For food bolus obstruction, intravenous glucagon may relax the oesophageal muscles enough to allow a bolus to pass through.³ This is less likely to be successful if the bolus is a piece of meat.⁴ An initial dose of 1 mg may be followed by a 2 mg dose if necessary. Complications are rare, but include allergy, nausea and hypotension. Phaeochromocytoma is a contraindication to the use of glucagon. Sublingual glyceryl trinitrate may be used as an alternative to glucagon, but hypotension is more likely. After glucagon, a gas-producing substance may be given in an attempt to dilate the oesophagus. Aerated drinks are adequate for this purpose.⁵ This technique should be used with great caution because a patient with upper oesophageal obstruction will be at greater risk of aspiration if given a foaming substance. This approach should be avoided if there is any suspicion of perforation. Endoscopic removal will be required in many cases, but this is usually attempted after a period of expectant treatment.

Oesophageal or pharyngeal perforation is a serious complication requiring cover with broad-spectrum antibiotics and urgent surgical referral.

Odynophagia may be relieved by parenteral or topical analgesia. Oral administration of a viscous preparation of lidocaine will ease the pain caused by luminal inflammatory disorders. The maximum recommended dose is 300 mg and should be reduced in the elderly, who may be more affected by systemic absorption.

Other issues

Appropriate disposition depends on the likely aetiology and the presence of complications. Admission is indicated for patients at risk of airway compromise, severe haemorrhage, sepsis, or those with high-grade oesophageal obstruction. It will also be indicated when dysphagia is part of a broader disease process.

If a food bolus has passed spontaneously, the patient should be referred for semi-elective endoscopy.

Controversies

• Choice between flexible and rigid endoscopy for removal of a food bolus. In many departments referral patterns will be fixed; however, if there is a choice, rigid endoscopy is preferred for removal of an upper oesophageal bolus and flexible endoscopy for boluses impacted more distally. Overall, flexible endoscopy has a lower complication rate.⁶

• Observation unit management. There may be arguments for a period of observation of 12 hours or more before referral for endoscopy, as the majority of food bolus obstructions will resolve spontaneously.⁷

References

1 Mendelson MH. Dysphagia. In: Tintinalli JE, Kelen GD, Stapczynski JS, editors. Emergency medicine: a comprehensive study guide. New York: McGraw Hill; 2004:509-510.

2 Palmer JB, Drennan JC, Baba M. Evaluation and treatment of swallowing impairments. American Family Physician. 2000;61:2453-2462.

3 Glauser J, Lilja GP, Greenfeld B, et al. Intravenous glucagon in the management of oesophageal food obstruction. Journal of the American College of Emergency Physicians. 1979;8:228-231.

4 Sodeman TC, Harewood GC, Baron TH. Assessment of the predictors of response to glucagon in the setting of acute oesophageal food bolus obstruction. Dysphagia. 2004;19:18-21.

5 Mohammed SH, Hegedus V. Dislodgement of impacted oesophageal foreign bodies with carbonated beverages. Clinical Radiology. 1986;37:589-592.

6 Gmeiner D, von Rahden BH, Meco C, et al. Flexible versus rigid endoscopy for treatment of foreign body impaction in the oesophagus. Surgical Endoscopy. 2007. (Epub ahead of print)

7 Tsikoudas A, Kochillas X, Kelleher, et al. The management of acute oesophageal obstruction from food bolus: Can we be more conservative? European Archives of Otorhinolaryngology. 2005;262:528-530.

7.2 Approach to abdominal pain

Kim Chai Chan, Eillyne Seow

Essentials

1 Abdominal pain accounts for 5–10% of all emergency department visits. A significant proportion of these patients will require hospital admission.

2 Abdominal pain most frequently arises from pathologies in the gastrointestinal and the genitourinary systems; however it may also result from cardiovascular, pulmonary, metabolic, infective and toxic causes.

