What is the initial approach to a 26-year-old female presenting with left iliac fossa pain?

Initial Approach to Left Iliac Fossa Pain in a 26-Year-Old Female

In a 26-year-old woman with left iliac fossa pain, immediately obtain a focused history targeting gynecological symptoms (menstrual history, vaginal discharge, sexual activity), bowel symptoms (constipation, vomiting, distension), and perform targeted physical examination followed by ultrasound as first-line imaging, with CT scan reserved for inconclusive cases or suspected complications. 1

Critical History Elements

• Gynecological factors: Menstrual cycle timing, history of ovarian cysts, endometriosis, or pelvic inflammatory disease, as salpingitis is the primary consideration in women of childbearing age 1
• Gastrointestinal symptoms: Constipation, vomiting (late sign), abdominal distension, and previous episodes of similar pain, which may suggest sigmoid pathology 2, 3
• Duration and character: Acute onset (hours) versus subacute (days), as this influences differential diagnosis 1
• Associated symptoms: Fever, vaginal discharge, urinary symptoms to differentiate between gynecological, gastrointestinal, and urological causes 1

Physical Examination Priorities

• Pelvic examination: Essential to assess for cervical motion tenderness, adnexal masses, or discharge suggesting pelvic inflammatory disease 1
• Abdominal examination: Look for peritoneal signs, asymmetric distension, and specifically assess for emptiness of the left iliac fossa with distension elsewhere (pathognomonic for sigmoid volvulus, though rare at this age) 2
• Rectal examination: May reveal empty rectum in bowel obstruction or tenderness suggesting diverticulitis 2
• Vital signs: Assess for systemic inflammatory response syndrome (SIRS) criteria, as presence significantly alters management urgency 4

Laboratory Investigations

• Complete blood count: White cell count and differential to assess for infection or inflammation 2
• Inflammatory markers: C-reactive protein to gauge severity of inflammatory process 2
• Pregnancy test: Mandatory in all women of childbearing age to rule out ectopic pregnancy 1
• Urinalysis: To exclude urinary tract infection or pyelonephritis 1
• Blood gas and lactate: If bowel ischemia suspected, though absence of hyperlactatemia does not exclude ischemia 2

Imaging Algorithm

First-line: Ultrasound

• Transvaginal and transabdominal ultrasound is the initial imaging modality of choice for gynecological pathology (ovarian cysts, tubo-ovarian abscess, ectopic pregnancy) 1
• Ultrasound can also identify sigmoid diverticulitis, though sensitivity is lower than CT 1

Second-line: CT with IV contrast

• Mandatory indications: Signs of peritonism, SIRS criteria present, ultrasound inconclusive, or suspected complications (perforation, abscess) 4, 1
• CT provides comprehensive assessment of sigmoid diverticulitis (uncommon but possible at age 26), appendicitis, epiploic appendagitis, psoas abscess, and other rare causes 1
• CT allows identification of complications including abscess, fistula, or perforation and can guide percutaneous drainage 1
• In patients over 50 years, CT has 97% sensitivity and should be mandatory, but in younger patients, clinical judgment determines necessity 4

Differential Diagnosis by Likelihood in This Age Group

Most common:

• Gynecological: Ovarian cyst (rupture or torsion), pelvic inflammatory disease/salpingitis, endometriosis 1, 3, 5
• Gastrointestinal: Non-specific abdominal pain, early sigmoid diverticulitis (rare but reported), epiploic appendagitis 1, 3

Less common but important:

• Sigmoid volvulus or fecal impaction (rare at this age but documented) 3
• Psoas abscess (consider if history of recent abdominal surgery) 6
• Renal pathology: Pyelonephritis, renal abscess 1
• Inflammatory bowel disease (Crohn's disease, ulcerative colitis) 1

Rare but critical:

• Catamenial pneumothorax with referred pain (if pain coincides with menstruation) 5
• Entero-retroperitoneal fistula (if history of previous cholecystectomy) 6

Common Pitfalls to Avoid

• Assuming gynecological cause without imaging: While gynecological pathology is most common, serious gastrointestinal causes can present similarly and require different management 1, 3
• Delaying CT when indicated: In patients with peritoneal signs or SIRS, CT should not be delayed as it changes management in the majority of cases 4, 1
• Missing bowel obstruction: Young patients can develop large bowel obstruction from unusual causes like fecal impaction, which can rapidly deteriorate 3
• Overlooking rare diagnoses: History of previous abdominal surgery should prompt consideration of complications like psoas abscess or fistula formation 6
• Inadequate assessment of hemodynamic stability: Monitor for signs of deterioration including tachycardia, hypotension, and metabolic acidosis, which mandate urgent surgical consultation 3

Disposition Decision

• Outpatient management: Mild symptoms, no peritoneal signs, normal vital signs, and reassuring imaging can be managed with analgesia and close follow-up 1
• Admission required: Peritoneal signs, SIRS criteria, imaging showing abscess or complicated pathology, or inability to tolerate oral intake 2, 1
• Urgent surgical consultation: Peritonitis, bowel obstruction, hemodynamic instability, or imaging suggesting perforation or ischemia 2, 3