Ultrasonography is a noninvasive, easily performed, readily available, and relatively inexpensive modality. Its use in the diagnosis of abdominal wall hernias was first described by Spangen [9], and it has since been well validated [10–12]. Images are acquired using grayscale imaging and a high-frequency 5 or 7-MHz transducer. Imaging is performed in the supine and standing positions, both with and without the performance of a Valsalva maneuver [13, 14].

Recent improvements in technology have resulted in notably improved images, with the dull gray abdominal wall muscles and “hyperechoic” bright fascia more easily visualized [15]. The hernia defect can be appreciated as a discontinuity in the structures of the abdominal wall, potentially with abdominal contents herniating through the defect (Fig. 6.3). Use of real-time imaging allows the dynamic visualization of the abdominal muscles with the hernia contents seen traversing through the defect [16]. The use of the Valsalva maneuver can further accentuate the herniation of contents, and it is especially useful when static imaging is equivocal and in certain anatomic locations, such as with a spigelian hernia. Imaging can assist in the detection of additional defects, the presence of which might alter the operative plan or constitute a potential cause of recurrence. US can furthermore distinguish between hernias and other abdominal wall masses, such as tumors, seromas, hematomas, and abscesses. As US is operator dependent, close communication between the surgeon and sonographer is critical.

Multidetector row CT with reformatting is currently the ideal modality for establishing the diagnosis [17–20]. Axial imaging is performed in the supine position with thin (5-mm) slices. Intravenous contrast is administered if there is need to assess the vascular supply of the hernia contents. Oral contrast helps visualize bowel loops and is routinely administered in all cases. In subtle hernias, image acquisition is performed using the Valsalva maneuver. Multiplanar reformatting allows better appreciation of the anatomy in a manner more familiar to the surgeon. CT is especially useful in identifying hernias in unusual locations, such as with lumbar [21, 22], obturator [23], sciatic [24], and perineal hernias [25]; these are challenging to detect either on physical examination or with US. CT not only identifies the presence of a hernia but also allows for the detection of complications, including bowel obstruction, incarceration, and strangulation. Bowel obstruction is identified when the transition point is located at the level of the hernia, and the bowel proximal and distal to the hernia is dilated and decompressed, respectively. Although incarceration is a clinical diagnosis, the hernia contents have bearing on the timing of the operation. The presence of bowel in the incarcerated hernia mandates immediate operative intervention to prevent strangulation of the contents, especially if there is fluid within the hernia sac, thickening of the bowel wall, or luminal dilation. Strangulation is suggested by the presence of fluid-filled loops of bowel with proximal dilation, abnormal attenuation of the thickened abdominal wall, engorgement of the mesenteric vessels, mesenteric haziness, and ascites (Fig. 6.4a, b). In contrast, the absence of these findings on imaging and clinical examination indicates a low risk for incarceration and strangulation, allowing an elective approach to the hernia repair after optimization of the patient’s general medical condition if necessary (Fig. 6.5).

Barium studies with small-bowel follow-through study and barium enemas have been described as a useful diagnostic modality [26]. Diagnosis of a hernia is made when contrast-filled bowel loops are seen extending beyond the fascial planes of the anterior abdominal wall (Fig. 6.6) [27]. Reducibility is determined by manual compression of the loops under fluoroscopy. The presence of obstruction can be identified by a difference in bowel caliber proximal and distal to the hernia and a failure to return the bowel loops to their normal position with manual reduction. Use of barium studies has largely been replaced by CT with oral or rectal contrast. Barium studies, however, might have utility in regions of the world with limited resources where CT might not be available.

MR I, similar to CT, allows delineation of the layers of the abdominal wall, highlighting the presence of the hernia and its contents (Fig. 6.7) [28]. However, MRI offers no particular advantage over CT and is not routinely obtained in making the diagnosis. Theoretically, MRI might be the preferred modality in the pregnant woman because of its favorable safety profile for the fetus.

No imaging modality in isolation can guide selection of the operative intervention best suited for the individual patient. Imaging must be used in conjunction with a clinical assessment of the patient to select the operation that has the greatest likelihood of success. Of the various imaging modalities, CT has the greatest impact on decision making. The use of multiplanar reconstruction allows the anatomy of the defect and abdominal wall musculature to be better understood. It also allows for better conceptualization of the defect in three dimensions, giving the surgeon a mental image of the operative intervention required (Figs. 6.8a, b and 6.9). CT also visualizes the entire abdominal wall, allowing multiple hernia defects to be identified (Fig. 6.10a–d). A failure to identify all defects present results in the selection of operative procedures that are less than ideal for the patient and increases the risk of hernia recurrence.

