Abdominal Imaging

ª Springer Science+Business Media, LLC 2007 Published online: 27 March 2007

Abdom Imaging (2007) 32:803–806 DOI: 10.1007/s00261-007-9194-4

The pubic tubercle: a CT landmark in groin hernia Eric Delabrousse,1 Pierre-Olivier Denue,2 Se´bastien Aubry,1 Philippe Sarlie`ve,1 Georges A. Mantion,2 Bruno A. Kastler1 1 2

Service de Radiologie A, CHU Jean Minjoz, 3 bvd Alexander Fleming, 25030, Besancon, France Service de Chirurgie Digestive, CHU Jean Minjoz, 3 bvd Alexander Fleming, 25030, Besancon, France

Abstract The aim of our study is to investigate the pubic tubercle as a reliable CT landmark in distinguishing the three types of groin hernia. CT scans of 42 patients with surgically confirmed groin hernia were reviewed. For each patient, both the anatomical structure within the hernia and the state of the hernia to the inferior epigastric artery were specifically recorded. Hernias were also located within a schematic construction of orthogonal lines focused on the pubic tubercle. In this construction, inguinal hernias were ventral to the X-axis while femoral hernias were dorsal to the X-axis. Among the inguinal hernias, direct inguinal hernias were located strictly lateral to the Y-axis while indirect inguinal hernias medially crossed the Y-axis. All these CT results were compared to the surgical findings. The inferior epigastric artery was visualized in 90% patients and, in these cases, the situation of the hernia to the artery on CT showed no discordance with surgical findings. Within the schematic construction of orthogonal lines focused on the pubic tubercle, 50% were considered as indirect inguinal hernias, 31% as direct inguinal hernias and 19% as femoral hernias. For each patient, the CT diagnosis was consistent with the surgical report. Key words: CT—Abdominal imaging—Groin— Hernia—Pubic tubercle

Groin hernia is a frequent condition. There are three types of groin hernia, classified according to the anatomical defect: direct and indirect inguinal hernias and femoral hernia. The ring of inguinal hernias and the ring of femoral hernia are located above and below the Correspondence to: Eric Delabrousse; email: [email protected]

inguinal ligament, respectively. Despite this important anatomical difference, the three types of groin hernia may be extremely difficult to distinguish clinically [1]. Whenever clinical diagnosis is uncertain and especially when bowel complication is suspected, computed tomography (CT) is considered the best imaging tool [2– 4]. Nevertheless, although the diagnosis of groin hernia may be easily provided by CT, the differential diagnosis between the three types of groin hernia often remains unclear [5, 6]. This diagnosis is though crucial since different surgical procedures are required according to the anatomical type of the hernia. Since the inguinal ligament cannot be demonstrated on CT, we undertook a retrospective study to determine the accuracy of the pubic tubercle as a CT landmark in distinguishing the three types of groin hernia.

Materials and methods Since our study was retrospective and did not modify the CT examination routinely performed in acute abdomen, no institutional review board approval and informed consent was requested. The surgical and CT records of 42 consecutive patients with groin hernia operated at our institution between June 2003 and June 2006 were retrospectively reviewed. There were 25 men and 17 women, aged 25–99 and mean age 76. The clinical symptoms present at the time of the CT examination were bowel obstruction with irreducible groin hernia (21/42, 50%), bowel obstruction with reducible groin hernia (6/42, 14%) and groin pain or groin swelling (15/42, 36%). All the CT scans were performed with a four-detector row CT scanner (Volume Zoom, Siemens Medical Systems, Forchheim, Germany). Fourteen (14/42, 33%) patients underwent unenhanced CT examination and twenty eight (28/42, 66%) patients underwent contrast-

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Fig. 1. Contrast-enhanced transverse CT scan at the level of the right pubic tubercle in a 68-year-old female patient. Right femoral hernia (white star), located dorsal to the X-axis (X–X¢) and lateral to the Y-axis (Y–Y¢), was correctly diagnosed.

