Small bowel stricture after blunt abdominal trauma: missed diagnosis?

Blunt and penetrating abdominal trauma is an important cause of morbidity and mortality. In blunt abdominal trauma (BAT), liver and spleen are the most commonly involved organs as reported in 35 - 55% and 40 - 50% of patients respectively.[1,2] Other solid organs that may be involved include the pancreas and kidney. Among hollow organs small intestinal injury is common and is the third most commonly involved organ.[1,3]

BAT is usually due to road traffic accidents. Modes of injury include seat belt or steering wheel injury. Other uncommon modes include falls, being hit by moving objects, or heavy objects falling over the abdomen. There has been a significant increase in road traffic accidents over the last decade due to increasing number of vehicles and deteriorating road traffic conditions. Thus the incidence of BAT is also on the rise. About two third of BAT patients are male, with a peak age of incidence between 30 - 40 yrs. [4]

Mechanism of BAT includes either a concussive or a decelerative force. [5] The former leads to sudden increase in intraluminal pressure with rupture of the bowel, localized perforation or abscess formation. This in long term results in healing and scarring.[6] Decelerating forces cause bowel or vascular damage due to difference in relative mobility of abdominal organs. This is evident by the preponderance of lesions near the areas where there is a high gradient of mobility between different structures. These includes duodeno-jejunal junction and within 50 cm of terminal ileum which when combined together constitute around 50 - 60% of all lesions.[4] Yet another mechanism involves a rent in the mesentery which may completely cutoff the vascular supply and precipitate ischemia in the perfused area.[7] The last mechanism proposed is thrombosis of mesenteric vessels.[8] This hypothesis has been validated by the findings of intimal thickening and recanalized thrombi in these vessels on histopathological examination of resected gut specimen.

Pediatric patients have a different organ injury profile from that of adults. There is significantly less protection, as the muscle walls are thinner and there is less fat. Ribs protecting the thoracic abdomen have greater flexibility compared to adults and while this protects the ribs from damage, it allows them to injure the abdominal organs more easily. The organ attachments are also more elastic, which increases the chances of tearing and shearing injuries. In the pediatric patient the bladder extends to the umbilicus, thus increasing its chance for injury. [9]

Histopathological examination of the resected specimen is crucial for determining the exact etiology. Lein et al have elegantly described the histopathology of post-traumatic small bowel strictures in their study. [10] They reported that on macroscopic examination the stenotic areas show healed and shallow ulcers. The proximal dilated segments may show deep ulcers that reach the submucosa or muscularis propria. These proximal ulcers may represent associated minor insults. On cut surface either entire or part of the bowel circumference is found scarred and fibrosed. On microscopic examination the shallow ulcers are floored by granulation tissue that is partially covered with regenerating surface epithelium. The submucosa shows fibromusculosis and neovascularization. Subserosal areas show chronic inflammatory cells and foreign body reaction.

Arterioles in the area have intimal thickening with organized thrombus in their lumen, which is partially recanalization. Initial assessment and management of patients with BAT remains a challenge because the spectrum of injuries ranges from trivial to catastrophic. The patient is initially evaluated based on history, clinical examination and basic imaging like X-rays. Tools for further specific evaluation include DPL (direct peritoneal lavage), FAST (focused assessment with sonography in trauma), CT scan of abdomen and sometimes diagnostic laparoscopy. DPL has excellent sensitivity for detecting BAT (98%) but has been criticized for being over sensitive to trivial injuries thus contributing to higher rate of nontherapeutic laparoscopies. FAST is an established modality for the evaluation of BAT. It is a cheap and easily accessible tool with very good sensitivity (76 - 90%), specificity (95 - 100%) and diagnostic accuracy. [11] Contrary to other reports a recent Cochrane database did not find sonography to offer any added advantage over other modalities of investigations.[12] CECT abdomen is the best among all existing modalities with a sensitivity of 97.7%, specificity of 98.5% and overall accuracy of 99.4%.[13] Despite the available array of diagnostic techniques, trivial injuries may still go undetected. One of the rare long term complications in these patients is small intestinal stricture, as has been reported in various case series. Such strictures present with features of small intestinal obstruction weeks to months or even years after the original trauma.[14,15,16] Usually there is single stricture, but multiple strictures have also been reported.[17] A 1967 review of world literature found only 48 cases of traumatic bowel strictures since 1901.[18]

Benign small bowel stricture is a common cause of small intestinal obstruction. In India tuberculosis is the most common identifiable cause of this entity (3 - 20%). [19] Other causes include Crohn’s disease, ischemic bowel disease, chronic NSAID use and idiopathic strictures. In case of idiopathic strictures it is possible that some of the patients might have past history of BAT that was trivial enough to be forgotten. Ischemia may be involved in the pathogenesis of these strictures. As reported by Mansad et al, about 70% of all strictures caused by either tuberculosis or Crohn’s disease are associated with blocked mesenteric vessels.[20] Thus, histology is helpful but not diagnostic and other causes of ischemia are difficult to exclude. The present study is a retrospective analysis of prospectively maintained data.[21] Eight consecutive patients of small bowel stricture after BAT were examined. The average time of presentation was 138 days after BAT, although the total number of BAT patients analyzed is not available. Thus it is not possible to calculate other epidemiological aspects of this entity. The symptoms range from non specific abdominal fullness, becoming worse postprandially to subacute onset abdominal distension associated with recurrent vomiting and obstipation. On evaluation the patients have dilated small bowel loops on X-ray FPA with or without air fluid levels. CECT abdomen reveals strictured segment(s) of small bowel with proximal dilation. Management includes resection of diseased segment(s) followed by end to end anastomosis. Long term results of the treatment are good.[22]

Given the rising incidence of RTA, the incidence of blunt abdominal trauma is bound to escalate. It will thus be wise to keep in mind the history of past abdominal injury while evaluating patients who presents with features of subacute small intestinal obstruction due to idiopathic strictures.

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