Modified Virtual Colonoscopy in the Diagnosis and Quantification of Bowel and Disseminated Endometriosis
ABSTRACT
JOHAN VAN DER WAT, MBBCH, FCOG DIREC TOR
ENDOMETRIOSIS AND ENDOSCOPIC SURGERY UNIT NETCARE PARKLANE HOSPITAL HONORARY CONSULTANT, ENDOSCOPIC SURGERY DEPARTMENT OF OBSTETRICS/GYNECOLOGY UNIVERSITY OF WITWATERSRAND JOHANNESBURG, SOUTH AFRICA
MITCH D. KAPLAN, MBBCH FFRAD(D) DIREC TOR
SCAN FOR LIFE
RADIOLOGY DEPARTMENT
THE ROSEBANK HOSPITAL JOHANNESBURG, SOUTH AFRICA
This article describes the basic technology and technique behind modified virtual colonoscopy (MVC). It is accompanied by images illustrating the possibility of MVC to advance the imaging for endometriosis beyond the current modalities of magnetic resonance imaging (MRI) and ultrasound. A quantification
system is described that will ultimately make staging and multicenter prospective scientific studies possible for rectogenital and disseminated endometriosis.
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SURGICAL TECHNOLOGY INTERNATIONAL XXVI
Surgical Overview
Modified Virtual Colonoscopy in the Diagnosis and Quantification of Bowel and Disseminated Endometriosis
VAN DER WAT/KAPLAN
INTRODUCTION
The idea of computerized tomogra- phy (CT) was raised early in the 20th century, but it was the work of Sir God- frey Newbold Hounsfield and Allan McLeod Cormack, who finally made CT a reality. In 1979, the Nobel Prize was awarded to them for their work. This technology advanced and eventual- ly made Virtual Colonoscopy ( VC) or C T Colonography (C TC) possible in 1993. Since the late 1990s, this technol- ogy has been used as a screening tool for colorectal polyps and cancers. In 2005, the standard VC/C TC technique was modified by van der Wat and Kaplan to study the effect of endometriosis on the bowel, abdominal organs, reproductive organs, and uri- nary tract.1
as accurate as optical colonoscopy for polyps larger than 5 mm and early col- orectal cancers. The study is FDA approved and supported by the Ameri- can Cancer Society, the American Col- lege of Gastroenterology, the American College of Radiology, and the American Gastroenterological Association for col- orectal cancer screening.
scan. The tampon additionally distends the vagina, thereby placing the RVS under stretch. This facilitates assessment of the septum and rectocervical spaces.
The Modified Virtual Colonoscopy
With MVC, a Foley catheter with a small volume bulb is inserted into the rectum. The bulb is only partially inflat- ed or uninflated to avoid distortion and effacement of the distal rectum and RVS plane. This catheter is connected to an automated carbon dioxide laparoscopic insufflator. CO2 is insufflated into the bowel to a maximum pressure of 25mm/Hg, thus safely distending the large bowel. This distention also allows for intraluminal, mural, serosal, and functional bowel distensibility assess- ment. Since volumetric data is obtained, the entire abdomen and pelvic contents are simultaneously visualized for extra colonic pathology additionally. This is a unique feature separating this technique from ultrasound and MRI, which primarily focus on the rectogeni- tal area thus lacking information on proximal colonic, multifocal colorectal, and other abdominal pathology. M VC is thus a single investigation that can visu- alize all affected organ systems in the pelvis and abdomen. This includes mul- tifocal bowel lesions, urinary tract lesions, reproductive organ lesions, and distant organ lesions such as liver involvement (Fig. 1).
(M VC) technique is designed to endometriosis, and the technique was
fir st published in
the diagnostic information for surgical decision making and also pre-surgical planning by accurately defining the extent of bowel and other organ involvement, including urogenital dis- ease, in a single examination.
detect
Rectal Foley’s Catheter and Bowel Insufflation
MODIFIED VIRTUAL COLONOSCOPY
MVC TECMHVCNTIEQCHUNEIQUE
Several modifications to standard VC
2007. 1 This provides
FOR ENDOMETRIOSIS
were introduced to accurately identify endometriosis in the bowel, pelvis, and abdomen. The major modifications are:
MODIFIED VIRTUAL COLONOSCOPY FOR
ENDOMETRIOSIS
The conventional VC/C TC scan is a noninvasive multidetector computed
Vaginal Tampon
A large-volume, obstetrical tampon is inserted into the vagina by the patient prior to scanning. High insertion is important to visualize the proximal rec- tovaginal septum (RVS). The air-filled tampon creates an RVS interface with the gas-insufflated rectum during the
Figure 1. This is a 3D transparent reconstruction of the rectum. It shows the tampon and the rectal catheter in place as well as a stricture at the rectosigmoid junction.
tomographic (MDC T) scan abdomen and pelvis performed while the colon is insufflated with air or car- bon dioxide via a rectal catheter, usually after a bowel-cleansing laxative prepara- tion.
of the This technique is now regarded to be
Low-dose Scans
Particular attention is paid to low- dose scanning protocols and technique, particularly on the second, prone scan. If uncomplicated disease is suspected, only the pelvis is scanned to further reduce dose in this patient population.