3 Special considerations should be given to four subgroups of patients: the elderly, the immunocompromised (including those with HIV infection), women of childbearing age and children. These patients require careful assessment to avoid missed diagnoses and poor outcomes.

4 In up to 25–40% of patients the exact cause of the abdominal pain may not be determined in the emergency department. After ruling out life-threatening causes, and with relief of symptoms, most of these patients may be discharged with appropriate advice.

5 Patients with abdominal pain should be given adequate analgesia (including the use of opioids). Adequate analgesia can aid diagnosis and does not conceal signs of an acute abdomen.

Introduction

The assessment of patients with abdominal pain is challenging because:

• The contact time with the patient is relatively short and diagnosis may be difficult, especially early on in the disease process.

• The patient’s presentation may be atypical, especially for the very young, the immunocompromised and the elderly.

• The degree of pain may not be commensurate with the severity of the disease.

• The absence of abnormal vital signs cannot rule out a serious underlying condition.

• The absence of physical findings of an acute abdomen does not rule out a surgical abdomen, e.g. serious conditions such as ischaemic colitis may have very non-specific physical findings.

• A large number of potential differential diagnoses may need to be considered.

The emergency department (ED) approach to acute abdominal pain emphasizes disposition over diagnosis: it is more important to recognize an acute abdomen than to identify the exact cause of the pain.¹

Epidemiology

It has been estimated that abdominal pain accounts for approximately 5–10% of all ED visits.² A significant proportion (18–42%) of these patients will require admission.¹ The elderly (aged 60 and over) are over-represented in the admitted patient group. In one study on elderly patients presenting with abdominal pain, at least 50% were hospitalized and about 30–40% eventually had surgery. Up to 40% of patients were initially misdiagnosed, and the overall mortality was about 10%.³

Pathophysiology and differential diagnosis

Abdominal pain may result from:

• Visceral pain: This pain is poorly localized, colicky, intermittent and recurrent in nature. Stimulation of autonomic nerves investing the visceral peritoneum causes visceral pain, e.g. when hollow organs are distended, or when capsules covering solid organs are stretched. Visceral pain localizes to the abdominal region that correlates with the embryonic segments of the viscera:

Foregut structures (stomach, duodenum, liver, biliary tract, pancreas) localize to the upper abdomen

Midgut structures (small bowel, proximal colon, appendix) localize to the periumbilical region

Hindgut structures (distal colon, genitourinary tract) localize to the lower abdomen.

• Somatic pain: This pain is well localized, and is often constant and intense. Somatic pain results from local irritation of the parietal peritoneum. It is localized more specifically to the area of pathology (Table 7.2.1). It is, however, important to recognize that the area of pain does not always correspond to the supposed anatomic location of the underlying pathology,⁴ e.g. acute appendicitis may present as suprapubic or flank pain.

• Referred pain: Pain felt at a distance from the site of origin. It is thought that referred pain occurs because afferent pain fibres from areas of high sensory input (e.g. the skin) enter the spinal cord at the same level as nociceptive fibres from an area of low sensory input (e.g. the viscera). The brain, being more used to pain signals from the skin, wrongly interprets the pain signal from the viscera as that from the dermatome.

Table 7.2.1 Differential diagnosis of pain by location (list not exhaustive)