In giant ventral hernias, a large proportion of abdominal contents is contained in the hernia (Fig. 6.11a–c). Consequently, there is a reduction in the volume of the peritoneal cavity, resulting in a loss of domain. Returning the abdominal contents into the peritoneal cavity during hernia repair has significant physiologic consequences because of the development of an abdominal compartment syndrome with respiratory consequences, renal dysfunction, intestinal ischemia, and hemodynamic compromise. Although some studies described complex calculations to help target patients at risk [29] and others relied on a defect size greater than 10 cm in width as an indicator for recurrence [30], neither approach is clinically useful. The best current approach likely relies on using axial CT scan images to compare the contents of the native abdominal cavity with that in the hernia or “second abdomen.” In giant hernias with over 50% of the contents located within the hernia sac, a progressive preoperative pneumoperitoneum is recommended [31].

A second important factor in decision making is the need for reapproximation of the musculature to create a dynamic functional abdominal wall. In the elderly, who typically lead a sedentary lifestyle with significant comorbidities, the use of a mesh to cover the defect with adequate overlap via open or laparoscopic techniques is sufficient. Here, no additional analysis of the CT is necessary. In contrast, for patients in whom a dynamic abdominal wall is desirable, a critical assessment of the CT is essential. It is important to measure the size of the defect, the size and mass of the rectus, and the quality of the lateral abdominal wall musculature.

CT images allow the dimensions of the hernia defect to be accurately measured. We use the size of the hernia defect in its largest dimension as a guide to subsequent operative intervention when a dynamic abdominal wall with medicalization of the rectus muscles is desired. The decision regarding need for approximation of the musculature is made after considering the patient’s general health status, functioning, and the need for a functional abdominal wall. In patients with significant underlying disease who would not tolerate an extensive reconstructive procedure and whose level of function and daily activities do not involve significant physical exertion, placement of a mesh in the intra-abdominal position with at least a 5-cm overlap beyond the edges of the hernia defect is generally adequate. However, there might be tension at the interface between the static mesh and the dynamic abdominal wall. Increased tension prior to incorporation of the mesh will result in disruption at the point of maximal stress, with resultant recurrence of the hernia (Fig. 6.12).

For defects with a size less than or equal to 6 cm, the hernia defect can almost always be closed primarily with reinforcement using a synthetic mesh [32] (Fig. 6.13). For hernia defects greater than 6 cm, release of myocutaneous flaps is performed to allow the muscles to come together in the midline. The nature of the myocutaneous flap procedure selected depends on the size and status of the abdominal wall musculature. If the rectus abdominus muscle is of adequate size, approximately 8 cm for an average size adult, component separation involving the external oblique muscles can be performed using open, minimally invasive, or endoscopic techniques (Fig. 6.14). If, despite adequate release of the external oblique, the defect cannot be closed, a posterior component separation is added. In contrast, if the rectus muscles are inadequate as a result of either previous operative intervention or fibrosis, the lateral musculature is evaluated. If adequate lateral musculature is present, a transversus abdominus release will allow for all but the largest of defects to be closed in the midline, supported in almost all cases by a synthetic or biologic prosthesis to potentially reduce recurrence rates. Large defects with a relatively inadequate rectus abdominis and lateral wall musculature suggest that the defect cannot be closed primarily. A bridging type of repair will most likely be necessary, requiring the surgeon’s and patient’s expectations for the repair to be adjusted accordingly (Fig. 6.15). In patients who have undergone damage control laparotomy because of severity of the injury or surgical process, bowel edema coupled with loss of domain caused by fascial retraction precludes closure in a large proportion of patients. Here, the exposed bowel is covered by a split-thickness skin graft with a planned ventral hernia accepted in lieu of almost certain death. Repair of the resultant defect requires a careful analysis of the relative size of the defect and the available abdominal wall musculature. In cases of large defects with limited lateral wall musculature, the Fabian modification of the component separation is preferred (Fig. 6.16). In certain circumstances, the hernia defect might involve the lateral aspect of the abdominal wall. This might be seen following the creation of a stoma, as with parastomal herniations; laterally placed incisions, as with incisional herniations; and with injury as occurs following penetrating trauma or blunt rupture of the abdominal wall (Figs. 6.17 and 6.18).