GI Radiology > Small Bowel > Quiz > Case 1 Answers

Quiz: Case 1 Answers

1. In which position is this patient?
Upright
Supine
Decubitus

This frontal abdominal film was taken with the patient in the supine position. Remember that fluid layers to the dependent portion, so that upright and decubitus views will demonstrate air-fluid levels in the stomach and possibly the bowel. Air-fluid levels are not typically seen on supine films, even in cases of SBO. In addition, evaluation of free air depends on patient positioning. Free air will manifest under the diaphragms on upright films and lateral to the liver on left lateral decubitus (left side down) films. Free air is generally much more difficult to see on supine films.


2. What is the salient abnormality?
Small bowel dilatation
Large bowel dilatation
Small and large bowel dilatation
Pneumoperitoneum

This supine abdominal film demonstrates multiple air-filled loops of dilated small bowel. Note that the loops are centrally located in the abdomen, taking on a stair-step configuration. An upright film on the same patient would demonstrate multiple air-fluid levels.


3. What is the upper limit of normal for luminal caliber of the small bowel?
3 mm
9 mm
3 cm
6 cm
9 cm

Remember the 3-6-9 rule. The upper limit of normal for small bowel is 3 cm, for large bowel is 6 cm, and for the cecum is 9 cm. 3 mm is the upper limit of normal for fold thickness.


4. Which of the following is not a cause of small bowel obstruction?
Hernia
Pancreatitis
Intussusception
Adhesions
Volvulus

Small bowel obstruction (SBO) occurs as a result of mechanical blockage. In adults, the vast majority of SBO are caused by hernias or adhesions, with much less likely etiologies including neoplasms and volvulus. The major differential consideration for dilated loops of small bowel is adynamic ileus, which causes a functional obstruction. The inflammatory changes of pancreatitis can cause a focal ileus, which may manifest as a "sentinel loop" of dilated bowel.

The differential for SBO in a pediatric patient can be remembered with the mnemonic AIM:

A - Adhesions
A - Appendicitis
I - Intussusception
I - Inguinal hernia
M - Malrotation (with volvulus)
M - Meckel's diverticulum

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