A gastroenterologist can perform Colonoscopy, Gastroscopy, Liver biopsy, Endoscopy, etc.
If you have a digestive problem like diarrhea, constipation, nausea for a long time, you should see a gastroenterologist.
A gastroenterology specialist gives accurate diagnosis of problems in gastrointestinal tract and provides proper treatment.
The recovery time differs based on the problem and organ involved but you can expect full recovery in about 6 weeks.