1 Introduction

Most inguinal and ventral hernias can be diagnosed using a thorough history and physical examination. Patients are usually referred to a surgeon for diagnosis confirmation and a discussion of treatment options. However, additional diagnostic imaging may be necessary to identify an occult hernia or to plan the operation. In this case, the surgeon has many choices depending on the hernia type or clinical problem and the information that is needed. In general, additional diagnostic tools include ultrasound, computed tomography (CT) scanning, and magnetic resonance imaging (MRI) with other adjuncts for inguinal hernias including herniography. Each imaging modality has strengths and weaknesses. Imaging choice is impacted by the local hospital environment and radiology department.

2 History and Physical

Patients with a hernia often complain of feeling a bulge. In this case, the surgeon should confirm hernia presence with a physical examination (Fig. 5.1). In some cases, an occult hernia (one that is difficult to detect) is present. This can be due to the small hernia size or other patient characteristics such as obesity. In this case, additional diagnostic imaging should be obtained.

Fig. 5.1
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Ventral hernia shown on physical exam

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3 Diagnostic Tools for Inguinal Hernia

3.1 Imaging in Inguinal Hernias

In most cases, a history of groin pain and an obvious inguinal bulge are all that are required to diagnose an inguinal hernia. In this case, the next step is operative repair. Diagnosis is less clear when there are no physical exam observations consistent with inguinal hernia. An occult inguinal hernia can be too small to detect on physical exam but can produce symptoms consistent with a groin hernia such as a feeling of a bulge or pain. Without physical exam evidence, imaging is crucial in diagnosis, because there are many causes of pain that should not be treated using surgery.

3.2 Ultrasound

Ultrasound is usually the first modality used to diagnose occult inguinal hernias because it is easily accessible and relatively inexpensive. An inguinal hernia ultrasound with and without Valsalva maneuver (Fig. 5.2), not a pelvic ultrasound, will provide the best information for accurate diagnosis of an occult inguinal hernia. The patient can be moved into different positions such as lying down and standing which can often aid in diagnosis of the hernia; as in some positions, the protrusion through the hernia defect may be more pronounced (Fig. 5.3). Although the dynamic nature of ultrasound is a distinct benefit, this characteristic also makes its accuracy operator dependent.

Fig. 5.2
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Ultrasound image showing of right groin showing fat protruding through a hernia defect that is more pronounced with Valsalva

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Fig. 5.3
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Ultrasound image showing bowel protruding through a left inguinal hernia

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Although ultrasound is the first-line imaging option for diagnosing an inguinal hernia, it is far from perfect. A recent meta-analysis comprised of five ultrasound studies totaling 716 patients showed that ultrasound had a sensitivity of 86% and specificity of 77% [1]. Though these numbers may seem reasonable for diagnosis, two recent studies reported that ultrasound has a low positive predictive value after the patient is evaluated in the operating room. The first study contained 116 patients who underwent surgery after a positive ultrasound and yielded only a 74% positive predictive value [2]. This correlated with another study of 118 patients who at the time of operation had a 70% positive predictive value for presence of a hernia. The same study followed 141 patients with a negative groin ultrasound for a median of 3 years, and no patients were later diagnosed with a hernia [3]. The most recent study on the subject by Miller showed a sensitivity of 0.33 and specificity of 0.0 [4]. These data indicate that ultrasound may be a better imaging method to help rule out a hernia diagnosis than to determine the need for surgery.

3.3 CT Scan

CT scan is also used to diagnose occult inguinal hernias. It is widely available, and many surgeons are accustomed to reading CT scans, which is not the case with most other imaging options. A CT scan facilitates evaluating the entire abdomen, which can occasionally identify other causes of pain or abnormalities. In a study comparing CT and herniography, CT identified bone spurs as the cause of pain in 2 of the 51 patients evaluated [5].

Despite these advantages, the usefulness of CT for inguinal hernia diagnosis is very limited. Studies using CT show a fairly low sensitivity and specificity but a fairly high positive predictive value for patients that undergo surgery. Recent data on the subject showed a sensitivity of 0.54, a specificity of 0.25, but a positive predictive value of 86% in 39 patients who underwent CT and subsequent surgery [4]. Another study evaluated 158 patients with groin pain. In these patients, 49 hernias were diagnosed via CT, and the patients were taken to surgery for evaluation and hernia repair. This study showed a positive predictive value of 92% and a negative predictive value of 96% [6]. These data indicate that CT is not the best option for the initial diagnosis of an occult hernia; however, when a hernia is identified on CT, the patient can proceed to surgery for hernia repair.

Although CT may not be the best option for the diagnosis of occult inguinal hernias, it can be useful for inguinal hernias in certain clinical circumstances such as when other intra-abdominal pathology is suspected or cases of difficult to diagnose hernias such as femoral and obturator hernias (Figs. 5.4, 5.5, and 5.6).

