What is the differential diagnosis and initial management for a 55-year-old female presenting with abdominal pain?

Differential Diagnosis for Abdominal Pain in a 55-Year-Old Female

In a 55-year-old woman presenting with abdominal pain, the most critical initial step is to rule out life-threatening conditions including bowel obstruction, mesenteric ischemia, perforated viscus, and malignancy, while systematically evaluating for the most common causes: diverticulitis, cholecystitis, bowel obstruction from adhesions, and gynecologic emergencies.

Immediate Assessment Priorities

Vital Signs and Red Flags

• Assess hemodynamic stability immediately: Check for tachycardia, hypotension, fever, or signs of shock, which indicate potential bowel ischemia, perforation, or sepsis requiring emergency intervention 1, 2
• Look for peritoneal signs: Guarding, rebound tenderness, and rigidity suggest perforation or ischemia and mandate urgent surgical consultation 1
• Evaluate for obstruction: Abdominal distension has a positive likelihood ratio of 16.8 for bowel obstruction; assess for colicky pain, vomiting, and absence of flatus 1

Critical History Elements

• Previous abdominal surgery: 85% sensitivity for adhesive small bowel obstruction, which accounts for 55-75% of small bowel obstructions 1
• Weight loss and rectal bleeding: Highly suggestive of colorectal cancer, which causes 60% of large bowel obstructions in this age group 1
• Diverticulitis history or chronic constipation: Suggests diverticular stenosis or volvulus 1
• Gynecologic symptoms: Despite age, consider ovarian pathology and ensure pregnancy is excluded 1, 2

Differential Diagnosis by Location and Characteristics

Right Upper Quadrant Pain

• Acute cholecystitis (most common)
• Hepatobiliary disease
• Pancreatitis
• Peptic ulcer disease 1, 2

Right Lower Quadrant Pain

• Appendicitis (5-10% of small bowel obstructions from malignancy in this age group)
• Diverticulitis (can occur in right colon)
• Ovarian pathology
• Inflammatory bowel disease 1

Left Lower Quadrant Pain

• Diverticulitis (accounts for 10% of large bowel obstructions)
• Colorectal cancer
• Ovarian torsion or cyst
• Urolithiasis 1

Diffuse/Nonlocalized Pain

• Small bowel obstruction from adhesions (most common if prior surgery)
• Large bowel obstruction from cancer (60% of cases)
• Volvulus (15-20% of large bowel obstructions)
• Mesenteric ischemia
• Peritonitis from perforation
• Carcinomatosis 1

Essential Laboratory Investigations

Order these tests systematically to narrow the differential:

• Complete blood count: Leukocytosis >14,000 suggests infection, ischemia, or inflammation; marked elevation indicates potential bowel ischemia 1, 2
• Metabolic panel: Low bicarbonate, elevated lactate, and elevated pH indicate intestinal ischemia 1, 2
• Liver function tests and lipase: Essential for hepatobiliary and pancreatic pathology 2, 3
• C-reactive protein: Marker of inflammation 2, 3
• Pregnancy test: Mandatory in all women of reproductive age before imaging, even at age 55 if any possibility of pregnancy 1, 2
• Urinalysis: To evaluate urologic causes 3

Imaging Algorithm Based on Clinical Presentation

Right Upper Quadrant Pain

Ultrasonography is the initial imaging of choice with 81% sensitivity and 83% specificity for cholecystitis 1, 2

Right or Left Lower Quadrant Pain

CT abdomen and pelvis with IV contrast is the preferred initial study with >95% sensitivity for appendicitis and high accuracy for diverticulitis 1, 2, 3

Diffuse or Nonlocalized Abdominal Pain

CT abdomen and pelvis with IV contrast is the imaging modality of choice, changing diagnosis in 49% of cases and management in 42% of patients 1, 2

Suspected Bowel Obstruction

CT with IV contrast is preferred; plain radiographs have only 49% sensitivity and should not be relied upon 1

Suspected Mesenteric Ischemia

CT angiography with IV contrast is essential; reduced bowel wall enhancement is 100% specific for segmental infarction 1

Age-Specific Considerations for 55-Year-Old Women

Cancer Screening Thresholds

• Urgent CT abdomen recommended for patients ≥60 years with abdominal pain and weight loss to exclude pancreatic cancer 1
• Urgent endoscopy warranted for patients ≥55 years with weight loss, or >40 years with family history of gastro-esophageal cancer 1
• Non-urgent endoscopy for patients ≥55 years with treatment-resistant symptoms or elevated platelet count 1

Gynecologic Considerations

• Despite perimenopausal age, ovarian torsion and pelvic inflammatory disease remain in the differential 1
• Pelvic ultrasound (transabdominal and transvaginal) should be considered if gynecologic etiology suspected 1

Initial Management Approach

Hemodynamically Unstable Patients

• Immediate IV crystalloid resuscitation 1, 2
• Emergency surgical consultation for peritonitis, perforation, or septic shock 1, 2
• NPO status, nasogastric decompression if obstruction suspected 1

Stable Patients

• Supportive care: IV fluids, antiemetics, bowel rest 1
• Antibiotics only if infection suspected: Not routine for all abdominal pain 2
• Percutaneous drainage for abscesses >3cm with antimicrobial therapy 2
• Small abscesses (<3cm) may respond to IV antibiotics alone 2

Critical Pitfalls to Avoid

• Do not rely on normal laboratory values in elderly patients: Many serious infections present with normal white blood cell counts in this age group 1, 2
• Do not delay imaging based on clinical impression alone: CT changes diagnosis in approximately 50% of cases with nonspecific pain 1
• Do not overlook malignancy: At age 55, colorectal cancer causes 60% of large bowel obstructions and requires high index of suspicion with weight loss or bleeding 1
• Do not forget pregnancy testing: Even in perimenopausal women, ectopic pregnancy can be catastrophic if missed 1
• Do not use plain radiographs as definitive imaging: They have limited sensitivity and should not replace CT when clinical suspicion is high 1
• Do not attribute all pain to functional disorders without excluding organic disease first: Particularly in new-onset symptoms at this age 1, 4