What is the differential diagnosis for a female patient presenting with sacral pain?

Differential Diagnosis for Sacral Pain in Female Patients

Sacral pain in women requires systematic evaluation across musculoskeletal, gynecologic, gastrointestinal, and neurologic etiologies, with sacroiliac joint dysfunction accounting for approximately 15-25% of cases presenting as axial low back pain. 1, 2, 3

Musculoskeletal Causes (Most Common)

Sacroiliac Joint Dysfunction

• Pain localizes inferolateral to the posterior superior iliac spine, rarely radiating above L5 2
• Presents with sharp pain and mobility limitation relative to baseline 1
• More common in females with shorter stature and history of falls on buttocks 4
• Diagnosis requires image-guided analgesic injections of the SI joint, as physical examination and imaging alone are insufficient 1, 2, 3
• Provocation tests (FABRE, distraction, thigh thrust, sacral compression, Gaenslen's, sacral thrust) have recently challenged validity but remain useful screening tools 1

Lumbar Radiculopathy with Sacral Radiation

• Distinguished by muscle weakness, positive Bragard or Kemp sign, positive leg raising test, and corkscrew phenomenon 4
• Finger-floor distance ≥25 cm and lumbar scoliosis more common with nerve root compression 4
• MRI of the spine is necessary to exclude radiologic nerve root compression, as clinical features overlap significantly with SI joint pain 4

Pelvic Girdle Pain

• Common musculoskeletal cause of chronic pelvic/sacral pain 5, 6
• Often related to lower back or pelvic musculoskeletal disorders 5, 6

Myofascial Pain

• Pelvic myofascial pain can refer to sacral region 5

Gynecologic Causes (Critical in Women)

Postmenopausal Women

• Ovarian cysts account for one-third of gynecologic pain cases 7, 5, 6
• Uterine fibroids are significantly more common than in premenopausal women, particularly with torsion or necrosis 7, 5, 6
• Ovarian neoplasm accounts for 8% of cases and must be prioritized given elevated malignancy risk 7, 5, 6
• Pelvic inflammatory disease (tubo-ovarian abscess, endometritis, cervicitis) remains frequent despite postmenopausal state 7, 6

Reproductive Age Women

• Ovarian torsion presents with asymmetrically enlarged ovary requiring urgent surgical intervention 7, 8
• Endometriosis causes chronic pain, typically regressing after menopause 5
• Adenomyosis is a gynecologic cause of chronic pelvic pain 5
• β-hCG must be obtained in all reproductive-age women before imaging to avoid missing ectopic pregnancy 7, 8

Pelvic Venous Disorders

• Pelvic congestion syndrome characterized by engorged periuterine and periovarian veins 7, 5
• More common in women with polycystic ovarian syndrome morphology 7

Gastrointestinal Causes

• Inflammatory bowel diseases can manifest as chronic pelvic/sacral pain 5, 6
• Diverticulitis or colonic pathology should be considered 6
• Right colonic diverticulitis accounts for 8% of right lower quadrant pain cases 8

Urologic Causes

• Urinary tract pathology including cystitis, urethral diverticulum, or bladder disorders 5, 6
• Ureteral calculi cause colicky pain radiating to pelvis 8

Neurologic/Neuropathic Causes

• Chronic pelvic pain as failed-back surgery syndrome or complex regional pain syndrome 9
• Perineal, anal, and coccygeal pain can be neuropathic in origin 9

Critical Red Flags Requiring Immediate Attention

• In postmenopausal women, vaginal bleeding and suspected adnexal masses take precedence due to significantly elevated risk of endometrial and ovarian malignancy 5, 6
• Any palpable mass requires urgent imaging and potential tissue diagnosis 6
• Acute severe pain with hemodynamic instability suggests ruptured cyst, torsion, or surgical emergency 6
• Unexplained vaginal bleeding mandates endometrial evaluation 6

Diagnostic Algorithm

Initial Assessment

• Localize pain precisely: pain inferolateral to posterior superior iliac spine suggests SI joint; pain radiating to groin suggests gynecologic origin 2, 4
• Document history of falls on buttocks, shorter stature (increases SI joint likelihood) 4
• Assess for muscle weakness, positive straight leg raise, Bragard/Kemp signs (suggests radiculopathy) 4

Laboratory Testing

• β-hCG in all reproductive-age women 7, 8

Imaging Strategy

• For suspected gynecologic etiology: transvaginal ultrasound is first-line due to superior sensitivity for ovarian pathology and lack of radiation 7, 8
• For nonspecific presentation or suspected SI joint pain: MRI of spine and pelvis necessary to exclude nerve root compression and evaluate pelvic organs 4
• CT abdomen/pelvis with IV contrast preferred for acute nonspecific right lower quadrant pain to evaluate appendicitis and alternative diagnoses 7, 8
• Radiographs, CT, bone scans, and MRI of SI joint cannot reliably determine if joint is pain source 2, 3

Confirmatory Testing

• Image-guided analgesic injections of SI joint are the most accurate diagnostic tool when SI joint is suspected 1, 2, 3
• Pain reduction after injection confirms SI joint as pain generator 1, 3

Common Diagnostic Pitfalls

• Assuming gynecologic origin without systematic evaluation of gastrointestinal, urologic, and musculoskeletal systems leads to missed diagnoses 5, 6
• Relying on physical examination or imaging alone for SI joint diagnosis without confirmatory injection results in misdiagnosis 2, 3
• Failing to recognize age-specific patterns: differential shifts dramatically from reproductive age to postmenopausal status with substantially increased malignancy risk 5, 6
• Dismissing pain as "normal aging" without proper workup may miss serious pathology including malignancy 6
• SI joint-related sciatica-like symptoms clinically mimic radiculopathy; MRI is mandatory to discriminate 4