DOI:10.2214/AJR.05.1251
AJR 2006; 187:1168-1178
© American Roentgen Ray Society
Inguinofemoral Hernia: Accuracy of Sonography in Patients with Indeterminate Clinical Features
Philip Robinson1,
Elizabeth Hensor2,
Mark J. Lansdown3,
N. Simon Ambrose3 and
Anthony H. Chapman3
1 Department of Radiology, Leeds Teaching Hospitals, St. James University
Hospital, Chancellor Wing, Beckett St., Leeds LS9 7TF, United Kingdom.
2 Department Of Epidemiology, University Of Leeds, Leeds, United Kingdom.
3 Department of Surgery, Leeds Teaching Hospitals, Leeds, United Kingdom.
Received July 19, 2005;
accepted after revision September 27, 2005.
Address correspondence to P. Robinson
(p.robinson{at}leedsth.nhs.uk).
Abstract
OBJECTIVE. The objective of our study was to investigate the
accuracy of sonography in patients with symptoms suggestive of a hernia and
normal or equivocal clinical examination findings.
SUBJECTS AND METHODS. Fifty-nine consecutive patients (47 men, 12
women; median age, 51 years; range, 19-82 years) were enrolled in a
prospective study of sonography and herniography for investigation of
inguinofemoral pain. All patients were referred with a history suggestive of
hernia but with equivocal clinical features by three experienced surgeons. All
patients underwent sonography and herniography examinations performed by
experienced radiologists blinded to clinical details. The imaging variables
recorded for each side were normal (including posterior inguinal wall
bulging), hernia (indirect, direct, femoral, and abdominal wall), or
nondiagnostic. The percentage of exact agreement, sensitivity, specificity,
positive predictive value (PPV), and negative predictive value (NPV) were
calculated for sonography and herniography and were compared with surgery when
performed; then all sides for sonography were compared with herniography.
RESULTS. Surgery was performed in 18 patients (31%) on 21 sides and
found hernia (n = 20) and patulous posterior inguinal wall (with no
hernia) (n = 1). Compared with surgery, the results of sonography
versus herniography, respectively, were exact agreement (91% vs 71%),
sensitivity (95% vs 70%), specificity (100% vs 100%), PPV (100% vs 100%), and
NPV (50% vs 14%). The sensitivity of sonography was significantly higher than
that of herniography (McNemar test, p = 0.025). Both techniques had
one false-negative in the same patient. Herniography had five additional
false-negatives identified as hernias at sonography and surgery. Compared with
herniography as the reference, the sonography findings were in exact agreement
in 91% (107/118) of the cases; and sensitivity was 90% (19/21); specificity,
91% (88/97); PPV, 68% (19/28); and NPV, 98% (88/90).
CONCLUSION. Sonography is an accurate technique for the detection of
inguinofemoral hernias in patients with clinically equivocal findings.
Keywords: abdominal imaging • dynamic sonography • inguinofemoral hernia • sonography
Introduction
Most clinically significant hernias can be diagnosed on clinical
examination and managed without the use of diagnostic imaging. However, there
are recognized limitations to clinical assessment, and a significant
proportion of patients with symptoms suggestive of a hernia are found to have
normal or equivocal clinical examination findings
[1-5].
In this patient group, the clinician can proceed to surgical exploration if
symptoms are severe enough, but surgery is invasive and is associated with
potential morbidity.
Herniography has been evaluated in patients with equivocal clinical
features and has been shown to be a very sensitive, but potentially
nonspecific, technique, for depiction of asymptomatic hernias. Herniography
has a low complication rate, but the procedure is still relatively invasive
and requires ionizing radiation
[6-10].
Sonography has been evaluated in infants for confirming clinically evident
inguinal hernias, but a varied accuracy is reported for the assessment of the
contralateral inguinal canal
[11-14].
Sonography has been shown to be an accurate preoperative technique in adults
for confirming hernias evident on clinical examination
[1,
15-20].
There have been no studies, to our knowledge, evaluating sonography in a large
cohort of adult patients with clinically equivocal features.
The aim of this study was to prospectively evaluate the accuracy of
sonography in assessing patients with symptoms suggestive of an inguinofemoral
hernia who have normal or equivocal clinical examination findings.
