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Acute Abdominal Pain

By

Parswa Ansari

, MD, Hofstra Northwell-Lenox Hill Hospital, New York

Last full review/revision Sep 2021| Content last modified Sep 2021
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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 Acute Perforation of the Gastrointestinal Tract Any part of the gastrointestinal tract may become perforated, releasing gastric or intestinal contents into the peritoneal space. Causes vary. Symptoms develop suddenly, with severe pain followed... read more Acute Perforation of the Gastrointestinal Tract can occur < 6 hours from onset of symptoms in certain conditions (eg, interruption of the intestinal blood supply due to 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 (including corticosteroids).

Textbook descriptions of abdominal pain have limitations because people react to pain differently. Some, particularly older people, are stoic, whereas others exaggerate their symptoms. Infants, young children, and some older people may have difficulty localizing the pain.

The term acute abdomen refers to abdominal symptoms and signs of such severity or concern that disorders requiring surgery should be considered.

Pathophysiology of Acute Abdominal Pain

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 genitourinary 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 gastrointestinal tract Acute Perforation of the Gastrointestinal Tract Any part of the gastrointestinal tract may become perforated, releasing gastric or intestinal contents into the peritoneal space. Causes vary. Symptoms develop suddenly, with severe pain followed... read more Acute Perforation of the Gastrointestinal Tract , which causes immediate chemical inflammation followed shortly by infection from intestinal organisms. Peritonitis can also result from any abdominal condition that causes marked inflammation (eg, appendicitis Appendicitis Appendicitis is acute inflammation of the vermiform appendix, typically resulting in abdominal pain, anorexia, and abdominal tenderness. Diagnosis is clinical, often supplemented by CT or ultrasonography... read more Appendicitis , diverticulitis Colonic Diverticulitis Diverticulitis is inflammation with or without infection of a diverticulum, which can result in phlegmon of the bowel wall, peritonitis, perforation, fistula, or abscess. The primary symptom... read more Colonic Diverticulitis , strangulating intestinal obstruction Intestinal Obstruction Intestinal obstruction is significant mechanical impairment or complete arrest of the passage of contents through the intestine due to pathology that causes blockage of the bowel. Symptoms include... read more Intestinal Obstruction , pancreatitis Overview of Pancreatitis Pancreatitis is classified as either acute or chronic. Acute pancreatitis is inflammation that resolves both clinically and histologically. Chronic pancreatitis is characterized by histologic... read more , pelvic inflammatory disease Pelvic Inflammatory Disease (PID) Pelvic inflammatory disease (PID) is a polymicrobial infection of the upper female genital tract: the cervix, uterus, fallopian tubes, and ovaries; abscess may occur. PID may be sexually transmitted... read more , mesenteric ischemia Acute Mesenteric Ischemia Acute mesenteric ischemia is interruption of intestinal blood flow by embolism, thrombosis, or a low-flow state. It leads to mediator release, inflammation, and ultimately infarction. Abdominal... read more Acute Mesenteric Ischemia ). Intraperitoneal blood from any source (eg, ruptured aneurysm, trauma, surgery, ectopic pregnancy Ectopic Pregnancy In ectopic pregnancy, implantation occurs in a site other than the endometrial lining of the uterine cavity—ie, in the fallopian tube, uterine cornua, cervix, ovary, or abdominal or pelvic cavity... read more ) is irritating and results in peritonitis. Barium causes severe caking and peritonitis and should never be given to a patient with suspected gastrointestinal tract perforation. However, water-soluble contrast agents can be safely used. Peritoneosystemic shunts, drains, and dialysis catheters in the peritoneal cavity predispose a patient to infectious peritonitis, as does ascitic fluid.

Peritonitis causes fluid to shift into the peritoneal cavity and bowel, leading to severe dehydration and electrolyte disturbances. Acute respiratory distress syndrome Acute Hypoxemic Respiratory Failure (AHRF, ARDS) Acute hypoxemic respiratory failure is severe arterial hypoxemia that is refractory to supplemental oxygen. It is caused by intrapulmonary shunting of blood resulting from airspace filling or... read more Acute Hypoxemic Respiratory Failure (AHRF, ARDS) can develop rapidly. Kidney failure, liver failure, and disseminated intravascular coagulation follow. Without treatment, death occurs within days.

Etiology of Acute Abdominal Pain

Many intra-abdominal disorders cause abdominal pain (see figure Location of abdominal pain and possible causes Location of abdominal pain and possible causes 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... read more ); some are trivial, but some are immediately life threatening, requiring rapid diagnosis and surgery. These include ruptured abdominal aortic aneurysm Abdominal Aortic Aneurysms (AAA) Abdominal aortic diameter ≥ 3 cm typically constitutes an abdominal aortic aneurysm. The cause is multifactorial, but atherosclerosis is often involved. Most aneurysms grow slowly (~10%/year)... read more Abdominal Aortic Aneurysms (AAA) (AAA), perforated viscus, mesenteric ischemia Acute Mesenteric Ischemia Acute mesenteric ischemia is interruption of intestinal blood flow by embolism, thrombosis, or a low-flow state. It leads to mediator release, inflammation, and ultimately infarction. Abdominal... read more Acute Mesenteric Ischemia , and ruptured ectopic pregnancy Ectopic Pregnancy In ectopic pregnancy, implantation occurs in a site other than the endometrial lining of the uterine cavity—ie, in the fallopian tube, uterine cornua, cervix, ovary, or abdominal or pelvic cavity... read more . Others (eg, intestinal obstruction Intestinal Obstruction Intestinal obstruction is significant mechanical impairment or complete arrest of the passage of contents through the intestine due to pathology that causes blockage of the bowel. Symptoms include... read more Intestinal Obstruction , appendicitis Appendicitis Appendicitis is acute inflammation of the vermiform appendix, typically resulting in abdominal pain, anorexia, and abdominal tenderness. Diagnosis is clinical, often supplemented by CT or ultrasonography... read more Appendicitis , severe acute pancreatitis Acute Pancreatitis Acute pancreatitis is acute inflammation of the pancreas (and, sometimes, adjacent tissues). The most common triggers are gallstones and alcohol intake. The severity of acute pancreatitis is... read more Acute Pancreatitis ) are also serious and nearly as urgent. Several extra-abdominal disorders also cause abdominal pain (see table Extra-Abdominal Causes of Abdominal Pain Extra-Abdominal Causes of Abdominal Pain 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... read more ).

