Since renal insufficiency is known to be one of the reported causes of hyperamylasemia, the incidence with which this occurs was investigated in patients with chronic renal failure and on chronic maintenance hemodialysis. Moreover, amylase clearance (C
Am) to creatinine clearance (C
Cr) ratios and amylase isoenzyme patterns were determined to evaluate their usefulness in differentiating the hyperamylasemia of such patients from others.
Hyperamylasemia (more than 186 Somogyi units/100ml, which is mean+3 standard deviations of 100 normal persons of 16 to 50 years old) was observed in 50% of the 26 patients with chronic renal failure and 86% of the 84 patients under hemodialysis. The highest serum amylase activity in these patients was 476S.U./100ml. Total serum amylase activity was inversely related to C
Cr?
Although it is generally accepted that renal insufficiency results in an elevated serum amylase level, the markedly reduced amylase clearance of these patients was not reflected by a proportional increase in the serum amylase level, because some patients with chronic renal insufficiency had the normal serum amylase activities. These results may suggest the existence of some extrarenal mechanisms to remove amylase from the serum or the reduction of amylase entering the serum in renal insufficiency.
Amylase clearance to creatinine clearance ratios of patients on hemodialysis and patients with chronic renal failure (5ml/min<C
Cr<70ml/min) was not significantly different from those normal subjects (2.9±0.4%), since amylase clearance was reduced in proportion to creatinine clearance in these patients. Unlike in those patients, the ratio C
Am/C
Cr was significantly increased (9.8±0.9%) in patients with severe impaired renal function (C
Cr less than 5ml/min). These observations indicate that C
Am/C
Cr ratios are of no value for diagnosing acute pancreatitis in patients with severe renal failure, as they elevate in the absence of any clinical signs and symtoms of pancreatitis.
However, analysis of amylase isoenzyme revealed the normal isoamylase pattern in most patients with renal insufficiency, even in those with elevated C
Am/C
Cr ratios. The ratios of the salivary to the pancreatic type isoamylase were similar in both the control and the patients with chronic renal failure. Normal isoamylase pattern probably excludes the diagnosis of pancreatitis in these patients.
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