Can someone with a swollen stomach and colon ailments eat a chocolate cake? 
According to Monash University , which first developed the low-fodmap diet for people with irritable bowel, yes, at least according to the list of low-fodmap foods, which are foods that are ideal for those with a bloated stomach. because they do not cause intestinal fermentation.

In particular, chocolate lovers can eat it without abusing it, as long as it is not milk or white chocolate: extra dark chocolate or bitter cocoa is better, but overall it should not exceed 20/30 grams per day.
A cake like this comes in handy : very chocolaty and easy to make, it does not contain wheat derivatives (it is also gluten free) or milk derivatives and we can afford to eat a slice a day without consequences.

CHOCOLATE CAKE FOR THOSE WITH SWELLING BELLY
Ingredients for 10 portions
230 gr of extra dark chocolate
150 gr of butter
200 gr of normal or cane sugar
a pinch of salt
4 large eggs at room temperature
30 gr of bitter cocoa

Procedure:
Grease a 22 cm cake pan with part of the butter and preheat the oven to 190 °. Melt the butter and the extra dark chocolate in a bain-marie, taking care that it does not burn, then let it cool so that it is warm but not very hot. Whip the whole eggs with the sugar and a pinch of salt, then add the cocoa and blend until you get a nice cream. Pour in the egg and chocolate mixture and mix well. Pour everything into the pan and cook for thirty minutes at 180 °.