An Unusual Cause of High Serum Amylase in Setting of Normal Serum Lipase
Medical textbooks usually list five causes of hyperamylasemia (high serum amylase) in the setting of normal serum lipase. These are salivary gland
inflammation (most usually the parotid gland), intestinal obstruction, inflammatory bowel disease (IBD), perforated peptic ulcer, and macroamylasemia.
A salivary gland source of high serum amylase can usually be ruled out by physical examination by an oral surgeon or otolaryngologist (ears, nose, and throat surgeon).
Macroamylasemia can be ruled out by obtaining a 2 hour amylase urine test. The level should be normal.
A perforated peptic ulcer can be ruled out by a CT (computed tomography) scan that does not show free air or inflammation in the post-pyloric area.
Intestinal obstruction can be ruled out by physical exam and radiological studies (plain films of the abdomen or CT scan of the abdomen).
Inflammatory bowel disease is usually a prediagnosed condition, leading to a high index of suspicion.
One cause that is unusual but that must be considered is a perforated esophagus that mimics the same pathophysiology as a perforated peptic ulcer. A typical scenario is when patients receive transesophageal echocardiogram, which is an ultrasound test that is performed by putting a probe down an anesthetized patient’s esophagus.
Placement of this probe can cause a mechanical perforation that may not be recognized, especially if the patient is under prolonged anesthesia such as that given during a cardiac (heart) surgery.
If the patient had undergone a heart surgery, they invariably have chest tubes in place and these can be used to indirectly rule out an esophageal perforation as the cause of the increased serum amylase.
If the amylase level in the pleural fluid (chest fluid) draining out of the chest tube is the same or greater than the serum level, it is highly suspicious for an esophageal perforation. To definitively rule out this injury, both a contrast swallow and endoscopy must be performed.
If the amylase in the pleural fluid is significantly less than the serum amylase, the risk of esophageal perforation is low.
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