Abdominal Pain Diagnosis

Differential Diagnosis by Location

• The American Academy of Family Physicians recommends considering gastrointestinal, gynecologic, urologic, vascular, and musculoskeletal etiologies for abdominal pain, based on anatomic quadrant and associated clinical features 1, 2
• Acute cholecystitis is a primary diagnostic consideration for right upper quadrant pain 2
• The American Academy of Family Physicians suggests hepatobiliary pathology, including choledocholithiasis and cholangitis, as potential causes of right upper quadrant pain 3
• Appendicitis is the most critical diagnosis to exclude in right lower quadrant pain 2, 4
• Ectopic pregnancy should be considered in women of reproductive age with right lower quadrant pain 2, 3, 4
• Diverticulitis is a leading consideration in older adults with left lower quadrant pain 2, 5
• The World Journal of Emergency Surgery recommends considering sigmoid volvulus, especially with a history of chronic constipation, for left lower quadrant pain 5
• Peptic ulcer disease or gastritis may cause epigastric or diffuse pain 4
• Acute pancreatitis is a potential cause of epigastric or diffuse pain 2, 3

Differential Diagnosis by Mechanism

• Adhesions account for 55-75% of small bowel obstructions, according to the World Journal of Emergency Surgery 5
• Hernias cause 15-25% of small bowel obstructions, as reported by the World Journal of Emergency Surgery 5
• Colorectal cancer causes 60% of large bowel obstructions, according to the World Journal of Emergency Surgery 5
• Volvulus causes 15-20% of large bowel obstructions, as reported by the World Journal of Emergency Surgery 5
• Appendicitis, cholecystitis, diverticulitis, pancreatitis, and pelvic inflammatory disease are potential inflammatory or infectious causes of abdominal pain 2
• Mesenteric ischemia, which can be arterial or venous thrombosis, is a vascular cause of abdominal pain 2, 4

Critical Red Flags

• Hemodynamic instability, such as tachycardia or hypotension, suggests bleeding or sepsis, according to Praxis Medical Insights 4
• Peritoneal signs, including a rigid abdomen or rebound tenderness, indicate perforation or ischemia, as reported by the World Journal of Emergency Surgery and Praxis Medical Insights 4, 5
• Pain out of proportion to physical findings strongly suggests mesenteric ischemia, according to Praxis Medical Insights 4
• Abdominal distension with vomiting indicates bowel obstruction, as reported by Praxis Medical Insights 4
• Fever with severe pain suggests infection, abscess, or perforation, according to Praxis Medical Insights 4

Common Pitfalls to Avoid

• Failing to obtain β-hCG testing in all women of reproductive age before imaging can delay diagnosis of ectopic pregnancy, as reported by the American Academy of Family Physicians and Praxis Medical Insights 2, 3, 6
• Overlooking hernia orifices and surgical scars during examination can miss incarcerated hernias, according to the World Journal of Emergency Surgery 5
• Dismissing atypical presentations in elderly patients can lead to missed diagnoses, as reported by Praxis Medical Insights 4
• Over-relying on normal laboratory values early in disease can lead to missed diagnoses, according to Praxis Medical Insights 6

Abdominal Pain Diagnosis

Approach by Location and Mechanism

• Non-appendiceal gastrointestinal, genitourinary, and gynecologic conditions remain equally possible in patients with right lower quadrant pain, according to the American College of Radiology 7
• Colitis and inflammatory bowel disease should be considered in the differential diagnosis of abdominal pain, as stated by the American College of Radiology 7
• Benign adnexal mass and pelvic congestion syndrome are potential causes of abdominal pain in women of reproductive age, as noted by the American College of Radiology 7

Diagnostic Approach to Abdominal Pain

Introduction to Diagnostic Considerations

• Pneumonie can cause referred abdominal pain 8
• The American College of Radiology recommends considering extra-abdominal causes of abdominal pain, such as pneumonia, in the diagnostic approach 8

Imaging Diagnostic Approach

• For non-localized or diffuse abdominal pain, computed tomography (CT) of the abdomen and pelvis with intravenous contrast is the imaging modality of choice, as it changes the primary diagnosis in 51% of cases and alters the admission decision in 25% of cases 8, 9
• For right upper quadrant pain, ultrasound is the initial imaging modality of choice for evaluating acute cholecystitis and hepatobiliary pathologies 9
• For right lower quadrant pain, CT of the abdomen and pelvis with contrast is the initial imaging modality of choice for suspected appendicitis 9