Subjects and Methods
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Fig. 1A —52-year-old man who presented with left inguinal pain; normal
findings were seen on sonography. Line drawing (A) and longitudinal
sonography image (B) of left inguinal canal show inferior epigastric
vessels (IE) laterally, hyperechoic fibrillar inguinal ligament
(arrowheads), and transversalis fascia (arrows). Canal
contents are fat, nerves, and hypoechoic vessels (asterisks).
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Fig. 1B —52-year-old man who presented with left inguinal pain; normal
findings were seen on sonography. Line drawing (A) and longitudinal
sonography image (B) of left inguinal canal show inferior epigastric
vessels (IE) laterally, hyperechoic fibrillar inguinal ligament
(arrowheads), and transversalis fascia (arrows). Canal
contents are fat, nerves, and hypoechoic vessels (asterisks).
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Fig. 1C —52-year-old man who presented with left inguinal pain; normal
findings were seen on sonography. Line drawing (C) and short-axis
sonography image (D) of inguinal canal show oval-shaped canal
(arrows) containing multiple hypoechoic vessels (small
asterisks). Inferior and deep in relation to canal is psoas muscle (P)
with rectus abdominis muscle (RAb) superiorly. Posterior and slightly superior
to canal is echogenic margin (arrowheads) of transversalis fascia
with preperitoneal fat (large asterisk), bowel, and peritoneum deep
to fascia.
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Fig. 1D —52-year-old man who presented with left inguinal pain; normal
findings were seen on sonography. Line drawing (C) and short-axis
sonography image (D) of inguinal canal show oval-shaped canal
(arrows) containing multiple hypoechoic vessels (small
asterisks). Inferior and deep in relation to canal is psoas muscle (P)
with rectus abdominis muscle (RAb) superiorly. Posterior and slightly superior
to canal is echogenic margin (arrowheads) of transversalis fascia
with preperitoneal fat (large asterisk), bowel, and peritoneum deep
to fascia.
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After obtaining institutional ethics committee approval for the study, 72
consecutive patients were enrolled in a prospective study of sonography and
herniography for the investigation of inguinofemoral pain. During the study,
13 patients were excluded for failing to attend herniography or clinical
appointments (or both), leaving 59 patients (47 men, 12 women; median age, 51
years; range, 19-82 years) in the study.
Clinical Features
All patients were referred by three surgeons experienced in hernia
management who completed an initial examination form with patient
demographics, clinical symptoms, and clinical findings. All patients had a
history of inguinofemoral pain (> 3 months) suggestive of a hernia in 64
sides (five patients had bilateral symptoms) but on clinical examination,
normal (n = 52) or equivocal (n = 12) clinical features were
present. Equivocal clinical features included tenderness but not a focal mass
or cough impulse. Thirty-six patients had right-sided symptoms and 28,
left-sided symptoms, including five patients with bilateral symptoms. Ten
patients had previously undergone herniorrhaphy presenting with recurrent pain
ipsilateral to the side of the previous surgery.
Sonography Examination
Each patient underwent sonography (Elegra or Antares, Siemens Medical
Solutions) performed by an experienced radiologist using a linear transducer
(13-5- or 9-5-MHz depending on patient body habitus). The radiologist was
blinded to the clinical information but was aware that the patient had been
referred with inguinofemoral symptoms suggestive of a hernia.
A longitudinal image of the inguinal canal was obtained, including the
inferior epigastric vessels at their origin from the femoral vessels as a
landmark for the deep inguinal ring (Figs.
1A and
1B). The inguinal ligament was
seen as a linear echogenic structure deep in relation to the subcutaneous fat
blending with the deep fascia. Deep in relation to the ligament were multiple
hyper- and hypoechoic linear structures, representing vessels, nerves, and
cords within the canal. Deep in relation to the canal, the psoas muscle,
peritoneum, bowel, and preperitoneal fat were identified. Assessment of the
canal with the patient at rest and during straining, coughing, and performing
a slow Valsalva maneuver was performed while maintaining light transducer
pressure.
The inguinal canal was then assessed in its short axis, which is the
anatomic sagittal plane (Figs.
1C and
1D). To obtain this view, the
radiologist scanned the femoral vessels longitudinally to view the inferior
epigastric vessels as they arise and pass superiorly toward the rectus
abdominis muscle. The transducer was then moved medially to show the short
axis of the inguinal canal and its hypoechoic tubular contents with
peritoneum, fat, and bowel lying posterosuperiorly. Assessment of this area
with the patient at rest and during straining, coughing, and performing a slow
Valsalva maneuver was performed while maintaining light transducer
pressure.
