Differential Diagnosis for a 30-year-old Male with Nausea, Emesis, and Leukocytosis

Single Most Likely Diagnosis

• Gastroenteritis: This is a common condition that can cause nausea, vomiting (emesis), and an elevated white blood cell count (leukocytosis) due to the body's inflammatory response to a gastrointestinal infection. The symptoms presented are classic for a viral or bacterial gastrointestinal infection.

Other Likely Diagnoses

• Appendicitis: Although more commonly associated with abdominal pain, nausea, and vomiting, appendicitis can also cause leukocytosis. The pain often starts near the belly button and then moves to the lower right abdomen.
• Food Poisoning: Similar to gastroenteritis, food poisoning from consuming contaminated food can lead to nausea, emesis, and an elevated white blood cell count as the body responds to the toxins or infectious agents.
• Urinary Tract Infection (UTI) or Pyelonephritis: While UTIs are more common in women, men can also be affected, especially if they have an underlying condition like an enlarged prostate. Symptoms can include nausea, vomiting, and leukocytosis, particularly if the infection has ascended to the kidneys (pyelonephritis).

Do Not Miss Diagnoses

• Septicemia or Sepsis: Although less common, any infection that leads to sepsis can present with nonspecific symptoms like nausea and vomiting, along with leukocytosis. Sepsis is a life-threatening condition that requires immediate medical attention.
• Pancreatitis: Acute pancreatitis can cause severe abdominal pain, nausea, vomiting, and an elevated white blood cell count. It's crucial to consider this diagnosis due to its potential severity and the need for prompt treatment.
• Diverticulitis: Inflammation of the diverticula in the digestive tract can lead to nausea, vomiting, and leukocytosis, especially if there's an associated infection or abscess.

Rare Diagnoses

• Mesenteric Lymphadenitis: An inflammation of the lymph nodes in the mesentery (the tissue that attaches the intestines to the back of the abdominal wall) can mimic appendicitis and cause similar symptoms, including nausea, vomiting, and leukocytosis.
• Intussusception: A condition where a part of the intestine slides into an adjacent part, potentially causing bowel obstruction. It's rare in adults but can cause nausea, vomiting, and abdominal pain, along with leukocytosis if there's an associated infection or ischemia.