Considerations for Specific Populations

• In elderly patients, atypical presentations are common, requiring a more thorough evaluation even if laboratory tests are normal, with a higher likelihood of malignancy, diverticulitis, and vascular causes 8
• The American Academy of Family Physicians recommends considering the higher probability of malignancy, diverticulitis, and vascular causes in elderly patients with abdominal pain 9

Diagnostic Approach to Transaminitis with Epigastric Subacute Pain and Normal CT

Imaging Limitations

• CT has a relatively low negative predictive value (64%) for upper abdominal pathology, with commonly missed diseases including pancreaticobiliary inflammatory processes, gastritis, and duodenitis 10

Diagnostic Approach to Lower Abdominal Pain

Initial Imaging Evaluation

• The American College of Radiology recommends CT abdomen and pelvis with IV contrast as the initial imaging modality of choice for most patients presenting with lower abdominal pain, with 95% sensitivity and 94% specificity for appendicitis, and identifies alternative diagnoses in 94% of cases, changing management decisions in 25% of patients 11, 12
• CT abdomen and pelvis with IV contrast has 98% diagnostic accuracy for diverticulitis and superior ability to detect complications such as abscess, perforation, fistula, and obstruction 13, 14

Imaging Strategy by Pain Location

• For right lower quadrant pain, CT abdomen and pelvis with IV contrast is the initial imaging of choice, with 95% sensitivity and 94% specificity for appendicitis, and identifies non-appendiceal diagnoses in 94% of cases 11
• For left lower quadrant pain, CT abdomen and pelvis with IV contrast has 98% diagnostic accuracy for diverticulitis, and is recommended for detecting complications and guiding treatment 13, 14
• For nonlocalized or diffuse abdominal pain, CT abdomen and pelvis with IV contrast is the preferred imaging option, changing the primary diagnosis in 51% of cases and altering admission decisions in 25% of patients 12

Special Population Considerations

• In elderly patients, atypical presentations are common, and a more extensive evaluation is warranted despite normal initial findings, with a higher likelihood of malignancy, diverticulitis, and vascular causes such as mesenteric ischemia 12
• In women of reproductive age, transvaginal ultrasound is the first-line imaging modality when gynecologic pathology is suspected, and mandatory β-hCG testing is recommended before imaging 13, 14, 15
• In immunocompromised patients, typical signs of abdominal sepsis may be masked, and a more extensive workup is necessary to avoid delayed diagnosis and high mortality rate 12

Radiologic Differentials and Critical Outcomes for Adult Abdominal Pain

Anatomic‑Specific Differentials

• Hepatitis or hepatic abscess should be considered in adults presenting with right‑upper‑quadrant abdominal pain. 16
• Nephrolithiasis (renal colic) can manifest as right‑lower‑quadrant pain in adult patients. 16
• Perforated viscus is a potential cause of epigastric or diffuse abdominal pain in adults. 16

Infectious/Inflammatory Causes Across All Locations

• Intra‑abdominal abscesses—including hepatic, splenic, diverticular, and appendiceal collections—are important infectious etiologies of abdominal pain regardless of location. 16

Special Population Considerations

• In immunocompromised adults, delayed diagnosis of abdominal pathology is associated with a high mortality risk. 16

Imaging Recommendations for Acute Left Upper Quadrant Pain

Primary Imaging Modality

• The American College of Radiology recommends contrast‑enhanced CT of the abdomen and pelvis as the first‑line imaging study for patients with acute left upper quadrant pain when serious pathology is suspected. This recommendation is based on expert consensus and imaging guideline statements. 17

Diagnostic Impact of CT

• Multidetector CT redefines the primary diagnosis in 49–51 % of patients presenting with abdominal pain and modifies clinical management in approximately 42 % of cases, highlighting its high diagnostic yield. Evidence derives from observational cohort studies. [17][18]

CT Utility for Specific Pathologies

• Contrast‑enhanced CT is essential for identifying splenic lesions (infarction, rupture, abscess), pancreatic tail disease, and vascular abnormalities that can present as left upper quadrant pain. This utility is supported by guideline‑based imaging criteria. 17

Limited Role of Conventional Radiography

• Plain radiography offers limited diagnostic value for left upper quadrant pain and is not recommended for routine evaluation, as supported by practice recommendations emphasizing more sensitive modalities. Evidence is based on comparative imaging studies. 18