Abdominal pain is common and often inconsequential. Acute and severe
abdominal pain, however, is almost always a symptom of intra-abdominal disease. It may be
the sole indicator of the need for surgery and must be attended to swiftly: Gangrene and
perforation of the gut can occur < 6 h from onset of
symptoms in certain conditions (eg, interruption of the intestinal blood supply from a
strangulating obstruction or an arterial embolus). Abdominal pain is of particular concern
in patients who are very young or very old and those who have HIV infection or are taking
immunosuppressants.
Textbook descriptions of abdominal pain have limitations because people
react to pain differently. Some, particularly elderly people, are stoic, whereas others
exaggerate their symptoms. Infants, young children, and some elderly people may have
difficulty localizing the pain.
Pathophysiology
Visceral pain comes from the abdominal viscera, which are
innervated by autonomic nerve fibers and respond mainly to the sensations of distention
and muscular contraction—not to cutting, tearing, or local irritation. Visceral
pain is typically vague, dull, and nauseating. It is poorly localized and tends to be
referred to areas corresponding to the embryonic origin of the affected structure. Foregut
structures (stomach, duodenum, liver, and pancreas) cause upper abdominal pain. Midgut
structures (small bowel, proximal colon, and appendix) cause periumbilical pain. Hindgut
structures (distal colon and GU tract) cause lower abdominal pain.
Somatic pain comes from the parietal peritoneum, which is
innervated by somatic nerves, which respond to irritation from infectious, chemical, or
other inflammatory processes. Somatic pain is sharp and well localized.
Referred pain is pain perceived distant from its source and
results from convergence of nerve fibers at the spinal cord. Common examples of referred
pain are scapular pain due to biliary colic, groin pain due to renal colic, and shoulder
pain due to blood or infection irritating the diaphragm.
Peritonitis: Peritonitis is
inflammation of the peritoneal cavity. The most serious cause is perforation of the GI
tract (see Acute
Abdomen and Surgical Gastroenterology: Acute Perforation), which produces immediate
chemical inflammation followed shortly by infection from intestinal organisms. Peritonitis
can also result from any abdominal condition that produces marked inflammation (eg,
appendicitis, diverticulitis, strangulating intestinal obstruction, pancreatitis, pelvic
inflammatory disease, mesenteric ischemia). Intraperitoneal blood from any source (eg,
ruptured aneurysm, trauma, surgery, ectopic pregnancy) is irritating and results in
peritonitis. Barium causes severe peritonitis and should never be given to a patient with
suspected GI tract perforation. Peritoneo-systemic shunts, drains, and dialysis catheters
in the peritoneal cavity predispose a patient to infectious peritonitis, as does ascitic
fluid. Rarely, spontaneous bacterial peritonitis occurs, in which the peritoneal cavity is
infected by blood-borne bacteria. Peritonitis causes fluid shift into the peritoneal
cavity and bowel, leading to severe dehydration and electrolyte disturbances. Adult
respiratory distress syndrome can develop rapidly. Kidney failure, liver failure, and
disseminated intravascular coagulation follow. The patient's face becomes drawn into the
masklike appearance typical of hippocratic facies. Death occurs within days.
Etiology
Many intra-abdominal disorders cause abdominal pain (see Fig. 1: Acute
Abdomen and Surgical Gastroenterology: Location of abdominal pain and possible causes.
); some are trivial but some are immediately life threatening,
requiring rapid diagnosis and surgery. These include ruptured abdominal aortic aneurysm
(AAA), perforated viscus, mesenteric ischemia, and ruptured ectopic pregnancy. Others (eg,
intestinal obstruction, appendicitis, severe acute pancreatitis) are also serious and
nearly as urgent. Several extra-abdominal disorders also cause abdominal pain (see Table
1: Acute
Abdomen and Surgical Gastroenterology: Extra-Abdominal Causes of Abdominal Pain
).