IMAGE FORMATS
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IMAGE FORMATS
The raw data is obtained by a single pass through the 160-slice multidetec- tor or multislice CT scanner (MDCT). The raw data set can then be recon- structed on a 3D workstation in a vari- ety of 2D and 3D formats:
2D multiplanar reconstruc- tions (MPR), oblique MPR, and curved MPR. These are user- definable “slices” of the 3D volume set to obtain images in the axial,
SURGICAL TECHNOLOGY INTERNATIONAL XXVI
Surgical Overview
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Figure 2. 3D transparent reconstruction of recto- genital area showing length of stricture, % stric- ture, and distance from anal verge. |
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Figure 3. Sagittal MPR reconstruction of a rectogenital nodule (yellow arrow indicating nodule). LSD quan- tification can be calculated from this image. |
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Figure 4A. Sagittal MPR reconstruction of a large endometriotic bowel nodule with a 90% stricture. |
Figure 4B. 3D endoluminal flythrough reconstruc- tion of large endometriotic nodule with a 90% stricture.
Figure 4C. 3D endoluminal flythrough reconstruc- tion of rectogenital nodule with 80% stricture.
Figure 5. Sagittal MPR reconstruction of high rec- togenital nodule.
Figure 6. Sagittal MPR reconstruction showing low rectogenital nodule with 90% stricture.
coronal, and sagittal planes, or oblique and curved user-definable planes. Slice thickness can be adjust- ed. This is the classic 2D recon- struction of raw scan data.
2D or 3D maximum intensi- ty projection (MIP) recon- struction. This reconstruction enhances hyper-dense or contrast- enhanced structures, and is useful for vascular or ureteric assessment (contrast-enhanced scan).
This is the classic 3D reconstruction for assessing the endoluminal bowel surface.
3D volume rendered ( VR) reconstruction. This is the classic 3D reconstruction of the raw data- set. It may be grey-scale or color- mapped based on the CT density of the tissue or structure. This can be manipulated in various ways by removing structures (segmenting) or cropping.
3D endoluminal flythrough reconstruction. A 3D air-shell of the insufflated colorectal loops is reconstructed that is then “flown” through. The speed of flythrough, viewing angle, and direction of fly- through may all be manipulated.
3D transparent view (TV) reconstruction. A semi-transpar- ent 3D air-shell of the bowel is reconstructed. This can be manipu- lated in 3D.
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3D cubed volume (C V) reconstruction. A reconstructed cropped “block” of bowel with a fly- through appearance. The block size, viewing angle, and “cut” planes can be manipulated.
Modified Virtual Colonoscopy in the Diagnosis and Quantification of Bowel and Disseminated Endometriosis
VAN DER WAT/KAPLAN
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Figure 8. Sagittal MPR reconstruction of the same patient showing the rectogenital and sigmoid lesion. |
Figure 7. 3D transparent reconstruction showing multifocal bowel disease. Yellow arrow showing rectogenital lesion and purple arrow showing recto-sigmoid lesion.
Figure 9. Axial MPR reconstruction showing a cea- cal lesion.
3D virtual dissection or fil- let view reconstruction. A vir- tual dissection of the bowel where it is “cut” along the long axis, “spread open,” and “laid out flat” so the endoluminal surface can be assessed in one plane.
It is again emphasized that all these image reconstructions are generated from two passes (supine and pro patient positions), within a breath-hold each, through the MDCT scanner. No additional investigative procedures such as intravenous pyelogram/uro- gram (IVP/IVU), optical colonoscopy, MRI, or ultrasound need to be per- formed This makes the procedure cost effective, as it obviates the need for any further investigation.
APPLAPIPCLIACATTIONNOFMOVFCIMN VC IN E N D O M E T E RN ID O O MS IE ST R I O S I S
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Figure 10. 3D endoluminal flythrough reconstruc- tion of previous patient showing view from terminal ilium into ceacum. The endometriotic nodule is clearly visible. |
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Figure 11. Picture of surgical specimen showing ceacal nodule. |
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Figure 13. 3D volume rendered (VR) reconstruc- tion showing ureteric obstruction close to entry into the bladder. |
After analysis of more than 500
consecutive cases
endometriosis, the following disease quantification system was structured.2 Three disease processes were identi- fied: rectogenital disease, disseminated disease, and a combination of both rec- togenital and disseminated disease. These disease processes are illustrated by the following MVC images.
Figure 12. Axial MPR reconstruction showing blad- der lesion (yellow arrows).
