Acute abdominal pain

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Chapter 7 ACUTE ABDOMINAL PAIN

KEY POINTS

• Acute abdominal pain is usually a surgical condition.
• Most conditions can be diagnosed by bedside assessment.
• Clinical peritonitis will usually require a laparotomy to clean the peritoneal cavity and stop continuing contamination from a perforated or ischaemic viscus.
• Peritonitis not caused by gut ischaemia or perforation of a viscus does not require a laparotomy, e.g. acute pancreatitis, salpingitis and spontaneous bacterial peritonitis.
• Surgery for localised peritoneal inflammation will not always be required and will be dictated by the presumed diagnosis and its natural history.
• Management of a patient with an acute abdomen should consist of:

– Initial assessment and resuscitation
– Focused assessment and investigation
– Decision and planning of management.

• Management should not be delayed by unnecessary investigations.
• Patients who require urgent surgery for intraperitoneal bleeding or peritonitis should be resuscitated in the operating theatre while surgery is being performed.
• Contact a surgeon quickly if the patient is unstable or the diagnosis is unclear.

INTRODUCTION

Acute abdominal pain should always be considered a surgical condition. The management of the patient with acute abdominal pain can be simplified by considering appropriate clinical management pathways and not focusing on the final diagnosis. The key to this is the use of clinical symptoms and signs in combination with limited special tests to decide if the patient is best treated by urgent or planned operation or conservative management. Many of these immediate decisions can be made by the bedside with a good history and examination.

DEFINITION

Acute abdominal pain is defined as the sudden onset of severe abdominal pain. The rapidity of onset may be over minutes to hours. The pain may be localised to a specific site of the abdomen or generalised.

CAUSES OF ACUTE ABDOMINAL PAIN

Generalised abdominal pain

Constant abdominal pain

In a patient with generalised constant abdominal pain and abdominal rigidity, the working diagnosis is peritonitis. This is always secondary to some other process. Often, but not always, this is due to a perforated viscus. The role of surgery is to provide peritoneal toilet and to prevent ongoing contamination by removing or repairing the perforated viscus. There are a number of conditions that fulfill this criterion. There are other conditions, however, that may demonstrate the signs of peritonitis but not require intervention (see Figure 7.1). Typically acute pancreatitis with generalised inflammation may have tenderness and guarding but does not require a laparotomy. A diagnostic elevated lipase may be very useful in this setting. In females, pelvic inflammatory disease may show generalised signs and does not benefit from laparotomy as there is no ongoing contamination. This should be considered in appropriate clinical contexts. Spontaneous bacterial peritonitis in portal hypertension should also be considered in patients presenting with generalised abdominal pain and portal hypertension with ascites.

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FIGURE 7.1 Management of acute abdomen.

Beware of the patient complaining of severe constant generalised abdominal pain who appears to have a relatively soft ‘doughy’ abdomen to palpation. This patient may have ischaemic bowel. Suspicion may be raised if they have bloody diarrhoea and atrial fibrillation. Investigations may reveal an elevated white cell count and a metabolic acidosis. Venous obstruction is often more subtle and slowly progressive.

Colicky abdominal pain

Colicky abdominal pain is episodic pain that comes in waves every 4–5 minutes. It is crescendo decrescendo in nature. When it is generalised the diagnosis is usually between gastroenteritis or a bowel obstruction. Gastroenteritis will often be associated with early vomiting and diarrhoea and abdominal distension will not be a feature. Some infective forms of gastroenteritis may not produce diarrhoea.

In contrast, a bowel obstruction will usually be associated with vomiting and constipation with progressive abdominal distension. The higher the obstruction is anatomically in the intestine, the earlier the vomiting and the later the constipation. The more distal the obstructing lesion, the greater the distension. A supine and erect plain abdominal film will usually confirm the diagnosis. An erect chest X-ray should always be ordered to look for free peritoneal gas. The supine abdominal film is the most useful. With the patient lying flat it will not show the fluid levels of the erect film but it will show gaseous distended bowel down to the level of obstruction. The ileum or small intestine can be distinguished by its central position and valvulae conniventes extending across the intestinal lumen. The jejunum or large intestine is distinguished by its incomplete valves and more peripheral position.

Be very wary of the diagnosis of constipation causing abdominal pain if the rectum is empty or if abdominal tenderness is present.

Surgery is indicated for an obstructed bowel when the cause for the obstruction is unlikely to resolve. The timing is a balance between appropriate resuscitation of the patient and avoiding the development of gut ischaemia.

Small intestine obstruction is more difficult to manage than colonic obstruction as there are no objective diagnostic indicators of early bowel ischaemia. Colonic ischaemia can be predicted if the bowel lumen is distended above a 10 cm diameter, as venous drainage in the bowel wall will be impaired at this level. The caecum is the part of the large intestine usually most susceptible to distension and can be monitored clinically and radiologically.

If constant abdominal pain, worsening tenderness, fever, leucocytosis and acidosis are present, gut ischaemia should be suspected and urgent surgery is indicted.

All these signs and symptoms can be absent or late.

