Gastroenteritis: This is often the most common cause of abdominal pain in patients presenting to the emergency department with stable vital signs. It is usually viral or bacterial in nature and can be accompanied by symptoms such as diarrhea, vomiting, and fever, although the latter may not always be present.

Constipation: A very common condition that can cause significant abdominal pain and discomfort. It is often associated with changes in bowel habits, straining during bowel movements, and hard or lumpy stools.
Irritable Bowel Syndrome (IBS): A functional gastrointestinal disorder characterized by chronic abdominal pain, bloating, and alteration of bowel habits in the absence of any mechanical, inflammatory, or biochemical abnormalities.
Urinary Tract Infection (UTI): While more common in women, UTIs can cause abdominal pain, especially in the lower abdomen, and are often accompanied by dysuria, frequency, and urgency.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can present with chronic abdominal pain, changes in bowel habits, weight loss, and sometimes blood in the stool.

Appendicitis: Although it often presents with unstable vital signs in its later stages, early appendicitis can have stable vital signs. It is crucial to consider this diagnosis due to the potential for severe consequences if missed, including perforation and peritonitis.
Ectopic Pregnancy: A life-threatening condition that should be considered in women of childbearing age presenting with abdominal pain, especially if there is a history of missed periods or positive pregnancy test.
Ovarian Torsion: Another gynecological emergency that can present with severe abdominal pain and may have stable vital signs initially. It requires prompt diagnosis and treatment to preserve ovarian function.
Intestinal Obstruction: Can present with abdominal pain, nausea, vomiting, and changes in bowel habits. Early recognition is crucial to prevent complications like bowel ischemia.

Porphyria: A group of disorders that can result in acute intermittent porphyria, characterized by severe abdominal pain, neurological symptoms, and sometimes psychiatric disturbances.
Henoch-Schönlein Purpura (HSP): A form of vasculitis that can cause abdominal pain, gastrointestinal bleeding, and a characteristic rash.
Abdominal Migraine: A condition seen in children and adolescents, characterized by recurrent episodes of severe abdominal pain, often accompanied by other migraine symptoms like headache and nausea.
Mesenteric Ischemia: A rare but serious condition caused by insufficient blood flow to the intestines, which can present with severe abdominal pain out of proportion to physical examination findings.