Closed-Loop Small Bowel Obstruction on Apixaban with a Rising Lactate
A 64-year-old man with atrial fibrillation on apixaban 5 mg twice daily and two previous abdominal operations (sigmoid colectomy for diverticulitis four years ago, open cholecystectomy) presents with 36 hours of crampy abdominal pain, bilious vomiting, distension, and no flatus or stool. He is alert and oriented and gives his own consent. Temperature 37.9 °C, pulse 112/min, blood pressure 104/66 mmHg, respiratory rate 22/min, oxygen saturation 96% on room air. The abdomen is distended and tympanic with diffuse tenderness and focal guarding in the right lower quadrant; bowel sounds are high-pitched. White cell count 15.8 ×10⁹/L, lactate 3.4 mmol/L, creatinine 1.6 mg/dL (baseline 0.9), potassium 3.2 mmol/L, bicarbonate 19 mmol/L. CT with intravenous contrast shows dilated small-bowel loops, two adjacent transition points in the pelvis with a collapsed segment between them, reduced mural enhancement in that segment, and a small amount of intramural gas; there is no free intraperitoneal air. The last apixaban dose was 10 hours ago.
1. Interpret the CT findings and explain why this is no longer a candidate for a water-soluble contrast challenge or a period of observation.
Read the worked answer
The CT describes a closed-loop obstruction: two adjacent transition points with a collapsed, trapped segment between them. Three additional findings indicate the bowel is already ischemic - reduced mural enhancement, intramural gas (pneumatosis), and a lactate of 3.4 mmol/L with tachycardia, guarding and a bicarbonate of 19 mmol/L. Absence of free intraperitoneal air is not reassuring; pneumoperitoneum is a late finding and its absence does not exclude strangulation.
Why the usual conservative pathway is now wrong:
- A water-soluble contrast challenge is diagnostic and therapeutic only for a partial, uncomplicated adhesive obstruction. In a closed loop it adds delay and risks aspiration and perforation.
- Serial examinations and nasogastric decompression for 24–48 hours are appropriate for a simple obstruction without signs of strangulation; here the peritonitis, lactate and CT features already indicate compromised bowel.
- The therapeutic window matters: gangrenous bowel requires resection, and every hour of delay increases the length of bowel lost, the risk of perforation and mortality.
In short, this is a surgical emergency with clinical and radiological evidence of strangulation, and the decision should be made on the CT and the examination rather than on repeat imaging.
2. Detail your actions in the first hour and your operative plan, including how you handle the apixaban.
Read the worked answer
Resuscitation and preparation (first hour): two large-bore intravenous lines; balanced crystalloid boluses (often 20–30 mL/kg total) guided by blood pressure, urine output and lactate; nasogastric tube to decompress; urinary catheter; arterial line if unstable; type and screen; correct potassium; broad-spectrum antibiotics (for example piperacillin-tazobactam 4.5 g, or ceftriaxone plus metronidazole); consent for laparotomy including possible stoma; notify theatre and anaesthesia immediately.
Anticoagulation. Apixaban was taken 10 hours ago, so meaningful drug effect is expected. For life-threatening bleeding or urgent surgery, use andexanet alfa, or four-factor prothrombin complex concentrate 50 units/kg if andexanet is unavailable, and involve haematology and anaesthesia. Routine coagulation tests (PT/INR) do not reliably reflect apixaban effect. Do not delay source control to wait for reversal or for drug levels - but plan the reversal so it is given before incision.
Operation: midline laparotomy, identify the transition points, resect clearly non-viable bowel with a stapler, and decide on anastomosis versus stoma based on perfusion, contamination and physiological state. If the patient becomes acidotic or unstable, a damage-control approach with temporary closure and a planned second look is preferable to a prolonged definitive procedure.
Post-operatively: critical care, continue antibiotics, monitor for recurrent obstruction and for bleeding.
3. The creatinine of 1.6 mg/dL prompted a junior colleague to argue that the CT should have been done without intravenous contrast. How do you justify the decision?
Read the worked answer
The contrast was appropriate, and the reasoning should be explained in explicit risk–benefit terms.
Benefit. The single question that determined this man's life-or-limb outcome was whether the bowel was strangulated. That answer came from mural enhancement, transition points and pneumatosis - all of which require intravenous contrast. An unenhanced scan or an ultrasound would have been substantially less sensitive, and oral contrast would have delayed the scan by hours and added aspiration risk without improving the diagnosis.
Risk. A creatinine of 1.6 mg/dL in a dehydrated, obstructed patient overstates his true baseline (0.9 mg/dL). The absolute risk of contrast-associated nephropathy in this setting is small, and it is dwarfed by the mortality of infarcted bowel. The dehydration was itself treatable - volume repletion before and after the scan mitigates the renal risk.
Practical measures. Use the lowest adequate volume of iso-osmolar contrast, avoid a second contrast study in the next 48–72 hours, continue crystalloid, monitor urine output, and recheck renal function in 48 hours.
The honest counterexample. The alternative is not a 'safe' scan; it is either a delayed diagnosis of gangrene or an immediate laparotomy without a map of the anatomy. In a stable-enough patient with a surgical abdomen, the contrast study is the lower-risk path.