Abdominal pain is a common complaint with a vast differential diagnosis, ranging from benign, self-limiting conditions to life-threatening surgical emergencies. For healthcare professionals, especially those in emergency medicine, surgery, and general practice, a systematic approach to abdominal pain is crucial for timely and accurate diagnosis. This guide provides a comprehensive overview of the Abdominal Pain Differential Diagnosis, categorized by anatomical location to aid in efficient clinical reasoning.
Understanding Acute Abdomen and Generalized Abdominal Pain
The term “acute abdomen” classically refers to the sudden onset of abdominal pain with tenderness and rigidity, often indicating a surgical emergency. However, abdominal pain can manifest in various ways and may not always present with these classic signs initially. When evaluating generalized abdominal pain, it is vital to consider conditions affecting the entire abdomen, as well as those that may initially present diffusely before localizing.
Causes of Generalized Abdominal Pain with Tenderness and Rigidity:
This presentation often signifies serious intra-abdominal pathology requiring urgent surgical intervention.
- Perforated Peptic Ulcer: Gastric or duodenal ulcer perforation leads to the release of gastric contents into the peritoneal cavity, causing severe peritonitis.
- Perforation of Other Intra-abdominal Organs: Rupture of the appendix, colon, gallbladder, or any other hollow viscus can result in widespread contamination and peritonitis.
- AAA Rupture (Abdominal Aortic Aneurysm Rupture): A ruptured AAA is a catastrophic event characterized by sudden, severe abdominal and back pain, often with hemodynamic instability.
- Aortic Dissection: While typically presenting with chest pain, aortic dissection can sometimes manifest with abdominal pain as it extends into the abdominal aorta.
- Pancreatitis: Severe acute pancreatitis can cause generalized abdominal pain due to inflammation extending beyond the pancreas itself.
- Ectopic Pregnancy Rupture: Ruptured ectopic pregnancy is a gynecological emergency causing severe abdominal pain and internal bleeding in women of reproductive age.
- Ischemic Gut (Mesenteric Ischemia): Reduced blood flow to the intestines can lead to severe, diffuse abdominal pain, often described as pain out of proportion to physical findings in the early stages.
Central or Peri-umbilical Pain without Abdominal Signs
Pain localized around the umbilicus can be challenging to diagnose initially, as it may represent early stages of various conditions before they become more localized or exhibit classic abdominal signs.
Differential Diagnosis for Central/Peri-umbilical Pain:
- Acute Small Bowel Ischemia: Early mesenteric ischemia can present with central abdominal pain before developing peritonitis.
- Acute Appendicitis (Early): Appendicitis often begins as vague peri-umbilical pain before migrating to the right iliac fossa.
- Acute Small Bowel Obstruction: Obstruction of the small intestine can cause crampy, peri-umbilical pain due to distention and increased peristalsis.
- Acute Pancreatitis (Early): Pain from pancreatitis may initially be felt in the upper abdomen or centrally before becoming more epigastric.
- Testicular Torsion: Pain from testicular torsion can radiate to the abdomen, especially in younger males.
- Medical Causes of Abdominal Pain: Various systemic conditions, such as gastroenteritis, diabetic ketoacidosis, and porphyria, can present with diffuse or central abdominal pain.
Epigastric Pain: Causes and Considerations
Epigastric pain, located in the upper central abdomen, is frequently associated with gastrointestinal conditions but can also originate from nearby organs.
Common Causes of Epigastric Pain:
Gastrointestinal Etiologies:
- Gastritis: Inflammation of the stomach lining, often caused by infection (H. pylori), NSAIDs, or alcohol.
- Peptic Ulcer Disease (Gastric or Duodenal Ulcers): Ulceration of the stomach or duodenum lining, typically caused by H. pylori or NSAIDs.
- Reflux Esophagitis (GERD): Acid reflux into the esophagus causing heartburn and epigastric discomfort.
- Pancreatitis: Inflammation of the pancreas, often due to gallstones or alcohol abuse.
- Gastric or Pancreatic Cancer: Malignancies of the stomach or pancreas can present with persistent epigastric pain.
- Boerhaave Syndrome (Esophageal Rupture): Spontaneous esophageal rupture, often associated with forceful vomiting, a surgical emergency.
- Dyspepsia (Indigestion): General term for upper abdominal discomfort, often functional but requires exclusion of organic causes.
- Irritable Bowel Syndrome (IBS): Functional bowel disorder that can sometimes manifest with upper abdominal pain, although more commonly associated with lower abdominal discomfort.
Pain from Nearby Areas Mimicking Epigastric Pain:
- Cardiac Causes: Myocardial infarction (especially inferior MI), pericarditis, and pleuritis can sometimes radiate pain to the epigastrium.
- Pulmonary Causes: Pneumonia (especially lower lobe), and pleurisy can refer pain to the upper abdomen.
Right Hypochondrium/Upper Quadrant (RUQ) Pain
RUQ pain is highly suggestive of hepatobiliary pathology but also includes other gastrointestinal, pulmonary, and renal conditions in the differential.