Right upper quadrant	Epigastrium	Left upper quadrant
Hepatobiliary pathology	Gastritis, peptic ulcer	Gastritis, peptic ulcer
Duodenal ulcer, duodenitis	Hepatobiliary pathology	Renal colic, pyelonephritis
Renal colic, pyelonephritis	Pancreatitis	Splenic pathology
Retrocaecal appendicitis	Aortic aneurysm	Pancreatitis
Pneumonia, pulmonary embolism	Early appendicitis	Pneumonia
	Myocardial infarction
Right lumbar or flank	Midline or periumbilical	Left lumbar or flank
Renal colic, pyelonephritis	Visceral pain from midgut structures	Renal colic, pyelonephritis
Aortic aneurysm	Early appendicitis	Aortic aneurysm
Psoas abscess	Aortic aneurysm	Psoas abscess
Appendicitis
Right lower quadrant	Suprapubic	Left lower quadrant
Appendicitis	Cystitis, bladder pathology	Similar to causes for right lower quadrant pain except for appendicitis (very rarely left sided)
Ectopic pregnancy, tubo-ovarian pathology, endometriosis, pelvic inflammatory disease	Urinary tract infection
Urinary tract infection, ureteric colic	Prostatitis
Diverticulitis	Ectopic pregnancy, tubo-ovarian pathology, endometriosis, pelvic inflammatory disease
Hernia
Aortic aneurysm
Testicular torsion, epididymo-orchitis
Pain radiating to the back
Perforated peptic ulcer
Acute pancreatitis
Abdominal aortic aneurysm, aortic dissection

Note: Pain from inflammatory bowel disease, diverticulitis, colitis, gastroenteritis, volvulus, intestinal obstruction, adhesions, ischaemic colitis and constipation may localized to any part of the abdomen.

Both visceral and somatic pain may manifest as referred pain. Some examples are:

• Shoulder pain due to diaphragmatic irritation.

• Pain at the tip of the scapula due to gallbladder pathology.

• Epigastric pain due to acute myocardial infarction.

Causes of diffuse abdominal pain

Generalized diffuse pain that is poorly localized may be due to benign causes (e.g. gastroenteritis, constipation and menstrual cramps) or from life-threatening conditions (Table 7.2.2).

Table 7.2.2 Some potentially life-threatening causes of generalized, diffuse abdominal pain

Haemoperitoneum from any cause, e.g. ruptured abdominal aortic aneurysm, ruptured ectopic pregnancy, trauma

Mesenteric ischaemia

Perforated viscus

Peritonitis (any cause)

Pancreatitis

Bowel obstruction

Diverticulitis

Inflammatory bowel disease

Metabolic disorders (e.g. diabetic ketoacidosis), sickle cell crisis, typhoid fever

Adapted from Gray-Eurom K, Deitte L. Imaging in the adult patient with non-traumatic abdominal pain. Emergency Medicine Practice 2007; 9: 2.

Extra-abdominal

There are a number of extra-abdominal causes for abdominal pain that must be considered along with abdominal causes (Table 7.2.3).

Table 7.2.3 Extra-abdominal causes of abdominal pain

Thoracic
Myocardial infarction/unstable angina Pneumonia Pulmonary embolism Herniated thoracic disc (neuralgia)

Genitourinary
Testicular torsion

Systemic
Diabetic ketoacidosis Alcoholic ketoacidosis Uraemia Sickle cell disease Systemic lupus erythematosus Vasculitis Hyperthyroidism Porphyria Glaucoma

Toxic
Methanol poisoning Heavy metal poisoning Scorpion bite Black Widow spider bite

Abdominal wall
Muscle spasm Muscle haematoma Herpes zoster

Infections
Strep pharyngitis (more often in children) Mononucleosis

Adapted from Purcell TB. Nonsurgical and extraperitoneal causes of abdominal pain. Emergency Medicine Clinics of North America 1989; 7: 721.

Clinical features

Vital signs and general condition

During triage a rapid assessment is made by looking at the patient’s general condition as well as vital signs. Obviously ill patients, those in severe pain or with abnormal vital signs should be given priority. However, one cannot rule out life-threatening causes of abdominal pain by the absence of abnormal vital signs. It has been estimated that up to 7% of patients with normal vital signs may have an underlying life-threatening process, and this percentage increases in the elderly.⁵ Tachycardia may be absent in patients with autonomic dysfunction, in the elderly, and in patients on medications that may blunt the cardiac response to illness or volume loss.⁶ The elderly, the immunocompromised, or those in severe septic shock may sometimes not mount a febrile response. Even in the immunocompetent, fever may not always accompany acute inflammatory conditions. In a study on patients with pathologically proven cholecystitis, only 32% had a documented temperature rise within 8 hours of arrival at the ED. The absence of fever was as likely in those below 60 as in those above.⁷

History

An accurate, focused history often provides the best clue to the possible aetiology of the abdominal pain. Clinical impression derived from the history will direct decisions regarding further diagnostic work-up.

