"If we do not do something now there will be a lot more bad news to come from Dunedin Hospital."
They invited Coleman to Dunedin Hospital to spend time with doctors and "walk in our shoes".
The pair took particular exception to Coleman's description of the struggling urology department as "toxic".
"This is completely untrue - it is, however, a department like several others at Dunedin Hospital, which is unable to cope with the demand for its services.
"I can certainly forgive your unfortunate choice of descriptors, however I would appreciate an apology to our valued colleagues, medical and nursing, as well as urgent steps to address the significant shortfall in resources," the letter says.
The health board has commissioned an external report into unacceptably long waits for assessment and cancer treatment in urology.
The surgeons said the hospital's urologists served more than 210,000 people.
"It is apparent why our three urologists, in spite of their best and considerable efforts, are overwhelmed."
The pair also talk about shortfalls in orthopaedics.
"There is a major mismatch between the demand for our services and our ability to deliver.
"In orthopaedics we are only able to see two-thirds of the people who are referred, and of those we think need an operation, we can only operate on about two-thirds.
"Reports from our colleagues in Auckland tell us that access to elective orthopaedic care in Auckland is significantly better than in Otago."
Nurses were under pressure.
"If you ask any patient who has been an inpatient recently at Dunedin Hospital, they will be able to confirm that the nurses are literally running for their whole shift."
Sacking the board in 2015 and installing a commissioner made things worse, as the budget took priority over patients.
"Financial performance has taken priority over clinical performance at the detriment to the care we can provide to our community."
The pair asked Coleman to take another look at the population-based funding formula which, they say, appears to penalise the South.
A spokeswoman for Coleman said he would respond to the letter directly.
The letter was copied to the Otago Daily Times, Radio New Zealand and several MPs.
Commissioner Kathy Grant said she would have preferred the surgeons wrote to the board rather than Coleman, but it was their choice.
Grant said the board was adequately funded.
"I acknowledge that there are challenges that we are dealing with in an open and transparent way."
Asked if she thought she was doing a good job, Grant said: "I can list a number of initiatives where we are investing in change management."
