Small bowel perforation after blunt injury abdomen and causes of delay in diagnosis

INTRODUCTION

The diseases of the small bowel are very rare in occurrence. In contrast, there are various kinds of contributory causes to perforation of the small bowel. These are classified as follows, traumatic, foreign body, ulcerative, tumorous, ileus, vessel originated-disease and idiopathic. Needless to say, the death of perforation is closely associated with the time interval from onset to operation.
The small intestine occupies a relatively large surface area within the peritoneal cavity and thus is frequently injured in patients with penetrating abdominal trauma. Because the small bowel is relatively mobile, has a lower bacterial flora, and has fewer anaerobes than the colon, peritoneal contamination secondary to small bowel injuries is better tolerated than that associated with colon injuries.
The Penetrating Abdominal Trauma Index (PATI), which quantitates the severity of abdominal injury based on risk factors associated with specific organs, employs a multiplier of 3 for small bowel injuries (compared with 4 for colon and liver, and 5 for pancreas and duodenum).

• The management of penetrating small bowel injuries for these reasons is generally straightforward, with simple repair being the rule.

INCIDENCE

• Estimates of the incidence of small bowel rupture associated with blunt abdominal injury range from 3 to 18%.
• The death related to perforation of the small bowel 17.1% which is between those of the colon (27.3%) and the stomach and duodenum (1 1.1%), respectively.

DELAY IN DIAGNOSIS

• It is generally accepted that delay in diagnosis in common because definite clinical signs is prone to being concealed. It is due to a low incidence of the appearance of free gas in the peritoneal cavity on abdominal X-ray film. To salvage the patients in early stage, surgeons should be alert to a latent interval in this stage.
• The diagnosis of SBI is now more frequently made on the basis of clinical signs or an abnormal CT scan, than as an associated injury during a trauma laparotomy. As a result, delays in the diagnosis of SBI may occur and contribute significantly to morbidity and mortality.
• Small-bowel perforations are often minute and may seal temporarily before free air is noted." Associated spasm of the circular muscle above and below the level of the perforation, results in a localised ileus which further prevents leakage. After 5 or 6 hours the spasm passes off and contamination of the peritoneal cavity occurs as the isolated segment takes part in the peristaltic activity again.
• ' Klinger" described 50 patients of all ages, in only 10 of whom he noted free air; in one of them the perforation only became evident on delayed films. Delay in diagnosis may occur as a result of late rupture of an intramural haematoma'" or after serosal and tunica muscularis tears, or after interference with the blood supply, as occurs in avulsion injuries." Delayed diagnosis may also be the result of lack of careful examination in patients with multiple injuries."
  
• In the digestive organ with the lumen, it is necessary that traumatic perforation should be quickly detected and treated. It is without saying that a presence of free gas is a confirmable finding.
• In contrast, abdominal free gas is unlikely to appear and often fails to detect in the early stage.

Pathogenesis of perforation of the gut is much different from each other. It is well known that perforation of lower part of the gut more frequently provokes endotoxic shock.

Summary of Amount and Location of Free Air according to Perforation Sites
Perforation ------------Site --------------Amount Location
Stomach/duodenum -----Abundant --------Around liver and stomach
Post-bulbar duodenum ---------------------Right anterior pararenal space
Small bowel -------------Small -------------Mesenteric folds, around liver
Appendix ---------------Small/absent -----Around appendix
Large bowel ------------Variable ----------Pelvis, mesenteric folds, retroperitoneal space

• Motor vehicle accidents are the main cause of blunt SBI. The increase in seat belt use has resulted in lower fatality rates and injury severity, but has been accompanied by a concomitant increase in rates of intestinal injuries.
• Blunt trauma commonly occurs as a result of motor vehicle crashes, falls from heights, and interpersonal assaults with blunt objects.
  

Intestinal injuries can occur secondary to blunt trauma by two major mechanisms:

1. Horizontal deceleration or shearing can occur in patients involved in collisions. The regions that are affected most commonly are near junctions between fixed and nonfixed points of bowel (i.e., proximal jejunum, terminal ileum).

2. Direct blow with a linear object (seat belt) across loop of bowel, with a subsequent "blowout" injury, can occur at any point of the intestine or the mesentery.

• Serial clinical evaluations of the abdomen are extremely useful in the diagnosis of SBI, particularly in patients with additional associated intra-abdominal injuries.
• A bruise across the abdomen inflicted by a seat belt ("seat belt sign") and ongoing abdominal pain are known associated risk factors of SBI.
• Fakhry et al. observed that 67.7% of 198 patients with blunt SBI initially presented with signs or symptoms highly suggestive of this lesion, and 84.3% were taken to the operating room without delay. In this study, of the patients involved in motor vehicle crashes, only 30% had the abdominal seat belt sign, which is less than that commonly reported in the literature (nearly 50%). Consistent with prior reports, the most frequent clinical signs were abdominal pain upon admission (75.6%) and abdominal tenderness upon physical examination (46.7%).
  
• Diagnosis of these injuries remains problematic. Early recognition of SBI is important in the prevention of morbidity. DPL is more sensitive than CT imaging for diagnosis of SBI; however, in many cases, it results in nontherapeutic laparotomy. CT imaging is newer than DPL, and it has become popular in recent years. The major advantages of CT include noninvasiveness, capacity to quantify free fluid, the ability to select patients with solid organ injury for non-operative management, and the ability to view retroperitoneal organs.
• Saku et al. analyzed the CT findings of 12 patients with SBI perforation due to blunt trauma, all patients underwent radiography and CT, and five underwent presurgical follow-up CT. Radiography demonstrated free air in only 8% (1/12) and 25% (3/12) at the initial and follow-up examinations, respectively. In contrast, the initial and followup CT scans detected extraluminal air in 58% (7/12) and 92% (11/12), respectively, suggesting that the incidence of extraluminal air increases as time elapses, prompting the authors to recommend a repeat CT, particularly after 8 h, in suspect cases to increase sensibility. Mesenteric fat obliteration was seen in 58% (7/12) and 75% (9/12) at initial and follow-up CT, respectively.