Appendicitis: This is the most common cause of right lower quadrant abdominal pain, especially in younger individuals. The pain often starts around the navel and then moves to the right lower quadrant. Appendicitis is an emergency that requires prompt surgical intervention.

Ovarian Cyst or Torsion: In females, ovarian cysts or torsion can cause severe right lower quadrant pain. The pain can be sudden and may be accompanied by nausea and vomiting.
Ectopic Pregnancy: Another condition in females, ectopic pregnancy can cause right lower quadrant pain, especially if the ectopic pregnancy is located in the right fallopian tube.
Diverticulitis: Although more common on the left side, diverticulitis can occur on the right side, causing right lower quadrant pain, especially in individuals with right-sided diverticula.
Intestinal Obstruction: Obstruction of the small or large intestine can cause abdominal pain that may be localized to the right lower quadrant, depending on the location of the obstruction.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause chronic or acute right lower quadrant pain, depending on the area of the bowel affected.

Ruptured Ectopic Pregnancy: A life-threatening condition that requires immediate medical attention. The pain can be severe and sudden, and the patient may exhibit signs of shock.
Ruptured Appendix: If appendicitis is not treated promptly, the appendix can rupture, leading to peritonitis, which is a life-threatening condition.
Ovarian Torsion: This condition can cut off blood supply to the ovary, leading to tissue death if not promptly treated.
Mesenteric Ischemia: A condition where blood flow to the intestines is compromised, leading to tissue death. It presents with severe abdominal pain out of proportion to the physical examination findings.

Right Lower Quadrant Hematoma: A collection of blood in the right lower quadrant, which can be due to trauma or a bleeding disorder.
Right Psoas Abscess: An abscess located in the psoas muscle, which can cause right lower quadrant pain, often accompanied by fever and back pain.
Carcinoid Tumor: A rare tumor that can cause abdominal pain, flushing, and diarrhea, depending on its location and secretion of serotonin.
Intussusception: A condition where a part of the intestine telescopes into another part, causing bowel obstruction and severe abdominal pain. It is more common in children but can occur in adults, often associated with a lead point like a tumor.