due to a tumour or twisting of the bowel. Nausea, vomiting, bloating and inability to pass stool or gas may be associated symptoms;
• Abdominal aortic aneurysm: These are dilations and out-pouchings of the wall of the main artery running through the abdomen. These areas are weak and prone to rupture. If this occurs severe abdominal pain, back pain and shock may occur;
• Peritonitis: This is generalised inflammation of the lining of the abdominal cavity. Remaining still helps to relieve this pain.

Other less common causes

• Metabolic disorders: Diabetes mellitus, porphyrias and lead poisoning are medical causes of acute abdominal pain;
• Abdominal malignancies: Colon, stomach or pancreatic cancers may cause abdominal pain;
• Lactose intolerance;
• Tropical infections;
• Psychogenic causes: Abdominal pain is often a feature of somatoform disorders.

Clinical presentation

As previously mentioned it can be very difficult for the doctor to determine the cause of your abdominal pain so don't expect an immediate diagnosis or cure at your first visit. Sometimes multiple visits and tests are needed before a diagnosis can be made and the doctor may start you on medications before confirming the cause.

When you see your doctor, be prepared to answer lots of questions about the pain, including:

• Character, duration and frequency of the pain;
• Location and distribution of referred painL: This gives a clue to the anatomical site;
• Aggrevating and relieving factors: The relationship of the pain to food and toileting gives your doctor clues to the possible cause;
• Any associated symptoms such as fever, chills, weight loss, nausea, vomiting, diarrhoea, constipation,jaundice, change in colour of the urine or stool, chest pain or shortness of breath;
• Which medications you are taking;
• Previous medical problems or past surgery;
• Menstrual history in women.

You can help your doctor by bringing lists of some of this information (such as medications) to your appointment. Next your doctor will examine you taking note of your general appearance, pulse, blood pressure and temperature. They may notice that your skin or eyes are yellow which is called jaundice. They will listen to your chest to exclude the cardiac and chest causes listed above. Next they will get you to lie flat on the examination bed and gently feel your tummy. This lets the doctor find where the abdomen is tender and where the problem may be arising. The doctor will also listen to your abdomen because high-pitched bowel sounds or absent bowel sounds may be a sign of bowel obstruction. Your pelvis (internal examination for a female) and rectum (back passage) will need to be examined to rule out other causes also.

Your doctor is likely to need to order some tests to confirm the diagnosis or to make sure there is nothing serious that they have missed. Possible investigations may include:

• Blood tests which can help find if there is an infection;
• Urine pregnancy test if you are a female of childbearing age presenting with an acute abdomen;
• Chest and abdominal x-rays which can show dilated areas of bowel;
• Ultrasound is useful for identifying cholecystitis, appendicitis (if examined by experienced personnel) aortic aneurysm and gynaecological problems;
• CT scan which is a very reliable and accurate investigation;
• Endoscopic procedures are useful in evaluating chronic causes of abdominal pain including peptic ulceration, inflammatory bowel disease and gastrointestinal cancers. The image below is a typical view seen during colonoscopy of the large intestine in a patient with Crohn's disease;
• Surgery: Sometimes a camera will need to be inserted into the abdomen (laparoscopy) or the abdominal wall opened up (open laparotomy) to directly examine the organs and find the possible cause. Treatment can often occur at the same time.




Management

The management of abdominal pain largely depends on the cause of your pain. Some conditions such as appendicitis always need surgery (either open or laparoscopic) whilst some infections can be treated easily with antibiotics only. Irritable bowel syndrome can be treated with lifestyle changes and the use of laxatives as required. Abdominal pain may require hospital admission to allow a surgical opinion and ensure appropriate access to all the required tests. If your abdominal pain is really severe and acute you may require drips, oxygen and close monitoring. Pain relief will be given to patients with abdominal pain if it is considered appropriate and will usually be a low dose morphine-derivative (opioid). If biliary problems are suspected NSAIDs are used instead because opioids can exacerbate these problems. If you feel your symptoms are getting worse or that the medications are not working, do not hesitate to consult your doctor again.