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Abdominal pain

Epidemiology
Abdominal pain is a very common problem. It accounts for around 5% of all visits to A & E. ¹

Correct diagnosis requires a systematic approach but it may still be necessary to cope with uncertainty. This may require re-appraisal with a view to reviewing the diagnosis or simply admitting the patient to hospital on the grounds that there is sufficient reason to believe that there may be a condition that requires observation, further investigation or even diagnostic laparotomy.

History and examination are of fundamental importance with particular attention to examination of the abdomen but remember that even quite low doses of steroids may mask physical signs. If there is a suggestion of an acute abdomen there is probably no time for special investigations in primary care other than stick testing of urine. It may be a more chronic problem and investigations in primary care are required. The primary differential diagnosis is vast but there are many features that may narrow it considerably:

• Age and sex of the patient
• Speed of onset of symptoms
• The position of the pain
• The nature of the pain
• Aggravating and relieving factors and whether it is continuous or intermittent
• Associated features such as pyrexia, diarrhoea, vomiting or dysuria
• Recurrent abdominal pain is a different matter from an isolated incident although the first episode of recurrent pain cannot be distinguished as such
• The acute abdomen and chronic pain raise different considerations. Abnormal weight loss must raise the spectre of malignancy but it is by no means the only consideration
• The finding of abdominal distension or abdominal masses raise their own issues.
• The patient may be jaundiced, suggesting gallstones or hepatitis. It is important to be aware of what may be seen as medical rather than surgical diagnoses
• Abdominal pain in pregnancy creates its own additional differential diagnoses as well as distorting the anatomy so that symptoms and signs may be atypical

To provide a systematic approach, this article will focus first on generalised abdominal pain, followed by pain in the various regions of the abdomen and finally some caveats about diagnosis. The scope of the subject is so vast that no attempt is made to cover all aspects and links to topics are freely used.

Generalised abdominal pain:
Children:

Childhood abdominal pain can provide a very difficult conundrum for diagnosis. There is a gradual transition from infancy to childhood into adolescence and adulthood. A small child will rarely complain of localised abdominal pain but will instead point to the umbilicus. Furthermore, in small children there is no certainty that this indicates that the abdomen is the seat of the pathology. Otitis media, tonsillitis and even meningitis in small children can lead them to point to the umbilicus as the source of the pain. Acute surgical problems in childhood must be seen alongside what may be regarded as medical causes of abdominal pain.

The general condition of the child is extremely important and if the child appears extremely unwell then no one should be apologetic about admitting that child without a working diagnosis and no admitting doctor in paediatrics will quibble. A very high temperature may suggest pyelonephritis or even otitis media but small children can produce a very high temperature very easily. Do not forget the risk of pyrexial convulsions. Taking a paediatric history is not like taking a history from an adult. Examining children is also a seperate art. If the abdomen is tender it is essential not to lose the child's trust and confidence. A technique that is often used is to take the child's hand in your own and use it to palpate his own abdomen. It may then be possible to get a much better idea of tenderness and local pain. In both children and adults it is often possible to get a better idea of the position and degree of tenderness from watching the face during palpation than by direct questioning. In a child presenting with abdominal pain, do not forget to examine the chest (for pneumonia) as well as ears, nose and throat (e.g. for mesenteric adenitis, infective mononucleosis). Remember the limitations of testing for meningitis in infants. Other medical causes of abdominal pain may include childhood ketoacidosis.

Adults:

The differential diagnosis of generalised abdominal pain in adults is entirely different from that in children, with the caveat that children gradually progress from infancy to adulthood and so an adolescent is more an adult than a child.

A colicky pain comes and goes or at least fluctuates in intensity. The patient may writhe about during the pain, seeking a comfortable position. The pain of peritonitis is constant and the patient lies still as movement aggravates the pain. Blood or pus under the diaphragm may cause referred pain to the shoulder. A patient with generalised peritonitis will be very toxic and ill. The abdomen shows a board-like rigidity and bowel sounds may be absent. Causes of peritonitis include acute appendicitis, perforation of diverticular disease and colo-rectal carcinoma and spontaneous peritonitis can occur in cirrhosis where it implies a poor prognosis. Blood is very irritant and blood in the peritoneal cavity causes much distress. 30% of ruptured ectopic pregnancies occur before a period has been missed and a young woman may lose a substantial amount of blood before her vital signs change. Peritonitis will be localised at first but will spread to generalised peritonitis if intervention does not occur.

