Hernia indd

Imaging Modalities
In the past, conventional radiographs or barium studies were pre-
dominantly used in confirming or excluding abdominal wall herni-
as. Currently computed tomography (CT) has the dominant role.
Ultrasound (US): US of the abdominal wall and pelvic region is a 
non-invasive and dynamic investigation, ideal for detection of oc-
cult hernias. Its sensitivity is operator dependant and is decreased 
in obese patients. Comparison with the other asymptomatic side is 
useful in delineating the normal anatomy. A Valsalva maneuver to 
increase intra-abdominal pressure can facilitate demonstration of 
hernias. US can determine hernia reducibility 
(3)
.
Computed Tomography: CT accurately defines the cross sectional 
anatomy and is especially useful in obese patients. The diagnosis of 
a hernia can be made on the basis of a fascia defect alone or with the 
presence of herniated contents. CT enables differentiation of hernias 
from other masses (e.g. seroma, tumour, abscess, undescended tes-
tes, haematoma, aneurysm). CT is sensitive for detecting complica-
tions like bowel incarceration, obstruction and strangulation 
(4)
. The 
CT signs of incarceration and impending obstruction include bowel 
wall oedema, mesenteric stranding, decreased post-contrast mu-
cosal enhancement, free air or free fluid within the hernia sac. One 
limitation of CT is that dynamic imaging is not always possible. The 
patient is often scanned supine without straining. CT carries a high-
er radiation dose than other imaging modalities.
Contrast Peritoneography (Herniography): Water soluble contrast is 
injected into the peritoneal cavity at the reverse McBurney’s point. 
The patient then undergoes fluoroscopic screening in a prone semi-
erect position. Peritoneal bulges and contrast tracking into the in-
guinal canal or scrotum are well demonstrated. This is a useful tech-
nique for demonstrating hernias, particularly inguinal and femoral 
hernias. It is less useful in ventral hernias. Spigelian hernias are 
better assessed by other methods 
(5)
. This technique however is not 
widely used due its invasive nature.
Above: E: epigastric, P: para-umbilical, U: umbilical, Div: divarica-
tion of linea alba, S: Spigelian, I: indirect inguinal, D: direct ingui-
nal, F: femoral