Differential Diagnosis for Left Lower Quadrant (LLQ) Pain

Single Most Likely Diagnosis

• Diverticulitis: The most common cause of LLQ pain, especially in older adults, due to inflammation of the diverticula in the sigmoid colon. Symptoms often include pain, tenderness, and changes in bowel habits.

Other Likely Diagnoses

• Irritable Bowel Syndrome (IBS): A common condition characterized by abdominal pain, bloating, and changes in bowel movements. While it can cause LLQ pain, it's often accompanied by other symptoms like diarrhea or constipation.
• Constipation: Can cause significant discomfort and pain in the LLQ, especially if there is a large fecal impaction.
• Ovarian Cyst or Torsion: In females, ovarian cysts can cause LLQ pain, and if the cyst ruptures or the ovary torsions, it becomes a medical emergency.
• Kidney Stone: While more commonly associated with flank pain, a stone in the lower ureter can cause pain that radiates to the LLQ.

Do Not Miss Diagnoses

• Appendicitis: Although appendicitis typically presents with right lower quadrant pain, in some cases (especially if the appendix is retrocecal), it can cause LLQ pain. Missing this diagnosis can lead to perforation and severe complications.
• Ectopic Pregnancy: A life-threatening condition in pregnant women where the embryo implants outside the uterus, often causing severe LLQ pain and vaginal bleeding.
• Intestinal Obstruction: Can cause severe abdominal pain, including in the LLQ, along with vomiting, constipation, and abdominal distension.
• Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic inflammation and pain in the LLQ, among other symptoms.

Rare Diagnoses

• Endometriosis: While not rare, endometriosis causing LLQ pain is less common than other symptoms like pelvic pain and dysmenorrhea. It involves tissue similar to the lining inside the uterus growing outside of it.
• Lymphoma: Abdominal lymphoma can cause pain in various locations, including the LLQ, along with systemic symptoms like weight loss and fever.
• Intra-abdominal shunt malfunction: In patients with a ventriculoperitoneal shunt, malfunction can cause abdominal pain, including in the LLQ, due to increased intracranial pressure or shunt infection.
• Abdominal Aortic Aneurysm: Although typically presents with back or abdominal pain, a leaking or ruptured aneurysm can cause pain that might be perceived in the LLQ, especially if it involves branches that supply the lower abdomen.