Plain abdominal x-ray can be very useful, especially erect and supine as the former may show air under the diaphragm with a perforation of the gut. This means not just a perforated peptic ulcer but diverticular disease and colo-rectal carcinoma can also perforate.

A rather flambouyant presentation may suggest Munchausen syndrome but this is very much a diagnosis of exclusion and even a known case may have organic illness.

Right upper quadrant pain:

Right upper quadrant pain is discussed more fully elsewhere. The liver and gall bladder are extremely important in this area. Stretching of the capsule of the liver will cause pain. This can be due to acute inflammation as in hepatitis or the congestion of right-sided congestive heart failure. The innervation of the diaphragm and gall bladder can produce pain that is referred to the shoulder. Cholecystitis is often associated with vomiting. The hepatic flexure of the colon may be involved. Abdominal pain may arise from outside the abdomen including the right lower lobe of the lungs. Pneumonia is a possibility as is pulmonary embolism that may not be obvious but in patients at risk, look for evidence of deep vein thrombosis. In late pregnancy, pain in the liver may be a sign of impending pre-eclampsia.

Left upper quadrant pain:

Left upper quadrant pain is discussed more fully elsewhere. The significant organs are the stomach and spleen. The spleen has to be at least twice its normal size before splenomegaly is palpable. The splenic flexure of the colon is also important and this is the commonest site for ischaemic colitis. The problems of lung disease with pneumonia, pulmonary embolism and deep vein thrombosis apply as for right upper quadrant pain. In addition, acute myocardial infarction may rarely present as upper abdominal rather than chest pain. The pancreas is in the left upper quadrant but the pain of acute pancreatitis and chronic pancreatitis is more often between the scapulae and it tends to be relieved by sitting forwards, often resting on the elbows.

Central abdominal pain:

As mentioned earlier, when children point to the umbilicus it can mean almost anything in terms of the origin of the pain. Adults are a little better. Central abdominal pain is often visceral pain originating around the T10 dermatome. It may be colic in the gut as in gastroenteritis. The pain of appendicitis often starts as central abdominal before moving to the right iliac fossa. Epigastric pain may also be non-specific but originating at a higher level in the gut in a T8 dermatome, whilst hypogastric pain may be a little lower, perhaps T12. Peptic ulcer often presents as intermittent epigastric pain. The symptoms of gastric cancer may be similar and also relieved by acid suppression.

Another very important cause of pain that is usually central abdominal in origin is aortic aneurysm. The great importance relates to aneurysms and dissection of arteries. By the time that ruptured aortic aneurysm occurs it is really too late. Very few will reach hospital alive and of those, few will survive surgery. The mortality of those who rupture an aortic aneurysm at home exceeds 90%. The risk group is aged 50 to 70 or perhaps a little older. There may be a palpable pulsatile mass, often just below and to the left of the umbilicus and it may be tender. There may be a bruit. It is not a common occurrence but in this age group it must be considered as the implications are such that it is a matter of life or death. Men outnumber women significantly. It is important to try to make the diagnosis before signs and symptoms of exsanguination and shock appear.

Loin pain:

Loin pain usually means pain originating from the kidney, but not invariably and it is also discussed in more detail elsewhere. Renal colic or ureteric colic is usually due to stones and a history a pain radiating from the loin to the groin is typical. It tends to be severe. Pyelonephitis is usually accompanied by a very high temperature. Urological history and examination is required. Haematuria may require evaluation. The possibility of clear cell carcinoma of kidney should be born in mind. In children Wilm's tumour usually presents as a mass, perhaps with haematuria.

About 10% of dissecting aortic aneurysm can present as loin pain like renal colic.²

Right iliac fossa pain:

Right iliac fossa pain is often taken as almost synonymous with appendicitis but it is far more complex than that, and is discussed in more detail elsewhere. Appendicitis is a common diagnosis with about 70,000 operations of appendicectomy performed each year but it is also a rather variable presentation.³ It is important to be very wary of the possibility in little girls as if peritonitis develops there is little peritoneum to wall off the appendix with the risk of tubal damage and future infertility. Delay in presentation seems to be an adverse factor in appendicitis but not watchful waiting in diagnostic uncertainty.⁴

Gynaecological causes of pain are important and pelvic inflammatory disease, torsion of an ovarian cyst or an ectopic pregnancy must also be considered.

Complications of inguinal hernia or femoral hernia such as incarceration of obstruction are possibilities.

