Differential Diagnosis for Daily Nausea and Pain in Lower Right Abdomen

Given the symptoms of daily nausea and pain in the lower right abdomen that occur most days after eating, with no gallstones, no celiac disease, and clear results from endoscopy and abdominal ultrasound (all four quadrants), the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Irritable Bowel Syndrome (IBS): This condition is characterized by chronic abdominal pain, bloating, and alteration of bowel habits in the absence of any mechanical, inflammatory, or biochemical abnormalities. The symptoms can be exacerbated by eating and can fit the patient's presentation, especially given the absence of other identifiable causes.

• Other Likely Diagnoses

  • Functional Dyspepsia: This disorder involves persistent or recurrent upper abdominal pain or discomfort that is not exclusively relieved by defecation or associated with the onset of a bowel movement. It can be related to eating and might explain the nausea and pain, especially if the pain is not strictly limited to the lower right abdomen.
  • Inflammatory Bowel Disease (IBD) - Crohn's Disease or Ulcerative Colitis: Although the endoscopy was clear, IBD can sometimes present with patchy inflammation that might be missed, especially if the disease is in its early stages or if the affected areas were not visualized during the endoscopy. The symptoms can include abdominal pain, nausea, and changes in bowel habits.
  • Lactose Intolerance or Other Food Intolerances: These conditions can cause nausea, bloating, and abdominal pain after eating, particularly if the patient consumes lactose or other problematic foods regularly.

• Do Not Miss Diagnoses

  • Appendicitis: Although the pain is chronic and not acute, atypical presentations of appendicitis can occur, especially in retrocecal appendicitis, where the appendix is located behind the cecum. Chronic or recurrent appendicitis is a rare condition but should be considered to avoid missing a potentially serious condition.
  • Ovarian Cysts or Torsion: In female patients, ovarian pathology can cause lower abdominal pain. While an ultrasound was performed, it's crucial to ensure that the ovaries were adequately visualized, as ovarian torsion is a medical emergency.
  • Intestinal Obstruction: Partial or intermittent obstruction can cause chronic symptoms, including nausea and abdominal pain, especially after eating.

• Rare Diagnoses

  • Chronic Intestinal Pseudo-obstruction: A rare condition characterized by the failure of the intestinal muscles to move food, fluids, and air through the intestines, leading to nausea, vomiting, and abdominal pain.
  • Eosinophilic Gastroenteritis: A rare condition involving eosinophilic infiltration of the gastrointestinal tract, which can cause abdominal pain, nausea, and vomiting.
  • Abdominal Migraine: A condition that can cause recurrent episodes of abdominal pain, often accompanied by other symptoms like nausea and vomiting, which can be related to eating in some cases.

Each of these diagnoses should be considered in the context of the patient's full medical history, physical examination, and further diagnostic testing as needed.