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1 All authors: Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC 27710.
Received May 10, 2004;
accepted after revision July 23, 2004.
Address correspondence to T. A. Jaffe
(jaffe002{at}mc.duke.edu).
Abstract
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SUBJECTS AND METHODS. From September 2002 to May 2003, 100 consecutive patients (37 men and 63 women; mean age, 53 years) with suspected anterior abdominal wall hernias underwent 4-, 8-, or 16-MDCT with and without Valsalva's maneuver. Patients received both oral and IV contrast material. On a workstation, three independent reviewers evaluated each scan obtained during rest and during Valsalva's maneuver for the following parameters: anteroposterior (AP) diameter of the abdomen; presence, location, and contents of the hernia; and transverse diameter of the fascial defect. The scans were compared to assess for changes in hernia size and contents and to determine whether the hernia would have been overlooked without Valsalva's maneuver. Fisher's exact test, the McNemar test, and Cohen's kappa coefficient were used to assess for significant differences.
RESULTS. The three reviewers identified a mean of 72 abdominal wall
hernias (72%). The reviewers agreed (
= 0.723) with respect to the
presence of a hernia. AP diameters increased an average of 1.33 cm during
Valsalva's maneuver (p < 0.001). The transverse diameter of the
fascial defect increased an average of 0.66 cm and the AP diameter of the
hernia sac increased an average of 0.79 cm during Valsalva's maneuver
(p < 0.001). Fifty percent of the hernias became more apparent
with Valsalva's maneuver. Ten percent of the hernias could be detected only on
the scan obtained during Valsalva's maneuver. Conversely, in no patients was
the hernia detected only on the rest scan.
CONCLUSION. As opposed to scans obtained at rest, scans obtained during Valsalva's maneuver aid in the detection and characterization of suspected abdominal wall hernias. A single scan obtained during Valsalva's maneuver is sufficient to detect 100% of anterior abdominal wall hernias identified on CT.
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Patients are often referred for imaging studies to confirm a suspected hernia. These studies include radiography, sonography, barium studies, and herniography. CT is being used increasingly to show the specific anatomy of the hernia sac and distinguish a hernia from its mimics. Although Valsalva's maneuver is often used in barium studies or sonography of the abdominal wall, we found no research that evaluated the role of Valsalva's maneuver in MDCT diagnosis of abdominal wall hernias [1, 2]. With MDCT, the short acquisition time allows imaging of the entire abdomen and pelvis within a single breath-hold including Valsalva's maneuver. The aim of our study was to determine the effect and benefit of Valsalva's maneuver in the MDCT diagnosis of abdominal wall hernias.
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The initial rest acquisition was performed at end-inspiration during a single breath-hold. For this acquisition, 150 mL of iopamidol (Isovue 300, Bristol-Myers Squib) was injected at a rate of 3 mL per second, unless contraindicated. Seventy-three of the 100 patients received IV contrast material. Scans were acquired during the portal venous phase of enhancement, with a delay determined by bolus tracking and automated triggering technology. Protocols varied depending on whether a 4-, 8-, or 16-MDCT scanner was used. Pitch ranged from 1.5 to 1.75, and table speed ranged from 15 mm per rotation to 17.5 mm per rotation. All scanners had a 0.5-sec tube rotation. Slice reconstruction thickness was 5 mm for all patients. Acquisition duration ranged from 12 to 20 sec.
Immediately after the initial scanning, at end-inspiration, the patient was instructed to "bear down" or "strain" and a second acquisition was completed during Valsalva's maneuver. No additional IV or oral contrast material was administered for the second acquisition. The technical parameters for the scan obtained during Valsalva's maneuver were identical to those of the scan obtained at end-inspiration.
Three experienced radiologists with subspecialty training in abdominal imaging reviewed, on a workstation (Centricity 1.0, GE Healthcare), each scan obtained at rest and during Valsalva's maneuver. The reviewers were unaware of patient identifiers and interpreted each scan independently. Clinical information was not provided to the reviewers. Most notably, reviewers were unaware of the patients' prior surgical histories. Each scan was evaluated for multiple parameters including presence, location, and contents of the hernia; anteroposterior (AP) diameter of the abdomen; and transverse diameter of the fascial defect.