Fig. 2. Unenhanced transverse CT scan at the level of the right pubic tubercle in a 80-year-old male patient. Right direct inguinal hernia (white star), located ventral to the X-axis (X– X¢) and strictly lateral to the Y-axis (Y–Y¢), was correctly diagnosed.

enhanced CT examination. When contrast-enhancement was performed, scanning began 50–80 s after the start of an intravenous injection of 120 mL of contrast material (Iomeron 300, Bracco Imaging SpA, Milan, Italy) delivered at the rate of 2–4 mL/s using a power injector (EnVision CT, MedRad, Maastricht, The Netherlands). No patient received an oral contrast agent. All images were obtained with 3 mm collimation and were reconstructed with a soft-tissue algorithm. The retrospective review of the cases was performed independently by two gastrointestinal radiologists without prior knowledge of the final diagnosis. For each patient, the anatomical structure contained within the hernia was noted. The inferior epigastric artery (IEA) was looked for and whenever visible enough the medial or lateral situation of the hernia to the artery was specifically recorded. The hernia was considered indirect inguinal when it was lateral to the IEA and direct inguinal or femoral when it was medial to the IEA. Schematic construction of orthogonal lines focused on the pubic tubercle situated on the side of the groin hernia was systematically carried out and the location of the hernia, ventral or dorsal to the X-axis and strictly lateral or crossing medially the Y-axis, was recorded. Inguinal hernia was defined when the hernia was located ventral to the X-axis while femoral hernia (FH) was located dorsal to the X-axis (Fig. 1). Moreover, the two types of inguinal hernia were also distinguished, using the Y-axis. Among the hernias located ventral to the Xaxis, direct inguinal hernia (DIH) was defined as hernia located strictly lateral to the Y-axis (Fig. 2) while indirect

inguinal hernia (IIH) was crossing medially the Y-axis (Fig. 3). All these results have been checked against the surgical findings.

Results Retrospective interpretation of the two reviewers for the anatomical structure contained within the hernia, the visibility of the IEA, the situation of the hernia to the IEA and the type of hernia according to its location within the schematic construction of orthogonal lines focused on the pubic tubercle were in agreement in all cases. Twenty-three (55%) patients operated for groin hernia were older than 75 years. Right-side hernias were observed in 22 (52%) patients and left-side hernias in 20 (48%) patients. The hernia was containing small bowel in 33 (79%) patients, sigmoid colon in 3 (7%) patients, mesenteric fat in 3 (7%) patients and ascites in 3 (7%) patients. The inferior epigastric artery (IEA) was visualized in 38 (90%) patients. The four (10%) IEA non visible on CT were in cases of unenhanced CT examination. Hernias were demonstrated lateral to the IEA in 21 (50%) patients and medial to the IEA in 17 (40%) patients. Whether the IEA was visible on CT, the situation of the hernia to the artery showed no discordance with surgical findings. Within the schematic construction of orthogonal lines focused on the pubic tubercle, 34 (81%) hernias were

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Fig. 3. Unenhanced transverse CT scan at the level of the left pubic tubercle in a 76-year-old male patient. Left indirect inguinal hernia (white star), located ventral to the X-axis (X– X¢) and crossing medially the Y-axis (Y–Y¢), was correctly diagnosed.

located ventral to the X-axis and 8 (19%) dorsal to the Xaxis, while 21 (50%) hernias were located strictly lateral to the Y-axis and 21 (50%) were crossing medially the Yaxis. As previously defined, femoral hernias (FH) were diagnosed on CT in 8 (19%) patients, direct inguinal hernias in 13 (31%) patients and indirect inguinal hernias in 21 (50%) patients. These results were in full accordance with the surgical findings.

Discussion Groin hernia is a category of abdominal hernia. It is more common in men than in women and become increasingly common with advancing age [7]. The three types of groin hernia are classified according on the anatomical defect: direct and indirect inguinal hernia and femoral hernia. Femoral hernias are more likely to strangulate than are inguinal hernias, and indirect inguinal hernias are more likely to strangulate than the direct ones. Whichever the type, groin hernia tends to increase in size and to become irreducible if left untreated. Clinical symptoms usually reported by patients are groin pain or groin swelling, reducible or irreducible groin mass, and bowel obstruction. The objectives of hernia management are to relieve symptoms and to prevent complications. Since there is no evidence base to support the truss as a definitive treatment, the only effective treatment is surgery [7]. Although it is sometimes possible to clinically distinguish between inguinal and femoral hernia, it is difficult in most instances when it comes to distinguishing between direct and indirect inguinal hernia; such

