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1. Abdominal rigidity
[Abdominal muscle spasm, involuntary guarding]
Detected by palpation, abdominal rigidity refers to abnormal muscle tension or inflexibility of the
abdomen. Rigidity may be voluntary or involuntary. Voluntary rigidity reflects the patient's fear or
nervousness upon palpation; involuntary rigidity reflects potentially life-threatening peritoneal irritation or
inflammation. (See Recognizing voluntary rigidity.)
Involuntary rigidity most commonly results from GI disorders but may also result from pulmonary and
vascular disorders and from the effects of insect toxins. It's usually accompanied by fever, nausea,
vomiting, and abdominal tenderness, distention, and pain.
After palpating abdominal rigidity, quickly take the patient's vital signs. Even though the patient may
not appear gravely ill or have markedly abnormal vital signs, abdominal rigidity calls for emergency
interventions.
Prepare to administer oxygen and to insert an I.V. catheter for fluid and blood replacement. The patient
may require drugs to support blood pressure. Also prepare him for catheterization, and monitor intake and
output.
A nasogastric tube may have to be inserted to relieve abdominal distention. Because emergency surgery
may be necessary, prepare the patient for laboratory tests and X-rays.
HISTORY AND PHYSICAL EXAMINATION
If the patient's condition allows further assessment, take a brief history. Find out when the abdominal
rigidity began. Is it associated with abdominal pain? If so, did the pain begin at the same time? Determine
whether the rigidity is localized or generalized. Is it always present? Has its location changed or remained
constant? Next, ask about aggravating or alleviating factors, such as position changes, coughing, vomiting,
elimination, and walking.
Then explore other signs and symptoms. Inspect the abdomen for peristaltic waves, which may be visible
in very thin patients. Also check for a visibly distended bowel loop. Next, auscultate bowel sounds.
Perform light palpation to locate the rigidity and to determine its severity. Avoid deep palpation, which
may exacerbate abdominal pain. Finally, check for poor skin turgor and dry mucous membranes, which
indicate dehydration.
MEDICAL CAUSES
♦ Abdominal aortic aneurysm (dissecting). Mild to moderate abdominal rigidity occurs in abdominal
aortic aneurysm, a life-threatening disorder. It's typically accompanied by constant upper abdominal pain

2. that may radiate to the lower back. The pain may worsen when the patient lies down and may be relieved
when he leans forward or sits up. Before rupture, the aneurysm may produce a pulsating mass in the
epigastrium, accompanied by a systolic bruit over the aorta. However, the mass stops pulsating after
rupture. Associated signs and symptoms include mottled skin below the waist, absent femoral and pedal
pulses, blood pressure that's lower in the legs than in the arms, and mild to moderate abdominal tenderness
with guarding. Significant blood loss causes signs of shock, such as tachycardia, tachypnea, and cool,
clammy skin.
♦ Mesenteric artery ischemia. This lifethreatening disorder is characterized by 2 to 3 days of persistent,
low-grade abdominal pain and diarrhea leading to sudden, severe abdominal pain and rigidity. Rigidity
occurs in the central or periumbilical region and is accompanied by severe abdominal tenderness, fever,
and signs of shock, such as tachycardia and hypotension. Other findings may include vomiting, anorexia,
diarrhea, and constipation. Always suspect mesenteric artery ischemia in patients older than age 50 who
have a history of heart failure, arrhythmias, cardiovascular infarct, or hypotension.
♦ Peritonitis. Depending on the cause of peritonitis, abdominal rigidity may be localized or generalized.
For example, if an inflamed appendix causes local peritonitis, rigidity may be localized in the right lower
quadrant. If a perforated ulcer causes widespread peritonitis, rigidity may be generalized and, in severe
cases, boardlike.
Peritonitis also causes sudden and severe abdominal pain that can be localized or generalized. It can also
produce abdominal tenderness and distention, rebound tenderness, guarding, hyperalgesia, hypoactive or
absent bowel sounds, nausea, and vomiting. Most patients also experience fever, chills, tachycardia,
tachypnea, and hypotension.
♦ Pneumonia. In lower lobe pneumonia, severe upper abdominal pain and tenderness accompany rigidity
that diminishes with inspiration. Associated signs and symptoms include blood-tinged or rusty sputum,
dyspnea, achiness, headache, fever, sudden onset of chills, crackles, egophony, decreased breath sounds,
dullness on percussion, and a dry, hacking cough.
OTHER CAUSES
♦ Insect toxins. Insect stings and bites, especially black widow spider bites, release toxins that can produce
generalized cramping abdominal pain, usually accompanied by rigidity. These toxins may also cause low-
grade fever, nausea, vomiting, tremors, and burning sensations in the hands and feet. Some patients
develop increased salivation, hypertension, paresis, and hyperactive reflexes. Children commonly are
restless, have an expiratory grunt, and keep their legs flexed.
SPECIAL CONSIDERATIONS

3. Continue to monitor the patient closely for signs of shock. Position him as comfortably as possible in a
supine position, with his head flat on the table, arms at his sides, and knees slightly flexed to relax the
abdominal muscles. Because analgesics may mask symptoms, withhold them until a tentative diagnosis
has been made. Also withhold food and fluids and administer an I.V antibiotic because emergency surgery
may be required. Prepare the patient for diagnostic tests, which may include blood, urine, and stool
studies; chest and abdominal X-rays; a computed tomography scan; magnetic resonance imaging;
peritoneal lavage; and gastroscopy or colonoscopy. A pelvic or rectal examination may also be done.
PEDIATRIC POINTERS
Voluntary rigidity may be difficult to distinguish from involuntary rigidity if associated pain makes the
child restless, tense, or apprehensive. However, in any child with suspected involuntary rigidity, your
priority is early detection of dehydration and shock, which can rapidly become life-threatening.
Abdominal rigidity in children can stem from gastric perforation, hypertrophic pyloric stenosis, duodenal
obstruction, meconium ileus, intussusception, cystic fibrosis, celiac disease, and appendicitis.
GERIATRIC POINTERS
Advanced age and impaired cognition decrease pain perception and intensity. Weakening of abdominal
muscles may decrease muscle spasms and rigidity.
Accessory muscle use
When breathing requires extra effort, the accessory muscles—the sternocleidomastoid, scalene, pectoralis
major, trapezius, internal intercostals, and abdominal muscles—stabilize the thorax during respiration.
Some accessory muscle use normally takes place during such activities as singing, talking, coughing,
defecating, and exercising. (See Accessory muscles: Locations and functions, page 26.) However, more
pronounced use of these muscles may signal acute respiratory distress, diaphragmatic weakness, or
fatigue. It may also result from chronic respiratory disease. Typically, the extent of accessory muscle use
reflects the severity of the underlying cause.
If the patient displays increased accessory muscle use, immediately look for signs of acute
respiratory distress. These include decreased level of consciousness, shortness of breath when speaking,
tachypnea, intercostal and sternal retractions, cyanosis, external breath sounds (such as wheezing or
stridor), diaphoresis, nasal flaring, and extreme apprehension or agitation. Quickly auscultate for
abnormal, diminished, or absent breath sounds. Check for airway obstruction and, if detected