Patient demographics and background history

• Age and gender: The likelihood of certain conditions is higher in patients of a specific age and gender (Table 7.2.4). For women of childbearing age it is important to ascertain the presence or absence of pregnancy.

Table 7.2.4 Common causes of abdominal pain according to age group and gender

Causes	Age group	Gender
Biliary tract disease	Peak age 35–50; rare in those < 20	Female:male 3:1
Ruptured ectopic pregnancy	Childbearing ages	Female
Appendicitis	All ages and both genders, peak at young adulthood; higher risk of perforation in the elderly, women, and children
Mesenteric ischaemia	Elderly, those with vascular, thrombotic or embolic risks
Abdominal aortic aneurysm	Increased with advancing age	Men more common
Diverticulitis	Increased with advancing age	Men more common

Pain attributes

The nature and time course of pain are key clues to diagnosis. The following attributes should be noted:

• Onset and progress of abdominal pain over time (Table 7.2.5): Acute vascular events and rupture of hollow viscus typically presents with maximal pain at the onset. Ureteric and biliary colic also often presents with severe pain in the early stages. This is in contrast to pain from inflammatory processes such as acute appendicitis, which tends to progress and ‘mature’ over hours.

• Location of pain (see Table 7.2.1), migration of pain, radiation of pain: Location of pain helps to localize the area of pathology, though occasionally this may be misleading, especially if the pain is referred. Migration of pain over time gives a clue to possible underlying aetiology, e.g. pain from appendicitis typically starts at the umbilicus or epigastrium and later localizes to the right iliac fossa.

• Radiation of pain may suggest specific conditions (Table 7.2.1), e.g. pain from acute pancreatitis and perforated peptic ulcers often radiates to the back.

• Severity of pain: Severity of pain experienced is dependent on a number of factors in addition to the underlying pathology, and is not always commensurate with the severity of the underlying illness. The elderly in particular often have a diminished sense of pain. Nonetheless, patients in severe pain should be assessed early and given pain relief. Pain scores may be used to record and monitor progress.

• Character of pain: Colicky abdominal pain results usually from obstruction of a hollow viscus. Constant non-colicky pain usually denotes an inflammatory or vascular process.

• Precipitating and relieving factors: Pain from peritonitis worsens with movement, deep breathing, coughing or sneezing. Pain from peptic ulcer disease classically increases with hunger and decreases with food, antacid or milk. Pain from biliary colic tends to occur after full or fatty meals. Pain from acute pancreatitis classically worsens with supine posture and is relieved by sitting up.

• Recurrent episodes of abdominal pain: This suggests chronic recurrent conditions, e.g. peptic ulcer, biliary colic, renal colic, diverticulitis. Mesenteric ischaemia and testicular torsion may also present with recurrent episodes.

Table 7.2.5 Temporal characteristics of abdominal pain

Sudden maximal pain at or near onset
Perforated peptic ulcer Ruptured abdominal aortic aneurysm Ruptured ectopic pregnancy, ruptured ovarian cyst Ovarian/testicular torsion Mesenteric infarction Pulmonary embolism? Acute myocardial infarction

Progression to maximal pain within minutes
Acute pancreatitis Renal and ureteric colic Biliary colic Strangulated hernia Volvulus Intussusception

Gradual onset (increased pain over hours)
Appendicitis Strangulated hernia Inflammatory bowel disease Chronic pancreatitis Salpingitis/prostatitis Cystitis

White MJ, Counselman FL. 2005 Troubleshooting acute abdominal pain Emedmag 2002 http://www.emedmag.com/html/pre/cov/covers/011502.asp.