An indirect inguinal hernia was defined as a protrusion of fat, bowel, or
both through the internal inguinal ring and extending along the inguinal canal
parallel to its long axis (Figs.
2A,
2B,
2C,
2D, and
2E). A direct inguinal hernia
was defined as a defect in the posterior inguinal wall within the transversus
abdominis fascia allowing protrusion of the hernia into the inguinal canal
(Figs. 3A,
3B,
3C,
3D, and
3E). An abdominal wall hernia
was defined as protrusion of the hernia through an abdominal wall defect into
the subcutaneous fat. Posterior inguinal wall bulging was recorded if there
was marked compression of the canal contents on straining by the transversus
abdominis fascia but with no fascial defect or hernia present (Figs.
4A,
4B, and
4C). Other features were
recorded as normal, including patent processus vaginalis, defined as two
opposing echogenic layers of peritoneum sliding over each other on
straining.
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Fig. 2A —61-year-old woman who presented with left inguinal pain from
left indirect inguinal hernia. Herniography image shows left indirect hernia
(arrows) with contrast material filling distally.
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Fig. 2B —61-year-old woman who presented with left inguinal pain from
left indirect inguinal hernia. Longitudinal sonography image obtained while
patient was at rest shows inferior epigastric vessels (IE), inguinal ligament
(arrowheads), and transversalis fascia (arrows).
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Fig. 2C —61-year-old woman who presented with left inguinal pain from
left indirect inguinal hernia. Sonogram obtained while patient strained shows
that hypoechoic hernia (asterisk) arises lateral to inferior
epigastric vessels (IE) expanding canal (thin arrows) and displacing
ligament (arrowheads) and transversalis fascia (thick
arrows).
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Fig. 2E —61-year-old woman who presented with left inguinal pain from
left indirect inguinal hernia. Sonogram obtained while patient strained shows
that canal is expanded (arrows) by extension of indirect hernia along
its long axis.
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Fig. 3B —73-year-old woman with left inguinal pain from left direct
inguinal hernia. Longitudinal sonography image obtained while patient was at
rest shows inferior epigastric vessels (IE), inguinal ligament
(arrowheads), transversalis fascia (arrows), and contents
including prominent vessel (asterisks).
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Fig. 3C —73-year-old woman with left inguinal pain from left direct
inguinal hernia. Sonogram obtained while patient strained shows that hernia
(asterisk) extends (small arrows) through posterior wall
defect (margin marked by large arrows) medial to inferior epigastric
vessels (IE).
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Fig. 3D —73-year-old woman with left inguinal pain from left direct
inguinal hernia. Short-axis sonography image obtained while patient was at
rest shows canal (arrowheads), prominent vessel (asterisk),
and transversalis fascia (arrows).
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Fig. 3E —73-year-old woman with left inguinal pain from left direct
inguinal hernia. Sonogram obtained while patient strained shows that hernia
(asterisk) enters through posterior wall defect (margin marked by
thick arrows) compressing (thin arrows) contents of inguinal
canal (arrowheads).
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Fig. 4B —33-year-old man who presented with right inguinal pain from
right posterior inguinal wall bulging. Short-axis sonography image of inguinal
canal obtained while patient was at rest shows inguinal canal
(arrowheads) and psoas muscle (P), with transversalis fascia lying
superiorly and posteriorly (arrows).
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Fig. 4C —33-year-old man who presented with right inguinal pain from
right posterior inguinal wall bulging. Sonogram obtained while patient
strained shows that bowel (two asterisks) and preperitoneal fat
(one asterisk) are displacing intact transversalis fascia
(arrows), which is markedly compressing inguinal canal
(arrowheads).
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The femoral vessels were then viewed in the transverse plane inferior to
the inguinal canal where the femoral canal lies medial to the femoral vein.
Assessment of the femoral canal with the patient at rest and during straining
(coughing and performing a slow Valsalva maneuver) was performed while
maintaining light transducer pressure. A femoral hernia was defined as a
protrusion of the hernia into the femoral canal.