Fig. 5.4
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Computed tomography scan showing portal venous gas from incarcerated right femoral hernia causing a bowel obstruction

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Fig. 5.5
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Computed tomography scan showing pneumatosis from incarcerated right femoral hernia causing a bowel obstruction

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Fig. 5.6
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Computed tomography scan showing incarcerated right femoral hernia causing a bowel obstruction which lead to ischemic intestine, pneumatosis, and portal venous gas

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3.4 MRI

MRI is useful in diagnosing occult inguinal hernias; however, it is not without disadvantages. It is more expensive than ultrasound or CT and also takes the most time to complete. Generally, surgeons are not as skilled at reading MRIs compared with reading CTs; however, MRI has several benefits. Like CT, MRI can be used to evaluate the entire pelvis. Because of the ability to closely assess the bones and soft tissues in the pelvic region, MRI is useful to diagnose hernias and other musculoskeletal etiologies for groin pain (Figs. 5.7 and 5.8).

Fig. 5.7
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MRI for chronic groin pain in a runner revealing mild degenerative changes of the pubic symphysis with parasymphyseal bone marrow edema suggestions stress/reactive edema due to repetitive stress

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Fig. 5.8
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MRI showing small fat containing left inguinal hernia

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There is increasing evidence that MRI should be the initial study to evaluate suspected occult inguinal hernias. A study by Miller compared the use of CT, ultrasound, and MRI in 34 patients and determined that MRI was the best option for diagnosing occult inguinal hernias. The study yielded a sensitivity and specificity of 0.91 and 0.92, respectively [4].

3.5 Herniography

Ducharne first described herniography, also known as peritoneography, in Canada in 1967 [7]. Herniography consists of injecting iodinated contrast into the peritoneum and imaging the area with X-ray or CT to evaluate possible hernia defects. This imaging modality is the most invasive of the options discussed. Because this procedure is done with X-ray or CT, it exposes the patient to radiation. Despite these negatives, it is considered one of the most accurate tests used to diagnose hernias; however, it is not widely used probably because of the lack of comfort and familiarity with the study both by surgeons and by the radiology teams that would perform them and the emergence of other more commonly used modalities such as ultrasound, CT, and MRI. Although invasive, herniography is a fairly safe procedure. In a large review of 17 studies including 1538 patients, only three patients had complications that required hospital admission (a 0.19% major complication rate) [8]. Another retrospective study evaluated 117 herniographs performed at one hospital and identified no complications recorded [9].

Multiple studies have shown that herniography is the most accurate imaging modality. A large review by Robinson compiled data from 16 studies and convincingly supported using herniography more often to diagnosis occult hernias compared with ultrasound and CT. The pooled data showed a sensitivity of 91% and a specificity of 83% for herniography, which was much higher than the study’s findings for CT scan [1].

3.6 Diagnostic Laparoscopy

Because diagnostic laparoscopy is an invasive procedure, it should be very seldom used in the diagnostic algorithm for inguinal hernias. However, it is useful to evaluate for an occult hernia when imaging is non-confirmatory or cannot be obtained. Diagnostic laparoscopy facilitates identifying hernias and other intra-abdominal pathology. Because female pelvic pain can be related to gynecologic issues, it is sometimes helpful to have an obstetrician/gynecologist available for these cases.

4 Summary and Recommendations for Diagnostic Tools in Inguinal Hernia

Most inguinal hernias can be diagnosed using a thorough history and physical examination. When the patient feels a bulge that is not felt during a clinical exam, an ultrasound is probably the most useful initial test. When the patient’s symptoms are not consistent with a hernia, no bulge is felt on physical exam, or the surgeon suspects other general surgical/intra-abdominal issues, a CT scan is likely the best test to identify intra-abdominal pathology. When there is concern for an occult hernia, musculoskeletal injury/core muscle injury, or pain related to previous hernia repair, an MRI is likely the best option. An MRI should be done using special protocols and should involve a radiologist comfortable with and interested in these techniques/imaging modalities.

5 Diagnostic Tools for Ventral Hernia

The principal imaging modalities for the diagnosis of ventral and incisional hernias and preoperative planning for their repair are ultrasound, CT, and MRI. Given their advantages and disadvantages, each has a role in specific clinical scenarios to produce favorable outcomes.

Ultrasound is the quickest, least expensive technique for detecting small ventral or incisional midline or lateral hernias. There were many different institution-based methods for the use of ultrasound until 2013 when Beck et al. published a standardized method called dynamic abdominal sonography for hernia (DASH). In this study, the DASH method achieved a sensitivity of 98% and specificity of 88% [10]. This method uses a standard linear ultrasound probe and requires the user to make five vertical passes starting at the midline and alternating laterally in parallel lines (Figs. 5.9 and 5.10). In a subsequent study, the DASH method was shown not only to have diagnostic ability but also to accurately characterize hernias, even very large defects (≥10 cm in diameter) and even in obese populations with an average BMI of 39.2 kg/m2 [11]. Historically, ultrasound has had several barriers to widespread use. One of the primary issues was difficulty in obtaining reliable image quality for obese patients. The DASH method may provide a solution to this problem for certain obese patients. Ultrasound has many benefits and can be a quick and relatively cost-effective way to diagnose smaller hernias; however, it still has not gained wide acceptance in the preoperative planning of known hernias or in patients with obese abdomens.