Associated symptoms

Patients with abdominal pain often have other associated symptoms that may give a clue to the possible cause. These include:

• Constitutional symptoms, e.g. fever, chills, rigors, weight loss, arthralgia.

• Gastrointestinal tract symptoms, e.g. anorexia, nausea, vomiting, diarrhoea, constipation. Nausea and vomiting are non-specific symptoms which may result from intra- and extra-abdominal causes. However, feculent vomitus is highly indicative of intestinal obstruction. Vomiting of fresh or altered blood, as well as the passage of black tarry stools, indicates gastrointestinal haemorrhage. Failure to pass stools and flatus over a 24–48-hour period suggests possible intestinal obstruction.

• Genitourinary tract symptoms, e.g. dysuria, frequency, urgency, haematuria, suggest urinary tract pathologies. A purulent discharge from the vagina suggests possible pelvic inflammatory disease.

Table 7.2.6 lists some of the historical high-yield questions in abdominal pain.

Table 7.2.6 High-yield historical questions

1 How old are you?

Advanced age means increased risk.

2 Which came first- pain or vomiting?

Pain first is more likely to be caused by surgical disease.

3 How long have you had the pain?

Pain for less than 48 hours is more likely to be caused by surgical disease.

4 Have you ever had abdominal surgery?

Consider adhesion or obstruction in patients with previous abdominal surgery.

5 Is the pain constant or intermittent?

Constant pain is more likely to be caused by surgical disease.

6 Have you had this before?

A report of no prior episode is more likely to be caused by surgical disease.

7 Do you have a history of cancer, diverticulosis, pancreatitis, kidney failure, gallstones, or inflammatory bowel disease?

All are suggestive of more serious disease.

8 Do you have human immunodeficiency virus (HIV)?

Consider occult infection or drug-related pancreatitis.

9 How much alcohol do you drink per day?

Consider pancreatitis, hepatitis, cirrhosis.

10 Are you pregnant?

Test for pregnancy; consider ectopic pregnancy.

11 Are you taking antibiotics or steroids?

These may mask infection.

12 Did the pain start centrally and migrate to the right lower quadrant?

High specificity for appendicitis.

13 Do you have a history of vascular or heart disease, hypertension, or atrial fibrillation?

Consider mesenteric ischaemia and abdominal aneurysm.

Adapted from Colucciello SA, Lukens TW, Morgan DL. Assessing abdominal pain in adults: A rational, cost-effective, and evidence-based strategy. Emergency Medicine Practice 1999; 1: 1.

Physical examination

A careful, systematic, directed and thorough physical examination can help strengthen the clinical impression formed from the history or to uncover unexpected abnormalities. Physical findings help to rule in, but not rule out, the underlying diagnosis.

General

Consider the general condition and the vital signs of the patient. Patients who look drowsy or unwell, or have abnormal vital signs, need urgent attention. The posture of the patient may give a clue to the possible underlying disease. Patients with renal colic typically roll about in pain, whereas those with peritonitis lie still to avoid movements that might aggravate the pain. Inspect for pallor, jaundice, hydration status, enlarged lymph nodes, and signs of chronic liver or renal disease.

The abdomen

This is carried out with the patient lying supine and the abdomen exposed from the costal margins to the pubic symphysis. Ideally the patient should be fairly relaxed, comfortable and cooperative; it is almost impossible to perform an abdominal examination in an uncooperative patient thrashing about in pain. Adequate pain relief should be given before examination if necessary. There is strong evidence that analgesia does not mask physical signs. Abdominal examination in an obtunded patient is unreliablem and other assessment modalities such as imaging have to be considered.

• Inspection: Look for movement with respiration, shape (e.g. distended or scaphoid), the presence of any surgical scars and external lesions (e.g. bruises, distended veins, hernias). Sometimes markedly enlarged organs (especially the liver or spleen) or distended bowels may be seen.

