Differential Diagnosis for Left Upper Quadrant Pain with Diarrhea

Single Most Likely Diagnosis

• Gastroenteritis: This is a common condition that can cause both abdominal pain and diarrhea. The left upper quadrant pain could be referred pain from the stomach or due to the involvement of the spleen in the inflammatory process. Viral or bacterial infections are typical causes.

Other Likely Diagnoses

• Irritable Bowel Syndrome (IBS): Although IBS typically presents with chronic symptoms, an acute exacerbation could manifest as left upper quadrant pain and diarrhea. The pain in IBS can be diffuse or localized and is often accompanied by changes in bowel habits.
• Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause chronic diarrhea and abdominal pain. The pain can be in any quadrant, depending on the area of the bowel affected.
• Diverticulitis: While more common in the left lower quadrant, diverticulitis can occasionally cause pain that is perceived in the left upper quadrant, especially if the inflammation involves the upper parts of the sigmoid colon.

Do Not Miss Diagnoses

• Splenic Infarction or Rupture: These are medical emergencies that can present with acute left upper quadrant pain and potentially diarrhea if there is associated gastrointestinal involvement. A history of trauma, sickle cell disease, or other conditions predisposing to splenic issues would increase suspicion.
• Pancreatitis: Although pancreatitis typically causes mid-abdominal pain radiating to the back, it can sometimes present with left upper quadrant pain. Diarrhea could be a secondary symptom due to the inflammatory response affecting bowel motility.
• Mesenteric Ischemia: This condition involves insufficient blood flow to the intestines and can cause severe abdominal pain and diarrhea. It is more common in older adults and those with cardiovascular disease.

Rare Diagnoses

• Intestinal Lymphoma: A type of cancer that can cause abdominal pain, diarrhea, and weight loss. It would be considered in the differential if there were systemic symptoms or a failure to respond to initial treatments.
• Splenic Abscess: A rare condition where the spleen becomes infected, leading to an abscess. It can cause left upper quadrant pain and systemic symptoms like fever.
• Gastric Volvulus: A rare condition where the stomach twists abnormally, which can cause severe abdominal pain and potentially diarrhea due to obstruction or ischemia.

Each of these diagnoses requires a careful history, physical examination, and potentially imaging studies or endoscopy for diagnosis. The approach to the patient should be tailored based on the severity of symptoms, patient history, and initial findings.