Keywords
Meckel's diverticulum - scintigraphy - SPECT/CT - ectopic gastric mucosa
Introduction
The frequency of Meckel's diverticulum (MD) in normal population is 0.14 to 4.5%[1]
[2] and rarely presents with complications (4.2–6.4%).[3] Due to the ectopic gastric mucosa (EGM) content which might be present in nearly
half of the patients, first presentation can be gastrointestinal bleeding. Scintigraphy
determines the EGM content of the MD thus depicts surgical resection candidates and
prevents from unnecessary surgery. The diagnostic accuracy of the modality is considerably
high with sensitivity and specificity of 80 to 90% and 95%, respectively, for children.[4] However, the diagnostic efficiency is hampered as the age of the patient increases
and significantly lower for the adults.[4] The possible contribution of the single-photon emission computed tomography/computed
tomography (SPECT/CT) to the diagnostic workup of MD scintigraphy was not sufficiently
considered previously in the literature. This may be due to high diagnostic efficiency
of the modality and because the SPECT/CT is not available in every nuclear medicine
department. There are case reports and a case series in the literature which address
significant impact on diagnostic confidence.[1]
[5]
[6]
[7]
[8] The aim of this study was to analyze the possible effect of SPECT/CT in the diagnostic
efficiency of the MD scintigraphy to determine EGM.
Materials and Methods
The patients (24 girls, 28 boys; mean age: 8.06 ± 5.22 years old) who were referred
to the nuclear medicine department for MD-EGM scintigraphy were retrospectively analyzed.
The patients were all at pediatric age (< 18 years) but equally distributed age population
including adolescent patients.
Scintigraphy and SPECT/CT Imaging
The informed consents of the patients' guardians were obtained prior to imaging procedure.
The imaging was performed with prior medication of proton-pomp inhibitors as a premedication.
No prior starvation was suggested. The radiopharmaceutical was injected via venous
line at a dose of approximately 0 mCi (37 mBq/adjusted according to the body weight).
Dynamic imaging was performed with following sequential planar anteroposterior and
lateral spot imaging and additional SPECT/CT were performed just after the planar
imaging procedure in case of undetermined results in planar imaging in five cases.
Two different scanners (Symbia, Siemens SPECT gamma camera and positron emission tomography
[PET]-CT scanners Siemens MCT 20, respectively) were used for the fusion SPECT/CT
imaging. The fusion analysis was performed with the MCT20 PET-CT scanners imaging
console and reevaluated by an experienced nuclear medicine physician at Mc-OsiriX
reading console. Focal significant increased activity in the abdominal region with
simultaneous gastric uptake was considered positive for MD. Additional erythrocyte-labeled
scintigraphy was performed in one case with inconclusive results in MD scintigraphy
by administration of Tc-99m pertechnetate adjusted according to the pediatric dosage
chart to the patient via direct intravenous administration of the radiopharmaceutical
and about 1 hour later direct intravenous administration of the pyrophosphate on the
other arm. The imaging was performed by the same methodology and equipment described
above. The dose for additional CT imaging was adjusted according to the body weight
by the automatic program of the PET/CT scanner (smart mA). The imaging results of
the patients were compared with the patient's endoscopy, follow-up, and pathology
surgery results and the diagnostic sensitivity, specificity, and accuracy of the study
were obtained.
Results
The imaging results were considered positive, negative, and equivocal regarding the
diagnosis of EGM-MD. In case of equivocal results, the erythrocyte-labeled scintigraphy
for bleeding site determination was performed in selected cases. The equivocal results
were considerably high in the patient group (n = 10). Nine patients were determined as MD positive and others were negative. All
the nine cases were verified by surgery pathology results. Only single patient's surgery
results were negative who had negative scintigraphy results also.
There were five patients with additional SPECT/CT imaging. Among these patients EGM
were determined in two. One of the patients' EGM in a duplication cyst was diagnosed
only by SPECT/CT whose planar imaging was considered equivocal ([Fig. 1]). Another patient with equivocal findings, bleeding site was determined by SPECT/CT
([Fig. 2]). Clear anatomic depiction of one of the patients was provided by SPECT/CT ([Fig. 3]). Diagnostic sensitivity, specificity, and accuracy of the imaging modality were
100, 95, and 96%, respectively.
