Differential Diagnosis
- Single most likely diagnosis
- Appendicitis: The patient's symptoms, including the initial periumbilical pain that migrated to the right lower quadrant, fever, nausea, and elevated white blood cell count, are classic for appendicitis. The presence of right lower quadrant tenderness without rebound or rigidity also supports this diagnosis.
- Other Likely diagnoses
- Gastroenteritis: The patient's symptoms of diarrhea, fever, and abdominal pain, as well as the similar illness in his younger brother, suggest a possible infectious cause. The presence of mucus in the stool and the absence of blood (unlike his brother) make bacterial gastroenteritis (e.g., Salmonella, Shigella) less likely, but viral gastroenteritis is still a possibility.
- Mesenteric lymphadenitis: This condition, which involves inflammation of the lymph nodes in the mesentery, can mimic appendicitis and is often associated with viral or bacterial infections. The patient's symptoms and laboratory results could be consistent with this diagnosis.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Intussusception: Although less common in adolescents, intussusception is a life-threatening condition that requires prompt diagnosis and treatment. The presence of abdominal pain, diarrhea, and fever, as well as the possibility of blood in the stool (as seen in the patient's brother), make this a "do not miss" diagnosis.
- Ectopic pregnancy (in female patients, not applicable in this case): Although the patient is male, it's essential to consider ectopic pregnancy in female patients presenting with similar symptoms, as it is a life-threatening condition.
- Inflammatory bowel disease (IBD): While IBD is less likely given the acute presentation, it is essential to consider this diagnosis, as it can have significant implications for the patient's long-term health.
- Rare diagnoses
- Yersiniosis: This bacterial infection can cause symptoms similar to appendicitis, including right lower quadrant pain and fever. However, it is relatively rare and often associated with exposure to contaminated food or water.
- Meckel's diverticulitis: This condition, which involves inflammation of a congenital anomaly of the small intestine, can present with symptoms similar to appendicitis. However, it is relatively rare and often diagnosed incidentally.