Urinary Tract Infection (UTI): Although the pyuria is described as aseptic, suggesting the absence of bacterial infection, UTIs are a common cause of abdominal pain and pyuria in children. The term "aseptic" might imply the absence of bacterial growth in culture, but it doesn't rule out the possibility of a viral or early bacterial infection not yet cultured.

Constipation: A common cause of abdominal pain in children, which can sometimes be associated with urinary symptoms due to the proximity of the bowel to the urinary tract.
Viral Gastroenteritis: Can cause abdominal pain and, in some cases, urinary symptoms if the child is dehydrated or if there's an associated viral infection affecting the urinary tract.
Stress or Functional Abdominal Pain: Children can experience abdominal pain due to stress or functional gastrointestinal disorders, which might be accompanied by urinary symptoms if the child has a habit of holding urine or has associated anxiety.

Appendicitis: Although less common in young children, appendicitis can present with abdominal pain and, occasionally, urinary symptoms if the appendix is located near the urinary tract. Missing this diagnosis can lead to severe consequences.
Kidney Stones: Though rare in children, kidney stones can cause severe abdominal or flank pain and urinary symptoms. The presence of aseptic pyuria might suggest a stone causing irritation.
Diabetic Ketoacidosis (DKA): Can present with abdominal pain and might have associated urinary symptoms. DKA is a medical emergency and must not be missed.

Tuberculosis (TB) of the Urinary Tract: A rare cause of aseptic pyuria and abdominal pain, especially if the child has been exposed to TB or has a weakened immune system.
Interstitial Cystitis/Painful Bladder Syndrome: Rare in children, this condition can cause chronic pain and urinary symptoms.
Schistosomiasis: In endemic areas, this parasitic infection can cause urinary symptoms and abdominal pain, though it's rare in most parts of the world.