RUQ pain
  1. Cholecystitis, choledocholithiasis,
  2. or cholangitis
  3. Hepatitis or hepatic
  4. abscess or tumor (eg, hepatoma)
  5. Pancreatitis
  6. Gastritis
  7. Intestinal obstruction
  8. Budd-Chiari syndrome
  9. Fitzhugh-Curtis syndrome
  10. Appendicitis (retrocecal)
  11. Perforated peptic ulcer

Extra-Abdominal:
  1. Right lower lobe pneumonia
  2. Empyema
  3. Pleuritis
  4. MI
  5. PE
  6. Rib fracture
  7. Herpes zoster
LUQ pain
  1. Gastritis
  2. Pancreatitis
  3. Splenic rupture
  4. infarction
  5. Splenomegaly
  6. Ruptured splenic artery aneurysm
  7. Perforated peptic ulcer
  8. Jejunal diverticulitis
  9. Diverticulitis (splenic flexure)

Extra-Abdominal:
  1. Left lower lobe pneumonia
  2. Pericarditis
  3. Pleuritis
  4. PE
  5. Empyema
  6. MI
  7. Herpes zoster
  8. Rib fracture
RLQ pain
  1. Appendicitis
  2. Crohn's ileitis
  3. Right sided diverticulitis
  4. Cecal diverticulitis
  5. Meckel's diverticulitis
  6. Mesentric adenitis
  7. Torsion of appendix epiploica
  8. Intestinal obstruction
  9. Perforated peptic ulcer
  10. Cholecystitis
  11. Rectus sheath hematoma
  12. Psoas abscess
  13. Herpes zoster
GU:
  1. Renal or ureteral calculi
  2. Pylonephritis

Gyn:
  1. Ovarian torsion
  2. Endometriosis
  3. Ectopic pregnancy
  4. Ruptured ovarian cyst (Mittelschmerz)
  5. PID
Vascular:
  1. Ruptured iliac artery aneurysm
LLQ pain
  1. Diverticulitis
  2. Appendicitis
  3. Perforated colon cancer
  4. Intestinal obstruction
  5. Inflammatory bowel disease (IBD)
  6. Ischemic colitis
  7. Psoas abscess
  8. Rectus sheath hematoma
  9. Herpez zoster

GU:
  1. Renal or ureteral calculi
  2. Pyelonephritis

Gyn:
  1. Ectopic pregnancy
  2. Ruptured ovarian cyst (Mittelschmerz)
  3. Ovarian torsion
  4. Endometriosis
  5. PID

Vascular:
  1. Ruptured iliac artery aneurysm

Diffuse Abdominal Pain
  1. Early appendicitis
  2. Perforated peptic ulcer
  3. Perforated diverticulitis
  4. Peritonitis
  5. Pancreatitis
  6. Mesenteric ischemia
  7. Ruptured AAA
  8. Stercoral perforation of colon

Nonsurgical causes:
  1. DKA
  2. Acute porphria
  3. Food poisoning
  4. Acute Leukemia
  5. Sickle cell crisis
  6. Heavy metal poisoning
  7. Gastroenteritis

Epigastric Pain
  1. Peptic ulcer
  2. Pancreatitis
  3. Gastritis
  4. Esophagitis
  5. Mesenteric ischemia
  6. Appendicitis
  7. Myocardial ischemia
  8. Pericarditis
  9. Cholecystitis
  10. IBD
  11. Intestinal obstruction
Periumbilical Pain
  1. Small intestinal obstruction or IBD
  2. Early appendicitis
  3. Pancreatitis
  4. Hernia
  5. Aneurysm

Hypogastric Pain
  1. Intestinal obstruction or IBD
  2. Intussusception
  3. Appendicitis
  4. Diverticulitis
  5. Enterocolitis
  6. Ovarian torsion
  7. Testicular torsion
  8. Degeneration or torsion of uterine fibroid
  9. Cystitis
  10. Endometriosis
  11. PID