A patient presents with abdominal pain in the left iliac region . What are the possibilities?
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I now have a comprehensive picture from multiple authoritative textbooks. Here is the full answer:
Differential Diagnosis: Left Iliac Fossa (Left Lower Quadrant) Pain
The left iliac fossa (LIF) / left lower quadrant (LLQ) is home to the sigmoid colon, the left ureter, left ovary and fallopian tube (in females), and nearby structures including the left iliac vessels and psoas muscle. The differential is best organized by system.
1. Colonic / GI Causes (most common)
| Condition | Key Features |
|---|---|
| Diverticulitis | Most common cause in adults >40. Triad: LLQ pain + fever + leukocytosis. The sigmoid colon is the predominant site in Western populations. Pain may be steady or cramping. |
| Sigmoid colon carcinoma | Insidious onset, change in bowel habit, weight loss, rectal bleeding, palpable mass. |
| Irritable Bowel Syndrome (IBS) | Recurrent pain, relieved by defecation, altered stool form, no systemic features. |
| Inflammatory Bowel Disease (IBD) | Crohn's or ulcerative colitis - diarrhea (may be bloody), systemic symptoms, extraintestinal features. |
| Ischemic colitis | Typically affects the splenic flexure/descending colon; sudden pain, bloody diarrhea, often in older patients with vascular disease. |
| Sigmoid volvulus | Acute abdominal distension, obstipation, colicky pain; more common in elderly. |
| Infectious/Infective colitis | Diarrhea (may be bloody), fever, recent travel or antibiotic use (C. difficile). |
| Constipation | Hard, infrequent stools; pain resolves with defecation. |
| Epiploic appendagitis | Self-limiting inflammation of a sigmoid epiploic appendage; mimics diverticulitis clinically. |
2. Gynaecological Causes (females)
| Condition | Key Features |
|---|---|
| Ectopic pregnancy | Sudden or subacute pain in a woman of reproductive age; missed period; ruptured ectopic is a surgical emergency with haemodynamic compromise. |
| Pelvic Inflammatory Disease (PID) / Salpingitis | Bilateral or unilateral pain, vaginal discharge, fever, cervical motion tenderness. |
| Ovarian cyst (ruptured or hemorrhagic) | Sudden-onset pain; fluctuates through menstrual cycles; may cause peritonism if ruptured. |
| Ovarian torsion | Sudden, severe, colicky pain; nausea/vomiting; absent Doppler flow on ultrasound - surgical emergency. |
| Endometriosis | Cyclical pain (dysmenorrhoea), dyspareunia, chronic pelvic pain. |
| Mittelschmerz | Mid-cycle pain coinciding with ovulation; self-limiting. |
| Fibroid (uterine leiomyoma) | Pelvic pressure, menorrhagia; may degenerate causing acute pain. |
3. Urological Causes
| Condition | Key Features |
|---|---|
| Ureteric calculus | Severe colicky loin-to-groin radiation, haematuria, restlessness. |
| Pyelonephritis (left) | Loin pain, fever, dysuria, positive urine culture. |
| Cystitis | Suprapubic/LIF pain, dysuria, frequency, haematuria. |
| Testicular torsion (males) | Pain may radiate to the left iliac region; absent cremasteric reflex; Doppler shows absent flow - surgical emergency. |
4. Vascular Causes
| Condition | Key Features |
|---|---|
| Aortic aneurysm (leaking/ruptured) | Sudden severe tearing pain radiating to back; pulsatile mass; haemodynamic instability - life-threatening emergency. |
| Iliac artery aneurysm | Similar to AAA; pulsatile LIF mass. |
5. Abdominal Wall / Musculoskeletal
| Condition | Key Features |
|---|---|
| Rectus sheath haematoma | Acute localised pain after exertion or coughing; tender firm mass; worsened by tensing abdominal muscles (Carnett's sign positive). |
| Psoas abscess | Deep aching pain, fever, hip flexion deformity, insidious onset; may complicate Crohn's, TB, or vertebral osteomyelitis. |
| Inguinal hernia (incarcerated/strangulated) | Visible/palpable groin lump; obstruction or strangulation is a surgical emergency. |
| Herpes zoster | Dermatomal burning pain precedes the rash (may confuse diagnosis early). |
6. Rare but Important
- Sigmoid tuberculosis - weight loss, chronic pain, history of TB exposure
- Actinomycosis - rare; associated with IUCDs
- Left-sided appendicitis - situs inversus (very rare)
- Mesenteric lymphadenitis - more common in children; often follows viral illness
Clinical Approach Summary
As Tintinalli's Emergency Medicine notes, the demographics of the patient matter enormously:
- Young women: always consider ectopic pregnancy (test beta-hCG), PID, ovarian pathology
- Older adults: diverticulitis, colon cancer, ischaemic colitis, vascular causes
- Young adults: IBD, IBS, infective colitis
- Males: testicular torsion (though rare), hernia, urological causes
The three most common causes overall are diverticulitis (most common in adults), colitis (inflammatory, ischaemic, or infectious), and gynaecological pathology (in females).
Sources: Harrison's Principles of Internal Medicine 22E, Table 739-536; Tintinalli's Emergency Medicine, Figure 77-1; Yamada's Textbook of Gastroenterology 7e, Ch. 37; Bailey and Love's Short Practice of Surgery 28e; Sleisenger and Fordtran's GI and Liver Disease
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