Differential Diagnosis for Fever for 18 Days without Clear Source and Mild Abdominal Pain
Single Most Likely Diagnosis
- Infectious Mononucleosis (Mono): This condition, caused by the Epstein-Barr virus, often presents with prolonged fever, mild abdominal pain due to splenomegaly, and other non-specific symptoms. The long duration of fever and the presence of abdominal pain make it a plausible diagnosis.
Other Likely Diagnoses
- Tuberculosis (TB): TB can cause prolonged fever and abdominal pain if it involves the gastrointestinal tract or abdominal lymph nodes. It's a consideration, especially in areas where TB is common or in individuals with risk factors.
- Intra-abdominal Abscess: An abscess within the abdominal cavity can cause prolonged fever and abdominal pain. The pain can be mild or severe, depending on the location and size of the abscess.
- Chronic Appendicitis or Mesenteric Lymphadenitis: These conditions can cause prolonged, low-grade fever and abdominal pain, often localized to the right lower quadrant or more diffuse.
Do Not Miss Diagnoses
- Appendicitis: Although it typically presents acutely, some cases can have a more prolonged and subtle onset. Missing appendicitis can lead to perforation and severe complications.
- Diverticulitis: Especially in older adults, diverticulitis can cause prolonged fever and abdominal pain, usually in the left lower quadrant. Complications like abscess formation or perforation are serious.
- Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can present with chronic fever and abdominal pain, among other symptoms. Early diagnosis is crucial for management.
- Malignancy: Although less common, certain cancers (like lymphoma) can present with prolonged fever and abdominal pain due to tumor involvement of abdominal organs or lymph nodes.
Rare Diagnoses
- Familial Mediterranean Fever (FMF): An autosomal recessive disorder characterized by recurrent episodes of fever and abdominal pain, among other symptoms. It's rare but should be considered in patients of Mediterranean descent.
- Whipple's Disease: A rare, systemic bacterial infection that can cause fever, abdominal pain, weight loss, and other symptoms. It's often diagnosed late due to its non-specific presentation.
- Systemic Lupus Erythematosus (SLE): An autoimmune disease that can cause a wide range of symptoms, including prolonged fever and abdominal pain, due to its systemic nature.