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Abdominal Pain 

Abdominal Pain
Abdominal Pain

Sameer D. Saini

, and Akbar K. Waljee

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date: 18 May 2022

  1. A. Introduction

    1. a. The evaluation of a patient with abdominal pain is complicated by the overabundance of potential diagnoses, the frequency of nonspecific signs and symptoms, and limitations of radiographic studies.

    2. b. Life-threatening conditions can easily “hide” in the abdomen, perhaps causing few, if any, symptoms. The consequences of wrongly attributing the pain to a benign condition (e.g., gastritis, gastroenteritis) can be catastrophic. Remember: “Always respect the belly.”

  2. B. Causes of Abdominal Pain. The list of diseases that can cause abdominal pain is almost endless and includes diseases of the liver, gallbladder, pancreas, spleen, kidneys, abdominal aorta, and the entire luminal gastrointestinal tract, including the appendix. Pain in the abdomen can also be referred from the thorax (e.g., myocardial infarction, pneumonia) and pelvis (e.g., pelvic inflammatory disease [PID], testicular torsion). In addition, myofascial, musculoskeletal, and neuropathic pain of the abdominal and flank region can be interpreted as abdominal pain and erroneously attributed to intra-abdominal organs. Therefore, it is essential to evaluate patients presenting with abdominal pain in a systematic fashion. A thorough approach to abdominal pain consists of the following three steps:

    1. a. Consider the abdominal organs. By remembering that inflammation (whether due to infection or otherwise), obstruction, ischemia, or malignancy may cause abdominal pain in any intraabdominal organ, one forms a broad differential diagnosis.

    2. b. Rule out referred pain from the thorax and pelvis.

    3. c. Consider metabolic and systemic causes of abdominal pain. These can be remembered using the following mnemonic.

      • MNEMONIC: Metabolic and Systemic Causes of Abdominal Pain (“Puking My BAD LUNCH”)

      • Porphyria

      • Mediterranean fever

      • Black widow spider bite

      • Addison’s disease or Angioedema

      • Diabetic ketoacidosis

      • Lead poisoning

      • Uremia

      • Neurogenic (impingement of spinal nerves or roots, diabetes, syphilis)

      • Calcium (hypercalcemia)

      • Herpes zoster

  3. C. Approach to the Patient

    1. a. Patient history

      1. i. Epidemiologic factors influence the likelihood of a particular diagnosis (e.g., intravenous drug use may suggest hepatitis; alcohol abuse raises suspicion for pancreatitis or alcoholic hepatitis; hypertension supports myocardial ischemia or abdominal aneurysm). Always obtain a good history from patients!

      2. ii. Time course. The progression of symptom complexes is critical. For instance, in appendicitis, pain almost always precedes nausea and vomiting. Similarly, acute abdominal pain generally has a differential diagnosis that is different from chronic pain.

      3. iii. Symptoms

        1. 1. Pain

          • a. Quality. Judgments regarding the quality of pain are often misleading, given the significant variation and overlap among diagnoses. However, acute abdominal pain is often more of a cause for concern than chronic pain, and the chances of finding pathology are significantly higher.

          • b. Location. The location of the pain is extremely important and may help order the differential diagnosis (Table 27.1). Because there is a great deal of overlap, one cannot be faulted for being too careful (e.g., checking a urinalysis in a patient who has upper quadrant symptoms but lacks classic costovertebral angle tenderness is not an unreasonable diagnostic approach).

            Table 27.1 Differential Diagnosis for Abdominal Pain by Location


            Associated Organs

            Common Diseases/Causes

            Right upper quadrant

            Liver, gallbladder, esophagus, spleen

            Hepatitis, hepatic tumor or abscess, acquired immunodeficiency syndrome, cholangiopathy, cholecystitis, choledocholithiasis, ascending cholangitis, peptic ulcer disease, inflammatory bowel disease, tumor, pneumonia (lower lobe)


            Stomach, pancreas, duodenum, abdominal aorta

            Gastritis, peptic ulcer disease, pancreatitis, abdominal aortic aneurysm, biliary tract disease, cardiac disease, pneumonia (lower lobe) gastric cancer, duodenal cancer, pancreatic (head) cancer

            Left upper quadrant

            Spleen, lung, stomach, kidney, colon, lung

            Splenic abscess or infarct, pneumonia, urinary tract disease, Fitz-Hugh–Curtis syndrome of pelvic inflammatory disease, gastroesophageal reflux disease, gastroparesis, functional dyspepsia, gastroesophageal cancer, mesenteric ischemia, cardiac disease

            Right lower quadrant

            Appendix, small and large intestine, kidneys, ureters, ovaries, fallopian tubes, testes

            Appendicitis, colon cancer, constipation, right-sided diverticulitis, hernia, pyelonephritis, nephrolithiasis, ovarian cyst or torsion, ectopic pregnancy, pelvic inflammatory disease, endometriosis, epididymitis, testicular torsion

            Left lower quadrant

            Appendix, sigmoid colon, rectum, kidneys, ureters, ovaries, fallopian tubes, testes