• Palpation and percussion: Palpation is usually the most informative part of the abdominal examination. Start with the abdominal region away from the area of pain. Perform light, followed by deep palpation systematically over all quadrants of the abdomen. Look for tenderness, guarding, rebound and masses. The area of abdominal tenderness helps to localize the pathology. The presence of involuntary guarding (or rigidity) and rebound indicates peritoneal irritation. Findings of abnormal abdominal masses may help point to the possible diagnosis. Finally, palpate and percuss for hepatosplenomegaly; palpate bimanually for renal masses, and examine for costovertebral angle tenderness (renal punch). Percussion for shifting dullness may be performed in patients with suspected ascites.

• Auscultation: This is performed to look for abnormal or absent bowel sounds, and for vascular bruits. In gastric outlet obstruction a succussion splash may be heard in the upper abdomen when the patient is shaken from side to side. Auscultation is the least rewarding aspect of physical examination: findings from auscultation have been found to be neither sensitive nor specific.⁸ However, high-pitched, tinkling or absent bowel sounds have been found to be associated with acute small bowel obstruction, especially in the presence of abdominal distension.⁸ Abnormal bowel sounds in the elderly may indicate serious underlying disease.³

• Specific abdominal signs (Table 7.2.7): Distinctive signs have been described that are associated with specific diagnoses. Some of these signs have not been studied and their sensitivity and specificity remain unknown.

Table 7.2.7 Specific abdominal signs

Sign	Description	Association
Murphy’s sign	Inability of patient to perform deep inspiration due to pain on palpation of right hypochondrium	Acute cholecystitis (sensitivity 97%; specificity 50%)³⁰
Kehr’s sign	Severe left shoulder tip pain especially when the patient is lying supine	Haemoperitoneum, e.g. from ruptured spleen or ectopic pregnancy
Cullen’s sign	Ecchymoses around the periumbilical area	Retroperitoneal haemorrhage (haemorrhagic pancreatitis, abdominal aortic aneurysm rupture)
Grey–Turner’s sign	Ecchymoses of the flanks	Retroperitoneal haemorrhage (haemorrhagic pancreatitis, abdominal aortic aneurysm rupture)
McBurney’s sign	Tenderness localized to a point at 2/3 distance on a line drawn from the umbilicus to the right anterior superior iliac spine	Appendicitis
Iliopsoas sign	Extension of right hip causes abdominal pain	Appendicitis (sensitivity 16%; specificity 95%)¹⁰
Obturator’s sign	Internal rotation of the flexed right hip causes abdominal pain	Appendicitis
Rovsing’s sign	Right lower quadrant (RLQ) pain with palpation of the left lower quadrant	Appendicitis
Heel-drop sign	RLQ pain on dropping heels on the ground after standing tiptoes; alternatively RLQ pain from forcefully banging the patient’s heel with the examiner’s hand	Appendicitis (sensitivity 93%)³¹
Cough test	Post-tussive abdominal pain	Peritonitis (sensitivity up to 95%)^32,³³

White MJ, Counselman FL. 2005 Troubleshooting acute abdominal pain Emedmag. 2002 http://www.emedmag.com/html/pre/cov/covers/011502.asp

Examination of extra-abdominal systems

Besides the abdomen, extra-abdominal systems, especially the cardiovascular and respiratory systems, should also be examined. Directed examination of extra-abdominal systems is important because:

• The cause of the abdominal pain may be extra-abdominal (Table 7.2.3).

• It may provide clues to the possible intra-abdominal pathology, e.g. the presence of atrial fibrillation or peripheral vascular disease suggests possible mesenteric ischaemia.

• There may be complications from the abdominal condition, e.g. associated chest infection.

Serial examination

Physical signs may often be non-specific in the early phases of the disease. Serial examinations over a period of hours can help to distinguish a surgical from a non-surgical abdomen and improve the diagnostic yield.

