Kaneria started the season with Essex but left in June to join up with Pakistan for the Asia Cup.
He failed to make the Pakistan squad for next month's Champions Trophy in London and, as a result, is likely to be back on duty for Essex when they take on Durham in a County championship match at Colchester next week.
Kaneria will join New Zealander Andre Adams as the County's two overseas players for the remainder of the campaign. Adams was originally signed as a replacement for Kaneria but will now cover for the injured Brant.
Essex physiotherapist Damien West said Brant was suffering from an extra bone fragment growing in his right heel.
"When he bowls the bone pinches on his joints, which causes a swelling. He has had injections to settle down the inflammation, which have helped a bit, but he is still very sore and it is difficult to predict if the condition can be resolved without surgery.
"In consultation with Queensland it has been decided that it would be in Scott's best interests to go home for further treatment and a possible operation."
Essex Chief Executive David East added: "We are obviously very disappointed for Scott.
"This is the second occasion that his season with Essex has been cut short through injury. It is everyone's view that he should return home to have the condition carefully monitored by the Queensland medical team, particularly as surgery may be required."