Discussion
Although hernial incarceration is usually diagnosed accurately by the clinicians, its diagnosis may be difficult when the clinical presentation is atypical or when the physical examination is limited, one patient in our study had the same scenario , where incarcerated hernia was not suspected by the clinicians and in whom sonography helped to reveal the correct preoperative diagnosis of this life-threatening condition . Because an incarcerated hernia presents as a complex mass on cross-sectional imaging and usually differs considerably in appearance from a non incarcerated hernia, radiologists performing abdominal imaging should be familiar with the spectrum of imaging signs of this entity. In addition, cross-sectional imaging is necessary when the surgeon believes it is important to preoperatively define the contents of an incarcerated hernia to determine the timing of surgery. If fatty tissue, fluid, or both are present in the incarcerated hernia, time is not a limiting factor in preparing a patient for surgery. This finding is especially an advantage in elderly and multi-morbid patients. In contrast, incarcerated bowel calls for immediate surgery to prevent bowel necrosis and the subsequent necessity to resect the affected bowel loop. (Rettenbacher T, et al . 2001)
Our data suggest that the absence of blood flow in the contents of a hernia is the most important sign of strangulation because almost all strangulated hernias in our series (20%) had no detectable blood flow on color Doppler sonography , The patients in whom color Doppler sonography did not detect blood flow in the incarcerated bowel loop are patients with incarcerated hernia and bowel necrosis confirmed by surgery .
Wall thickening of herniated bowel is an important sonographic sign of incarceration in our patients , yet it does not help to distinguish obstructed from strangulated hernias . Wall thickening indicated incarceration of the hernias containing bowel with an excellent specificity but with limited sensitivity. A cutoff point of 3 mm for wall thickening in this study was obtained Some sonographic and CT studies reported in the literature state that wall thickening of the herniated bowel loop is suggestive of hernial incarceration [Stabile Ianora AA, et al. 2000]. Wall thickening of incarcerated bowel may be explained by blood congestion and edema.
Our study results show that the absence of peristalsis should be considered a sign of incarceration because strangulated herniated bowl did not show peristalsis during the sonographic investigation in a relatively high percentage of patients and if peristalsis is present in an incarcerated hernia on sonography, bowel resection at surgery is probably not necessary ( High sensitivity but low specificity ) .
Free fluid in the hernia sac is another important sign o incarceration in our study . Free fluid is an eye-catching finding on sonography because of the great difference in echogenicity between the usually anechoic fluid and the other hernial contents or surrounding tissue . This single sign immediately indicates to the investigator that a hernial complication had a high probability of being present. Free fluid in an incarcerated hernia may be explained by transudation into the hernial sac caused by the compromised blood supply of hernial contents. The fluid in the hernial sac may be clear or sanguineous at surgery [Motta J, et al.1997 ]. Although it has, this criterion alone cannot predict strangulation; it is highly sensitive for incarceration.
Another sign of hernial incarceration that we investigated was fluid within the herniated bowel loop , diameter of the herniated bowel .The free fluid indicated incarceration of the hernias containing bowel with high specificity but limited sensitivity. The reason for the presence of fluid in an incarcerated bowel loop may be exudation into the bowel lumen, causing more fluid in the bowel in cases of bowel obstruction.
An indirect sign of an incarcerated hernia was evidence of dilated, fluid-filled bowel loops in the abdomen. This sign indicated incarceration but not strangulation of the hernias containing bowel with excellent specificity but limited sensitivity . Dilated, fluid-filled bowel loops are an important sign because they may be the only suspicious cross-sectional imaging finding in patients who clinically present only with vomiting, diffuse abdominal pain, or both. We observed this scenario in one patient. Almost all patients with an incarcerated hernia containing bowel can be expected to have complete bowel obstruction. For the absence of this sign in a relatively high percentage of patients we suggest the following explanations: incarceration is not complete and some chyme passes through, the time from the onset of incarceration to diagnostic imaging is too short to develop dilatation of bowel loops in the abdomen, and a Richter’s hernia is present in which only part of the bowel wall is herniated.
Gas in the bowel wall or free gas, either in the abdomen or the hernia sac, is considered a sign of a complicated hernia, but in our study, no patient had such an advanced stage of an incarcerated hernia.
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