Sonography variables recorded for each side were normal (including
posterior wall bulging), hernia (indirect, direct, femoral, and abdominal
wall), or nondiagnostic. If a hernia was detected, its contents were recorded
as fat, bowel, or both (Figs.
5A,
5B,
5C,
5D, and
5E).
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Fig. 5A —56-year-old woman with right inguinal pain. Herniography
findings were false-negative; right indirect hernia was detected at sonography
and confirmed at surgery. Herniography image shows no evidence of inguinal
hernia.
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Fig. 5B —56-year-old woman with right inguinal pain. Herniography
findings were false-negative; right indirect hernia was detected at sonography
and confirmed at surgery. Longitudinal sonography image obtained while patient
was at rest shows inferior epigastric vessels (IE), inguinal ligament
(arrowheads), and transversalis fascia (arrows).
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Fig. 5C —56-year-old woman with right inguinal pain. Herniography
findings were false-negative; right indirect hernia was detected at sonography
and confirmed at surgery. Sonogram obtained while patient strained shows that
hypoechoic hernia (asterisk) consisting of fat arises laterally to
inferior epigastric vessels (IE), expanding canal (arrows) and
displacing inguinal ligament (arrowheads).
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Fig. 5D —56-year-old woman with right inguinal pain. Herniography
findings were false-negative; right indirect hernia was detected at sonography
and confirmed at surgery. Short-axis sonography image of inguinal canal while
patient was at rest shows round canal (arrowheads).
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Fig. 5E —56-year-old woman with right inguinal pain. Herniography
findings were false-negative; right indirect hernia was detected at sonography
and confirmed at surgery. Sonogram obtained while patient strained shows that
canal is expanded by extension of indirect hernia (asterisk) along
its long axis, which results in compression of other canal contents
(arrowheads).
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Herniography
All patients underwent herniography on the same day within 4 hours of
sonography (range, 1-4 hours). All examinations were performed by an
experienced radiologist blinded to clinical features and sonography findings.
The examination was performed with the patient supine and with an empty
bladder. A puncture site was chosen halfway between the umbilicus and the
pubis symphysis, and the skin was infiltrated with local anesthetic. If there
was a scar in the vicinity of the proposed puncture site, an alternative site
was chosen to the left or right of the midline. A 3.5-inch (8.9-cm) 20-gauge
spinal needle was advanced through the abdominal wall, and additional local
anesthetic (10 mL) was injected to flush bowel loops away from the needle tip
as the peritoneal cavity was entered. Iohexol 300 (Omnipaque, Nycomed) was
injected, and the flow into the peritoneal cavity was observed under
fluoroscopy with an additional 50 mL of contrast medium then injected into the
peritoneal cavity. The needle was removed, and the patient was turned to
ensure that the contrast medium flowed over the peritoneal surface.
With the patient straining, the filming sequence used was as follows: erect
posteroanterior, right and left posteroanterior oblique, and lateral and prone
posteroanterior with the head of the table elevated 30° and with 30°
cranial tube angulation relative to the table. The same variables as those
recorded for sonography were recorded for each side: normal (including
posterior wall bulging), hernia (indirect, direct, femoral, and abdominal
wall), or nondiagnostic.
Clinical Outcome
Referring surgeons were not blinded to the imaging results, because doing
so was considered unethical. All cases were reviewed with the results of both
techniques and the clinicians blinded to the findings of a specific
technique—that is, if there was a discrepancy, the clinician did not
know which technique had detected the hernia. A management plan was recorded
with four possible outcomes: discharge to primary care referrer, discharge to
pain management consultant, further review in surgical clinic, or schedule for
surgery. The clinical case notes were then reviewed at 3-month intervals with
the outcome recorded each time. If surgery was not performed, follow-up was
for a minimum of 12 months.
Statistical Analysis
The Stuart-Maxwell test of marginal homogeneity was applied to assess the
agreement between surgery and herniography and between surgery and sonography
when the outcome was normal, bulge, or hernia.
The sensitivity, specificity, positive predictive value (PPV), and negative
predictive value (NPV) of sonography and herniography were separately compared
with surgery, when performed, on the basis of a binary outcome (normal or
hernia) with bulges considered "normal." Of these measures, only
the differences in sensitivity and specificity were statistically compared,
using the McNemar test, with 95% CIs for the difference in sensitivity and
specificity calculated [21].
