Thank you for your question. Here is an excerpt from Vol 110 No 45 of The Nursing Times (05.11.14 21) (pg.21) re tx of granulomas on a gastrostomy site:

"The evidence base for the management of granulomas is weak (Warriner and Spruce, 2012); however, there are recommendations based on clinical expertise. It is vital to check the external fixation plate is in the correct position and that patients and/or carers know the correct position. A barrier cream can be used to protect the skin from any exudate that may come from the granuloma. The amount of times the site needs to be cleaned and dressed per day will depend on the amount of exudate; a swab can be taken if an infection is suspected.

The National Nurses Nutrition Group (2013) recommends the use of an antimicrobial-impregnated foam dressing, which should be changed as required. It is advised that the treatment plan should be reviewed after one week or as per local guidelines. The NNNG good-practice guidelines (2013) also give further guidance on how to progress treatment if this first plan is unsuccessful. Warriner and Spruce (2012) have looked extensively into the management of granulomas and have devised a flowchart to inform patient care.”

Hope this helps!

I will suggest to use Silver Nitrate and foam dressing. Besides, when granuloma over stoma site comes from friction, should work on prevention subsequently; when it comes from leakage, should reinforce care giver training of feeding. 

I  would also recommend the use of an antimicrobial-impregnated foam dressing, which should be changed as required. Recognising the evidence base identified by Shakib. I have had success with this. 

We use in Brazil Sodium Chloride 20% if in light bulb, soak a gauze and apply on the granuloma. There is a product in gel form, Hypergel of the Molnlycke which is a gel with 20% sodium, it may also be applied a thin layer on granuloma and cover with gauze.