A hernia is a protrusion of any viscus from its normal cavity, for example, bowel bulging through the abdominal wall. Hernias are classified by anatomic location, hernia contents, and the status of those contents (e.g., reducible, incarcerated, or strangulated). The most common abdominal hernias are inguinal, ventral, and femoral hernias (Fig. 46-1).
Predisposing factors include family history, lack of developmental maturity, undescended testes, genitourinary abnormalities, conditions that increase intraabdominal pressure (e.g., ascites or pregnancy), chronic obstructive pulmonary disease, and surgical incision sites.
Most hernias are detected on routine physical examination or inadvertently by the patient. When the contents of a hernia can be easily returned to their original cavity by manipulation, the hernia is defined as reducible. A hernia becomes incarcerated when its contents are not reducible. Incarcerated hernias may lead to bowel obstruction and strangulation. Strangulation refers to vascular compromise of the incarcerated contents and is an acute surgical emergency. When not relieved, strangulation may lead to gangrene, perforation, peritonitis, and septic shock.
Symptoms other than an obvious protruding mass from the abdominal wall include localized pain, nausea, and vomiting. Signs of strangulation include severe pain and tenderness, induration, and erythema over the site. Children may exhibit irritability and poor feeding. Careful evaluation for obstruction is essential.
DIAGNOSIS AND DIFFERENTIAL
Physical examination is the predominant means of diagnosis. Laboratory testing is of minimal value. Ultrasonographic detection of hernias is operator and body habitus dependent but can be helpful in pediatric and pregnant patients where radiation exposure is a concern (Fig. 46-2). Computed tomography remains the best radiographic test for the evaluation of hernias and can more easily identify the less common hernia types such as Spigelian or obturator.
Ultrasonographic detection of incarcerated hernia. A. An incarcerated femoral hernia is demonstrated as a small - bowel segment herniated through the femoral canal. B. In an incarcerated incisional hernia, a small-bowel segment (arrow) is demonstrated as herniated through a small orifice in the abdominal wall. Dilated small-bowel loops are evident proximal to the incarceration. C. In an umbilical hernia, a herniated small - bowel segment is demonstrated within the fluid space in the hernia sac. The segment was softly strangulated at the femoral orifice (arrow) formed by a defect of the fascia and was easily reduced by manipulation in this case. D. An incarcerated obturator hernia is demonstrated deep in the femoral region. It locates posterior to the pectineus muscle (arrows) and medial to the femoral artery (A) and vein (V).Reproduced with permission from Ma OJ, Mateer JR, Reardon RF, et al: Ma and Mateer's Emergency Ultrasound, 3rd ed. New York: The McGraw-Hill Companies; 2014
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