Differential Diagnosis of Right Upper Quadrant Pain:
Gallbladder and Biliary Tract:
- Biliary Colic: Pain caused by gallstones temporarily obstructing the bile duct, typically intermittent and postprandial.
- Cholecystitis: Inflammation of the gallbladder, usually due to gallstone obstruction of the cystic duct, causing constant RUQ pain, fever, and Murphy’s sign.
- Cholangitis: Infection of the bile ducts, often due to gallstone obstruction, a serious condition characterized by Charcot’s triad (RUQ pain, fever, jaundice).
Liver Pathology:
- Hepatitis: Inflammation of the liver, viral or alcoholic, causing RUQ pain and jaundice.
- Hepatomegaly (Liver Congestion): Liver enlargement due to conditions like right heart failure can cause RUQ discomfort.
- Hemorrhage into Hepatic Tumor: Bleeding within a liver tumor can cause acute RUQ pain.
- Liver Trauma: Injury to the liver from blunt or penetrating trauma.
- Hepatic or Subdiaphragmatic Abscess: Collections of pus in or around the liver.
- Fitz-Hugh-Curtis Syndrome (Peri-hepatitis): Inflammation of the liver capsule associated with Pelvic Inflammatory Disease (PID).
- Pre-eclampsia and HELLP Syndrome: Pregnancy-related conditions causing RUQ pain due to liver involvement.
Other Gastrointestinal Causes:
- Appendicitis with High Appendix: In pregnancy or individuals with anatomical variations, the appendix can be located in the RUQ.
- Perforated or Penetrating Duodenal Ulcer: Can sometimes present with RUQ pain.
- Colon Cancer (Hepatic Flexure): Cancer in the right side of the colon can cause RUQ discomfort.
Pain from Nearby Areas:
- Right Lower Lobe Pneumonia, Pleurisy, or Other Lung Disease: Can refer pain to the RUQ.
- Subphrenic Abscess: Abscess below the diaphragm.
- Acute Pyelonephritis (Right Kidney): Kidney infection can cause flank pain radiating to the RUQ.
Left Hypochondrium/Upper Quadrant (LUQ) Pain
LUQ pain, while less common than RUQ pain, still encompasses a range of serious conditions, particularly splenic and gastric issues.
Causes of Left Upper Quadrant Pain:
- Pancreatitis (Tail of Pancreas): Inflammation of the pancreatic tail can cause LUQ pain.
- Subphrenic Abscess (Left): Abscess below the left diaphragm.
- Diverticulitis (Splenic Flexure of Colon): Inflammation of diverticula in the left colon.
- Ruptured Spleen: Splenic rupture due to trauma or underlying hematologic conditions, a surgical emergency.
- Acute Pyelonephritis (Left Kidney): Kidney infection can cause flank pain radiating to the LUQ.
- Leaking Aneurysm of the Splenic Artery: Rare but life-threatening cause of LUQ pain.
- Acute Gastric Distention: Severe stomach bloating can cause LUQ pain.
Right Iliac Fossa (RIF) Pain
RIF pain, commonly known as right lower quadrant pain, is classically associated with appendicitis, but the differential is broad, including gastrointestinal, gynecological, urological, and musculoskeletal causes.
Right Lower Quadrant Pain Differential Diagnosis:
Gastrointestinal Causes:
- Appendicitis: Inflammation of the appendix, the most common surgical emergency causing RIF pain.
- Crohn’s Disease: Inflammatory bowel disease that can affect the ileum and cecum, causing RIF pain.
- Inflamed Meckel Diverticulum: A congenital pouch in the small intestine that can become inflamed, mimicking appendicitis.
- Cholecystitis with Low Gallbladder: Rarely, a gallbladder located lower than usual can cause RIF pain.
- Mesenteric Adenitis: Inflammation of mesenteric lymph nodes, often viral, mimicking appendicitis, especially in children.
- Epiploic Appendagitis: Inflammation of small, fat-filled sacs attached to the colon, causing localized RIF pain.
- Colon Cancer (Cecum or Ascending Colon): Cancer in the right colon.
- Constipation: Fecal impaction can cause abdominal discomfort in various locations, including the RIF.
- Irritable Bowel Syndrome (IBS): Can manifest with lower abdominal pain.
Reproductive (Female) Causes:
- Ectopic Pregnancy (Right Fallopian Tube): Pregnancy outside the uterus in the fallopian tube, causing RIF pain and potentially rupture.
- Acute Ovarian Event (Cyst Rupture, Hemorrhage, Torsion): Ovarian cysts can rupture, bleed, or undergo torsion, causing acute RIF pain.
- Mittelschmerz (Ovulation Pain): Mid-cycle ovulation pain, usually mild and self-limiting.
- Pelvic Inflammatory Disease (PID): Infection of the female reproductive organs, causing lower abdominal pain.
- Endometriosis: Condition where uterine tissue grows outside the uterus, causing chronic pelvic pain that can exacerbate acutely.
