Differential Diagnosis for LLQ Pain

The differential diagnosis for left lower quadrant (LLQ) pain can be organized into several categories based on the likelihood and potential impact of missing the diagnosis.

• Single Most Likely Diagnosis

  • Diverticulitis: This is often the most common cause of LLQ pain in adults, especially those over 40 years old. Diverticulitis occurs when diverticula (small pouches) in the wall of the colon become inflamed. Symptoms include pain, tenderness, and guarding in the LLQ, fever, 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 pain in any quadrant, it's often associated with LLQ pain due to the sigmoid colon's location.
  • Constipation: Can cause significant discomfort and pain, often localized to the LLQ due to the accumulation of stool in the sigmoid colon.
  • Ovarian Cysts: In women, ovarian cysts can cause LLQ pain, especially if they rupture or torsion occurs.
  • Ectopic Pregnancy: Though more commonly associated with right-sided pain if the implantation is in the right fallopian tube, ectopic pregnancies can cause LLQ pain if the implantation occurs in the left fallopian tube.

• Do Not Miss Diagnoses

  • Appendicitis (if appendix is located in the LLQ): Although appendicitis typically presents with right lower quadrant pain, in some cases (about 1%), the appendix is located in the left lower quadrant, leading to left-sided pain.
  • Intestinal Obstruction: Can cause severe abdominal pain, vomiting, and constipation. Early diagnosis is crucial to prevent complications like bowel ischemia.
  • Inflammatory Bowel Disease (Crohn’s Disease, Ulcerative Colitis): These conditions can cause chronic inflammation and damage to the digestive tract, leading to severe LLQ pain among other symptoms.
  • Kidney Stones: While typically associated with flank pain, stones can cause referred pain to the LLQ if they are moving down the ureter.

• Rare Diagnoses

  • Colonic Volvulus: A condition where the colon twists around itself and its mesentery, cutting off the blood supply. It's rare but can cause severe abdominal pain.
  • Endometriosis: Though not exclusively causing LLQ pain, endometriosis can lead to chronic pelvic pain, including in the LLQ, especially during menstruation.
  • Lymphoma: Abdominal lymphoma can cause pain in various locations, including the LLQ, depending on the lymph nodes involved.
  • Intra-abdominal shunt malfunction (in patients with ventriculoperitoneal shunts): A rare but critical condition where the shunt, used to treat hydrocephalus, malfunctions and causes abdominal pain and other symptoms.