Resepcted user, hi I evaluated your query thoroughly.
*Fissure is a clinical finding by inspection only it doesn`t require   
sigmoidoscopy at all.
*For 
Chronic constipation of 7-8 years , 
Colonoscopy has better positive results
  as compared to sigmoidoscopy.
*Take following caring steps for your intestines & then see what happens in 
  coming time :
- drink plenty of liquids in form of boiled water, coconut water, lemon juice,
  green tea, home made juices , butter milk etc.
- have more green leafy vegetables, cereals , pulses, legumes, yoggurt .
- balance diet in carbohydrates, vitamins , minerals , anti-oxidants , trace
  elements , proteins , iron .
- avoid all oily / spicy / nonveg stuffs / beverages / junk foods / cheese / 
  items with menda / excess ghee / sugars / artificial sweeteners .
- chew your food very thoroughly.
- have small amount of food at intervals .
- keep fix timings of breakfast, lunch , dinner till possible .
- avoid prolong fasting / overeating .
- avoid sleeping for atleast 2 hours after lunch / dinner .
- avoid 
smoking / alcohol / abuse substances used if any .
- do regular walking , light exercises at home with YOGA compulsorily .
- avoid 
stress / 
anxiety .
- have regular sound sleep of 8 hours .
- Use Sitz bath regualarly for fissure .
- Can apply local 
ointments for fissure & bulk laxative agents for 
  constipation .
Hope this clears your doubts .
Thanks for using Health care magic & giving me an opportunity to assist you.
Wishing you a very happy healthy life ahead.
Welcome for any further assistance.
Regards dear take care.