The AP diameter of the abdomen was determined by measuring the distance from the anterior aspect of the L5 vertebral body to the anterior skin surface. This distance was measured on both scans. For the purposes of this study, a hernia was defined as a protrusion of abdominal contents through a defect in the normally restraining muscles of the abdomen and pelvis. The location of the hernia was designated as ventral, inguinal, or other. Contents were designated mesenteric or omental fat, colon, small bowel, stomach, bladder, or other. The transverse diameter of the hernia sac aperture and the AP diameter of the hernia sac were measured on both scans.
The scans obtained at rest and during Valsalva's maneuver were compared to assess changes in hernia size and contents and to determine whether the hernia was more conspicuous after Valsalva's maneuver. The reviewers determined whether the hernia would have been overlooked without Valsalva's maneuver. In addition, they assessed whether evidence of a prior hernia repair was present or whether postoperative complications were present. In the patient with multiple hernias, the reviewers were instructed to characterize the largest defect.
The data were collected and entered into a database by the principal investigator. No clinical information was included in this study. The department statistician analyzed the data using version 8.2 of the SAS software system (SAS Institute). The statistical reliability of a given difference in response rates between respondent subgroups for specific questions was analyzed with Fisher's exact test, the McNemar test, and Cohen's kappa coefficient. A p value of less than 0.05 was considered statistically significant. A kappa value of greater than 0.5 supported agreement between reviewers.
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= 0.72). Most hernias were ventral (Figs.
1A and
1B) (R1, 63 [91%]; R2, 66
[89%]; R3, 67 [93%]); the inguinal hernias were fewer (R1, 5 [7%]; R2, 7 [9%];
R3, 4 [5%]). One hernia was posterior intercostal. The reviewers did not
differ in the identification of hernias between men and women.
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Valsalva's maneuver was associated with an increase in AP diameter in 82 patients (82%) (Figs. 2A and 2B), a decrease in 14 patients (14%), and no change in four patients (4%). The mean increase in diameter was 1.40 cm, as detailed in Table 1. The change in mean AP diameter was statistically significant for all three reviewers (p < 0.001). The AP diameter of the hernia sac increased by an average of 0.8 cm with Valsalva's maneuver (p < 0.001). With Valsalva's maneuver, the transverse diameter of the hernia sac increased in 51 patients (72%) (Figs. 2A and 2B), decreased in 11 patients (15%), and did not change in 10 patients (14%). For all three reviewers, the mean change in transverse diameter was 1.40 cm, which was statistically significant (p < 0.001).
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Hernias became more conspicuous after Valsalva's maneuver (Table 2). Reviewers noted that the appearance of 56–77% (mean, 70%) of the hernias changed with Valsalva's maneuver, and 32–72% (mean, 36%) of the hernias became more apparent with Valsalva's maneuver. The contents of the hernia sac changed with Valsalva's maneuver, as the maneuver caused small bowel, colon, liver, or fat to protrude into the hernia (Figs. 3A and 3B). Most important, R1, R2, and R3 found that the hernias in 10, seven, and four patients, respectively, (mean, 7) would have been overlooked if Valsalva's maneuver had not been not performed (Figs. 4A and 4B). Conversely, in no patient was a hernia detected only on a rest scan.
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R1, R2, and R3 identified 32 of 68, 37 of 74, and 46 of 72 hernias, respectively, as craniad to the umbilicus. The remaining hernias were caudad to the umbilicus. For each reviewer, the effect of Valsalva's maneuver, change in AP diameter, change in transverse measurement of the fascial defect, and conspicuity were similar regardless of whether the hernia was craniad or caudad to the umbilicus (p > 0.2 in all cases). Similarly, whether the hernia was craniad or caudad to the umbilicus had no bearing on the likelihood that a hernia would be missed without the Valsalva's maneuver scan (p > 0.4).
