What is the initial approach to a patient presenting with low abdominal pain?

Initial Approach to Low Abdominal Pain

For patients presenting with low abdominal pain, begin with vital sign assessment focusing on tachycardia (the most sensitive early warning sign of surgical complications), followed by location-specific imaging: ultrasound for right lower quadrant pain in most patients, and CT abdomen/pelvis with contrast for left lower quadrant, pelvic, or non-specific presentations. 1

Immediate Clinical Assessment

Vital Signs and Red Flags

• Tachycardia is your most critical early warning sign—it predicts surgical complications including anastomotic leak, perforation, or sepsis even before other symptoms develop 1
• The combination of fever, tachycardia, and tachypnea together predicts serious complications requiring urgent intervention 1
• Hypotension or hemodynamic instability suggests bleeding or sepsis and requires immediate resuscitation 1
• Fever with abdominal pain indicates infection or abscess formation 1

Physical Examination Priorities

• Assess for peritonitis: rigid abdomen, rebound tenderness, or guarding indicate perforation or ischemia requiring urgent surgical consultation 1, 2
• Pain out of proportion to physical findings strongly suggests mesenteric ischemia, though classic peritoneal signs are often absent in early ischemia 1
• Abdominal distension with vomiting suggests bowel obstruction 1
• Asymmetric gaseous distention with emptiness of the left iliac fossa is pathognomonic for sigmoid volvulus 1

Critical History Elements

• Pain location guides your entire diagnostic approach: right lower quadrant suggests appendicitis, left lower quadrant suggests diverticulitis, diffuse pain suggests obstruction or gastroenteritis 1, 3
• Document last bowel movement and passage of gas—this has 85% sensitivity and 78% specificity for adhesive small bowel obstruction in patients with prior abdominal surgery 1
• Prior laparotomy makes adhesive obstruction the leading diagnosis, accounting for 55-75% of small bowel obstructions 1
• Colicky pain indicates bowel obstruction as the bowel attempts to overcome occlusion 1

Mandatory Laboratory Testing

Initial Laboratory Panel

• Complete blood count to evaluate for leukocytosis suggesting infection or inflammation 1, 4
• Beta-hCG test is mandatory in all women of childbearing age before any imaging to rule out ectopic pregnancy 1, 4
• C-reactive protein has superior sensitivity and specificity compared to white blood cell count for ruling in surgical disease 1
• Comprehensive metabolic panel including liver function tests 4
• Urinalysis to evaluate for urinary tract infection or nephrolithiasis 4

Additional Tests Based on Clinical Suspicion

• Elevated lactate suggests ischemia or sepsis, though normal levels do not exclude internal herniation or early ischemia 1
• Procalcitonin is helpful for assessing inflammatory response in suspected sepsis 1
• Serum lipase for epigastric pain suggesting pancreatitis 4

Location-Specific Imaging Strategy

Right Lower Quadrant Pain

• Abdominal ultrasound is the most appropriate initial imaging method for acute right lower quadrant pain, avoiding radiation exposure 1, 3
• If ultrasound is inconclusive and clinical suspicion remains high, proceed to CT abdomen/pelvis with IV contrast, which has sensitivity >95% for appendicitis 2

Left Lower Quadrant Pain

• CT abdomen and pelvis with contrast is recommended, especially for suspected diverticulitis 1, 3

Pelvic or Non-Specific Low Abdominal Pain

• CT abdomen and pelvis with IV contrast is the optimal choice, especially if there is fever or suspicion of serious illness 1, 3
• CT frequently identifies the cause requiring hospitalization and invasive treatment 5

Common Differential Diagnoses for Low Abdominal Pain

Surgical Emergencies Requiring Immediate Consultation

• Acute appendicitis: frequency of 15.9-28.1% of cases requiring surgery 1
• Bowel obstruction: accounts for 15% of acute abdominal pain admissions, with small bowel obstruction most commonly caused by adhesions, hernias, and neoplasms 1
• Sigmoid volvulus: classic triad of abdominal pain, constipation, and vomiting, especially with previous episodes of distention 1
• Ectopic pregnancy: must be excluded in all women of reproductive age 1, 4
• Ovarian torsion or pelvic inflammatory disease in women 1

Non-Surgical Causes

• Diverticulitis (left lower quadrant) 1
• Gastroenteritis 1
• Constipation 1
• Inflammatory bowel disease 5
• Urinary tract infection or nephrolithiasis 4

Critical Pitfalls to Avoid

• Never assume normal lactate excludes bowel ischemia—internal herniation and early ischemia can present with normal lactate levels 1
• Classic peritoneal signs are often absent in patients with chronic distension (such as sigmoid volvulus) despite established ischemia 1
• Failing to obtain pregnancy testing in women of reproductive age before imaging can lead to delayed diagnosis of ectopic pregnancy 4
• Elderly patients have higher likelihood of malignancy, diverticulitis, and vascular causes, and may present with atypical symptoms requiring more thorough evaluation even with normal laboratory tests 1
• Post-bariatric surgery patients often present with atypical symptoms, and tachycardia is the most critical warning sign for internal herniation 1

Disposition Decisions

Immediate Surgical Consultation Required

• Hemodynamic instability 2
• Peritoneal signs (rigid abdomen, rebound tenderness, guarding) 1, 2
• Suspected perforation, volvulus, or bowel ischemia 2

Hospital Admission Indicated

• Severe pain with inability to tolerate oral intake 2
• Suspected surgical conditions requiring observation 2
• Unclear diagnosis with concerning features 2

Outpatient Management Appropriate

• Mild gastroenteritis, constipation, or nonspecific abdominal pain with reassuring examination and normal vital signs 2