Localised abdominal pain

The management of focal abdominal pain relates very much to the presumed or proven diagnosis, the natural history of the condition and the morbidity if treated conservatively or operatively. Typically, appendicitis is usually treated operatively as it is known that the natural history may lead to perforation and generalised peritonitis. Appendicectomy is straightforward and is associated with low morbidity. Acute diverticulitis of the colon is usually treated conservatively with antibiotics. Diverticulitis may sometimes perforate but operative resection of the affected bowel will usually lead to a temporary colostomy and will not prevent further recurrence. Surgery is therefore reserved for the patient whose condition does not resolve with conservative management.

It is best to consider these conditions in relation to the position in the abdomen in which the signs occur.

Right upper quadrant

Pain in this region may be due to pathology in the liver, gall bladder, bile duct, hepatic flexure of the colon, appendicitis in the high-riding caecum or the duodenum. The conditions that might require early intervention include the subhepatic appendix or a perforated viscus such as the duodenum or the hepatic flexure. Pain and jaundice in this region suggests a biliary cause.

Cholecystitis may be treated conservatively but is best treated by early laparoscopic cholecystectomy. Cholangitis may respond to antibiotics but may need biliary drainage by endoscopic retrograde cholangiopancreatography (ERCP) if this fails.

Right upper quadrant pain of a sudden onset with minimal signs will frequently be due to biliary colic. Characteristically, the pain is sudden in onset, epigastric or right upper quadrant in site with radiation around or through to the back. Biliary colic is due to a stone obstructing either the gall bladder or the bile duct. The latter may be associated with jaundice.

Left upper quadrant

The diagnosis of acute pain in this area can often be the most challenging. Peptic ulcer disease and colonic pathology should be considered as well as, rarely, pancreatitis. A splenic infarct should also be considered which might be due to an embolic event in a normal spleen or a spontaneous infarct if the spleen is palpable. It should also be remembered that both upper quadrant and epigastric pain can be caused by some pathology above the diaphragm such as basal pneumonia, pleurisy, ischaemic heart disease or pericarditis.

Right iliac fossa

Any patient who complains of periumbilical pain that radiates to the right iliac fossa should be considered to have appendicitis until proven otherwise. The patient will usually have a low-grade fever and anorexia with an elevated white cell count and significant tenderness in the right iliac fossa. Abdominal imaging is usually not required in such a patient although a pelvic ultrasound may be considered in a female if a ruptured ovarian cyst is considered. Initial periumbilical pain does not usually occur in primary pelvic pathology.

Remember that the sigmoid colon can sometimes lie in the right iliac fossa and may mimic appendicitis clinically in the older patient.

In females of child-bearing age, ruptured ovarian cysts, pelvic inflammatory disease and ectopic pregnancy must always be considered. Estimation of β-hCG and pelvic ultrasound are valuable investigations here for lower abdominal and pelvic pain.

Left iliac fossa

Left iliac pain and tenderness is usually due to diverticulitis. There is often associated fever. Occasionally a palpable mass may be present, which may be an inflammatory mass or an abscess.

Loins

Loin pain is usually due to renal tract disease. The typical ‘loin to groin pain’ is characteristic of ureteric colic and may be associated with sepsis if the ureter is blocked. Other retroperitoneal structures such as the pancreas and the aorta may present with back or loin pain. Occasionally ureteric colic may focus with predominant pain in the iliac fossa. Local tenderness is usually not a feature. Remember both appendicitis and ureteric colic may cause microscopic haematuria.

ASSESSMENT

History and physical examination is the cornerstone of diagnosis in the acute abdomen. Most decisions concerning acute abdominal pain can be made by the bedside.

History

Taking a history of pain must begin with inquiring about the rapidity of onset. A true sudden onset of significant pain without prodromal symptoms usually indicates a perforated, obstructed or an acutely ischaemic viscus. This would include perforated peptic ulcer, biliary colic, foreign body perforation of bowel, mesenteric embolus, ureteric colic or a ruptured aneurysm. A sudden exacerbation of pain with preceding symptoms of malaise and fever may suggest perforated diverticulitis or appendicitis. If the pain is generalised, a perforated viscus is most likely.

The presence of colic and duration of symptoms will differentiate between viscus obstruction and inflammation. The presence of vomiting, diarrhoea or constipation and a previous history suggests bowel obstruction.

Physical examination

Examination should begin with a global look at the patient to assess toxicity, discomfort and distress and overall nutritional status. The presence of jaundice and anaemia and the overall hydration of the patient can also be assessed.

The vital signs—temperature pulse and blood pressure—should also be recorded.

Examination of the abdomen should be gentle. If there is significant tenderness, there is no need to make the patient unnecessarily uncomfortable. If hurt, the patient will voluntarily guard their abdominal wall, making palpation difficult. Rebound tenderness is not necessarily useful and can be more humanely replaced by eliciting percussion or cough tenderness.

As a routine, it is always important to palpate for an aortic aneurysm. The hands must be placed in the epigastrium for at least 10 seconds to feel for an expansile mass of greater than 2 cm to make the diagnosis. All hernial orifices must be palpated for a mass. A hernia causing a bowel obstruction will not always be locally painful to the patient. It will be palpable and irreducible.