Investigations

Although the history and physical examination may give a clue to the possible underlying pathology, many patients with abdominal pain do not present ‘classically’. Investigations may assist in determining diagnosis and disposition.

Bedside tests

• Urine pregnancy tests: Bedside urine tests are rapid and accurate. Most are able to detect β-hCG to a level as low as 25 mIU/mL of urine. It has been estimated that up to 1% of ectopic pregnancies are associated with β-hCG values lower than this.¹²

• Urine analysis: This provides useful early information for patients with suspected urinary tract infection and ureteric colic. However, it is important to interpret urine analysis results in the context of the patient’s clinical presentation. About 30% of patients with acute appendicitis may present with blood and leukocytes in their urine;¹³ about 30% of patients with ruptured aortic abdominal aneurysm may have haematuria.¹⁴

• Electrocardiogram (ECG): Acute coronary events may manifest as abdominal symptoms, e.g. epigastric pain, nausea and vomiting. ECG should be performed in cases where there is suspicion of ACS, especially in patients with cardiovascular risks or in the elderly. ECG may also suggest the possible cause of the abdominal pain in some cases, e.g. mesenteric ischaemia from atrial fibrillation, abdominal pain and vomiting from digoxin toxicity.

• Capillary blood sugar: Patients with diabetic ketoacidosis (DKA) may present with symptoms and signs mimicking an acute abdomen. Capillary blood sugar should be performed in all patients with known diabetes mellitus, or in cases where there are clinical suspicions of DKA (e.g. dehydration, Kussmaul breathing, ketotic breath).

Laboratory tests

Most laboratory tests do not aid in differentiating surgical from non-surgical causes of abdominal pain.¹⁵

• Full blood count: This most commonly ordered laboratory study does not add value to the assessment of patients with abdominal pain. A normal white count (including normal absolute neutrophil count) may lead to a false sense of security even though it does not rule out a surgical cause of pain. Ten to 60% of patients with surgically proven appendicitis have a normal initial white count;¹ only about 50% of patients with severe intra-abdominal pathology have an elevated white count.¹⁶ On the other hand, an elevated white count may lead to further investigations which may not add to the information already gleaned from the history and physical examination.¹⁷

• Amylase and lipase: These tests are most useful in patients with suspected pancreatitis. Serum lipase has been found to be more accurate than serum amylase.¹⁸ Both lipase and amylase may be normal in patients with CT-proven pancreatitis, especially in those with recurrent disease.

• Liver function test: This should only be ordered selectively, in cases where there is suspicion of hepatobiliary disease, or when urine tests detect the presence of urobilinogen.

• C-reactive protein (CRP): This has been found to be about 62% sensitive and 66% specific for appendicitis.¹⁹ The sensitivity improved in patients with more than 12 hours of symptoms, and appendicitis is rare in those with two normal CRPs performed 12 hours apart.²⁰

Imaging

Plain X rays

The value of plain radiographs for evaluation of patients with abdominal pain is limited. However, there is still a place for plain X-rays as a first-line investigation in patients with suspected bowel obstruction, bowel perforation and foreign body. A three-view series comprising the upright chest, supine and upright abdominal radiographs is recommended.⁶ X-ray findings for bowel obstruction and perforation are fairly specific but not sensitive, i.e. they help to establish, but not exclude, these diagnoses.

Ultrasound

Ultrasound does not involve ionizing radiation, is rapid, non-invasive, and may be performed at the bedside. This makes it the ideal evaluation tool in unstable patients or those who are pregnant. Selective use of focused ultrasound in the appropriate clinical setting maximizes its diagnostic sensitivity. However, ultrasound is operator dependent and appropriate training is necessary to ensure competence. The sensitivity of ultrasound may also be reduced by technical limitations (e.g. obesity, bowel gas, subcutaneous emphysema). Focused bedside emergency ultrasound examination has significantly affected the diagnosis and management of the following life-threatening conditions:

• Abdominal aortic aneurysm (AAA): Ultrasound is a useful screening tool for the presence of AAA (defined as an aortic diameter >3 cm), especially when the patient is not suitable for transfer to a CT facility. Ultrasound cannot reliably identify rupture, but the detection of an AAA in a hypotensive patient with symptoms suggestive of rupture (abdominal pain, backache or flank pain) is an indication for urgent intervention.

