The retrorectal space

Rectal cancer lexicon 2023 revised and updated consensus statement from the Society of Abdominal Radiology Colorectal and Anal Cancer Disease-Focused Panel

The Society of Abdominal Radiology's Colorectal and Anal Cancer Disease-Focused Panel (DFP) first published a rectal cancer lexicon paper in 2019. Since that time, the DFP has published revised initial staging and restaging reporting templates, and a new SAR user guide to accompany the rectal MRI synoptic report (primary staging). This lexicon update summarizes interval developments, while conforming to the original lexicon 2019 format. Emphasis is placed on primary staging, treatment response, anatomic terminology, nodal staging, and the utility of specific sequences in the MRI protocol. A discussion of primary tumor staging reviews updates on tumor morphology and its clinical significance, T1 and T3 subclassifications and their clinical implications, T4a and T4b imaging findings/definitions, terminology updates on the use of MRF over CRM, and the conundrum of the external sphincter. A parallel section on treatment response reviews the clinical significance of near-complete response and introduces the lexicon of "regrowth" versus "recurrence". A review of relevant anatomy incorporates updated definitions and expert consensus of anatomic landmarks, including the NCCN's new definition of rectal upper margin and sigmoid take-off. A detailed review of nodal staging is also included, with attention to tumor location relative to the dentate line and locoregional lymph node designation, a new suggested size threshold for lateral lymph nodes and their indications for use, and imaging criteria used to differentiate tumor deposits from lymph nodes. Finally, new treatment terminologies such as organ preservation, TNT, TAMIS and watch-and-wait management are introduced. This 2023 version aims to serve as a concise set of up-to-date recommendations for radiologists, and discusses terminology, classification systems, MRI and clinical staging, and the evolving concepts in diagnosis and treatment of rectal cancer.

Risk of rectal puncture due to needle entry into the presacral space: Importance of measuring the distance between the rectum and sacrococcyx, and the thickness of the sacrococcyx

During ganglion impar block, the needle may approach the presacral space and the sacrum may be penetrated during caudal anesthesia. Because the rectum is in front of the sacrococcyx and is thus at risk for puncture, it is important to determine the distance between the sacrococcyx and rectum, as well as the thickness of the sacrococcyx.Computed tomography was used to measure the distance between the rectum and sacrococcyx, as well as the thickness of the sacrococcyx. The distances between the coccyx and rectum, sacrococcygeal joint and rectum, sacral level 5 ('sacrum 5') and rectum, and 'sacrum 4 to 5 junction' and rectum were measured. The results were compared based on the presence or absence of stools in the rectum. The thickness of the sacrococcyx was measured at the sacrum 4 to 5 junction and sacrococcygeal joint.In total, 1264 patients were included in this study. All distances were less than 1 mm in both males and females, with the exception of the distance between the coccyx and rectum in males. In both males and females, there was no significant difference in distance between the sacrococcyx and rectum according to the presence or absence of feces in the rectum, but there was a difference in the distance between sacrum 5 and the rectum in males (P = .048). Several male and female patients showed thicknesses of less than 5 mm at the sacrococcygeal joint.Some patients have a distance of less than 1 mm between the sacrum and rectum. Practitioners should exercise caution when applying a needle to the presacral space. If the sacrum is accidentally penetrated during caudal block, rectum puncture cannot be ruled out. Excretion of feces does not influence the distance between the sacrococcyx and rectum in females.

Suspensory Ligaments of the Female Genital Organs: MRI Evaluation with Intraoperative Correlation

The uterus, which plays an important role in the reproductive process, provides a home for the developing fetus and so must be in a stable, though flexible, location. Various structures with suspensory ligaments help provide this berth. MRI with high spatial resolution allows us to detect and evaluate these relatively fine structures. Under physiologic conditions, MRI can be used to depict uterine and ovarian ligaments (ie, the uterosacral, cardinal, and round ligaments, as well as the suspensory ligament of the ovary). In the presence of pathologic conditions (inflammation, endometriosis, tumors), the suspensory ligaments may appear thickened or invaded, which makes their delineation easier. Understanding the normal anatomy of the suspensory ligaments of the female genital organs and using a standardized nomenclature are essential for identifying and reporting related pathologic conditions. The female pelvic anatomy and the suspensory ligaments of the female genital organs are described as depicted with MRI. Also, the compartmental anatomy of the female pelvis is explained, including the extraperitoneal pelvic spaces. Finally, a checklist is provided for structured reporting of the MRI findings in the female pelvis. Online supplemental material is available for this article. ^©RSNA, 2018.