Fig. 1 SPECT-CT images of a 15 year old adolescent girl with verified Ectopic Gastric Mocase
at a Dublication cyst as determined by Meckel's Diverticulum Scintigraphy.
Fig. 2 Single-photon emission computed tomography/computed tomography (SPECT/CT) images
of a 13-year-old female patient demonstrating focal uptake of Tc-99m pertechnetate
in the bowel at left midline with pathological diagnosis of Meckel's diverticulum
and ectopic gastric mucosa.
Fig. 3 Erythrocyte-labeled scintigraphy—single-photon emission computed tomography/computed
tomography (SPECT/CT) images of a patient whose Meckel's diverticulum scintigraphy
pointed out gastrointestinal bleeding rather than ectopic gastric mucosa (EGM) and
finally the bleeding site was determined only by SPECT/CT at splenic flexure adjacent
to spleen activity.
Discussion
The determination of the MD-EGM by means of MD scintigraphy is possible with high
diagnostic accuracy according to the study results. However, there are some considerable
numbers of equivocal cases and overlap patients with gastrointestinal bleeding. This
may be due to the age of the study group which consists of adolescent patients as
well. Previous literature data suggest that the diagnostic accuracy of the MD scintigraphy
decreases as the age of the patients increases and the diagnostic efficacy of the
MD scintigraphy is considerably low in adults.[4] In case of these situations, SPECT/CT imaging provides true positive results. The
patient with an EGM in the duplication cyst would be the only false negative case
in the study group if we did not perform additional SPECT/CT. EGM of tubular intestinal
duplication was also determined by SPECT/CT in another patient in the literature previously.[9]
MD scintigraphy usually is considered sufficient for diagnosis of EGM in MD. However,
there are false positive and false negative results as the patients' age increase.
Additionally, in the problematic cases with previous abdominal surgery history of
SPECT/CT with additional radioguided surgery provided promising results.[10]
[11]
Previous data also suggested that the contribution of anatomical detail information
increases the surgical success.[12]
There is a considerable number of false positives in the MD imaging especially due
to the excretion of the radiopharmaceutical through urine. The possible intervention
to exclude this false positivity is to obtain lateral spot imaging which indicate
activity in the posterior aspect of the verifying urinary tract. However, there are
specific exceptions that this intervention could not benefit. In a previous case series
one of the patients with pelvic ectopic kidney was only determined by SPECT/CT.[8]
SPECT/CT provided clear delineation of the EGM in another patients' MD. Another patient
who was considered equivocal was also determined as gastrointestinal bleeding by SPECT/CT.
These encouraging results showed that SPECT/CT might contribute to diagnostic accuracy
of MD in case it is performed in special cases with equivocal results. There are previous
case report and review about the contribution of SPECT/CT in the diagnosis of bleeding
site as an adjunct with MD scintigraphy.[13]
[14] Especially in the adolescents or adults the possible diagnosis of non-MD bleeding
and additional bleeding scintigraphy with SPECT/CT should be considered. The equivocal
results in our series usually belong to the adolescent patients. This issue should
be considered as the age increases the results of the MD scintigraphy might be challenging.
A recent case report verified the role of SPECT/CT in a 17-year-old boy with atypical
presentation of MD which was false negative with only scintigraphy imaging.[5] Similarly, in case of complicated MD the diagnostic interpretation might be challenging
and SPECT/CT could demonstrate which was shown in a report of a 15-year-old boy.[6] Adjacent anatomic structures including a diverticulum might also complicate diagnosis.[15] Previous studies have shown that false negativity might be a significant problem
as well as false positivity.[16]
[17] SPECT/CT might also contribute in these problems.
The limitation of this report is the small number of patients with SPECT/CT results
which can be explained by the fact that additional CT dose concern to the children.
The SPECT/CT should be preserved for the selected patients with equivocal results.
Although the dose of CT is usually adjusted in pediatric patients in most of the centers,
the dose consideration is the most important problem against these kinds of studies.
However, in case of missed diagnosis possible complications and unnecessary surgical
interventions should be considered for decision also. The SPECT/CT should be preferred
for the selected patients with equivocal results.
Conclusion
The MD scintigraphy is a highly accurate modality in the determination of EGM but
SPECT/CT might be considered in special circumstances especially in equivocal scintigraphy
results in adolescent cases. This approach might decrease false positive and false
negative interpretations.
