A 67 year old man has been unwell for 10 days. He had some right upper quadrant pain, fevers, and then in that last 3 days has had abdominal distension, vomiting and has stopped passing stool or flatus. You suspect bowel obstruction.
Describe and interpret these scans
Image 1: The linear transducer is placed over the right lower abdomen.
A fluid filled distended loop of aperistaltic small bowel is seen. The valvulae conniventes are beautifully outlined by luminal fluid, this is called the keyboard sign – the image is thought to evoke the image of a piano keyboard.
Image 2: The curvilinear transducer is placed over the right iliac fossa and the small bowel followed searching for a transition point.
A round luminal mass is seen causing the obstruction. This has a rounded shaped and casts a dense and dark acoustic shadow. It is a large gallstone that has eroded through the gallbladder wall into duodenum and passed distally until the smaller ileum where it causes obstruction – gallstone ileus. Image 3: The left upper quadrant.
A nasogastric (NG) tube is passed to empty the fluid filled stomach. Ultrasound confirms the intragastric position of the NG tube. Swirling fluid is seen filling the stomach, soon to be drained!
Ultrasound can be very useful in detecting bowel obstruction but often the cause is more elusive and CT is more reliable. Fluid filled distended bowel loops with varying degrees of peristalsis are typical. Early intestinal fluid can be seen to flow too and fro as peristalsis pushes it forward, then as relaxation occurs it flows back. Later aperistalsis occurs. Air fluid levels can be seen but are more difficult to interpret.
Sometimes a transition point and cause for obstruction is seen. Hernia, tumour, intussusception and gallstone ileus are some of the causes that can be sonographically identified.