The percentage of exact agreement, sensitivity, specificity, PPV, and NPV of
all sonography findings were compared with herniography as the imaging
reference.
Results
None of the sonography or herniography examinations was classified as
nondiagnostic and no complications were reported. For all sonography
examinations, the canal and inferior epigastric vessels were visible. In
patients who had undergone previous surgery for hernia, focal acoustic
shadowing from scar tissue was present but did not undermine the assessment of
the inguinal canal for the presence of a hernia.
Surgery
Eighteen patients (18/59 = 31%) underwent surgery, with 21 sides (21/118 =
18%) operated on. Surgical findings included hernia (n = 20) and
patulous posterior inguinal wall (with no hernia) (n = 1). Hernias
were classified as direct inguinal hernia (n = 10), indirect inguinal
hernia (n = 8), spigelian hernia (n = 1), and incisional
hernia (n = 1). Six of these hernias were on the original
asymptomatic side: three were repaired as part of bilateral surgery and the
other three, although initially on the asymptomatic side, subsequently became
symptomatic on follow-up.
Correlation of Sonography and Herniography with Surgery
Sonography and herniography findings are separately compared with surgical
findings in Tables 1 and
2, respectively. The
sensitivity, specificity, PPV, and NPV for sonography and herniography are
compared with surgery in Table
3. The sensitivity of sonography was significantly higher than
that of herniography for the patients who underwent surgery (difference in
sensitivity, 0.25; 95% CI, 0.02-0.47; McNemar test, p = 0.025). The
NPV appeared to be higher for sonography than for herniography, but these
values could not be statistically examined beyond comparison of the CIs for
sonography NPV and herniography NPV, which were wide and overlapping because
of the small sample size. It is therefore unlikely that the results differ
significantly. The specificity and PPV did not differ at all.
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TABLE 3: Performance Measures for Sonographic Detection of Abnormalities in 118
Sides with Herniography Findings as the Reference Standard
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Sonography—Classification of the 19 hernias detected on
sonography was correct in all cases. In one case, sonography showed normal
findings, but an indirect hernia was found at surgery (Tables
1 and
3). For another case,
sonography depicted posterior inguinal wall bulging and a patulous posterior
inguinal wall was found at surgery. The sonography results did not differ
significantly from the surgery findings (Stuart-Maxwell test, p =
0.607).
Herniography—Classification of the 14 hernias detected on
herniography was correct in all cases. For another five cases, herniography
reported findings of no hernia with four hernias (three direct and one
indirect) and one patulous posterior wall detected at surgery (Tables
2 and
3). For one of these cases in
which a hernia was found at surgery, sonography findings were also normal, but
for the remaining four cases, sonography depicted posterior inguinal wall
bulging in one case and a hernia consisting of preperitoneal fat in three
cases. In another two cases, herniography showed posterior inguinal wall
bulging with two direct hernias found at surgery, and in both of these cases
sonography also detected direct hernias. The herniography results differed
significantly from the surgery findings (Stuart-Maxwell test, p =
0.040).
Correlation of sonography and herniography—The findings and
accuracy of sonography compared with herniography are presented in Tables
4 and
5, respectively. Both
techniques showed normal findings in all 118 femoral canals and in 69 inguinal
canals (Tables 4,
5,
6).
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TABLE 5: Performance Measures for Sonography and Herniography in the Detection of
an Abnormality in 21 Sides with Surgical Findings as the Reference
Standard
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TABLE 6: Frequency of Hernias and Posterior Wall Bulging Detected in 64
Symptomatic Sides and 54 Asymptomatic Sides on Herniography and
Sonography
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Sonography showed posterior inguinal wall bulging in nine sides for which
herniography findings were normal. One of these sides underwent surgery,
during which a patulous posterior wall was detected. Herniography depicted
posterior inguinal wall bulging in 11 sides; for those sides, findings on
sonography were normal in five cases, a bulge in four cases, and direct
inguinal hernias in the remaining two cases. Surgery was performed in the
latter two cases and confirmed the diagnoses of direct inguinal hernia.
Sonography and herniography both depicted hernias in 20 sides: 14 were
confirmed at surgery and six sides did not undergo surgery. In another nine
sides, sonography depicted an inguinal hernia, whereas herniography revealed
normal appearances in seven sides and bulging in two sides. Surgery was
performed in three of these cases and confirmed three inguinal hernias. In two
sides with normal findings at sonography, herniography showed inguinal
hernias; however, surgery was not performed in either patient.
