1. Visceral . Gut organs are insensitive to stimuli as burning& cutting but are sensitive to distension, contraction, torsion & stretching. Pain from unpaired structures is usually but not always felt in the midline.
2.Parietal . The parietal peritoneum is innervated by somatic nerves& its involvement by disease processes, e.g. inflammation, infection or neoplasia, causes sharp, well-localised, lateralised pain.
3.Referred pain . (For example, gallbladder pain is referred to the back or shoulder tip.)
4.Psychogenic . Cultural, emotional & psychosocial factors influence everyone's experience of pain. In some patients, no organic cause can be found despite investigation& psychogenic causes (depression or somatisation disorder) may be responsible
Accounts 50% of all urgent admissions to general surgical units.
The acute abdomen is a consequence of one or more pathologies:
Inflammation . Pain develops gradually, usually over several hours. It is initially rather diffuse until the parietal peritoneum is involved, when it becomes localised. Movement exacerbates the pain, and abdominal rigidity and guarding occur.
Perforation . When a viscus perforates, pain starts abruptly; it is severe and leads to generalised peritonitis.
Obstruction . Pain is colicky, with spasms which cause the patient to writhe around and double up. Colicky pain which does not disappear between spasms suggests complicating inflammation
In the majority of patients full blood count (leucocytosis?), urea & electrolytes (dehydration?) & a serum amylase level (acute pancreatitis?) are measured.
Further information can be obtained from an erect chest X-ray (air under the diaphragm?) & abdominal X-ray (obstruction?).
An abdominal U/S may help if:
Acute gallstone disease (cholecystitis or cholangitis)
Soft tissue mass is suspected.
Detection of free fluid & any possible intra-abdominal abscess.
Contrast studies, by either mouth or anus, are useful in the further evaluation of intestinal obstruction& essential in the differentiation of pseudo-obstruction from mechanical large bowel obstruction.
Other investigations commonly used include CT (pancreatitis, retroperitoneal collections or masses, including an aortic aneurysm) & angiography (mesenteric ischaemia).
Multi-slice CT angiography is now replacing angiography in many centres.
In those patients in whom the decision to operate remains in doubt & in whom the diagnosis has not been revealed by the appropriate investigations, diagnostic laparoscopy may be advised.
All patients must be carefully & regularly reassessed (every 2-4 hours) so that any change in condition which might alter both the suspected diagnosis & clinical decision can be observed & acted upon early.
If the cause is obvious & surgery inevitable (e.g. for an external hernia) an early operation is appropriate.
If the suspected cause is adhesions from previous surgery, only those patients who do not resolve within the first 48 hours or who develop signs of strangulation (colicky pain becomes constant, peritonitis, tachycardia, fever, leucocytosis) will require surgery.
Although surgical closure of the perforation is standard practice, some patients without generalised peritonitis in whom a water-soluble contrast meal has confirmed spontaneous sealing of the perforation can be treated non-operatively.
Adequate /aggressive resuscitation is mandatory before surgery.
Detailed history, with particular attention to the features of the pain & any associated symptoms is essential.
Note should be made of the patient's general demeanour, mood & emotional state, signs of weight loss, fever, jaundice or anaemia.
If a thorough abdominal &rectal examination is normal, a careful search should be made for evidence of disease affecting other structures, particularly the vertebral column, spinal cord, lungs &cardiovascular system
The initial choice of investigations will depend on the clinical features elicited during the history & examination:
Epigastric pain, dyspepsia & relationship to food suggest gastroduodenal or biliary disease:Endoscopy &U/S are indicated.
Altered bowel habit, rectal bleeding or features of obstruction suggest colonic disease: Ba enema & sigmoidoscopy/ colonoscopy.
Pain provoked by food in a patient with widespread atherosclerosis indicate mesenteric ischaemia: Mesenteric angio.
Persistent symptoms require exclusion of colonic or small bowel disease. However, young patients with pain relieved by defecation, bloating & alternating bowel habit are likely to have IBS. Simple investigations (blood tests & sigmoidoscopy) may be sufficient.
Upper abdominal pain radiating to the back, a history of alcohol misuse, weight loss & diarrhoea suggest chronic pancreatitis or pancreatic cancer:U/S, CT& pancreatic function tests.
Recurrent attacks of pain in the loins or radiating to the flanks with urinary symptoms suggest renal or ureteric stones:U/S,IVU.
A past history of psychiatric disturbance, repeated negative investigations or vague symptoms which do not fit any particular disease or organ pattern may point to a psychological origin for the patient's pain.
Careful review of case notes & previous investigations, along with open & honest discussion with the patient, may reduce the need for further cycles of unnecessary & invasive tests.
Care must always be taken, however, not to miss rare pathology or atypical presentations of common disease.
Usually have features to suggest the underlying diagnosis, e.g. malignancy (gastric, pancreatic, colonic, hepatic metastases), chronic pancreatitis or intra-abdominal abscess.
In a minority no cause will be found despite thorough investigation, leading to the diagnosis of 'chronic functional abdominal pain'.
In these patients a psychological cause is highly likely& the most important tasks are to provide symptom control, if not relief& to minimise the effects of the pain on social, personal&occupational life.
Patients are best managed in specialised pain clinics where, in addition to psychological support, appropriate use of drugs including amitriptyline, gabapentin, ketamine& opioids may be necessary.
Presentation: severity & localisation may blunt with age.
Presentation may be atypical, even with perforation of a viscus.
Cancer: a more common cause of acute pain in those over 70 years than in those under 50 years.
Older people with vague abdominal symptoms should therefore be carefully assessed.
Non-specific symptoms: intra-abdominal inflammatory conditions as diverticulitis may present with non-specific symptoms as acute confusion or anorexia & relatively little abdominal tenderness, may be from altered sensory perception.
Outcome of abdominal surgery: determined by the degree of comorbid disease&whether surgery is elective or emergency, rather than by chronological age.