Auscultation is of limited benefit. The presence or absence of bowel sounds has little diagnostic significance, even in the context of a bowel obstruction.

A rectal examination should always be performed in acute abdominal pain as an inflammatory or malignant intraluminal or peritoneal mass may be palpated. The presence and consistency of the stool and the presence of blood can be useful signs.

MANAGEMENT

The approach to managing the patient should be performed in three steps:

1. Immediate assessment and management
2. Focused assessment and investigation
3. Decision and plan of management.

Immediate assessment and management

This is really the initial resuscitation phase and should stabilise the patient’s airway, breathing and circulation. This phase should only take a few minutes. If the patient can speak then the airway is clear, if not the airway will need to be secured and oxygen applied. Breathing is the mechanical act of ventilation and may be compromised by altered consciousness or a splinted diaphragm due to severe abdominal pain. Circulation may be compromised by sepsis or dehydration. Venous access should be achieved by a large bore peripheral cannula, bloods drawn for assessment and a crystalloid fluid administered. A bolus of 10 mL/kg should be administered initially. If the patient is hypoperfused, the bolus should be increased to 20 mL/kg. Next the level of consciousness and mental state of the patient should be documented. The patient should be exposed for any obvious finding, such as distension, and then covered to keep them comfortable.

Focused assessment and investigation

Once the initial resuscitation phase is initiated then a more focused assessment can be made. A history is initially taken to include a description of the presenting illness as well as past medical and surgical history, medications, allergies and fasting state. A focused abdominal examination is then performed and all findings recorded.

Decision and plan of management

A plan of action now needs to be formulated. The management decision can be enhanced by the use of appropriate blood tests, plain X-ray, abdominal ultrasound, computed tomography (CT) scan, angiography and endoscopy. The use of plain X-ray and ultrasound can be very useful in the assessment of patients with acute abdominal pain. CT may be useful if the diagnosis is unclear. It must be stressed that overinvestigation can lead to unnecessary delay and must be avoided. An investigation should only be ordered if its outcome is likely to have a significant impact on management.

Initially it must be decided if the patient requires immediate surgery, delayed surgery or observation with conservative management and further investigations. If immediate surgery is required, it should be established whether there is time or the need for preoperative stabilisation. The patient with a bleeding condition, such as a ruptured aortic aneurysm or ruptured ectopic pregnancy or a perforated viscus, is often best managed by urgent surgical intervention with no delay. Further resuscitation can occur while surgery is performed. A delay in intervention in these conditions is associated with increased morbidity and mortality.

A bowel obstruction will benefit from fluid resuscitation prior to surgery as long as bowel viability is not compromised.

The management of focal abdominal sepsis is dependent on specific factors that depend, in turn, on potential complications of the intervention. As a general rule, a focal acute inflammation of the colon is usually treated conservatively with antibiotics. If there is a large associated abscess, this will usually be treated by imaging guided percutaneous drainage or open surgery.

Appendicitis and acute cholecystitis are usually be treated surgically. In the event of a delay of more than 72 hours, both conditions are often treated conservatively with antibiotics. This is because resection of these organs at this time may lead to damage of the surrounding organs due to the attempts by these structures to wall off the inflammation. The bile duct with the gall bladder and surrounding small intestine and caecum with the appendix could be placed in jeopardy.

If a plan of management cannot be decided upon, then the role of further observation or an intervention must be considered. It is also important to decide whether the patient needs to be placed in a high dependency area based on their condition or comorbidity.

A patient should never be left in pain. Appropriate analgesia should be administered early in small frequent doses. Analgesia will not mask signs but will reduce the patient’s awareness of pain. There is a duty of care to ensure frequent pain reassessment.

It is essential that communication with the treating clinician is both timely and accurate. If the patient is unstable or the diagnosis unclear, early communication with the consultant is mandatory.

SUMMARY

History and clinical examination are the cornerstones of diagnosis in the acute abdomen. Most decisions can be made at the bedside. A rectal examination should always be carried out.

The management centres on three core issues:

1. Initial assessment and management
2. Focused assessment and investigations
3. Decision and plan of management including appropriate laboratory investigations and imaging.

FURTHER READING

Abu-Yousef MM, Bleicher JJ, Maher JW. High resolution sonography of acute appendicitis. Am J Roentgenol. 1987;149:53-58.

Anderson ID. Care of the critically ill surgical patient, 2nd edn. London: Arnold; 2003.

Dang C, Aguilera P, Dang A. Acute abdominal pain. Geriatrics. 2002;57:30-42.

Davidson SJ, Murphy DG, Barbaro G. Missed diagnosis of acute cardiac ischemia. N Engl J Med. 2000;343:1492-1494.

Oria A, Cimmino D, Ocampo C, et al. Early endoscopic intervention versus early conservative management in patients with acute gallstone pancreatitis and biliopancreatic obstruction: a randomized clinical trial. Ann Surg. 2007;245:10-17.

Thomas SH, William S, Cheema F. Effect of morphine analgesia on diagnostic accuracy in emergency department patients with abdominal pain. J Am Coll Surg. 2003;196:18-31.

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