D I S E D A I S S E E A O S F E T O HF E T H R E E CR TE C O T GO G E NE N I T I AT A L L A A R R E E A A
Disease of the rectogenital area sig- nifies pathology in the area from the lower sigmoid to the anal verge. This disease is quantified by the LSD system wherein:
of M VC for
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Figure 14. Coronal MIP reconstruction of the same patient (Fig. 13) showing endometrioma obstruct- ing and displacing ureter. |
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Figure 15. 3D volume rendered (VR) reconstruc- tion showing obstruction of ureter (yellow arrow). |
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L = Length of Stricture
S = % Stricture
D = Distance from Anal Verge
SURGICAL TECHNOLOGY INTERNATIONAL XXVI
See Figures 2, 3, 4A, 4B, 4C, 5, and 6.
DISSEDMISSIENMAINTAETDEDDISEAASESE
Disseminated disease is disease that has spread to the abdomen beyond the recto- genital area, this includes further spread to the bowel (multifocal disease) and spread to the urinary tract, reproductive organs, and abdominal organs. It is quanti- fied by the MURO system in which:
M = Multifocal Bowel Disease
U = Urological Disease
R = Reproductive Organ Disease O = Abdominal Organ Disease
Surgical Overview
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Figure 17. 3D endoluminal flythrough reconstruc- tion of compressed bowel. |
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Figure 19. Sagittal MPR reconstruction showing endometriotic omental infiltration (yellow arrow). |
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Figure 21. 3D endoluminal flythrough reconstruc- tion of the same patient showing the 95% stricture (purple arrow). |
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Figure 23. Axial MPR reconstruction in the same patient (Fig. 22) showing hydronephrosis with con- comitant renal damage. |
Multifocal Bowel Disease (M)
See Figures 7, 8, 9, 10, and 11.
Urological Disease (U)
See Figures 12, 13, 14, and 15.
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Figure 18. Axial MPR reconstruction of endometri- otic liver lesion (blue script). |
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Figure 20. 3D transparent reconstruction showing 95% stricture in sigmoid colon (yellow arrow). |
Reproductive Organ Disease (R)
See Figure 16 and Figure 17.
Abdominal Organ Disease (O)
See Figure 18 and Figure 19.
COMMBIBNIANTIAONTIOFNREOCTFOGREENCITAOL AGNEDNI- TAL ANDDDISISSESMEIMNAITNEDATDIESDEADSEISEASE
Often both forms of the disease coexist and quantification is then expressed by the LSD/MURO system (See Figs. 20, 21, 22, 23).
CONCLUSCIONNCLUSION
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Figure 22. 3D volume rendered (VR) reconstruc- tion in the same patient showing bilateral ureteric obstruction with hydronephrosis on the left with impeded renal function. |
M VC is a single, comprehensive imaging system to accurately assess a patient with suspected bowel and dis- seminated endometriosis. It is a noninva- sive, safe, and rapid outpatient scan, with a relatively low dose exposure.
The current diagnostic modalities of ultrasound and MRI are unable to effec- tively diagnose multifocal and proximal bowel disease, and do not predict the surgical course.3 This diagnostic inability has made counseling and surgical plan- ning problematic.
Figure 16. Axial MPR reconstruction showing bilat- eral endometriomas compressing bowel.
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Modified Virtual Colonoscopy in the Diagnosis and Quantification of Bowel and Disseminated Endometriosis
VAN DER WAT/KAPLAN
nated and rectogenital endometriotic dis- ease. STI
To overcome these limitations, MVC was developed to diagnose colorectal endometriosis, multifocal disease, stric- tures, retroperitoneal, urinary tract, and
A U T HA U OT H RO R S S ’ ’ D I S DC L I O S S CU R L E OS S U R E S The authors have no financial rela-
colonoscopy: a noninvasive technique for the diagnosis of rectovaginal septum and deep infiltrating pelvic endometriosis. J Mimim Invasive Gyn 2007;14:638–43.
distant disease. M VC findings and
will take the diagnosis of rectogenital and disseminated disease beyond that of MRI and ultrasound. This information can be used to undertake multicenter, prospec- tive studies to investigate the correlation between images and surgical findings. This has the potential to institute and standardize the appropriate surgical inter- vention for the management of dissemi-
2. van der Wat J, Kaplan M. The use of modi- fied virtual colonoscopy to structure a descriptive imaging classification with implied severity for rectogenital and disseminated endometriosis. J Min Invasive Gyn 2013; 20(5):543–46.
images
tionships to disclose.
1. van der Wat J, Kaplan M. Modified virtual
3. Exacoustos C, Malzoni M, Di Giovanni A, et al. Ultrasound mapping system for the sur- gical management of deep infiltrating endometriosis. Fertility and Sterility 2014;102(1):143–50.
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