Saturday, June 11, 2005

Altered States/Altered Anatomy

All physicians are acquainted with normal anatomy. What can be hard, however, is to know what happens when folks like me alter that anatomy.

A 25 year old young lady presents to the ED with a 12 hour history of vague mid abdominal pain. The pain is across the mid abdomen, radiating through to the back. She denies nausea and vomiting initially, but subsequently admits to some "queasiness." Normal bowel function. No fevers. The pain has been persistent, and by the way, has occurred to a lesser degree on three other occasions since she underwent laparoscopic RYGB (gastric bypass) a few years ago. This pain prompted laparoscopic cholecystectomy several months after the bypass.

She has a completely normal lab evaluation, with a white cell count of 5K and a normal differential. Plain abdominal films are normal. Her exam is very benign, but she complains of discomfort in the right and left mid-abdomen. Next stop: the CT scanner. Score one for the ED -- gotta give due credit to the ED physician (as much as it pains me, GruntDoc and Dr. Tony) for ordering it, with no real abnormal findings and a very unremarkable exam. When going through the images, there is a very obvious abnormality occupying the middle of the abdomen (circled):

There is a large, sausage-shaped soft tissue density in what appears to be the small bowel mesentery; on the larger view, vessels can be seen, and the mass has the density of essentially water. A second view from a few cuts lower:

Once again, the majority of the mass is significantly lower in density than the normal fat of the mesentery. There is no dilated bowel anywhere in the abdomen (arrows denote normal caliber small bowel):

The radiologist's differential diagnosis includes lymphoma, sarcoma, inflammatory change, and hemorrhage. The key, however, lies in the area just above the fluid density mass:

There is a "swirl" in the root of the small bowel mesentery (circled), indicating a likely volvulus. This is certainly a soft call, but given the known history of altered anatomy with a Roux-en-Y, there is the possibility of an internal hernia. An internal hernia is something I've encountered before, but the mass seen on this CT is certainly not typical.

With persistent pain, abnormal CT, and potential for an internal hernia, we needed to spend a little time under the bright lights of the OR. Upon opening the abdomen, we were greeted with a modest amount of chylous ascites (milky white fluid resulting from obstructed lymphatic drainage). The fluid-density mass seen on CT was a large portion of the small bowel mesentery which was acutely and chronically edematous due to a large volvulus accompanying an internal hernia. The base of the mesentery was quite thick with edema, and its periphery (along with the mesenteric aspect of the small bowel -- the entire ileum and half the jejunum) was bright white with chyle in obstructed lymphatics. Interestingly, unlike a more typical presentation, there was absolutely no bowel obstruction. Here is a series of films of a more classical presentation of internal hernia (click the arrows for all of the pictures). This abstract lists the 7 most common CT findings of bowel obstruction in post-RYGB patients.

It is easy to overlook that often the difficulty in caring for gastric bypass patients is not the actual surgery -- it is being aware of the potential complications of that operation, both acutely and long term. Without an ED physician aware that these patients can do "funny things," she would not have had a CT. Without the knowledge of her altered anatomy, it would be easy to take a "wait and see" approach before operating; this can lead to ischemic bowel and a much worse outcome. For these patients, if there is any doubt, the OR is a very good place to be.