            Sigmoid volvulus, diverticulitis, infectious or inflammatory colitis, inflammatory bowel disease, colon cancer, pyelonephritis, nephrolithiasis, ovarian cyst or torsion, ectopic pregnancy, pelvic inflammatory disease, endometriosis, epididymitis, testicular torsion

            Periumbilical region

            Appendix, small bowel, large bowel, abdominal aorta

            Early appendicitis (pain migrates to the right lower quadrant), constipation, mesenteric ischemia


            Bladder, uterus, ovaries, fallopian tubes

            Cystitis, urethritis, nephrolithiasis, bladder stone, pelvic inflammatory disease, endometriosis, testicular torsion

            Variable or diffuse

            Ischemic bowel, perforation, inflammatory bowel disease, gastroenteritis, constipation, irritable bowel syndrome, ectopic pregnancy, metabolic and systemic causes (see mnemonic)

          • c. Radiation. The patterns of radiation of the pain can be useful. As an example, epigastric pain radiating through to the back is often related to pancreatitis. Evaluation of the pain should always include questions regarding radiation.

          • d. Alleviating and aggravating factors. Identifying alleviating and aggravating factors of the pain can be helpful in the differential diagnosis. Pain exacerbated by movement and bending may reflect myofascial and musculoskeletal pain. Pain improved with defecation or flatulence is often related to visceral hypersensitivity and increased gas production.

            Hot Key

            The pattern of pain migration may help in making the proper diagnosis. For example, pain from appendicitis often begins in the periumbilical region and then shifts and settles to the right lower quadrant.

        2. 2. Other symptoms. Common symptoms and associated organs or organ systems are summarized in Table 27.2. Remember to ask about cardiac, pulmonary, and pelvic symptoms as well.

          Table 27.2 Symptoms and Associated Organ Systems

          Symptom or Sign

          Likely Site of Pathology

          Dysuria, frequency

          Kidney, bladder

          Nausea, vomiting, diarrhea

          Gastrointestinal tract

          Jaundice, pruritus

          Liver, gallbladder

          Pain that decreases on sitting up


          Abrupt onset of midline pain that is out of proportion to the examination

          Mesenteric vessels

          Pain increases when abdominal wall musculature is tensed (Carnett’s sign)

          Abdominal wall source

    2. b. Physical examination

      1. i. Vital signs are essential for determining the severity of the patient’s disease and may be helpful in narrowing the differential diagnosis.

      2. ii. Auscultation may not be helpful because the presence or absence of bowel sounds usually does not help narrow the differential diagnosis. However, absence of bowel sounds after one minute of auscultation should make one think of peritonitis or ileus.

      3. iii. Palpation should at first proceed gently from a point distal toward the area of the patient’s complaint.

      4. iv. Rectal and pelvic examination. Consider performing a rectal examination and a pelvic examination in patients with abdominal pain. A stool guaiac should be performed. Pain during rectal or pelvic examination may indicate pelvic pathology or a disorder involving a lower intra-abdominal structure (e.g., a retrocolic appendix). Care must be taken in interpreting the guaiac results; the stool guaiac results add no value in patients with frankly bloody or melenic stool. In addition, negative stool guaiac tests do not rule out serious intraabdominal pathology.

    3. c. Diagnostic tests

      1. i. Basic tests. The results of the following tests provide a starting point to narrow the differential diagnosis.

        1. 1. Complete blood count (CBC). Evaluate for leukocytosis or anemia.

        2. 2. Renal panel. Electrolyte disturbances can be the cause or result of the illness. Elevated blood urea nitrogen (BUN) and creatinine levels may suggest volume depletion or renal pathology. Elevated BUN can also suggest reabsorption of blood from a location above the ligament of Treitz. In the setting of a euvolemic patient with a suggestion of a possible gastrointestinal (GI) bleed, an elevated BUN supports an upper GI source.

        3. 3. Liver tests. Screen for liver or biliary pathology.

        4. 4. Amylase and lipase. Evaluate for pancreatitis. Amylase levels greater than three times the upper limit of normal is very specific for acute pancreatitis.

        5. 5. Urinalysis. Rule out diabetic ketoacidosis, urinary tract infection, and/or other renal pathology (e.g., nephrolithiasis).

        6. 6. Urine pregnancy test. If the patient is a woman of childbearing age, a pregnancy test should be performed regardless of how probable pregnancy seems to the patient. Ectopic pregnancies can often present with abdominal pain.

        7. 7. Coagulation studies. Prothrombin time (PT) and partial thromboplastin time (PTT) are important for any patient who may need an invasive procedure. They also may reveal pathology in which liver synthetic function is affected.

      2. ii. Ancillary tests. Given one’s initial diagnostic impressions and workup, the following tests may be indicated.

        1. 1. Serum calcium. This test can rule out hypercalcemia as a possible diagnosis.

        2. 2. Serum albumin. A low value may increase suspicion of an intraabdominal malignancy, pathology causing decreased synthetic function, or high metabolic stress.

