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RD7.4 | Imaging in Surgery — PBL Case

CLINICAL SETTING

You are the surgical house officer on the acute take at a district general hospital. A 58-year-old woman is referred from the emergency department with a 3-day history of colicky central abdominal pain, several episodes of bilious vomiting, abdominal distension and absolute constipation (no flatus for 24 hours). Her past history is notable for an open appendicectomy in her twenties and a caesarean section. On examination she is dehydrated, the abdomen is distended and tympanitic with high-pitched bowel sounds, and there is a soft, non-tender, reducible umbilical swelling. She is not peritonitic. Work through this case as a group, deciding what to investigate, how to interpret the images, and how the imaging changes management.

Trigger 1: The first film

You suspect intestinal obstruction clinically. An erect and supine abdominal radiograph is obtained. The supine film shows multiple dilated loops of bowel in the central abdomen with mucosal folds (valvulae conniventes) that cross the full width of the lumen; the loops measure up to 4 cm. The erect film shows several air-fluid levels. There is no free gas under the diaphragm.

DISCUSSION POINTS

  • Why is an erect and supine abdominal X-ray the appropriate first investigation in suspected intestinal obstruction, and what is its logic in the speed-then-detail imaging strategy?
  • From the described folds, loop position and calibre, is this small-bowel or large-bowel obstruction? Explain how valvulae conniventes (full-width) differ from haustra and how loop position and calibre support your answer.
  • What does the absence of free gas under the diaphragm tell you, and what would free gas have indicated?
Click to reveal Trigger 2: Mapping the level and cause (discuss previous trigger first!)

Trigger 2: Mapping the level and cause

The patient is resuscitated with intravenous fluids and a nasogastric tube is placed (drip and suck). Because the cause and level are not yet clear and you must exclude a closed loop and ischaemia, a contrast-enhanced CT of the abdomen and pelvis is performed. It confirms small-bowel obstruction with a transition point in the right iliac fossa, adhesional banding at the site of the previous surgery, normally enhancing bowel walls, and no closed loop or free fluid. The reducible umbilical hernia contains only fat and no obstructed bowel.

DISCUSSION POINTS

  • What does CT add beyond the plain film in intestinal obstruction (level, cause, closed-loop, ischaemia), and why is this information needed before deciding on surgery?
  • What is the commonest cause of small-bowel obstruction, and how does this patient's surgical history fit?
  • Why is barium contraindicated when perforation is possible, and what contrast strategy is preferred in this setting?
Click to reveal Trigger 3: When the picture changes (discuss previous trigger first!)

Trigger 3: When the picture changes

Twelve hours into conservative management the patient develops increasing, now constant, abdominal pain, tachycardia and localised tenderness. A repeat CT shows a closed-loop segment with bowel-wall thickening, reduced wall enhancement and a moderate volume of free fluid.

DISCUSSION POINTS

  • Which CT findings now indicate ischaemia and a closed loop, and how do these differ from the earlier reassuring scan?
  • How does this change the management decision from conservative (drip and suck) to emergency operative intervention, and why is timing critical?
  • How does this case illustrate the integrate (KH) principle of RD7.4 — converting an imaging picture into a surgical decision — and what is the role of serial imaging when the clinical picture changes?

Group Task Assignments

  • Create a side-by-side comparison table of small-bowel versus large-bowel obstruction on plain film (loop position, fold type, calibre thresholds, caecal diameter) and present it to the group.
  • Draft a one-page algorithm for the imaging of suspected intestinal obstruction, from clinical suspicion through erect/supine AXR to CT, including the signs that mandate emergency surgery.
  • List the imaging red flags across the four surgical emergencies in this module (head injury, strangulated hernia, appendicitis, intestinal obstruction) that should trigger immediate surgical referral.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [RD7.4] What is the rational imaging sequence in suspected intestinal obstruction (erect/supine AXR first, then CT), and what does each step contribute?
  2. [RD7.4] How are small-bowel and large-bowel obstruction distinguished radiologically using fold type, loop position and calibre?
  3. [RD7.4] Which imaging signs indicate closed-loop obstruction, ischaemia and perforation, and how do they convert conservative management into an emergency operation?