Sign in →

Test ID: AMSU Amylase, Timed Collection, Urine

Reporting Name

Amylase, Timed Collection, U

Useful For

Assessment of acute rejection of bladder-drained pancreas transplants

 

As an aid in the diagnosis of acute pancreatitis

Specimen Type

Urine


Necessary Information


For any timed collection the volume and length of collection is required.



Specimen Required


Supplies: Aliquot Tube, 5 mL (T465)

Container/Tube: Plastic, 5-mL tube (T465)

Specimen Volume: 5 mL

Collection Instructions:

1. Collect a 2-hour urine specimen.

2. The patient should have nothing by mouth except water between the hours of 6 p.m. and 10 a.m.

3. The bladder should be completely emptied at 8 a.m. This urine is discarded.

4. An adequate urine specimen (>100 mL) is ensured if the patient drinks 3 or more 8-ounce glasses of water. Half of this amount should be ingested between 7:30 a.m. and 8 a.m. The second half should be ingested at 8:30 a.m.

5. Collect all urine after 8 a.m. in container supplied.

6. The collection ends at 10 a.m. Include the 10 a.m. void in the collection container.

7. Measure and record the 2-hour volume.

8. Overlay urine with toluene (5 mL), and send aliquot. If no toluene is available, refrigerate specimen during collection, and send the aliquot specimen frozen.

9. Record the date and time (the exact start and completion times of the 2-hour collection) on the container label.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 7 days
  Frozen  7 days

Reference Values

3-26 U/hour

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

82150

LOINC Code Information

Test ID Test Order Name Order LOINC Value
AMSU Amylase, Timed Collection, U 15350-2

 

Result ID Test Result Name Result LOINC Value
AMY_U Amylase, Timed Collection, U 15350-2
TM21 Collection Duration 13362-9
VL19 Urine Volume 28009-9
AMYCN Amylase Concentration 38192-1

Clinical Information

Amylases are enzymes that hydrolyze complex carbohydrates. They are produced by a number of organs and tissues, predominantly the exocrine pancreas (P-type amylase) and salivary glands (S-type amylase). Plasma amylases are of relatively low molecular weight for an enzyme (55,000-60,000 daltons) and enter the urine through glomerular filtration. Conditions that cause increased entry of amylase into plasma (eg, acute pancreatitis) will thus result in increased urinary excretion of amylase. Therefore, urinary amylase is sometimes used in the diagnosis of acute pancreatitis. However, the rate of urinary amylase excretion appears to be less sensitive than plasma markers, and is not specific for the diagnosis of acute pancreatitis.

 

Similar to other low-molecular-weight proteins filtered by glomeruli, amylases are reabsorbed to an extent by the proximal tubule. Thus, conditions associated with increased production and glomerular filtration of other low-molecular-weight proteins that compete with tubular reabsorption of amylase or conditions of proximal tubular injury may increase urinary amylase excretion. Also, a number of disorders other than acute pancreatitis may cause increases in plasma amylase concentrations and consequent increases in urinary amylase excretion. These conditions include burns, ketoacidosis, myeloma, light-chain proteinuria, march hemoglobinuria, acute appendicitis, intestinal perforation, and following extracorporeal circulation.

 

Quantitation of urinary amylase excretion is also useful in monitoring for rejection following pancreas transplantation. The duodenal cuffs of donor pancreases are often surgically anastomosed to the recipient's bladder at the time of pancreas transplantation, allowing for drainage of exocrine pancreas fluid into the bladder. In pancreatic rejection, urinary amylase excretion decreases.

Interpretation

Decreases in urinary amylase excretion of greater than 30% to 50%, relative to baseline values, may be associated with acute pancreas allograft rejection. Because there is large day-to-day variability in urinary amylase excretion following pancreas transplantation, if a significant decrease is noted, it should be confirmed by a second collection. There is also large inter-individual variability in urinary amylase excretion among pancreas transplant recipients. Collecting a timed urine specimen and expressing the urinary amylase level as Units excreted/hour might reduce variability and improve test performance. However, acute rejection is usually not established solely by changes in urinary amylase excretion, but by tissue biopsy.

 

Urinary amylase is elevated in acute pancreatitis, but the test has poor sensitivity and specificity.

Clinical Reference

1. Tietz Textbook of Clinical Chemistry. 3rd edition. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Co., 1999, pp 689-698

2. Munn SR, Engen DE, Barr D, et al: Differential diagnosis of hypo-amylasuria in pancreas allograft recipients with urinary exocrine drainage. Transplantation 1990;49:359-362

3. Klassen DK, Hoen-Saric EW, Weir MR, et al: Isolated pancreas rejection in combined kidney pancreas transplantation. Transplantation 1996;61:974-977

4. Benedetti E, Najaran JS, Gruessener AC, et al: Correlation between cystoscopic biopsy results and hypoamylasuria in bladder-drained pancreas transplants. Surgery 1995;118:864-872

Analytic Time

1 day

Method Name

Enzymatic Rate

Forms

If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Client Test Request (T728) with the specimen.

Mayo Clinic Laboratories | Gastroenterology Catalog Additional Information:

mml-gi-pancreas-pancreatitis