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Abstract
Injury to the superior mesenteric artery and branches is an uncommon event, which is typically associated with penetrating injury and high mortality. A case is presented of rupture of a branch of the superior mesenteric artery (iliocolic artery) after blunt trauma. The case illustrates the more occult presentation and better overall prognosis associated with this type of injury as compared with injury to the proximal superior mesenteric artery. In addition this case highlights the importance of vigilance in patients who deteriorate after initial resuscitation.
- trauma
- iliocolic artery
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Abdominal vascular injury and specifically injury to the visceral arteries occurs uncommonly after blunt trauma.1 Injury to the superior mesenteric artery and resultant haemorrhage is associated with high mortality rates.2,3 This is a report of disruption to the iliocolic artery, a branch of the superior mesenteric artery, after blunt trauma.
CASE REPORT
A 29 year old man was the restrained driver of a car, which collided at approximately 60 mph with a stationary car. He was trapped in the car for one hour. The patient was alert and orientated; he had not exhibited any signs or symptoms consistent with concussion. He was transported from the accident scene by helicopter. On arrival his blood pressure was 100/70 mm Hg with a pulse of 110, within 20 minutes the systolic blood pressure had decreased to 70 mm Hg. He initially complained of right sided abdominal and leg pain. Examination revealed right sided abdominal tenderness that was maximal in the right iliac fossa with associated guarding and rebound.
He was subsequently resuscitated over the following two hours with three units of O negative blood and three litres of crystalloid solution. A standard trauma series of radiographs revealed a fracture of the right hemi-pelvis, through the iliac wing and down towards the sciatic notch, together with fractures of all four pubic rami. In addition radiographs of the right femur showed an intertrochanteric and subtrochanteric fracture.
After initial resuscitation the patient's blood pressure stabilised at between 110 mm Hg and 120 mm Hg systolic with a pulse of between 80 and 100. Abdominal ultrasound showed a small amount of free fluid around the liver but no definite liver laceration. At this stage the patient was diagnosed as having had a retroperitoneal bleed secondary to the above mentioned pelvic fractures.
After two hours, in which the patient remained stable, his blood pressure decreased 80/60 mm Hg. In view of this a laparotomy was performed, a ruptured iliocolic artery and associated tears to the mesentery of the terminal ileum were found. There was an estimated three litres of intraperitoneal blood. The injured artery was resected and repaired with an end to end anastomosis using interrupted sutures.
The patient's postoperative course was unremarkable and the patient was discharged 24 days after injury.
DISCUSSION
Blunt abdominal trauma rarely causes isolated vascular injuries. It is estimated that the superior mesenteric artery branch is affected in 9% of cases of abdominal vascular trauma.1
The small studies available indicate that the mortality rate for injury to the superior mesenteric artery is between 33% and 68%.2,3 Blunt trauma is the mechanism of injury in 23% of cases.4 With blunt trauma, the abdominal viscera are forced into the pelvis and subsequently pull on their vascular attachment. This combined with unequal deceleration can result in rupture of the mesenteric vessels.5 The injury observed in this patient was probably attributable to the abrupt deceleration resulting from impact with a stationary vehicle at 60 mph and the restraining action of the seat belt.
In 1972 Fullen et al,6 subdivided the superior mesenteric artery circulation into four zones (fig 1).
Subdivision of superior mesenteric artery into Fullen's zones.
Mortality rates vary from 100% in zone 1 to 25% in zone 3 and 4, however there were no isolated cases of zone 4 trauma.4 Patients sustaining proximal superior mesenteric artery injuries usually present with a systolic blood pressure of less than 90 mm Hg (68%–93%).2,3
This case is consistent with the assumption that zone 4 injuries may have a more occult presentation and carry a better overall prognosis. The occult presentation illustrates the difficulties inherent in making an accurate clinical diagnosis when haemorrhage is from a small intra-abdominal artery. This was further compounded by the erroneous assumption that the cause of the patient's initial hypotension was a retroperitoneal bleed secondary to pelvic fractures. It is possible that further investigation when the patient was haemodynamically stable might have resulted in earlier diagnosis of the underlying problem. Computed tomography has been shown to be both sensitive and specific in the diagnosis of intra-abdominal injury in the blunt trauma patient.7 Successful treatment of patients with injury to the visceral arteries continues to include volume replacement and rapid exposure of injuries.
Contributors
C Dewar searched the literature and wrote the paper. C.Dewar is the guarantor for the paper. D Gorman reviewed and advised on the paper.