You are scanning the abdomen of a dog with ascites, and a possible ruptured bladder, when all of a sudden something catches your eye. That loop of small intestine is very abnormal looking. It’s not thickened, and the wall layers are normal, how do you describe it? “Corrugated” and “lasagna” are adjectives that come to mind.
Most small intestinal diseases we think of have characteristic ultrasound findings, like dilated, fluid filled loops in an intestinal foreign body, and loss of wall layering in neoplasia and IBD. While we look for these changes, peristalsis is a natural background to the ultrasound exam. Loops of small intestine occasionally dilate and contract, propelling the hyperechoic mucus or hypoechoic fluid toward the colon. But what happens when this normal motility is disturbed?
The corrugated small intestinal loop is a pattern caused by altered peristalsis. The bowel contracts in a spastic, abnormal pattern, resulting in the “corrugated” pattern, or ruffled appearance. It is most apparent in the sagittal, or longitudinal section of small intestine (figure 1, a dog with uroabdomen). You may see one loop that looks like this, or several at different times. It’s a sign of mild intestinal dysfunction.
Causes of the corrugated small intestinal loop include peritonitis, enteritis, pancreatic neoplasia, diffuse abdominal neoplasia, enteritis, thrombosis/infarction, protein losing enteropathy and acute renal failure (1). It’s a non-specific sign, but can help you to interpret other findings in the abdomen such as effusion or pancreatitis. The bowel is reacting to the local environment with its abnormal contractions. If you see this pattern, be alert for possible causes of pancreatitis, peritonitis, neoplasia, renal disease or neoplasia.
1. Moon ML, Biller DS, Armbrust LJ. Ultrasonographic appearance and etiology of corrugated small intestine. Veterinary Radiology & Ultrasound 2003;44:199-203.
Could a longitudinal foreign body like string also cause this pattern?
It could look similar, but there are differences for a linear foreign body. Linear foreign bodies cause a pattern that we call plication. In this case, the small intestine is bunched around the string with a more asymmetric pattern. The loop of small intestine can also travel back and forth since it is shortened after contracting on the string, where the corrugated loop travels fairly straight.