Transsacrococcygeal Approach for Resection of Retrorectal Tumors

Retrorectal tumors, are a rare and interesting entity, traditionally managed with surgery. The surgical approach is a key to get an easy and safe access. The purpose of this study was to evaluate the results of resection by a transsacrococcygeal approach. Thirty-six patients had retrorectal tumors resected by a transsacrococcygeal approach in our department. All the tumors were en bloc resected, irrespective of size and anatomical depth. The clinic data were retrospectively reviewed. Tumor mean size was 10 ± 4.4 cm. In 16 cases, tumors were 10 cm or more in size. The largest tumor measured 20 cm. The estimated mean blood loss was 130 ml. No mortality and severe postoperative complications were observed. The most significant issues were wound infection and delayed healing. Pathology showed 15 cases of epidermal cysts, two cases of enterogenous cyst, one case of bronchogenic cyst, 12cases of teratoma, two cases of schwannoma, two cases of low-grade malignant fibrous myxoma, one case of aggressive angiomyxoma, one case of desmoid tumor. The trans-sacrococcygeal approach gives an easy access and good visualization with fewer complications. This surgical approach shows to be safe and effective for resection of retrorectal tumors.

The presacral space and its impact on sacral neuromodulator implantation

PURPOSE

We describe the presacral space and its potential impact on sacral neuromodulator implantation and bowel injury.

MATERIALS AND METHODS

Parasagittal images containing bilateral sacral foramina (S2-S4) were examined on 45 pelvic magnetic resonance images. Images were excluded from analysis if they were poor quality or had any history causing distortion of normal anatomy. We measured the natural angle between the foramina and the dorsal skin to approximate the needle angulation during neuromodulator electrode placement. Using these angles we measured the distance from the skin to any bowel (D1), the skin to the dorsal sacrum (D2) and then calculated the distance from the dorsal sacrum to any bowel (D3).

RESULTS

Mean subject age was 45 years (range 19 to 78) and body mass index was 27.9 kg/m(2) (range 18.6 to 56.2). At S3 the mean foraminal angle and D3 were 46 +/- 8.4 degrees and 27.4 +/- 11.7 mm, respectively. Increasing age was moderately correlated to widening D3 at each foramina (r = 0.3, Pearson's p <0.05). Body mass index did not consistently vary with D3 at any foramina.

CONCLUSIONS

Our measurements suggest that the presacral space can be expected to be approximately 27 mm at the level of S3 where the neuromodulator electrode is implanted. It is possible to encounter bowel while performing this implantation using standard techniques and equipment. We recommend the standard use of fluoroscopy during placement.

Determination of the width of the presacral space on magnetic resonance imaging

Presacral space enlargement may be the first sign of certain diseases. The normal width of the presacral space has not been widely investigated and in all previous studies was calculated from lateral radiographs obtained at barium enema examination. Our study determined the normal width of the presacral space on MRI and investigated a possible difference between men and women. The width of the presacral space was measured retrospectively from sagittal T2-weighted MR images of 193 patients (87 males; 106 females, aged 18-83 years). Presacral space width was measured separately for S1, S2, and S3 vertebral levels from the anterior surface of the vertebral bodies to the closest part of the posterior wall of the rectum. Differences between male and female subjects were analyzed by t-tests. Normal mean widths of the presacral space in men and women were 16.2 mm and 11.9 mm for S1, 14.9 mm and 11.2 mm for S2, and 13.0 mm and 10.6 mm for S3, respectively. Measurements of the presacral space width in men were significantly larger than in women at all three levels (P < 0.001 for S1, P < 0.001 for S2, P = 0.006 for S3). In summary, the presacral space width measured on MRI was found to be significantly larger in the male than in the female population.

