Incarcerated obturator hernia: pitfalls in the application of ultrasound
© Springer-Verlag 2009
Published: 18 November 2009
To describe ultrasonographic appearance and diagnoses of incarcerated obturator hernia.
Three consecutive cases of incarcerated obturator hernia examined preoperatively with ultrasound were presented to show the pitfalls in the application of ultrasound for the recognition of the entity. Retrospectively reviewed, ultrasound directly demonstrated an incarcerated obturator hernia in all the cases.
The herniated segment was delineated posterior to the pectineus muscle in the femoral triangle. However, the sonographer mistakenly interpreted it showed a femoral hernia in the first case. In the third case, the sonographer did not scan the femoral regions in the initial examination although he confirmed the evidence of small bowel obstruction. The evidence of an incarcerated obturator hernia was detected in the re-examination with ultrasound after it had been revealed by CT scan. Consequently, ultrasound was evaluated as applicable and useful for the recognition of incarcerated obturator hernia.
Ultrasound is an useful tool for detecting obturator hernia. However, adequate education and training for examiners are required to prevent false interpretation or overlooking of the entity.
Incarcerated obturator hernia is a relatively rare cause of small bowel obstruction and rather difficult to diagnose preoperatively with physical examinations and plain X-rays. Delayed recognition has been related to increased morbidity and mortality [1–3]. However, the application of CT scan for acute abdomen has made it easier to visualize an incarcerated obturator hernia in the pelvis [4–8]. On the other hand, the application of ultrasound for acute abdomen has been widely discussed in recent years. However, very few reports were published for demonstrating the usefulness of ultrasound for the diagnosis of incarcerated obturator hernia [9–13]. In this report, we retrospectively evaluated the significance of ultrasound for the recognition of incarcerated obturator hernia and demonstrate some of the potential pitfalls of ultrasound in this application.
Materials and methods
Three consecutive cases of incarcerated obturator hernia admitted in the Kobe City Medical Center West Hospital were reviewed retrospectively. All of them were examined preoperatively with ultrasound. CT scan was utilized in two of them. In this report we reviewed the age, sex, body height/weight, past history of delivery and laparotomy, associated medical conditions, clinical symptoms, physical findings, laboratory data, plain X-ray images, ultrasonograms, CT images, operative findings, and outcome.
The clinical pictures of the three cases of incarcerated obturator hernia
Body height/weight (cm/kg)
Previous history of delivery/laparotomy
Associate medical conditions
COPD, Angina, AR
Diffuse abdominal pain
Duration from the onset to admission
Physical findings in the femoral triangle
Bulge with tenderness
CPK 110 IU
CPK 21 IU
CPK 3,498 IU
Amylase 1,466 IU
Plain X-ray diagnosis
(initial exam. → re-exam.)
SBO due to incarcerated femoral hernia
SBO due to incarcerated obturator hernia
SBO due to unknown cause → incarcerated obturator hernia
SBO due to incarcerated obturator hernia
SBO due to incarcerated obturator hernia
Herniorrhaphy without enterectomy
Herniorrhaphy without eneterectomy
Herniorrhaphy with enterectomy
CT scan demonstrated an incarcerated obturator hernia in Cases 2 and 3 (Figs. 1d, 2b). In Case 1, it was not performed for the preoperative evaluation. In each case urgent laparotomy showed an incarcerated obturator hernia and relieved the obstruction. Partial enterectomy was required for hemorrhagic necrosis of the incarcerated intestinal segment only in Case 3. No postoperative complications occurred in their clinical courses.
Obturator hernia is defined as an abdominal wall hernia protruded through the obturator canal, and usually consists of a hernia sac containing small bowel. The entity is relatively rare, but a significant cause of small bowel obstruction, especially in thin, elderly females [1–3]. It is also reported to occur more often in the multipara. The female predominance of the entity has been supposed to be the results of pregnancy which leads to relaxation of the pelvic peritoneum and a wider and more horizontal obturator canal. The herniated intestinal segment is often incarcerated and strangulated because the hernia orifice is small, about 1 cm in diameter . Consequently, early recognition of the entity is crucially important because delay in diagnosis and treatment is often associated with its high mortality and morbidity.
Clinical symptoms and signs are usually consistent with acute or recurrent bowel obstruction, but in the majority of the cases no symptoms characteristic to the obturator hernia can be obtained. Howship–Romberg sign, which stands for pain radiating along the medial aspect of the thigh when the leg is extended or abducted because of obturator nerve compression by the hernia contents, has been reported to be recognized in less than half the patients [1–3]. It may not be checked preoperatively unless obturator hernia is considered as one of the disorders to be differentiated. A groin mass is rather difficult to recognize with palpation because the herniated mass locates deep in the femoral triangle, concealed beneath the pectineus muscle. Plain abdominal X-rays usually show the evidence of small bowel obstruction, but are not diagnostic for obturator hernia. Consequently, obturator hernia has been a diagnostic challenge before CT of the pelvis becomes a standard diagnostic tool for the entity. With CT of the pelvis, the herniated segment covered with the hernia sac is demonstrated as a soft tissue mass or opacified loop between the pectineus muscle and the obturator externus muscle [4–8].
On the other hand, the application of ultrasound for obturator hernia has been limited, but a few investigators reported that ultrasound was useful for the early recognition of the entity [9–13]. In our case series, ultrasound directly showed an incarcerated obturator hernia, and was evaluated as applicable and useful for the recognition of the entity. The opportunities for sonographers to encounter with some cases of obturator hernia may increase, as ultrasound has become widely used for the evaluation of acute abdomen including bowel obstruction, Therefore, it is required to clarify the ultrasonographic features of incarcerated obturator hernia, and the pitfalls in the application of ultrasound for the entity.
In our case series, we also indicated pitfalls for applying ultrasound for incarcerated obturator hernia. In the Case 1, the examiner made a misdiagnosis by careless interpretation of the ultrasonograms and a belief that the palpated bulge in the femoral triangle stood for an incarcerated femoral hernia. In the Case 3, the examiner overlooked the obturator hernia in the initial examination because he did not hit the entity at the time and consequently, skipped scanning around the femoral triangle. These misdiagnoses were related with lack of knowledge or lapse of memory on the entity, and therefore, expected to be preventable by routine scanning around the groin and femoral triangle in addition to adequate education and training for examiners. Generally speaking, ultrasonography as well as the physical examinations are dependent on the examiners’ skill and experience and consequently, may fail to demonstrate the incarcerated obturator hernia in the femoral region. Therefore, it is important to manage the operator-dependent nature of ultrasound properly by developing the competency of sonographers and the systematic ways of scanning.
Ultrasound has been increasingly used for acute abdominal disorders in recent years and consequently, has been evaluated as useful for the diagnosis of bowel obstruction. Furthermore, our case series suggest that it can be applied for the recognition of incarcerated obturator hernia. The early recognition of the entity will consequently reduce its morbidity and mortality and also reduces the cost for CT scan and other imaging modalities. Therefore, important are the use of ultrasound to make a rapid evaluation for acute abdominal disorders including bowel obstruction, and routine scanning around the groin and femoral triangle so as not to overlook the entity when ultrasound is applied for the evaluation of small bowel obstruction.
The author thanks the staff of the ultrasound section in the Kobe City Medical Center West Hospital for their assistance in obtaining the images used in this article.
Conflict of interest statement
There is no conflict of interest related to the publication of this article.
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