Constipation: This is a common issue in children that can cause abdominal pain and, due to referred pain, hip pain. The absence of other symptoms like nausea, vomiting, or fever makes this a plausible first consideration.

Musculoskeletal strain: Given the age of the patient, musculoskeletal issues from physical activity are common and could explain both abdominal and hip pain, especially if the strain affects the lower back or pelvic area.
Stress or anxiety: Abdominal pain in children can sometimes be related to psychological factors. The hip pain could be a manifestation of tension or stress, especially if the child is experiencing anxiety or stress at school or home.
Gastroenteritis (non-infectious): Although the child is negative for UTI and does not have fever, nausea, or vomiting, a non-infectious cause of gastroenteritis (like food intolerance or reaction) could still cause abdominal pain, and referred pain could affect the hips.

Appendicitis: Although less common in this age group and typically presenting with fever and vomiting, appendicitis can occasionally present atypically. It's crucial to consider this diagnosis due to its potential severity and need for prompt surgical intervention.
Intussusception: A condition where a part of the intestine slides into an adjacent part, which can cause severe abdominal pain and potentially affect the hips due to radiation of pain. It's more common in younger children but should be considered due to its urgency.
Ovarian torsion or ovarian cyst: Although rare, ovarian torsion or a ruptured ovarian cyst can cause severe abdominal pain that might radiate to the hips. These conditions are emergencies and require immediate medical attention.

Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause chronic abdominal pain and, less commonly, hip pain due to extraintestinal manifestations. These are less likely but should be considered if other diagnoses are ruled out and symptoms persist.
Neurological conditions: Certain neurological conditions, such as neuropathic pain or early signs of a neurological disorder, could potentially cause both abdominal and hip pain, although these would be rare and typically accompanied by other neurological symptoms.