In 24% of the patients scanned, prior hernia repair was evident through the presence of mesh or coils on CT. The reviewers identified 14 postoperative complications, including seroma, hematoma, and abscess.
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All our patients received oral and IV contrast material unless clinically contraindicated. Oral contrast material helps distend bowel loops and enhances the differentiation of small bowel from colon. We used IV contrast material to help distinguish between the presence of a hernia and its mimics, to assess for inflammation, and to increase the sensitivity for incidental abnormality in the solid organs [11, 16].
Valsalva's maneuver was originally described in 1704 by Antonio Maria Valsalva, an Italian anatomist who developed this method for inflating the middle ear. By creating force against a closed glottis, this exercise increases pressure within the thoracic and abdominal cavity. The proposed and desired effect of Valsalva's maneuver in this study was to increase intraabdominal pressure and accentuate any herniation that may have been occult at rest [3]. Ventral hernias have been evaluated using both rest scans and Valsalva's maneuver scans at our institution for a number of years. This study was designed to evaluate the role of a scan obtained during Valsalva's maneuver. Our study showed that Valsalva's maneuver has an effect on the abdomen and its contents that aids in the detection and characterization of anterior abdominal wall hernias.
To our knowledge, no published norms exist on the expected change in intraabdominal morphology on CT after Valsalva's maneuver. We hypothesized that measurement of AP diameter changes would reflect an increase in intraabdominal pressure. In patients with or without identifiable hernias, AP diameter increased during Valsalva's maneuver, suggesting an increase in intraabdominal pressure and producing a satisfactory result from the Valsalva's maneuver. This was a consistent observation and provided evidence that patients can be instructed in the performance of Valsalva's maneuver and can maintain the maneuver throughout an MDCT scan.
With Valsalva's maneuver, the transverse measurement of the fascial defect increased. The change in size implies that the abdominal wall musculature changes with Valsalva's maneuver. These changes accentuate the aperture of the hernia sac. In addition, the AP diameter of the hernia sac changes with the addition of Valsalva's maneuver, implying that the increase in intraabdominal pressure also is transmitted to the hernia sac and its contents.
More important, a mean of 51% of hernias become more conspicuous with Valsalva's maneuver because of protrusion of mesenteric or omental fat, bowel, or solid organs into the hernia sac. Valsalva's maneuver simulates certain activities of daily living such as heavy lifting, making these findings more clinically relevant.
Most important, there are hernias (10% in this series) that will not be diagnosed unless a scan is obtained with Valsalva's maneuver. These defects are subtle. At rest, the hernia sac is confined within the abdominal wall and not detected. It is only with the increased pressure from Valsalva's maneuver that these fascial defects and hernia sacs become identifiable. The identification of this subset of patients provides a strong argument that in patients referred with suspected hernia, it is imperative to obtain a scan during Valsalva's maneuver. Absence of hernia on a scan obtained at rest cannot exclude the presence of a hernia.
This study had some limitations. First, the Valsalva's maneuver scan was obtained immediately after the rest scan. The scans were not identical because no additional IV contrast material was administered for the second scan. We do not think that this discrepancy in technique affected the final characterization of the anterior abdominal wall. Second, the rest scan and the Valsalva's maneuver scan were interpreted at the same time. This design may have created a bias that would not be present if the studies were interpreted individually and randomly. Third, we reviewed only 100 patients, and only ventral hernias were well represented. Finally, we did not study the clinical impact of the noted increase in hernia conspicuity.
In our series, no patient showed a hernia on the rest scan but no hernia on the Valsalva's maneuver scan. This finding suggests that a single scan during Valsalva's maneuver would identify most, if not all, anterior abdominal wall hernias. On the basis of our results, we have altered our practice: In patients referred for suspected hernia, we obtain a scan only during Valsalva's maneuver, as opposed to both at rest and during Valsalva's maneuver. This approach will reduce the radiation dose to the patient and lower the cost, scanner time, and archive memory. A single scan obtained during Valsalva's maneuver is sufficient to detect 100% of anterior abdominal wall hernias identified on CT.
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