Final answer:
To diagnose the cause of a 6-year-old's intermittent encopresis, a microscopic stool examination should be carried out over a week. The treatment depends on the diagnosis, including antibiotics for bacterial causes or antiparasitic drugs for parasitic infections.
Step-by-step explanation:
The most appropriate next diagnostic step for a 6-year-old presenting with intermittent encopresis (stooling in clothes) would be a microscopic examination of stool over several days, ideally at least 7, to determine the presence of any pathogens, parasites, or abnormalities. If the history suggests possible ingestion of undercooked food or exposure to contaminated water or food, specific tests for bacterial or viral gastroenteritis such as stool cultures and enzyme immunoassays may be appropriate. Other tests like acid fast staining and molecular analysis (PCR) could also be considered depending on clinical suspicion.
Regarding treatment (Tx), the management will depend on the final diagnosis. If a particular pathogen such as ETEC (Enterotoxigenic Escherichia coli) is identified, an antibiotic such as ciprofloxacin may be prescribed. However, if a parasitic infection is diagnosed, antiparasitic medications like ivermectin or albendazole could be recommended.