Initial investigations for a patient presenting with perianal itching should include:
Careful inspection of the perianal area to assess for signs of infection (such as perianal streptococcal infection), skin changes, fissures, fistulae, or other abnormalities.
General physical examination including abdominal and neurological examination to exclude underlying causes such as constipation, neurological impairment, or systemic disease.
Consideration of stool tests or swabs if infection is suspected, especially bacterial or fungal causes.
Referral for further investigations if red flags are present, such as signs of malignancy, inflammatory bowel disease, or other serious pathology.
Digital rectal examination should be performed only by trained healthcare professionals if indicated by history or examination findings.