British Journal of Radiology (2009) 82, 79-81
© 2009 British Institute of Radiology
doi: 10.1259/bjr/29342394
British Journal of Radiology 82 (2009),79-81 ©2009 The British Institute of Radiology
Flank swelling following abdominal trauma: an easily overlooked injury
S NAZIR, BA, BM, BCh
A F SCARSBROOK, BMBS, BMedSci, FRCR
and
N R MOORE, MB, BChir, FRCP, FRCR
Department of Diagnostic Radiology, John Radcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU, UK
Correspondence: S Nazir, Milestone, 283 London Road, Headington, Oxford OX3 9EH, UK. E-mail: sarfraznazir{at}doctors.org.uk
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Introduction
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A 56-year-old man was admitted to his local hospital following a road traffic accident. He sustained multiple injuries as a result of a high-energy head-on collision. In the emergency department, he was resuscitated according to Adult Trauma Life Support (ATLS) guidelines.
Clinical examination revealed several injuries that were confirmed by plain radiography and CT from the head to pelvis: a right flail chest, a small haemo-pneumothorax, a complex open olecranon fracture, a Galeazzi fracture dislocation and a fracture dislocation of the right hip and acetabulum.
He remained unwell for the next 4 days, mainly as a result of poor ventilatory function. The patient was then transferred to a tertiary centre for definitive treatment of his injuries, where another injury was noted. From the original CT scan (Figure 1
), what was this diagnosis?
At the tertiary centre, the patient was observed to have a 3 x 3 cm tender fluctuant swelling over the right posterior abdominal wall and a contusion over the anterior abdominal wall consistent with a seat belt injury. As this injury was not previously documented, a further CT of the chest, abdomen and pelvis was performed (Figure 2). Is the diagnosis more evident?
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Figure 2. Sagittal multiplanar reconstruction(MPR) derived from the contrast-enhanced CT performed at the tertiary centre. The arrow shows the injury.
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Diagnosis
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An acute traumatic lumbar hernia, containing retroperitoneal fat, through an avulsion of the origin of the conjoined tendon of the external and internal oblique muscles with transversus abdominis from quadratus lumborum was detailed within the right posterolateral abdominal wall. This injury had not been diagnosed either clinically or radiologically at the referral centre, even though a radiological abnormality was present. Figure 1
shows that the tendon injury was evident, albeit subtle. There was adjacent surgical emphysema and increased attenuation within the overlying subcutaneous fat, signifying haematoma.
Fortunately, apart from two small minor liver contusions, there were no other hollow or solid organ injuries. Surgical assessment was advised and, at 3 months, a primary repair was performed; the patient made an uneventful post-surgical recovery.
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Discussion
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In 1672, Barbette first suggested that herniae could arise in the lumbar region. Lumbar herniae are generally uncommon; however, acute lumbar herniae resulting from blunt trauma are extremely rare [1]. The vast majority are not diagnosed at initial presentation and present some time following the trauma.
Despite their rarity, acute lumbar herniae are a significant abnormality that radiologists need to be aware of. The herniae may contain fat, omentum, sigmoid colon, caecum, appendix, small bowel, stomach or kidney. If they are not recognized, herniae typically increase in size [2], and can cause chronic lower back pain, bowel incarceration (in 25% of patients) and strangulation (in 10% of patients) [1]. If the injury is detected, it is imperative to conduct a thorough examination of the patient because a significant majority of patients have serious additional injuries [3].
Diagnosis is complicated by the fact that the location of the hernia is usually at a point of anatomic weakness, rather than the site of impact. Lumbar herniae almost always occur in two well-documented anatomical triangles reflecting areas of relative vulnerability in the posterolateral abdominal wall: the inferior lumbar space of Petit and the larger and more frequently affected superior lumbar space of Grynfeltt–Lesshaft (Figure 3) [4].
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Figure 3. Demonstration of the relationship between the superior and inferior lumbar triangles in the lumbar region[4].
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A quarter of all lumbar herniae are caused by trauma. The typical injury is a sudden blunt force to the abdomen, usually as a result of seat belt trauma (70% of cases). The consequential increase in intra-abdominal pressure from the force is sufficient to cause disruption of the abdominal wall musculature. The ensuing defect varies from being small and focal (in cases of direct injury) to a more extensive one attributable to a complex combination of compressive and shearing forces.
The "seat belt sign" — visible contusions or lacerations resulting from deceleration forces through a seat belt — is an invaluable clinical sign and should raise clinical suspicion of a traumatic abdominal hernia. However, in the setting of polytrauma, clinical examination findings are variable. A palpable hernia or a flank haematoma is present in less than one-third of cases [5] but even these may be easily missed in patients with multiple injuries because they are overlooked while other more life-threatening injuries are addressed. Historically, diagnosis was made at exploratory laparotomy or, more commonly, at a delayed stage following trauma.
Abdominal CT is the most valuable imaging test because it can distinguish accurately the anatomy of disrupted muscular and fascial layers, visualize herniated fat or viscera, show associated intra-abdominal injuries and allow differentiation of a hernia from haematoma or abscess, both of which are relatively common following blunt trauma [6]. Lumbar herniae should be considered in every patient suffering serious blunt abdominal trauma, especially in those with large flank haematomas, pelvic fractures, a history of seat belt restraint or clinical evidence of seat belt injury. All should undergo CT examination unless they are unstable and require immediate surgical intervention. This will help diagnose more cases at initial presentation and expedite definitive treatment. Radiologists must be vigilant when reviewing CT images and should pay careful attention to the abdominal wall and muscular insertions.
After diagnosis, the hernial defect should be repaired surgically because of the risk of subsequent obstruction or strangulation and the high incidence of associated hollow viscus and mesenteric injuries [3]. On this basis, some authors recommend treatment of asymptomatic impalpable lumbar herniae identified on CT imaging [6]. With the trend for more conservative management, and the fact that CT allows the detection of associated injuries, retroperitoneal repair is generally advocated rather than the classical transperitoneal repair first described by Dowd in 1907.
In conclusion, a post-traumatic lumbar hernia is a rare but serious condition that remains a challenge to diagnose in the acute setting. Cross-sectional imaging is extremely useful for the examination of trauma patients. It allows earlier detection and is excellent in portraying the contents of the hernia, associated injuries and disrupted muscle layers. However, radiologists require a high index of suspicion of less common traumatic injuries such as this to avoid the potential sequelae of missed injuries.
Received for publication October 22, 2006.
Revision received May 13, 2007.
Accepted for publication May 27, 2007.
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References
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- Esposito TJ, Fedorak I. Traumatic lumbar hernia: case report and literature review. J Trauma 1994;37:123–6.[Medline]
- Swartz WT. Lumbar hernia. In: Nyhus LM, Condon RE, editors. Hernia, 2nd edn. Philadelphia, PA: Lippincott, 1978; 409–426.
- Florer RE, Kiriluk L. Petit's triangle hernia, incarcerated: two case reports. Am Surg 1971;37:527–30.[Medline]
- Henry MH, Thompson JN. Hernia. In: Nyhus LM, Condon RE, editors. Clinical Surgery, 2nd edn. Philadelphia, PA: Saunders, 2004: 431–46.
- Chanvitan A. Traumatic abdominal wall hernia: a case report. J Med Assoc Thai 1986;69:341–5.[Medline]
- Faro SH, Racette CD, Lally JF, Wills JS, Mansoory A. Traumatic lumbar hernia: CT diagnosis. AJR Am J Roentgenol 1990;154:757–9.[Abstract/Free Full Text]
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Introduction
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