What causes abdominal pain at the bottom of the abdomen?

Lower Abdominal Pain: Causes and Diagnostic Approach

CT of the abdomen and pelvis with IV contrast is the optimal initial imaging study for evaluating acute lower abdominal pain when the diagnosis is unclear, particularly when fever or serious pathology is suspected. 1, 2, 3

Most Common Causes by Location

Right Lower Quadrant Pain

• Appendicitis is the single most common surgical cause, accounting for 15.9-28.1% of acute abdominal pain cases requiring surgery 2
• Inflammatory bowel disease (Crohn's disease) can cause right lower quadrant pain, particularly during active flares 4
• Start with ultrasound as the initial imaging modality for right lower quadrant pain before proceeding to CT 2, 3

Left Lower Quadrant Pain

• Diverticulitis is the leading cause in adults, especially in elderly patients 2, 3
• CT abdomen and pelvis with contrast is the preferred imaging study 3

Pelvic/Suprapubic Pain

• Gynecologic conditions in women of childbearing age: ectopic pregnancy, ovarian torsion, pelvic inflammatory disease 1, 2
• Urinary tract pathology: cystitis, urinary retention 1
• CT abdomen and pelvis with contrast is recommended 2, 3

Diffuse Lower Abdominal Pain

• Bowel obstruction accounts for 15% of acute abdominal pain admissions, most commonly from adhesions (in patients with prior surgery), hernias, or neoplasms 2
• Mesenteric ischemia presents with severe pain out of proportion to physical findings and carries 30-90% mortality 2, 4

Critical Red Flags Requiring Urgent Evaluation

Tachycardia is the most sensitive early warning sign of surgical complications and should trigger urgent investigation even before other symptoms develop. 2, 3

Additional red flags include:

• Severe pain out of proportion to physical examination findings suggests mesenteric ischemia until proven otherwise 2, 3, 4
• Fever + tachycardia + tachypnea predicts serious complications including anastomotic leak, perforation, or sepsis 2, 3
• Abdominal distension with vomiting suggests bowel obstruction 2
• Hemodynamic instability suggests bleeding or sepsis 2

Essential Initial Workup

Mandatory Laboratory Tests

• Beta-hCG in ALL women of childbearing age before any imaging 1, 2, 3
• Complete blood count to evaluate for leukocytosis 2, 3
• C-reactive protein has superior sensitivity and specificity compared to white blood cell count for ruling in surgical disease 2, 3
• Elevated lactate suggests ischemia or sepsis, though normal levels do not exclude internal herniation or early ischemia 2, 3

Physical Examination Pearls

• Carnett's sign (pain unchanged or increased when abdominal muscles are tensed) indicates abdominal wall pain rather than intra-abdominal pathology 5
• Absence of peritonitis does NOT exclude bowel ischemia—patients with sigmoid volvulus often lack peritoneal signs despite established ischemia due to chronic distension masking the examination 2, 3
• Empty rectum on digital examination is classic for sigmoid volvulus 2

Imaging Algorithm by Clinical Scenario

Nonlocalized or Diffuse Lower Abdominal Pain

• CT abdomen and pelvis with IV contrast is the gold standard 1, 2, 3
• This provides broad evaluation for appendicitis, diverticulitis, bowel obstruction, abscess, perforation, and malignancy 1

Suspected Appendicitis

• Ultrasound first in younger patients to minimize radiation exposure 2, 3
• Proceed to CT with contrast if ultrasound is negative or inconclusive 2

Suspected Kidney Stones

• Non-contrast CT abdomen and pelvis is the imaging study of choice 2, 3

Suspected Mesenteric Ischemia

• CT angiography of the abdomen is the gold standard 2, 4

Special Population Considerations

Elderly Patients

• Have higher likelihood of malignancy, diverticulitis, and vascular causes 2, 3
• Laboratory tests may be normal despite serious infection—do not be falsely reassured 1, 2, 3
• Symptoms are often atypical and require more thorough evaluation 1, 3

Post-Surgical Patients

• Prior laparotomy makes adhesive obstruction the leading diagnosis, accounting for 55-75% of small bowel obstructions 2
• Asking about last bowel movement and passage of gas has 85% sensitivity and 78% specificity for predicting adhesive small bowel obstruction 2

Post-Bariatric Surgery Patients

• Often present with atypical symptoms 2, 3
• Classic peritoneal signs are frequently absent 2, 3
• Tachycardia is the most critical warning sign—consider internal herniation even with normal lactate 2, 3

Common Pitfall: Abdominal Wall Pain

Chronic, unremitting lower abdominal pain with minimal relationship to eating or bowel function but related to posture suggests abdominal wall pain rather than intra-abdominal pathology. 6, 5

• Most commonly located in the semilunar line (39/55 patients in one study) 6
• Positive Carnett's sign (tenderness unchanged or increased when abdominal muscles are tensed) confirms abdominal wall origin 5
• Associated with obesity, chronic straining during defecation, and exercise 6
• Injection of local anesthetic into the trigger point is both diagnostic and therapeutic 5
• Recognizing this condition avoids repeated costly investigations and relieves patient anxiety 6

When to Avoid Imaging

• Conventional radiography has limited diagnostic value in most patients with abdominal pain and should not be routinely ordered 2
• In low-risk patients (based on clinical scoring systems), imaging for appendicitis is not required, and other causes should be sought 1