Left iliac fossa pain:

Left iliac fossa pain is also discussed in more detail elsewhere. Considerations are very much as for right-sided pain except that appendicitis is excluded (assuming no situs invertus) and constipation and disease of the sigmoid colon is added.

Pelvic pain:

Pelvic pain is also discussed elsewhere. In women it is often gynaecological in origin and pain outside the pelvis rarely has a gynaecological cause. Dysmenorrhoea is usually obvious from the history. There may be complications of pregnancy, including miscarriage that is usually accompanied by bleeding. Fluid or blood in the pouch of Douglas often produces pain in the rectum. In men prostatic disease must be considered. Prostatitis is a possibility. Pelvic or hypogastric pain may arise from the bladder. Urinary tract infection in adults and urinary tract infections in children have different implications. Retention of urine will be painful if acute but painless if chronic. Urinary problems often produce dysuria, urinary frequency and possibly haematuria, microscopic or gross.

Ectopic pregnancy will produce pain that starts in the pelvis, often centrally but possibly to one side. Bleeding into the pouch of Douglas may cause rectal pain. If rupture occurs haemorrhage is very profuse. Hence it is most desirable to make the diagnosis before rupture. It must be considered in any woman of reproductive age with pelvic pain, possibly spreading. It is less likely if adequate contraception is used unless it is a IUCD when ectopic pregnancy is more likely.

Caveats:

The potential differential diagnosis of abdominal pain is vast but a systematic approach will reduce it considerably. Always be prepared to reconsider your original working diagnosis, especially as things change. Time will help distinguish between a self-limiting cause such as mild gastroenteritis, an acute abdomen and malignancy but if the condition is a serious one, then time is precious. The progress of the disease is very important which is why re-assessment should not be shunned. The beatitude blessed is he who sees the patient last is most applicable to abdominal pain. What starts as simple diarrhoea and vomiting without physical signs, may well progress to an acute appendicitis. Never fail to palpate the abdomen. If matters change and you have not done so, you cannot assert that it was not an acute abdomen when you saw the patient.

Medical rather than surgical conditions and pathology outside the abdomen should not be overlooked. Hepatitis can present as gastroenteritis with jaundice becoming apparent only later. Diabetic ketoacidosis may cause abdominal pain. Children may have mesenteric adenitis. A tabetic crisis is rarely seen these days. Shingles can cause abdominal pain for a day or so but no more before the rash appears but the rash may not involve the whole dermatome and can be missed. The segmental distribution of the pain is not easy to define but it may seem that it is the skin rather than deep palpation that is painful. Back pain, especially sinister causes of back pain, may produce pain in the abdomen.

Be very wary about diagnosing dyspepsia or irritable bowel syndrome for the first time in a patient over 40. Malignancy needs to be excluded. Especially in the man over 50, never forget the possible abdominal aortic aneurysm.

Traditional teaching has often been that analgesia should not be given before assessment by a surgeon as it masks signs. A controlled trial showed that this was not so and analgesia can safely be given if required. ⁵

References:

1. Kamin RA, Nowicki TA, Courtney DS, et al; Pearls and pitfalls in the emergency department evaluation of abdominal pain.;Emerg Med Clin North Am. 2003 Feb;21(1):61-72, vi.[abstract]
2. Eckford SD, Gillatt DA; Abdominal aortic aneurysms presenting as renal colic.;Br J Urol. 1992 Nov;70(5):496-8.[abstract]
3. Styrud J, Eriksson S, Segelman J, et al; Diagnostic accuracy in 2,351 patients undergoing appendicectomy for suspected acute appendicitis: A retrospective study 1986-1993.;Dig Surg. 1999;16(1):39-44.[abstract]
4. Eldar S, Nash E, Sabo E, et al; Delay of surgery in acute appendicitis.;Am J Surg. 1997 Mar;173(3):194-8.[abstract]
5. Zoltie N, Cust MP; Analgesia in the acute abdomen.;Ann R Coll Surg Engl. 1986 Jul;68(4):209-10.[abstract]

Internet:

• Appendicitis  Acute appendicitis from surgical-tutor.org.uk
• www.pediatriconcall.com Acute abdomen in children
• Causes of pain Lists the type of pain with its cause [pain.health-info.org]
• French's Index of Differential Diagnosis. Eds Mark Kinirons, Harold Ellis. Hodder Arnold. The classic textbook of differential diagnosis, latest edition.

Acknowledgements EMIS is grateful to the Mentor authoring team for writing this article. The final copy has passed peer review of the independent Mentor GP authoring team. ©EMIS 2006.

Last issued 30 Aug 2006