Spigelian Hernia Secondary to Blunt Trauma

Introduction Blunt abdominal trauma is a common injury with varying complications that roughly correlate with the mechanism of injury. Traumatic abdominal wall hernias (TAWH) represent a small percentage of cases and these develop when a blunt force causes a defect to the abdominal wall musculature and fascia which may lead to the protrusion of bowel (1). Spigelian hernias are rare, making up only 0.1% to 2% of all ventral hernias, with chronic abdominal wall weakening being the most common cause of spigelian hernias (2). Typical risk factors for developing a spigelian hernia include multiparity, chronic cough, obesity, and chronic comorbidities, such as diabetes, peripheral vascular disease, chronic obstructive pulmonary disease, cerebrovascular disease, and myocardial infarction (2). This is in contrast to TAWH where motor vehicle accidents, seatbelt injuries, and handlebar injuries are the most common mechanism of injury (3). We present a case report of blunt abdominal trauma secondary to a bicycle handlebar injury resulting in the development of a spigelian hernia in an otherwise young and healthy man. Case Report A 41-year-old man without any prior medical or surgical history presented to the emergency department (ED) 1 d following a bicycle accident. He reported striking a “bump” in the asphalt, causing the handlebar end to strike him in the abdomen. The patient was not wearing any protective equipment aside from a t-shirt and a thin sweatshirt. Subsequently, the patient developed what he described as a tender protrusion at the site of impact, which worsened when he coughed or bared down. The patient denied other injuries. The tender mass in his abdomen persisted until morning, at which time he decided to present for evaluation. In the ED, the patient was in no acute distress and hemodynamically stable. His examination was unremarkable, barring the presence of a reducible hernia located inferior to the umbilicus and along the lateral abdomen, superior to the iliac crest. The site was tender to palpation, exhibited localized ecchymosis, and was without crepitus. Bowel sounds were present. The patient denied changes to his urinary or bowel habits since the event, citing a normal bowel movement and micturition prior to arrival. He also had not experienced any nausea or vomiting since the accident. A computed tomography (CT) scan of the abdomen and pelvis with intravenous (IV) contrast was ordered and basic laboratories were sent for further evaluation. Laboratory values did not reveal any specific findings. CT revealed a hernia in the left lower quadrant of the abdomen containing the small bowel. There was no evidence of obstruction reported. The official radiology report cited nonspecific stranding in the region of the hernia suspected to be secondary to trauma. Trauma surgery was consulted, and the patient was offered admission for elective repair, although this was declined, because he preferred to follow-up in the outpatient clinic for future surgical planning. Discussion Traumatic spigelian hernias are exceedingly rare, accounting for less than 1% of abdominal hernias with less than 10 cases reported in children and even fewer in adults (4,5). Blunt injury causes an increase in intra-abdominal pressure leading to a disruption in the abdominal wall musculature and fascial planes where weak points exist. The compromised abdominal wall loses its ability to contain the underlying organs in anatomic position leading to the development of herniated tissue in previously nonexistent spaces. In the case of spigelian hernia, the defect is located along the linea semilunaris (spigelian line), at or below its junction with the linea semicircularis (Douglas' line). This specific region is the site of overlap between the internal oblique, transversus abdominis, and overlying external oblique. Hernias rarely penetrate the external oblique and, therefore, are typically seen in the layer underlying this muscle group (3,4,6). Clinical findings to suggest its presence can include new palpable mass, abdominal pain, or sensation or pressure over the spigelian aponeurosis (Fig. 1). Overlying skin may be normal or show signs of abrasion, swelling, hematoma, or ecchymosis. The most serious complication arising from this condition being small bowel obstruction due to incarcerated or strangulated bowel. The hernia may be more easily palpated while the patient is standing, inducing increased intra-abdominal pressure by Valsalva maneuver (Fig. 2) and thus creating a more visible or tactile bulge on examination. Lying the patient flat or in a Trendelenburg position can lead to spontaneous reduction of the abdominal contents from the herniated space (7). In the setting of trauma, these examination techniques may be challenging and limited because of co-occurring injuries.Figure 1: A visible and palpable mass is present along the left lateral abdominal wall with overlying ecchymosis indicative of trauma.Figure 2: Spigelian hernia of the left lateral abdominal wall with demonstration of 4-cm protrusion.CT of the abdomen pelvis with IV contrast is the imaging of choice for evaluating and classifying abdominal wall hernias (Figs. 3 and 4). CT also allows for the assessment of hernia incarceration or strangulation while ruling out the presence of other traumatic abdominal pathology (8). For patients who present with abdominal pain without a palpable defect or mass indicative of a hernia, dynamic ultrasound evaluation offers the advantage of imaging the region in question with the patient in supine and standing positions while providing a Valsalva maneuver. Ultrasound provides a cost-effective evaluation of a possible hernia while allowing for the visualization of the hernia contents through the abdominal musculature (9).Figure 3: Axial view of CT abdomen/pelvis left lower quadrant spigelian hernia containing small bowel.Figure 4: Coronal view of CT abdomen/pelvis. A defect in the spigelian aponeurosis, causing an inconsistent appearance in the fascia on CT.Emergent or delayed surgical repair are the primary treatment options over conservative management. Surgical repair is favored because of the increased risk of strangulation with spigelian hernias, and operative timing is dependent on the presence of other intra-abdominal pathology. Conservative treatment is reserved for patients who have multiple medical comorbidities, asymptomatic hernias, no intra-abdominal injuries, and large abdominal wall defects, which reduce the risk of strangulation (3,6,7). Conclusions A 41-year-old man presented to the ED for abdominal pain and palpable mass the day following a traumatic handlebar injury. Workup revealed herniation of small bowel at the site of injury, without evidence of an obstructive process. The patient elected for delayed surgical repair to be done outpatient. Return precautions and follow-up information with the trauma surgery clinic were provided upon discharge. At the time of publication, this individual has been lost to follow-up with the trauma surgery service and has not returned to the ED.