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distinction may only be made more reliably correct during surgery. A study comparing pre-operative diagnosis of inguinal hernia with peri-operative diagnosis found that surgeons correctly diagnosed only 76.9% of indirect hernia and 58.9% of direct hernia [8]. However, it seems very important to distinguish reliably between types of groin hernia, since the clinical course and recommended treatment will depend on the type of hernia. At present, CT is considered the best diagnostic modality for the evaluation of acute abdomen and particularly for the diagnosis of the cause and complications of bowel obstruction [2–4]. On the basis of anatomical relationships, the situation of the hernia to the IEA on CT scan is accepted to be predictor of the direct or indirect type of inguinal hernia [6, 9]. Nevertheless, as confirmed in our study, the IEA is not always visible, especially on unenhanced CT examination. Moreover, only indirect inguinal hernia, which is lateral to the IEA, may be reliably diagnosed, since direct inguinal hernia and femoral hernia are both medial to the artery. Considering that the inguinal ligament cannot be demonstrated on CT, the pubic tubercle, which corresponds to the inferior insertion of the ligament, has been first proposed as a valuable CT reference point in distinguishing between inguinal and femoral hernia by Wechsler [10]. A preliminary study based on 12 patients using a schematic construction of orthogonal lines focused on the pubic tubercle seemed to confirm this hypothesis [11]. In our series of 42 patients with surgically confirmed groin hernias, we decided to further evaluate this schematic construction of orthogonal lines focused on the pubic tubercle as a reliable CT landmark in distinguishing the three types of groin hernia. Our hypothesis is that if inguinal hernia anatomically goes above the inguinal ligament, it must be ventral to the X-axis within a schematic construction of orthogonal lines focused on the pubic tubercle on transverse CT scan, whereas if femoral hernia anatomically goes below the inguinal ligament, it should be dorsal to the X-axis. Moreover, within this schematic construction of orthogonal lines focused on the pubic tubercle, only indirect inguinal hernia, which tends pathophysiologically to reach the scrotum, should be able to medially cross the Y-axis. Then, we checked the CT results obtained through this schematic construction of orthogonal lines focused on the pubic tubercle against the surgical findings of the 42 patients operated for groin hernia. The results of our study provided evidence as to the validity of our hypothesis, since all femoral hernias (8/42, 19%) were correctly distinguished from inguinal hernias (34/42, 81%), among which the direct type (13/42, 31%) and the indirect type (21/42, 50%) were also correctly distinguished. Moreover, in our study the pubic tubercle appears to be more reliable than the IEA as a CT landmark in distinguishing the three types of groin hernia, principally

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because of its bone attenuation, which makes it easier to establish whether CT examination is enhanced or not. There are several limitations to our study. Firstly, this study is retrospective. Secondly, with 42 patients, the number of cases analyzed remains limited. Thirdly, only surgically confirmed groin hernias, corresponding to almost complicated hernias were reviewed in our study. In conclusion, the results of our study demonstrate that the pubic tubercle may be clearly used as an accurate CT landmark for the diagnosis of the three types of groin hernia. In our opinion, the major interest of the pubic tubercle is to provide a reliable pre-operative diagnosis, especially since the surgical approach and the precise nature of the surgical repair may be very different according to the type of groin hernia. Further prospective studies are needed to confirm these data. References 1. Naude GP, Ocon S, Bongard F (1997) Femoral hernia: the dire consequences of missed diagnosis. Am J Emerg Med 15:680–682

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2. Lee GHM, Cohen AJ (1993) CT imaging of abdominal hernias. AJR Am J Roentgenol 161:1209–1213 3. Hojer AM, Rygaard H, Jess P (1997) CT in the diagnosis of abdominal wall hernias. Eur Radiol 7:1416–1418 4. Miller PA, Mezwa DG, Feczko PJ, Jafri ZH, Madrano BL (1995) Imaging of abdominal hernias. Radiographics 15:333–347 5. Zarvan NP, Lee FT, Yandow DR, Unger JS (1995) Abdominal hernias: CT findings. AJR Am J Roentgenol 164:1391–1395 6. Stabile Ianora AA, Midiri M, Vinci R, Rotondo A, Angelelli G (2000) Abdominal wall hernias: imaging with spiral CT. Eur Radiol 10:914–919 7. Cheek C, Black N, Devlin H, Kingsnorth A, Taylor R, Watkin D (1998) Groin hernia surgery: a systematic review. Br J Surg 80 (Suppl 1) 8. Ralphs DN, Brain AJ, Grundy DJ, Hobsley M (1980) How accurately can direct and indirect inguinal hernias be distinguished?. BMJ 280:1039–1040 9. Harrison LA, Keesling CA, Martin LL (1995) Abdominal wall hernias: review of hernioraphy and correlation with cross-sectional imaging. Radiographics 15:315–332 10. Wechsler CJ, Kurtz AB, Needleman L, et al. (1989) Cross-sectionnal imaging of abdominal wall hernias. AJR Am J Roentgenol 153:517–521 11. Delabrousse E, Michalakis D, Sarlie`ve P, Paratte B, Rodie`re E, Kastler BA (2005) Value of the pubic tubercle as a CT reference point in groin hernias (French). J Radiol 86:651–654