Reproductive (Male) Causes:
- Seminal Vesiculitis: Inflammation of the seminal vesicles.
- Undescended Testicle Pathology: Problems with an undescended testicle can cause RIF pain.
Urinary Causes:
- Renal Colic (Right Ureteric Stone): Kidney stones passing down the ureter, causing severe, colicky flank pain radiating to the groin and RIF.
- Urinary Tract Infection (UTI): While typically causing suprapubic pain, UTI can sometimes present with RIF discomfort.
Pain from Nearby Areas:
- Hip Pathology: Hip joint problems can sometimes refer pain to the RIF.
- Psoas Abscess: Abscess in the psoas muscle, which can irritate the RIF region.
- Rectus Sheath Hematoma: Bleeding within the rectus abdominis muscle.
- Right Lower Lobe Pneumonia: Can refer pain to the RIF.
Left Iliac Fossa (LIF) Pain
LIF pain, or left lower quadrant pain, is commonly associated with diverticulitis but shares a similar broad differential with RIF pain, considering gastrointestinal, gynecological, and urological conditions.
Left Lower Quadrant Pain Differential Diagnosis:
Gastrointestinal Causes:
- Diverticulitis: Inflammation of diverticula in the colon, most commonly in the sigmoid colon (LIF), often presenting with LIF pain, fever, and altered bowel habits.
- Colitis (Inflammatory or Infectious): Inflammation of the colon.
- Colon Cancer (Descending or Sigmoid Colon): Cancer in the left side of the colon.
- Constipation: Fecal impaction.
- Irritable Bowel Syndrome (IBS): Lower abdominal pain.
Reproductive (Female) Causes:
- Ectopic Pregnancy (Left Fallopian Tube):
- Acute Ovarian Event (Cyst Rupture, Hemorrhage, Torsion):
- Mittelschmerz (Ovulation Pain):
- Pelvic Inflammatory Disease (PID):
- Endometriosis:
Reproductive (Male) Causes:
- Seminal Vesiculitis:
- Undescended Testicle Pathology:
Urinary Causes:
- Renal Colic (Left Ureteric Stone):
- Urinary Tract Infection (UTI):
Pain from Nearby Areas:
- Hip Pathology:
- Psoas Abscess:
- Rectus Sheath Hematoma:
- Left Lower Lobe Pneumonia:
Suprapubic Pain
Suprapubic pain, located in the lower central abdomen above the pubic bone, is often associated with urinary and gynecological conditions.
Causes of Suprapubic Pain:
- Urinary Retention: Inability to empty the bladder, causing bladder distention and pain.
- Cystitis (Bladder Infection): Inflammation of the bladder, often with urinary frequency, urgency, and dysuria.
- Uterine Origin (PID, Fibroids, Menstruation): Conditions affecting the uterus, including PID, uterine fibroids, and menstrual cramps.
- Referred Pain from RIF or LIF Causes: Pain from conditions in the right or left lower quadrants can sometimes be felt in the suprapubic region.
Loin Pain (Flank Pain)
Loin pain refers to pain in the flank area, between the ribs and the hip, and is most commonly associated with renal pathology.
Differential Diagnosis of Loin Pain:
Renal Tract:
- Pyelonephritis (Kidney Infection): Infection of the kidney, causing flank pain, fever, and urinary symptoms.
- Renal Colic (Kidney Stones): Kidney stones obstructing the ureter, causing severe, colicky flank pain.
- Renal Carcinoma: Kidney cancer, which can sometimes present with flank pain.
- Renal Vein Thrombosis: Blood clot in the renal vein, causing flank pain and potentially kidney dysfunction.
- Polycystic Kidney Disease: Genetic disorder causing cysts in the kidneys, which can cause flank pain.
- Adrenal Hemorrhage: Bleeding into the adrenal gland, causing flank pain.
Other Causes:
- Retroperitoneal Hemorrhage: Bleeding in the retroperitoneal space.
- Retroperitoneal Infection: Infection in the retroperitoneal space.
- Vertebral Pathology: Spinal problems can sometimes refer pain to the flank.
Groin Pain
Groin pain, located in the area between the abdomen and the thigh, can be due to various conditions, including urological, musculoskeletal, and vascular etiologies.
Causes of Groin Pain:
- Renal Calculi (Ureteric Stones): Pain from kidney stones often radiates to the groin.
- Scrotal Pain (Testicular Torsion, Epididymo-orchitis, Trauma): Conditions affecting the testicles and scrotum can cause groin pain.
- Inguinal Hernia: Protrusion of abdominal contents through the inguinal canal, causing groin pain and a bulge.
- Hip Pathology: Hip joint problems can refer pain to the groin.
- Pelvic Fracture: Fracture of the pelvic bones.
This guide provides a broad overview of the abdominal pain differential diagnosis. Clinical evaluation should always include a thorough history, physical examination, and appropriate investigations to reach an accurate diagnosis and guide management. Remember to always consider the patient’s age, sex, medical history, and associated symptoms when evaluating abdominal pain.