Location of abdominal pain and possible causes

Location of abdominal pain and possible causes
Table
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Abdominal pain in neonates, infants, and young children has numerous causes not encountered in adults. These causes include necrotizing enterocolitis Necrotizing Enterocolitis Necrotizing enterocolitis is an acquired disease, primarily of preterm or sick neonates, characterized by mucosal or even deeper intestinal necrosis. It is the most common gastrointestinal emergency... read more Necrotizing Enterocolitis , meconium peritonitis, pyloric stenosis Hypertrophic Pyloric Stenosis Hypertrophic pyloric stenosis is obstruction of the pyloric lumen due to pyloric muscular hypertrophy. Diagnosis is by abdominal ultrasonography. Treatment is surgical. Hypertrophic pyloric... read more , volvulus of a gut with intestinal malrotation Malrotation of the Bowel Malrotation of the bowel is failure of the bowel to assume its normal place in the abdomen during intrauterine development. Diagnosis is by abdominal x-ray. Treatment is surgical repair. (See... read more Malrotation of the Bowel , imperforate anus Anal Atresia Anal atresia is an imperforate anus. (Also see Overview of Congenital Gastrointestinal Anomalies.) In anal atresia, the tissue closing the anus may be several centimeters thick or just a thin... read more , intussusception Intussusception Intussusception is telescoping of one portion of the intestine (intussusceptum) into an adjacent segment (intussuscipiens), causing intestinal obstruction and sometimes intestinal ischemia.... read more , and intestinal obstruction caused by atresia Jejunoileal Atresia Jejunoileal atresia is incomplete formation of part of the small intestine. Diagnosis is by abdominal x-ray. Treatment is surgical repair. (Also see Overview of Congenital Gastrointestinal Anomalies... read more Jejunoileal Atresia .

Evaluation of Acute Abdominal Pain

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 and a diagnostic evaluation may be best.

History

A thorough history usually suggests the diagnosis (see table History in Patients with Acute Abdominal Pain History in Patients with Acute Abdominal Pain 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... read more ). Of particular importance are pain location (see figure Location of abdominal pain and possible causes Location of abdominal pain and possible causes 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... read more ) and characteristics, history of similar symptoms, and associated symptoms. Concomitant symptoms such as heartburn, 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 gastrointestinal upset. Prednisone or immunosuppressants may inhibit the inflammatory response to perforation or peritonitis and result in less pain, tenderness, or leukocytosis than might otherwise be expected. Anticoagulants can increase the chances of bleeding and hematoma formation. Alcohol predisposes to pancreatitis.

Table
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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. Blood pressure, 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 Hernias of the Abdominal Wall A hernia of the abdominal wall is a protrusion of the abdominal contents through an acquired or congenital area of weakness or defect in the wall. Many hernias are asymptomatic, but some become... read more Hernias of the Abdominal Wall .

Red flags

Certain findings raise suspicion of a more serious etiology:

  • Severe pain

  • Signs of shock (eg, tachycardia, hypotension, diaphoresis, confusion)

  • Signs of peritonitis

  • Abdominal distention

Interpretation of findings

Ecchymoses of the costovertebral angles (Grey Turner sign) or around the umbilicus (Cullen sign) suggest hemorrhagic pancreatitis Acute Pancreatitis Acute pancreatitis is acute inflammation of the pancreas (and, sometimes, adjacent tissues). The most common triggers are gallstones and alcohol intake. The severity of acute pancreatitis is... read more Acute Pancreatitis but are not very sensitive for this disorder.

Testing

Tests are selected based on clinical suspicion:

  • Urine pregnancy test for all women of childbearing age

  • Selected imaging tests based on suspected diagnosis

Standard tests (eg, complete blood count, 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 do not need to be otherwise automatically done. Ultrasound should be done for suspected biliary tract disease or ectopic pregnancy (transvaginal probe) and for suspected appendicitis in children. Ultrasound can also detect abdominal aortic aneurysm but cannot reliably identify rupture. Noncontrast helical CT is the modality of choice for suspected renal stones. CT with oral and IV 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 of Acute Abdominal Pain

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 mcg, morphine 4 to 6 mg) do not mask peritoneal signs and, by diminishing anxiety and discomfort, often make examination easier.

Key Points

  • Look for life-threatening causes first.

  • Rule out pregnancy in women of childbearing age.

  • Seek signs of peritonitis, shock, and obstruction.

  • Blood tests are of minimal value.

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