        3. 3. Fecal white blood cell (WBC) count. A fecal WBC count should be performed to screen for bowel inflammation in any patient with diarrhea. The presence of white cells can indicate infection or inflammation but is not specific for any particular pathology.

        4. 4. Radiologic examination of the abdomen. Flat and upright radiographs are useful for evaluating bowel obstruction, intestinal perforation by the presence of free air, or the presence of radiopaque kidney stones.

        5. 5. Radiologic examination of the chest. Posterior-anterior (PA) and lateral views are indicated when the patient is experiencing upper abdominal pain (to rule out a lower lobe pneumonia) or when there is any suspicion of intestinal perforation (see Chapter 16).

          • a. A lateral radiograph sometimes demonstrates free air not seen on the PA film. The patient should remain upright for at least 5 minutes before PA and lateral radiographs are taken to increase the sensitivity for detecting air beneath the diaphragm. In a patient who cannot sit upright (e.g., because of pain or hypotension), a left lateral decubitus view can be used to evaluate for free air.

          • b. Enlargement of the aortic or cardiac silhouette may suggest an abdominal aortic aneurysm or a cardiac cause of pain.

        6. 6. Abdominal ultrasound. This is often the best noninvasive way to evaluate gallbladder, biliary, and renal pathology. Diseases in the liver, spleen, pancreas, abdominal aorta, and some intraabdominal abscesses can also be detected.

        7. 7. Abdominal computed tomography (CT) scan. An abdominal CT scan is better than ultrasound for evaluating most intraabdominal structures (except for the biliary tree and kidney). Triple-contrast studies (intravenous, oral, and rectal) are usually preferred because they yield much finer detail. For patients with elevated creatinine levels, intravenous contrast can sometimes be avoided if the bowel is of primary concern; however, abscesses may be missed unless intravenous contrast is used. Abdominal magnetic resonance imaging (MRI) is an option for patients in whom radiocontrast dye is contraindicated.

        8. 8. Paracentesis. Just as in the case of pleural effusion (see Chapter 98), one should always consider performing a paracentesis to rule out peritonitis and evaluate the etiology of the fluid in patients with ascites. Even if likelihood of bacterial infection is low, a paracentesis should be performed within the first few hours if the reason for fluid accumulation is unclear or if the possibility of infection exists.

        9. 9. Electrocardiogram. Every patient with a history of cardiac disease or risk factors who presents with abdominal pain—especially upper abdominal pain—should have an electrocardiogram (EKG) to rule out myocardial ischemia. Inferior wall myocardial ischemia often presents with abdominal pain.

    4. d. Recommendations for managing patients with abdominal pain

      1. i. The patient should have nothing by mouth (NPO) during the initial evaluation because surgery may be necessary.

      2. ii. Associated conditions (e.g., severe volume depletion or electrolyte imbalances) should be expeditiously corrected while the diagnostic workup is proceeding. Intravenous treatment is usually necessary because the patient will remain NPO; therefore, consideration of securing reliable venous access should occur early.

      3. iii. In the past, it was thought that the use of analgesics (e.g., opiates) during evaluation of the patient would “mask” potential diagnoses. However, it is now generally considered inappropriate to withhold medication in a patient with severe pain. The use of short-acting opiates (e.g., fentanyl) allows careful titration, which helps prevent hypotension and allows for unmasking of pain if needed.

      4. iv. A nasogastric tube is indicated in patients with severe vomiting or concerns for bowel obstruction. Patients with gastroparesis who present with severe flares should also be considered for nasogastric decompression.

      5. v. Early consultation with a surgeon when certain disorders are clinically suspected (e.g., appendicitis, peritonitis, cholecystitis) can prevent long delays, unnecessary testing, and delays in appropriate treatment. Similarly, early consultation with a gastroenterologist when suspecting gallstone-related disease (biliary obstruction) or luminal disease (e.g., colitis) may be appropriate.

      6. vi. When an etiology is not apparent and the patient appears ill (e.g., fever, diaphoresis, resting tachycardia, abdominal tenderness), observation in the hospital is necessary. In these situations, there is no substitute for frequent follow-up examinations and the “tincture of time.” In addition, advanced imaging (CT scan with contrast) is often indicated to ascertain the cause of the patient’s pain.

Hot Key

Have a low threshold to obtain an abdominal CT scan in older adult patients with unexplained abdominal pain.

Suggested Further Readings

Brunham RC, Gottlieb SL, Paavonen J. Pelvic inflammatory disease. N Engl J Med 2015;372:2039–48.Find this resource:

Flum DR. Clinical practice. Acute appendicitis: appendectomy or the “antibiotics first” strategy. N Engl J Med 2015;372:1937–43.Find this resource:

Morris AM, Regenbogen SE, Hardiman KM, Hendren S. Sigmoid diverticulitis: a systematic review. JAMA 2014;311:287–97.Find this resource:

Talley NJ, Ford AC. Functional dyspepsia. N Engl J Med 2015;373:1853–63.Find this resource: