Preoperative imaging in hernia surgery

General principles and indications

Preoperative imaging has a role in hernia surgery, in both guiding the surgeon in diagnosis and planning a repair. Imaging provides critical information on hernia characteristics (such as the number and location of hernias, defect size, hernia content and volume, presence of loss of domain, the quality of abdominal wall musculature, and the presence of mesh) that guide repair decisions. ^, This information allows the surgeon to select the appropriate operation to maximize the likelihood of successful repair. As a surgeon considers a robotic approach to hernia repair, defect size, in particular, is important as larger defects will increase the technical difficulty. Defect size also informs the surgical decision-making as to whether primary fascial closure is possible or whether consideration of a component separation is necessary. Additionally, larger defects may preclude successful robotic repair and necessitate an open operative approach.

Additional consideration should be given to the degree of concern for occult hernias. Such hernias are not present on physical examination and may have no associated symptoms but can be present in as many as 48% of patients at the time of laparoscopy. In patients at low risk for occult hernias (such as those with isolated primary umbilical hernias), physical examination alone may be sufficient and no imaging may be required. In patients at higher risk for occult findings (such as those with multiple previous incisions), imaging represents the standard of care. This is especially important in cases where the presence of occult hernias would significantly alter the operative plan. For example, the finding of an off-midline (lateral zone) hernia might significantly alter an operation that was intended to address midline defects only, particularly in terms of the amount of sublay dissection required or the steps necessary to achieve adequate mesh overlap ( Fig. 5.1 ).

Indications for imaging in incisional hernias

Our practice is to apply cross-sectional imaging routinely for incisional hernias, given the reported high incidences of occult defects not previously identified on clinical examination alone. We believe that hernias should be identified and planned for before the surgery, not incidentally discovered during surgery. Prospective evaluation of this topic has demonstrated a 23% incidence of missed incisional hernias from physical examination alone. When further stratifying for body mass index, that same study noted that the missed incisional hernia rate increased to 31% in patients with Centers for Disease Control-defined obesity.

Recurrent incisional hernias, particularly those following prior mesh-based repair, represent another subcategory of incisional hernias that we believe warrant preoperative imaging. A case series of 50 patients with a history of mesh herniorrhaphy and symptoms of recurrence demonstrated lower sensitivity of clinical examination alone than that of computed tomography (CT) imaging. More importantly, the ability of imaging to define the location of the mesh in relation to the hernia and to evaluate mesh-related complications (such as adhesion formation or ‘meshomas’) influences the choice of operation offered to the patient. As such, it is our practice to perform preoperative cross-sectional imaging in all patients presenting with recurrent hernias.

Indications for imaging in parastomal hernias

Physical examination is insufficient to diagnose the majority of parastomal hernias for several reasons. The presence of the bowel within the abdominal wall is a normal finding in patients who underwent an ostomy. Moreover, the presence of the ostomy appliance faceplate interferes with the ability to adequately examine the patient without removal, which is often impractical in the outpatient setting. Therefore imaging is indicated, particularly in symptomatic patients with no clear diagnosis of hernia on physical examination. The diagnostic utility of imaging is underscored by a study that demonstrated poor interobserver reliability when patients with parastomal hernias were examined by multiple different surgeons, with 37% disagreement on clinical examination. Despite the paucity of existing objective evidence, the European Hernia Society (EHS) recommends CT imaging or ultrasonography (US) in uncertain cases of parastomal hernia.

Indications for primary ventral hernias

In midline primary ventral hernias (such as epigastric and umbilical hernias), preoperative imaging is often not necessary. In general, primary ventral hernias tend to be more symmetric with round or oval shapes. This characteristic allows for more straightforward diagnosis through physical examination alone. Despite sharing similar characteristics to midline primary ventral hernias, lateral primary ventral hernias (such as Spigelian and lumbar hernia) are two categories of primary ventral hernias that can benefit from preoperative imaging.

There are several reasons to consider imaging in a primary hernia patient. The first is to assure that all defects are being considered, for example, the patient with a symptomatic umbilical hernia who also has an asymptomatic epigastric hernia. Although robotic hernia repairs would generally uncover such defects when the falciform fat pad is taken down, the ‘incidentally noted’ hernia may lengthen the operative time, require additional steps (such as additional superior dissection), necessitate a larger piece of mesh, and result in suboptimal port placement to address all the defects. These repairs can be planned for, in advance, with preoperative imaging. The second indication for imaging is hernia defects whose fascial dimensions cannot be determined due to incarcerated content or patient habitus. Knowledge of the fascial defect size and content may alter the decision to pursue open, laparoscopic, or robotic repairs.