A comparison of the incidence of hernias and posterior wall bulging on
symptomatic and asymptomatic sides for herniography and sonography is shown in
Table 6.
The findings of herniography and sonography did not differ significantly;
however, there was some evidence that if the sample size had been slightly
larger, a difference might have emerged (Stuart-Maxwell test, p =
0.077).
Clinical Outcome
The median follow-up for all patients was 6 months (range, 3-18 months).
The clinical outcome for all patients is summarized in
Figure 6.
Of the 18 patients who underwent surgery, three patients developed
recurrent pain, including the one patient with posterior wall bulging detected
on sonography and at surgery. All three patients underwent repeat sonography;
two patients had normal findings (including the previously reported bulging)
and one patient had findings suggestive of a small recurrent indirect hernia
(thought to be not consistent with the current symptoms). All three patients
were referred to the anesthetic pain management service with a clinical
diagnosis of ilioinguinal neuralgia.
In the remaining 41 patients who did not undergo surgery, two patients were
scheduled for surgery; in one, a hernia was present on both sonography and
herniography, and in the other, a hernia was seen on sonography only. Both
operations were cancelled because the patients became asymptomatic before
surgery. Alternate diagnoses were made in four patients— namely,
adhesions, irritable bowel, adductor longus tendinopathy, and varicocele. The
latter two cases were diagnosed on the basis of sonography findings, and the
patients were pain-free after subsequent injection (adductor longus
tendinopathy) and embolization (varicocele).
Discussion
A number of articles have reviewed the accuracy of herniography in patients
with clinically equivocal findings
[4,
6,
8,
10,
22,
23]. In the series involving
the general population (range, 70-146 patients), hernias were detected on the
symptomatic side in 27-40% of patients and asymptomatic hernias were detected
in 6-18% of patients [4,
6,
8,
23]. In this current study,
herniography depicted hernias in 27% of the 64 symptomatic sides (33% on
sonography) and 9% of the 54 asymptomatic sides (15% on sonography). In the
previous herniography series, all the imaging features could not be verified
because a variable number of patients underwent surgery (range, 14-33% of
cases) [4,
6,
8,
23]. In addition, not all
patients with symptomatic hernias proceeded to surgery because some symptoms
resolved spontaneously [8]. In
those patients who did undergo surgery, high sensitivities (96-100%) and
specificities (98-100%) for herniography are reported.
False-negative herniography findings can potentially occur because of small
hernias and loculation of contrast material, which prevents flow into the
hernia sac, or hernias predominantly consisting of fat
[6,
23]. False-positive
herniography findings can occur when the hernia reduces completely at surgery
while the patient is under anesthesia. In the current study, 31% of the
patients underwent surgery (18 of the cases), and herniography had a
significantly lower sensitivity (70%) than sonography (95%). This difference
in sensitivity was mainly because five false-negative cases at herniography
were identified as fat-containing inguinal hernias at sonography and
surgery.
The previous herniography series that have reported higher accuracies than
our study had no other imaging techniques to influence management. This may
have led to a lower level of surgical intervention in patients with negative
herniography findings compared with this study. Our study shows sonography can
depict fat-filled hernias, probably because it allows real-time visualization
of the hernia contents and does not depend on the secondary sign of contrast
movement within the peritoneum.
Studies of CT and MRI have not been performed in patients with equivocal
clinical findings of inguinal hernia, to our knowledge. Reviews of abdominal
CT series have shown CT to be an effective technique for detecting and
classifying abdominal hernias predominantly in patients with diffuse symptoms
and a palpable abnormality
[19,
24-28].
Although some studies of dynamic MR technique have been presented, those
series were performed in patients with clinically evident hernias before
surgery [1,
29,
30]. In their 1999 study
[1], van den Berg et al.
reported a slightly superior accuracy of MRI to sonography, which is discussed
later in this article. At present, these MR techniques have not been widely
accepted or evaluated in clinical practice.
In a number of sonography studies, researchers have assessed adult patients
with clinical findings of inguinal or abdominal wall hernias before surgery
[1,
15-20].
