Diagnostic peritoneal lavage (DPL) was invented by David Root at this hospital (Ancker Hospital, which then became St. Paul Ramsey, now Regions Hospital) in the 1960’s. It enjoyed its heyday during the 70’s and 80’s, when it was done hundreds of times per year at most major trauma hospitals. Now, we do it about 5 times per year. What happened?

As you know, DPL is a qualitative test. It gives a yes/no answer to the question “does this patient need an operation?” based on red and white blood cell counts. During the mid-1980s, CT scanning was introduced, which provides much more quantitative information about injuries in the abdominal cavity. The improved ability to diagnose abdominal injury, especially solid organ injury, has led to the demise of DPL.

Most solid organ injury results in some free blood in the peritoneal cavity. It doesn’t take much blood (10 cc of whole blood mixed with 1 liter of infused crystalloid) to exceed the threshold of 100,000 RBC per ml of aspirate that will send the surgeon off to the OR. Therefore, pretty much any liver or spleen laceration would have to be taken to the OR based on a DPL.

But we know that very few liver/spleen injuries actually need an operation. So DPL cannot be used, or the negative laparotomy rate for blunt trauma would escalate. The other downside to DPL is that it’s not possible to get all of the infused crystalloid back out of the abdomen. This leads to a confusing amount of free fluid seen on any CT scan done after a DPL.

So DPL is now down but not out. Some practical pointers:

• DPL should be used primarily as a backup to an equivocal or unbelievable FAST exam in an unstable patient. An example would be a patient who is hypotensive, has a negative FAST and no other obvious bleeding sources.
• Remember to insert a gastric tube and urinary catheter so the stomach and bladder are decompressed before the procedure. The easiest way to remember this is to tape these catheters to the DPL procedure tray.
• A DPL is actually 2 procedures: peritoneal tap and lavage. Once the catheter is in, it should be aspirated. If 10cc of gross blood is returned, the test is positive and the patient needs to go immediately to OR.
• For blunt trauma, the threshold for RBC per µl is 100,000. The threshold for WBC is 500 per µl. If particulate material or weird colors are seen (stool or bile), the test is also considered positive. Send the sample for cell counts only. Don’t send for any other assays (e.g. amylase). 
• For penetrating trauma, the thresholds have never been well defined. A number around 25,000 RBC per µl probably provides the best balance between sensitivity and negative laparotomy rate.

Reference: Diagnostic peritoneal lavage. HD Root, CW Hauser, CR McKinley, JW LaFave, RP Mendiola Jr. Surgery 57(5):633-637, 1965.