Fig. 5.9
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The use of dynamic abdominal sonography for hernia (DASH) to evaluate for a ventral hernia

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Fig. 5.10
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Layers of the abdominal wall seen on dynamic abdominal sonography for hernia (DASH)

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CT is the most widely used imaging modality for the characterization of known ventral hernias and has the benefit of being a relatively quick study that produces images with excellent image quality for many different types of ventral hernias (Figs. 5.11, 5.12, 5.13, and 5.14). In contrast to ultrasound, the images can characterize large defects and can be used with severely, morbidly obese patients. Preoperative planning has been enhanced by CT measurements of ventral hernia defect size and abdominal wall thickness, which have been used to predict wound complications and the need for component separation [12]. Prior techniques on estimating the need for component separation relied on hernia location, and unique variabilities in the patient’s anatomy were not considered. In a retrospective review of patients who underwent abdominal wall reconstruction, Franklin et al. demonstrated that CT could be used to predict midline approximation using abdominal wall defect ratios and hernia defect areas [13]. The predictive value of CT imaging is very important in preoperative planning to avoid bridged repairs. A recent investigation into a quantitative anatomical labeling protocol was undertaken to predict the need for mesh bridge closure and was able to more accurately predict this than the metrics used in the European Hernia Society Classification for Ventral Hernia (EHSCVH) [14]. Calculating loss of domain is a challenge for the preoperative assessment of ventral hernias. CT 3D reconstruction continues to improve its predictive capacity and has been shown to predict hernia area and volume, which may contribute to more accurate preoperative risk assessment of loss of domain and risk of abdominal compartment syndrome [15]. Unfortunately, CT requires exposure to ionizing radiation; however, the excellent image quality and recent advances in 3D reconstruction have facilitated better characterization of large, complex hernias and assessment of potential loss of domain while attempting to avoid bridged repairs.

Fig. 5.11
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Computed tomography scan showing lumbar hernia

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Fig. 5.12
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Computed tomography scan showing Spigelian hernia

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Fig. 5.13
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Computed tomography scan showing recurrent hernia with mesh being pushed into hernia sac

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Fig. 5.14
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Computed tomography scan showing recurrent hernia and tack fixation in hernia sac

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MRI has shown some utility in the assessment of patients with adhesions to mesh after ventral hernia repairs and could be of value in patients requiring complex mesh repairs when explantation of mesh is being considered. MR has been shown to detect adhesions between both bowel and the abdominal wall in patients who have a history of both laparoscopic and open VHR [16]. Functional cine MRI has been used to evaluate intra-abdominal adhesions and preoperative planning for mesh explantation. This method is used to detect “visceral slide” by comparing images when the patient is at rest and when performing the Valsalva maneuver. Lienemann et al. demonstrated that when this method was compared with intraoperative findings in a group of 27 patients, the sensitivity was 87.5%, and the specificity was 92.5% [17]. In a larger retrospective study enrolling 90 patients, similar results were obtained in which the overall MRI accuracy was 89% [18]. While cine MR has the benefit of visualizing ePTFE mesh, it has not been shown to adequately visualize polypropylene mesh [19]. There are benefits in the appropriation of MR in the analysis of complex ventral hernias, patients with adhesions or abdominal wall dysmotility, or when explantation of synthetic mesh is considered. However, MRI should be used judiciously and should not be used for routine classification of hernias due to cost, length of exam, and marginal improvements in picture quality compared with CT.

6 Summary and Recommendations for Diagnostic Tools in Ventral/Incisional Hernia

Most simple ventral/incisional hernias in nonobese patients can be diagnosed using a thorough history and physical examination. Table 5.1 is a list of advantages and disadvantages of the various diagnostic technologies. Due to the complex nature of incisional hernias, imaging is often warranted. The well-described DASH technique gives the surgeon a reproducible and standardized way to use ultrasound for diagnosing ventral/incisional hernias; however, it hasn’t gained widespread acceptance. Because of the many advantages associated with this technique, we encourage surgeons to learn about the DASH technique and to use this as a first-line diagnostic tool in appropriate patients when the technology and training are available. CT scanning is likely the most common imaging tool for diagnosing ventral/incisional hernias, because it not only helps with diagnosis but also with operative planning and can help identify other intra-abdominal pathology or previous mesh in some cases. Another benefit of CT is that most surgeons are skilled in reading CTs. Because of these advantages, for complex cases or when ultrasound is not available, CT is likely the best option. Although MRI has some indications for diagnosing ventral/incisional hernia, unless your center/hospital/radiology department has a special interest in this technology, it should be used rarely and only in special circumstances.

Table 5.1 Advantages and disadvantages of imaging modalities for diagnosing ventral/incisional hernia
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Conclusion

Surgeons should understand the various imaging and diagnostic tools for inguinal and ventral/incisional hernias. Although history and physical examination will most certainly be the mainstay for diagnosis in most patients, surgeons interested in hernia disease should learn about new diagnostic technologies and should become skilled in the DASH technique and in reviewing imaging studies. Surgeons should work closely with their local institutions and specifically their radiology departments to successfully use these tools in appropriate patients.