Development and organization of the pelvic connective tissue in the human fetus

The developmental changes in the pelvic connective tissue were studied in 200-600 microns sections through the pelves of human fetuses and newborn children, plastinated with an epoxy resin. Three periods are important for the differentiation of the pelvic connective tissue in fetuses. During a first or mesenchymal period (9-12-week-old fetuses), all pelvic regions identical with the so-called pelvic spaces in the adult are filled with loose undifferentiated mesenchyme. Some pelvic organs are covered by a layer of condensed mesenchyme which later constitutes the connective tissue sheath of these organs. During a second or fibrous period (13-20-week-old fetuses), dense connective tissue predominates. It is arranged in circular and semicircular systems covering the rectum, the bladder and the urethra as well as the peritoneal pouches. The arrangement of dense connective tissue is the same in the male and in the female fetus. No ligaments were found within the pelvic cavity apart from the pubovesical and the puboprostatic ligaments. The connective tissue sheaths of the pelvic organs differ from one another. At the level of the pelvic floor only some of them are directly connected with the parietal pelvic fascia. The pelvic spaces are filled by loose connective tissue. During a third or adipose period (21-38-week-old fetuses) adipose tissue develops within the different compartments of the pelvic cavity so that the clear organization found during the second period is abolished.

Diagnosis and management of giant intrasacral schwannoma

Giant intrasacral schwannoma is a rare cause of a retrorectal mass in an adult patient. Only 21 such tumors have been reported. The diagnosis of this intraosseous nerve sheath tumor is heralded by its minimal symptoms in relation to its often striking radiographic findings and is verified by its unique morphology. Surgical resection is complex because of its anatomic location and propensity for local recurrence. The need for adequate tumor removal must be balanced against the preservation of nerve function. The presentation, diagnosis, and management of intrasacral schwannomas are reviewed, as exemplified in this case presentation and literature review.

Xanthogranulomatous abscess of a mullerian duct remnant. A rare lesion of the rectum and anus

A rare example of xanthogranulomatous inflammatory mass and abscess of a Mullerian duct remnant involving the anorectal area is reported. A barium enema showed a bilobed precoccygeal mass of moderate size involving the posterior aspect of the distal rectum. Computed tomography (CT) showed two nonfatty, round masses, one of which contained a small central cystic area. The other mass had a homogeneous appearance and was believed to be in the wall of the rectum. The pathologic specimen showed organizing abscesses and a chronic xanthogranulomatous inflammation in tissue compatible with urogenital tissue, presumably a Mullerian duct remnant. This is the first documented report of anorectal xanthogranulomatous abscess in a Mullerian duct remnant with radiologic findings and histopathologic correlation. Though rare, this lesion should be considered in the differential diagnosis of extrinsic and intramural rectal masses seen on barium enema and CT examinations.

Width of the presacral space in Nigerian adults

The width of the presacral space and the thickness of the rectal valve were measured on lateral radiographs obtained during barium enema examinations performed on 182 Nigerian adult patients over a 5-year period (1980-1984). The mean width of the presacral space was 0.78 cm, the value in men being significantly higher than in women (p less than 0.01). Although these values are similar to those reported among Caucasians, a wider range of normal values was obtained in this study. There is also no significant difference between the mean value of the rectal valve thickness of 4.3 mm obtained in this study and that obtained from previous studies.

Computed tomography in the differential diagnosis of the enlarged retrorectal space

The value of computed tomography (CT) in the differentiation of an enlarged retrorectal space was analyzed in 132 cases. Classification of barium enema findings into those with simultaneous mucosal alterations and those without any visible lesions of the rectal mucosa seems to be useful. Computed tomography helps in those cases without mucosal changes to differentiate between retrorectal fibrosis, tumorous masses, and inflammatory diseases of the colon. It also demonstrates the lack of pathologic lesions in equivocal cases of pelvic lipomatosis and so-called "normal variants." If simultaneous mucosal involvement on barium enema--especially in rectal carcinoma or recurrent carcinoma of the rectum--is found, CT may show the perirectal extension of tumorous masses and thus help to clarify local operability.

The instant enema in inflammatory disease of the colon

The instant, or unprepared, double contrast barium enema has been used routinely at St Mark's Hospital in the investigation of active inflammatory disease of the colon since 1963. The use of air contrast is preferred to show the fine detail of the mucosal changes and to detect early involvement. With the instant enema technique the diagnostic results are satisfactory and patients are minimally disturbed by the procedure. The majority of examinations consist of a total of four films, which includes a plain film of the abdomen prior to the administration of contrast. For short-term follow-up a repeat enema with a single film is usually adequate.