• Ectopic pregnancy: In a patient with a positive pregnancy test, an empty uterus (especially in the presence of free intraperitoneal fluid) implies ectopic pregnancy until proven otherwise. Other ultrasound findings include detection of an adnexal mass, an extrauterine gestational sac, extrauterine blood clots and interstitial ectopic pregnancy. On the other hand, identification of intrauterine pregnancy (IUP) essentially reduces the risk of an ectopic pregnancy to < 1:5000 (1:50 for women undergoing assisted reproduction). Transvaginal ultrasound is more sensitive than transabdominal ultrasound in detecting early IUPs. Repeat examination in a stable patient may be needed if the study is inconclusive (e.g. a positive pregnancy test but no IUP and no adnexal mass).¹

• Haemoperitoneum from abdominal trauma: The focused abdominal sonogram for trauma (FAST) examination is now considered to be an essential evaluation in unstable patients who have sustained abdominal trauma. The presence of free intraperitoneal fluid implies the development of haemoperitoneum. FAST is highly specific (99%), although its overall sensitivity is about 66% compared to CT. FAST is almost 100% sensitive in the hypotensive patient. The sensitivity of FAST improves with serial examination.

Ultrasound may also be used for evaluation of patients in the following conditions that may not be immediately life threatening:

• Assessment of suspected gallbladder disease: Ultrasound is the recommended imaging study of first choice for suspected gallbladder disease. Discretion should be applied to avoid over-interpretation, e.g. the mere presence of gallstones does not imply choleolithiasis as the cause of the abdominal pain.

• Tubo-ovarian pathologies: Ultrasound is the first-line investigation for patients with suspected pelvic inflammatory disease or tubo-ovarian pathology. Transvaginal ultrasound provides detailed visualization of the pelvic organs, and trans-abdominal ultrasound provides a complementary global view.

• Ureteric colic: Ultrasound combined with abdominal radiographs may be used to screen patients with suspected ureteric colic. The diagnostic sensitivity for nephrolithiasis is about 63–85%,⁶ fairly similar to that for intravenous urography (IVU), which has a sensitivity of 64–90%. The advantages of this imaging technique over IVU are that the use of radiocontrast is avoided, and the radiation dose involved is much lower.

• Detection of free peritoneal fluid in non-traumatic abdominal pain: In the appropriate clinical context this may suggest the presence of ascites, intraperitoneal haemorrhage, pus or leakage of gut content.

• Appendicitis: Ultrasound may be used to evaluate for the presence of appendicitis if there are contraindications to CT (e.g. pregnancy) or if CT is unavailable. Ultrasound is not as sensitive as CT and helps to rule in but not rule out this diagnosis.

Computed tomography (CT)

With the advent of helical and multidetector scanning technology, CT has become the imaging modality of choice for evaluation of abdominal pain in the non-obstetric patient.

A survey of emergency physicians ²¹ ranked CT of the abdomen and pelvis as the most valuable diagnostic test in evaluating patients with non-traumatic abdominal pain. It has a high degree of accuracy, establishing diagnoses in more than 95% of cases in one study.²² In the elderly, CT resulted in changes to the management and disposition of significant proportion of patients.²³

CT allows for detailed visualization of intra-, extra- and retroperitoneal structures. It identifies the exact site of disease, as well as its impact on the surrounding structures, thereby guiding further management. CT may be performed with or without intravenous and oral contrast agents. In the emergency setting, CT is useful for:

• Assessment in abdominal trauma.

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