An X-ray can sometimes show stool loading and rectal dilatation, but it alone cannot confirm functional megarectum. Your symptoms of overflow leakage and incomplete emptying suggest severe constipation, so you should consult a gastroenterologist for proper evaluation and treatment.
Next Steps
A doctor may recommend examination and tests like abdominal X-ray, contrast study, or anorectal manometry to confirm the diagnosis and start appropriate treatment.