Anal fistulae can present with many different symptoms:
Pain
Discharge - either bloody or purulent
Pruritus ani - itching
Systemic symptoms if abscess becomes infected.
At birth, the infant has difficulty swallowing. Eating produces severe coughing spells that interfere with breathing. Aspiration pneumonia can develop from fluid breathed into the lungs.
Anal and rectal fistulas are treated by draining the pus the infected area. The individual also is usually given antibiotics to help prevent recurrence of the abscess. If this fails to heal the...
Butt scooting is one symptom. Take the dog to a groomer (cheaper than a vet) and ask the groomer to "Express the anal gland". Maybe they could show you how it's done. (Ain't pretty).
A dog may walk hunched have difficulty defecating or seem constipated they may drag or scoot their anus across carpet and be excessively licking themself.