Differential Diagnosis

Given the information that the condition is unilateral and presents with slight leucocytosis, we can approach the differential diagnosis as follows:

• Single Most Likely Diagnosis

  • Acute appendicitis: This condition is often unilateral, typically presenting on the right side, and can cause a slight increase in white blood cell count (leucocytosis) due to the body's inflammatory response to the appendiceal infection.

• Other Likely Diagnoses

  • Diverticulitis: Although it can be bilateral, diverticulitis often presents unilaterally, usually on the left side, and can cause leucocytosis due to inflammation of the diverticula.
  • Cholecystitis: Inflammation of the gallbladder, often due to gallstones, can present unilaterally and cause leucocytosis as part of the inflammatory response.
  • Pyelonephritis: A kidney infection that can cause unilateral symptoms, such as flank pain, and leucocytosis due to the bacterial infection.

• Do Not Miss Diagnoses

  • Ectopic pregnancy: Although less common and typically presenting with more specific symptoms like missed periods and severe abdominal pain, an ectopic pregnancy can cause unilateral pain and slight leucocytosis. Missing this diagnosis can be fatal.
  • Ovarian torsion: This is a gynecological emergency that can present with sudden, severe unilateral pain and may have a slight increase in white blood cell count. It requires immediate attention to preserve the ovary.
  • Testicular torsion: Similar to ovarian torsion, testicular torsion is a surgical emergency that presents with acute unilateral testicular pain and can have associated leucocytosis.

• Rare Diagnoses

  • Mesenteric lymphadenitis: An inflammation of the lymph nodes in the mesentery, which can mimic appendicitis but is less common. It can present unilaterally and cause leucocytosis.
  • Intussusception: A condition where a part of the intestine slides into an adjacent part, which can cause intestinal obstruction. It's rare in adults but can present with unilateral abdominal pain and leucocytosis.
  • Splenic infarct: Although more commonly associated with left upper quadrant pain, a splenic infarct can present unilaterally and cause leucocytosis due to the inflammatory response to the infarcted tissue.