The Case: 38 year-old-male no PMH presents with severe RUQ pain for 1 day with nausea and nonbloody/nonbilious vomiting but no diarrhea. No history of abdominal surgeries. BP 155/103 HR 61 RR 18 Sp02 100% on room air temp 97F. On physical exam patient was pale, diaphoretic, and in severe distress. His abdomen was distended and the epigastrium/RUQ was tender with +guarding and +rebound.
The initial concern was for RUQ pathology. Bedside sono showed a normal gallbladder, but fluid in Morrison’s pouch. An upright CXR did not demonstrate free air under the diaphragm. Patient had multiple bilious blood-tinged vomitus in the ED and his abdomen became rigid. Surgery was consulted and CT abdomen/pelvis was ordered. Labwork was significant for: lactate 6.1, WBC 17.53. 3L of crystalloid was given rapidly. CT showed “midgut malrotation and dilated loops of jejunum with wall thickening and ascites concerning for early or partial obstruction due to volvulus”. Patient was immediately taken to OR for ex-lap and Ladd’s procedure. Per surgery note, “The entire small bowel was blackened, and following detorsement, regained its pink color within minutes, suggesting reversible ischemia.” The patient’s post-op course was eventful, and he was discharged on post-op day #14.
Background: Midgut volvulus is a surgical emergency that can quickly progress to bowel necrosis and death. It is a rare presentation in adults that easily masquerades as other abdominal pathology, which may delay definitive care. Selecting the appropriate imaging investigation can be a challenge in the ED.
Pathophysiology: During normal embryonic development, the GI tract herniates through the abdominal cavity and undergoes 2 counterclockwise rotations around the superior mesenteric vessels followed by a fixation of the bowels. Any variation in the rotation or the fixation is known as malrotation and this strongly predisposes to volvulus, the complication whereby a portion of a bowel twists around its mesentery causing bowel obstruction and ischemia. Midgut volvulus refers to when the entire small bowel is involved. Presentation can occur at any age, however 75% of cases present in the first month of life. Symptoms may include vomiting, constipation, abdominal pain and distention, but all of these are non-specific.
free fluid in Morison's pouch
possible distended bowel with wall edema
transposition of SMA/SMV with SMA on the right and SMV on the left
"whirlpool sign" is the swirled appearance of the mesentery and SMV around the SMA, appears clockwise on sono
"whirlpool sign" appears counter-clockwise on CT
red arrow: dilated loops of bowel with gray attenuation indicating ischemia orange arrow: radial array of dilated small bowel loops with the mesenteric vessels converging to a central point, very specific for midgut volvulus
air fluid levels
"string of pearls" sign as a result of the trapped air, peristaltic hyperactivity, and fluid-filled bowel
hyperdense echogenic area indicating free air
pediatric midgut volvulus xray demonstrating "corkscrew sign", the spiral appearance of the distal duodenum and proximal jejunum
Plain films are of little utility. They may be useful in ruling out other pathology such as a perforated viscous. Radiographs are 50-60% sensitive for small bowel obstructions, but lack sensitivity or specificity for midgut volvulus. The classic “coffee bean sign” is pathognomonic for sigmoid volvulus (not midgut) and this up to 80% sensitive for that pathology
Upper GI series is the preferred diagnostic test for midgut volvulus in neonates with sensitive ranging between 85-95% and specificity > 95%. Because the incidence of midgut volvulus in adults is so rare, dedicated fluoroscopy to look for midgut volvulus as an initial ED test would not be practical.
CT scan is a useful imaging modality for adult patients with non-specific presentations. In midgut volvulus, small bowel obstruction, bowel ischemia, free fluid, and pneumoperitoneum may be seen. Specific findings of midgut volvulus include:
- whirlpool sign- swirled appearance of the mesentery and superior mesenteric vein (SMV) around the superior mesenteric artery (SMA)
- malrotated bowel configuration
- SMA/SMV transposition
- bowel obstruction
Ultrasound is useful for quickly assessing for free fluid, free air, gall bladder pathology, and bowel obstruction. It can detect as little as 2cc of free air and 50-70cc of free fluid. Morison’s pouch is the most sensitive area for free fluid collection. Free air is assessed using a high frequency linear probe in the RUQ where there is no bowel. If free air is present, there will be a hyperdense echogenic area in the dependent peritoneal stripe. Additionally, specific findings of midgut volvulus seen on sono include:
- whirlpool sign
- malrotated bowel configuration
- SMA/SMV transposition
- solitary hyperdynamic pulsating SMA
- inappropriate SMV
- truncated SMA
Treatment: Management of midgut volvulus starts with resuscitation and ends with surgery as the definitive treatment. Patients with ischemic bowel may present in shock with metabolic acidosis or have severe electrolyte derangements that should be aggressively addressed with IV fluids and electrolyte repletion.
Vasopressors may be required to maintain MAP. Dopamine has traditionally been recommended for ischemic bowel because low-dose dopamine causes splanchnic vasodilation whereas noriepinephrine and high dose epinephrine cause intense splanchnic vasoconstriction. Selecting the appropriate vasopressor is critical when any worsening ischemia could threaten any marginally viable bowel.
In multiple animal trials, dopamine was found to hasten gut ischemia in subjects with hemorrhagic shock. Moving on to human cohorts, JAMA published a randomized interventional study comparing dopamine and norepinephrine on systemic and splanchnic oxygen utilization in sepsis. In both groups, oxygen delivery was improved, however the gastric intramucosal pH increased significantly in the norepinphrine group and decreased significantly in the dopamine group (P<.001) leading the authors to conclude that norepinephrine may have a more favorable effect on splanchnic perfusion. There are no meta-analyses on the subject, however there is substantial literature on the lack of renal perfusion benefits of low-dose dopamine. We conclude that the supposed benefits of low-dose dopamine in patients with gut ischemia was theoretical and has been mostly debunked, despite a paucity of literature.
- Midgut volvulus is a rare and potentially deadly cause of abdominal pain in adults
- Time is bowel and early diagnosis is critical
- Ultrasound is the ideal early diagnostic modality
- Aggressively resuscitate with fluids, add pressors if needed
- Avoid dopamine as this may paradoxically exacerbate bowel ischemia
Blog Post by: Dr. Wendy Chan
Case Presentation on 3/9/16 by: Dr. Carla Sterling
Faculty Advisor: Dr. Ian DeSouza
Special Thanks: Dr. Andy Grock
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