Inclusion of patients
This was a retrospective study,
approved by our institutional review board.
The primary study groups were derived from 400 consecutive patients,
200 undergoing CT-WE and 200 undergoing CTC at our unit of radiology starting from January 1,
2013.
The mean age of the CT-WE cohort (118 women,
82 men) was 66.5 ± 14.2 (SD) years,
while the mean age of the CTC group (127 women,
73 men) was 65.7 ± 12.4 (SD) years.
Among the patients with a HH at CT-WE and CTC,
PACS record review identified 59 subjects (31 in the CT-WE group and 28 in the CTC group) who also underwent a routine abdominal CT evaluation on a different time and this groups of patients served as internal control subjects; a total of 44 abdominal CT examinations were performed before CT-WE (21) or CTC (23) and 15 CT examinations were performed after CT-WE (10) or CTC (5).
A separate group of 200 consecutive patients who underwent abdominal CT evaluation at our institution in the same period was used as external control: the mean age of this cohort was 67.4 ± 13.2 (SD) years and included 111 women and 89 men.
All the studies were performed for a variety of diagnostic indications (e.g.
suspect IBD,
evaluation of colon cancer,
evaluation of diverticulitis); emergency cases and ER patients,
unable to undergo a proper intestinal preparation before the CT exams,
were not included.
CT-WE and CTC techniques
Bowel cleansing consisted in a low-fiber diet for 3 days before the CT-WE or CTC examination.
The day before the examination,
after a low-fiber meal at noon,
each patient was instructed to drink continuously four doses of a granular powder (Isocolan; Bracco,
Milan,
Italy; each dose contains 34.8 g polyethylene glycol 4000,
1.42 g anhydrous sodium sulfate,
0.42 g sodium bicarbonate,
0.36 g sodium chloride,
and 0.18 g potassium chloride) dissolved in 2 liters of water.
CT-WE technique was performed as previously described by Paparo et al.
[16].
All examinations were performed with a 64-slice multidetector CT scanner (Light Speed VCT,
GE Medical Systems,
Milwaukee,
WI) with the patient in supine position and end inspiration apnea.
Contrast-enhanced CT was performed using the following scanning parameters: 120 kV,
300mAs (with automatic mA modulation in the z axis),
0.7 sec rotation time,
detector collimation 40mm,
section thickness 5 mm,
table speed 39,37mm per rotation.
Bowel wall enhancement was produced by intravenous injection of iodinated contrast medium with an iodine concentration of 350 mg/mL (Iobitridol,
Xenetix,
Guerbet).
The flow rate was set at 3.2–3 mL/s with an automatic injector and acquisition was started in the portal phase,
45 s after the arterial peak in the upper abdominal aorta using a bolus-tracking software.
Immediately before CT acquisition,
bowel hypotonia was obtained by i.v.
injection of 2 mL hyoscine-N-butylbromide 20 mg/mL (Buscopan,
Boehringer Ingelheim),
in order to reduce abdominal discomfort of patients and to avoid motion artifacts during the acquisition.
The estimated mean effective dose for CT-WE protocol was 11 mSv.
CTC technique was performed for the purpose of colorectal evaluation [17],
as described in previous works [18].
The pre-imaging protocol for colonography included bowel preparation (as described for CT-WE) and,
the day before examination,
fecal tagging with oral iodinated contrast media.
Gas distention of the colon was obtained with room air gently pumped using a hand-held squeeze bulb in the rectum through a short cannula [18].
CTC was performed during end inspiration apnea.
Supine and prone acquisitions were obtained with the same 64-slice multidetector CT scanner with the following protocol: 120 kV,
80 mA,
0.7 sec rotation time,
detector collimation 40mm,
section thickness 5 mm,
and table speed 39,37mm per rotation.
No iv iodated contrast medium was used in our CTC protocol.
The CTC protocol has an average effective dose of 6 mSv.
Only the supine series was used in this study to evaluate for the presence of HH.
For the internal and external abdominal CT control groups,
standard diagnostic supine imaging used routine technique without colonic distention performed at end inspiration apnea.
These CT exams were performed for various indications and comprehended both unenhanced and contrast-enhanced CT examinations,
with acquisitions tailored on the basis of the clinical query.
Hiatal hernia evaluation
Retrospective assessment of the CT study groups for the presence or absence of a sliding hiatal hernia was performed by two board-certified abdominal radiologists,
both with more than 5 years of experience in abdominal CT interpretation.
The findings used to identify a HH at CT included: gastric rugal folds; soft-tissue fullness separate from the tubular esophagus; lobulated or irregular enteral contour above the esophageal hiatus; a combination of these signs.
If a HH was present,
the size was subjectively graded as small,
moderate,
or large by the reader.
After the assessment of the single groups,
the internal control groups of CT-WE and CTC groups were directly compared with the corresponding CT-WE or CTC study to evaluate for a change in hernia size.
If more than one routine CT study was available for the internal control groups,
the closest examination before/after CT-WE or CTC was used.
Statistical analysis
Data were analyzed with SPSS software (IBM,
Statistical Package for Social Science).
Values are considered significantly different when p<0.05.
Difference between groups were assessed with Fisher test and ANOVA for difference in mean values,
Mann-Whitney test for data not normally distributed,
difference in counts and frequency.
A size-specific correction factor was empirically derived and was applied to the baseline hernia rate using the results from the internal control group,
in order to account for the effect of colonic distention at CTC.
Specifically,
the percentages of hernias that resolved or decreased in size in patients with an internal control examination were used to estimate the expected underlying baseline hernia rates at CT-WE and CTC: these values were then individually compared with the external control group.