Table 1 |
 |
|
|
| Extra-Abdominal Causes of Abdominal Pain |
Abdominal
wall |
|
Gu |
|
Infectious |
|
Metabolic |
|
|
|
|
Thoracic |
|
|
|
|
Toxic |
|
|
|
|
|
|
Abdominal pain in neonates, infants, and young children has numerous
causes not encountered in adults, including meconium peritonitis, pyloric stenosis,
esophageal webs, volvulus of a gut with a common mesentery, imperforate anus,
intussusception, and intestinal obstruction from atresia.
Evaluation
Evaluation of mild and severe pain follows the same process, although
with severe abdominal pain, therapy sometimes proceeds simultaneously and involves early
consultation with a surgeon. History and physical examination usually exclude all but a
few possible causes, with final diagnosis confirmed by judicious use of laboratory and
imaging tests. Life-threatening causes should always be ruled out before focusing on less
serious diagnoses. In seriously ill patients with severe abdominal pain, the most
important diagnostic measure may be expeditious surgical exploration. In mildly ill
patients, watchful waiting may be best.
History: A thorough history usually
suggests the diagnosis (see Table 2: Acute
Abdomen and Surgical Gastroenterology: History in Patients with Acute Abdominal Pain). Of particular importance are pain location (see Fig. 1: Acute
Abdomen and Surgical Gastroenterology: Location of abdominal pain and possible causes.) and characteristics, history of similar symptoms, and associated
symptoms. Concomitant symptoms such as gastroesophageal reflux, nausea, vomiting,
diarrhea, constipation, jaundice, melena, hematuria, hematemesis, weight loss, and mucus
or blood in the stool help direct subsequent evaluation. A drug history should include
details concerning prescription and illicit drug use as well as alcohol. Many drugs cause
GI upset. Prednisone or immunosuppressants may inhibit the inflammatory response to perforation
or peritonitis and result in less pain and leukocytosis than might otherwise be expected.
Anticoagulants can increase the chances of bleeding and hematoma formation. Alcohol
predisposes to pancreatitis.
Table 2 |
|
|
|
| History in Patients with Acute Abdominal Pain |
Question |
Potential Responses
and Indications |
Where is the pain? |
See Fig. 1: Acute
Abdomen and Surgical Gastroenterology: Location of abdominal pain and possible causes. |
What is the pain
like? |
Acute waves of
sharp constricting pain that "take the breath away"ݠ(renal or biliary colic)
Waves of dull pain with vomiting (intestinal obstruction)
Colicky pain that becomes steady (appendicitis, strangulating
intestinal obstruction, mesenteric ischemia)
Sharp, constant pain, worsened by movement (peritonitis)
Tearing pain (dissecting aneurysm)
Dull ache (appendicitis, diverticulitis, pyelonephritis) |
Have you had it
before? |
Yes suggests
recurrent problems such as ulcer disease, gallstone colic, diverticulitis, or
mittelschmerz |
Was the onset
sudden? |
Sudden: “like
a light switching on†(perforated ulcer, renal stone, ruptured ectopic pregnancy,
torsion of ovary or testis, some ruptured aneurysms)
Less sudden: most other causes |
How severe is the
pain? |
Severe pain
(perforated viscus, kidney stone, peritonitis, pancreatitis)
Pain out of proportion to physical findings (mesenteric ischemia) |
Does the pain travel
to any other part of the body? |
Right scapula
(gallbladder pain)
Left shoulder region (ruptured spleen, pancreatitis)
Pubis or vagina (renal pain)
Back (ruptured aortic aneurysm) |
What relieves the
pain? |
Antacids (peptic
ulcer disease)
Lying as quietly as possible (peritonitis) |
What other symptoms
occur with the pain? |
Vomiting
precedes pain and is followed by diarrhea (gastroenteritis)
Delayed vomiting, absent bowel movement and flatus (acute intestinal
obstruction; the delay increases with a lower site of obstruction)
Severe vomiting precedes intense epigastric, left chest, or shoulder
pain (emetic perforation of the intra-abdominal esophagus) |
|
Known medical conditions and previous abdominal surgeries are important
to ascertain. Women should be asked whether they are pregnant.
Physical examination: The general
appearance is important. A happy, comfortable-appearing patient rarely has a serious
problem, unlike one who is anxious, pale, diaphoretic, or in obvious pain. BP, pulse,
state of consciousness, and other signs of peripheral perfusion must be evaluated.
