Saw a patient today in clinic who was s/p simultaneous pancreas-kidney transplant about 15 years ago.
The kidney is hanging in there (Cr 2.5mg/dl) and the patient does not require insulin, so we have to consider the transplant a success. However in going through her medication list, I noticed that the patient was on massive doses of oral sodium bicarbonate, plus they have instructions to take oral salt tablets during the summer months. What does this tell us about pancreas transplant?
Drainage of the exocrine contents of the transplanted pancreas can be achieved surgically in two different ways: either bladder drainage or enteric drainage.
Bladder drainage is apparently technically easier, and initial reports suggested fewer pancreatic allograft failures using bladder drainage than with enteric drainage. In addition, bladder drainage also allows for monitoring of urinary amylase levels, which can be used as a marker for pancreatic transplant rejection (monitoring rejection of pancreatic allografts is more difficult than rejection of kidney allografts, where one can use creatinine as a relatively sensitive marker for rejection...by the time blood sugars begin to rise as a result of pancreatic rejection, it's basically game over and the pancreas can't be rescued by increasing immunosuppression). However, one of the main side effects of bladder drainage of the pancreatic exocrine fluid is that it leads to a situation of unregulated sodium and bicarbonate loss. These patients are quite sensitive to hypovolemia (as they cannot retain sodium like a normal kidney can) and can develop chronic metabolic acidosis. Thus, our patient had been given a pancreatic transplant with bladder drainage, which accounts for her dependence on salt tablets and oral bicarbonate therapy.