In one of the earliest studies, Deitch and Soncrant
[16] evaluated 95 patients,
with the radiologists not blinded to the heterogeneous clinical features in
the cohort. Their cohort included 25 patients with normal sonography findings
who did not proceed to surgery, which may imply that the referring clinicians
did not have a definite diagnosis of hernia in this subgroup. However, the
remaining 70 patients who did undergo surgery had fixed abdominal masses or
clinically evident hernias. Most other sonography studies have involved
assessment of patients (range, 19-220 patients) before surgery. This study
design results in a high surgical correlation, but it also results in bias
with no significant number of clinically equivocal cases being evaluated.
In most other studies, researchers have reported a high sensitivity
(86-100%) and specificity (82-97%) for sonographic diagnosis of inguinal
hernias, with more varied accuracies (45-85%) for hernia classification
[1,
15-20].
However, some of these studies used lower-frequency transducers than we used,
which may have resulted in poor visualization of the landmarks used to
classify hernia type [1,
17]. In our study of
clinically equivocal cases, the sensitivity and specificity for sonography
were high in cases in which surgical verification was available.
Classification of hernia type was correct for both sonography and herniography
in all true-positive cases.
Few studies have compared different imaging techniques in the assessment of
patients with clinically suspected hernias. One study compared MRI,
sonography, and clinical examination in patients with clinically evident
hernias before surgery [1].
Those researchers found that clinical examination was less accurate than
sonography (sensitivity, 92.7%; specificity, 81.5%) and reported a slightly
higher specificity for dynamic MRI than sonography. However, four of the five
false-positive sonography findings resulted from bulging of the posterior
inguinal wall being recorded as "direct inguinal hernia."
In previous sonography studies, most of the false-negative findings have
been attributed to small hernias (not quantified) or technical errors due to
operator inexperience [1,
17,
18]. False-positive findings
have been attributed to reporting cases of bulging and inguinal lipoma as
"direct inguinal hernia" and "indirect inguinal
hernia," respectively [1,
16-19].
Bulging of the transversalis fascia, in which the posterior inguinal wall
almost occludes the inguinal canal on straining but with no actual herniation,
has been proposed as a source of pain or as a "prehernia"
condition [1,
9,
23,
31]. Unfortunately, the
literature does not show that this feature correlates with pain or is part of
the spectrum of direct inguinal hernia
[19,
32].
Two articles have reviewed sonography assessment of the transversalis
fascia in athletes with chronic groin symptoms and found posterior wall
bulging did not correlate with the side or severity of pain
[31,
32]. Another study of athletes
found posterior wall bulging in seven symptomatic and four asymptomatic sides
using herniography, but surgery was not performed in eight of those 11 cases
[9]. In our series,
herniography showed posterior inguinal wall bulging in 11 sides (seven
symptomatic and four asymptomatic), and sonography showed bulging in 13 sides
(eight symptomatic and five asymptomatic)
(Table 6). We believe that
these findings do not represent a hernia and should be cautiously interpreted
as a positive feature because these findings may represent a variation of
normal. In the one case in which herniography was normal and sonography showed
unilateral bulging, the patient underwent surgery, with mesh reinforcement
performed. However, this procedure did not relieve the patient's symptoms
despite bulging being absent on sonography postoperatively. Limitations of
this study include the fact that the clinicians could not ethically be blinded
to the imaging findings, which may explain why most of patients with the
normal imaging findings did not proceed to surgery. Although this does not
allow an accurate evaluation of NPV for both techniques, the proportion of
patients who did proceed to surgery compares favorably with herniography
studies consisting of similar patient profiles
[4,
6,
8,
23]. After imaging and the
initial review by the referring surgeon, patients were followed by case note
review, not by pain scores, because a scoring system has not been standardized
for primary inguinofemoral pain or presented in previous herniography
studies.
In conclusion, this prospective study of patients with equivocal clinical
features for hernia has shown sonography to be an accurate technique with a
higher sensitivity and NPV than herniography in the patients who underwent
surgery (p < 0.05). Sonography and herniography had a high level
of exact agreement, with the main disagreement occurring in cases of
fat-filled hernias detected on sonography that appeared normal on
herniography. Although sonography is operator-dependent, we believe that when
the expertise is available, sonography should be the first-line imaging
investigation of abdominal wall and inguinal hernias in patients with
clinically equivocal findings and herniography should be reserved for use in
cases in which sonography findings are inconclusive.
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