Etiology

• Differential is broad so history should guide workup.
• History: OPQRSTi (Onset, Provocation, Quality of pain, Region/Radiation, Severity, Time, interventions attempted, especially including NSAIDs).
• All patients:
  • Ask about current medications and drug use: steroids/NSAIDs, immunosuppressants, opioids, cocaine (can cause intestinal or cardiac ischemia), alcohol (gastritis, alcoholic hepatitis, pancreatitis), any medications that can cause constipation (opioids, anticholinergics).
  • Review chronic medical conditions for possible relationship to acute abdominal pain (e.g. atrial fibrillation, cardiovascular disease, and HFrEF are risk factors for mesenteric ischemia).
• See section Acute Abdominal Pain: Emergencies for “can’t miss” diagnoses. Some include:
  • Obstruction (SBO, ileus): recent surgery, C. diff, IBD, volvulus (elderly patients – sigmoid, mesenteric), radiation, hernia (incarcerated/strangulated), malignancy.
  • Perforation (peptic ulcer, appendicitis, diverticulitis, ischemia, IBD, surgery, malignancy).
  • Ectopic pregnancy, ovarian torsion: female patients of childbearing age.
  • Referred ACS pain: patients with cardiac risk factors, diabetes, CHF, older patients.
  • Ruptured AAA, dissection: patients with tobacco use, with vasculopathy, elderly.
• Once emergencies have been ruled out, consider cause of abdominal pain by quadrant:
  • Epigastric: GERD, AAA, ACS, PUD, gastritis (alcohol, NSAIDs, other meds), esophagitis (especially in patients who are immunocompromised), pancreatitis (radiating to back).
    • Pending workup, can trial “GI cocktail” of H2RB, viscous lidocaine, sucralfate and/or Maalox, in addition to Tylenol.
    • Set clear end-date for PPI trial.
  • RUQ: biliary colic, cholecystitis (RUQ US>CT), GERD, cholangitis (see Acute Cholangitis section), liver capsule stretch (e.g., large hematoma, Fitz-Hugh-Curtis adhesions over liver in females of reproductive age with STD risk factors – most intrahepatic pathologies are painless absent mass effect), pancreatitis, pneumonia, pyelonephritis referred from flank, ACS.
  • LUQ: GERD, pancreatitis, splenic pathologies (relatively uncommon), pneumonia, pyelonephritis referred from flank, ACS.
  • RLQ: appendicitis (high perforation rate, can be tricky to diagnose), nephrolithiasis, ectopic pregnancy, tubo-ovarian abscess, ovarian/testicular torsion, diverticulitis, constipation, UTI, IBD, hernia.
  • LLQ: diverticulitis, nephrolithiasis, ectopic pregnancy, TOA, ovarian/testicular torsion, diverticulitis, constipation, UTI, IBD, hernia.

Adapted from Brown 2014.

Evaluation

History:

• Visceral pain: poorly localized, dull, aching, gnawing, colicky, often perceived as occurring in the midline, unable to find a comfortable position. Can be related to mechanical causes (obstruction), chemical (peritonitis), acute inflammation or ischemia.
• Somatic pain: often well-localized, sharp or stabbing. Be concerned if the patient describes change from visceral to somatic pain. In the abdomen this often implies peritonitis.
• Colicky pain: biliary colic, nephrolithiasis.
• Radiation: 
  • Epigastric: foregut (stomach, pancreas, liver, biliary system, proximal duodenum).
    • Pearl: biliary colic pain in particular is very poorly localized. It can be felt almost anywhere in the epigastrium or lower chest. Studies show that patients are more likely to have epigastric than RUQ pain, despite the traditional teaching.
  • Peri-umbilical: midgut (rest of small bowel, proximal 1/3 of colon, including the appendix).
  • Suprapubic: hindgut (bladder, distal 2/3 colon, pelvic genitourinary organs).
  • Back: retroperitoneal organs (including aorta, kidneys).
  • Remember common patterns of referred pain (organs under the diaphragm to ipsilateral shoulder, ureteral colic to testes/vagina, etc.).
• Associated symptoms: 
  • Vomiting: consider contents (blood, bile, feculent material), time course. Can have large bowel obstruction without emesis. 
    • Frequent nonproductive retching: gastric volvulus.
    • Non-bilious vomiting: gastric outlet obstruction.
  • Diarrhea may occur with an obstruction of large or small bowel, acute mesenteric ischemia, or inflammatory/infectious conditions.
    • Absence of flatus is more reliable than constipation in bowel obstruction (gas clears more rapidly than solid material).
    • Bloody stool + pain – think about ischemia.

Physical exam:

• Vital signs: normal VS do not exclude serious illness.
• Signs of peritoneal irritation: rebound tenderness with depression of abdominal wall for 15-30 seconds is 80% sensitive, only 40-50% specific.
• Exam maneuvers that may be useful but are no substitute for a CT A/P w contrast: 
  • Murphy’s sign: arrest of inspiration while palpating the RUQ. 65% sensitive. Sonographic Murphy’s sign: 75% sensitive, 55-80% specific (operator dependent).
  • Psoas sign: pain with flexion of thigh against resistance, or passive flexion while lying on contralateral side. When positive on the right, classic sign of appendicitis. Positive in other inflammatory conditions involving the retroperitoneum (pyelonephritis, pancreatitis, psoas abscess).
  • Obturator sign: pain with passive internal rotation of flexed thigh. On right, also sign of appendicitis.
  • Rovsing sign: indirect rebound testing – pressure applied in LLQ produces rebound pain in the RLQ when the examiner releases pressure.
    • Psoas, obturator, and Rovsing signs have low sensitivity (15-35%) but are highly specific (85-95%) for appendicitis. 
  • Rectal exam: rarely necessary; could consider in certain cases of lower abdominal pain but is unlikely to change the need for imaging.

Workup:

• Labs: CBC, CMP, lipase, VBG+lactate for most patients.
• Imaging: consider CXR/KUB (evaluate for free air), however CT A/P with contrast (difficult to see abdominal organs without contrast) or ultrasound (RUQ vs. renal vs. transvaginal US depending on suspected etiology) are likely higher yield. CT best for undifferentiated abdominal pain.

Management

Depends on Etiology – see related sections.

Key Points

• Differential for abdominal pain is broad. Use historical data and knowledge of anatomy to guide diagnostic evaluation.

Brown HF, Kelso L. Abdominal Pain: An Approach to a Challenging Diagnosis. AACN Advanced Critical Care. Jul-Sep 2014 Volume 25 (3), 266-278.

McNamara R, Dean AJ. Approach to acute abdominal pain. Emerg Med Clin North Am 2011. May; 29 (2):159-73.

McNamara RM, Yeh EL. Abdominal Pain. Clin Geriatr Med. 2007 May; 23(2):255-70.

Woo, SY et al. Clinical Outcome of Fitz-Hugh-Curtis syndrome mimicking acute biliary disease. World J Gastroenterol. 2008 Dec 7; 14(45):6975-6980.