However, the focus of the examination is the abdomen, beginning with inspection and
auscultation, followed by palpation and percussion. Rectal examination and pelvic
examination (for women) to locate tenderness, masses, and blood are essential.
Palpation begins gently, away from the area of greatest pain, detecting
areas of particular tenderness, as well as the presence of guarding, rigidity, and rebound
(all suggesting peritoneal irritation) and any masses. Guarding is an involuntary
contraction of the abdominal muscles that is slightly slower and more sustained than the
rapid, voluntary flinch exhibited by sensitive or anxious patients. Rebound is a distinct
flinch upon brisk withdrawal of the examiner's hand. The inguinal area and all surgical
scars should be palpated for hernias.
Red flags: Certain findings raise
suspicion of a more serious etiology.
Interpretation of findings: Distention,
especially when surgical scars, tympany to percussion, and high-pitched peristalsis or
borborygmi in rushes are present, strongly suggests bowel obstruction. Severe pain in a
patient with a silent abdomen who is lying as still as possible suggests peritonitis;
location of tenderness suggests etiology (eg, right upper quadrant suggests cholecystitis,
right lower quadrant suggests appendicitis) but may not be diagnostic. Back pain with
shock suggests ruptured abdominal aortic aneurysm (AAA), particularly if there is a
tender, pulsatile mass. Shock and vaginal bleeding in a pregnant woman suggest ruptured
ectopic pregnancy. Ecchymoses of the costovertebral angles (Grey Turner's sign) or around
the umbilicus (Cullen's sign) suggest hemorrhagic pancreatitis but are not very sensitive
for this disorder.
History is often suggestive (see Table 2: Acute
Abdomen and Surgical Gastroenterology: History in Patients with Acute Abdominal Pain). Mild to moderate pain in the presence of active peristalsis of
normal pitch suggests a nonsurgical disease (eg, gastroenteritis) but may also be the
early manifestations of a more serious disorder. A patient who is writhing around trying
to get comfortable is more likely to have an obstructive mechanism (eg, renal or biliary
colic).
Previous abdominal surgery makes obstruction from adhesions more likely.
Generalized atherosclerosis increases the possibility of MI, AAA, and mesenteric ischemia.
HIV infection makes infectious causes and drug adverse effects likely.
Testing: Tests are selected based on
clinical suspicion.
Standard tests (eg, CBC, chemistries, urinalysis) are often done but are
of little value due to poor specificity; patients with significant disease may have normal
results. Abnormal results do not provide a specific diagnosis (the urinalysis in
particular may show pyuria or hematuria in a wide variety of conditions), and they can
also occur in the absence of significant disease. An exception is serum lipase, which
strongly suggests a diagnosis of acute pancreatitis. A bedside urine pregnancy test should
be done for all women of childbearing age because a negative result effectively excludes
ruptured ectopic pregnancy.
An abdominal series, consisting of flat and upright abdominal x‑rays
and upright chest x‑rays (left lateral recumbent abdomen and anteroposterior chest
x‑ray for patients unable to stand), should be done when perforation or obstruction
is suspected. However, these plain x‑rays are seldom diagnostic for other
conditions and need not be automatically done. Ultrasound should be done for suspected
biliary tract disease or ectopic pregnancy (transvaginal probe). Ultrasound can also
detect AAA but cannot reliably identify rupture. Noncontrast helical CT is the modality of
choice for suspected renal stones. CT with oral contrast is diagnostic in about 95% of
patients with significant abdominal pain and has markedly lowered the negative laparotomy
rate. However, advanced imaging must not be allowed to delay surgery in patients with
definitive symptoms and signs.
Treatment
Some clinicians feel that providing pain relief before a diagnosis is
made interferes with their ability to evaluate. However, moderate doses of IV analgesics
(eg, fentanyl 50 to 100 μg, morphine 4 to 6 mg) do not mask peritoneal signs and, by diminishing anxiety and
discomfort, often make examination easier.
Key Points
Last full review/revision September 2007 by Parswa
Ansari, MD
