Consensus Statement Of Definitions For Anorectal Physiology And Rectal Cancer

Ann C. Lowry,M.D.,* Clifford L. Simmang,M.D.,M.S.,* Paul Boulos,M.D.,** K. Chip Farmer,F.R.A.C.S.,*** Paul J. Finan,M.D.,F.R.C.S.,** Neil Hyman,M.D.,* Mark Killingback,F.R.A.C.S.,*** David Z. Lubowski,F.R.A.C.S.,*** Richard Moore,M.D.,* Campbell Penfold,F.R.A.C.S.,*** Paul Savoca,M.D.,* Russell Stitz,F.R.A.C.S.,*** Joe J. Tjandra,F.R.A.C.S.***

From *The American Society of aColon and Rectal Surgeons, **The Association of Coloproctology of Great Britain and Ireland, and the ***Colorectal Surgical Society of Australia

"If terms be incorrect, then statements do not accord with facts; and when statements and facts do not accord, then business is not properly executed." Confucius 1

As surgeons work to improve the quality of patient care it is important that data and results are communicated and compared accurately. For that to happen, the terminology utilized must be precise and uniform. With medical information increasingly shared globally, an international consensus about the terminology is desirable.

The Standard Committee of The American Society of Colon and Rectal Surgeons initiated an effort to define the commonly used terms in the areas of colon and rectal cancer and anorectal physiology testing. Drafts were circulated and reviewed. At the Tripartite meeting in 1999, representatives from The American Society of Colon and Rectal Surgeons, the Colorectal Surgical Society of Australia and The Association of Coloproctology of Great Britain and Ireland convened a meeting. Two task forces met; one focused on the cancer definitions and the other one on the anorectal physiology terms. The resulting drafts were circulated to selected experts for comment and within each represented society for approval.

The purpose of these efforts is to develop standardized terminology for use in academic presentations and publications. All three societies have agreed to simultaneously publish and encourage the use of these terms in presentations and publications. Although great effort and care has gone into the process, it is recognized that the terminology will evolve with its use and future advances in surgical knowledge. A process for review and refinement will be instituted. In addition, terms from other areas of colon and rectal surgery will be added if these definitions are found to be useful.(1)

Anal Sensation

Anal sensation is the sensation in the anal canal measured by anal mucosal electrosensitivity. It reflects the somatic sensory component of the pudendal nerve.

Anorectal Angle

The anorectal angle is the proctographic angle between the mid-axial longitudinal axis of the rectum and the anal canal. Normal values range from 90 to 110 degrees at rest.

Balloon Expulsion Test

The balloon expulsion test measures the ability of the patient to expel a balloon inflated with 50 to 60 ml of water.

Defecography

Defecography is a dynamic fluoroscopic examination performed with rectal contrast to study the anatomy and function of the anorectum and pelvic floor during defecation.

Triple Contrast Defecography

Triple contrast defecography is standard defecography with the addition of contrast into the small bowel and vagina.

Electromyography Recruitment

Electromyography recruitment records the change from basal electrical activity of motor units of the external anal sphincter and levator muscles during muscle activity.

Perineal Descent

Perineal descent is the caudad movement of the pelvic floor with straining. It is measured clinically by the position of the anal verge in relationship to the plane of the ischial tuberosities at rest and during maximal straining. It is measured on defecography as the difference between the position of the anorectal junction at rest and during maximal straining. Normal values are <2 cm.

Pudendal Nerve Latency

Pudendal nerve latency is the measurement of the time from stimulation of the pudendal nerve at the ischial spine to the response of the external anal sphincter. Normal pudendal nerve terminal motor latency is <2.2 ms.

Rectal Compliance

Rectal compliance is the measured change in pressure in response to change in volume within a water-filled or air-filled balloon within the rectum.

Rectal Inhibitory Reflex

Rectoanal inhibitory reflex is the transient decrease in resting anal pressure by >25 percent of basal pressure in response to rapid inflation of a rectal balloon, with subsequent return to baseline.

Measurements for Rectal Sensation

Evaluation of rectal sensation is performed by placing a balloon catheter above the anorectal ring. The balloon is gradually inflated with air.

Sensory threshold is the minimum rectal volume perceived by the patient.

Urge sensation is the volume associated with the initial urge to defecate.

Maximum tolerated volume is the volume at which the patient experiences discomfort and an intense desire to defecate.

Anal Pressures

High-pressure zone is the length of the anal canal with resting pressures at least 30 percent higher than rectal pressure.

Resting pressure is the pressure in the high-pressure zone at rest after a period of stabilization.

Maximum resting pressure is the highest resting pressure recorded.

Mean resting pressure is the mean of the resting pressures recorded within the high-pressure zone.

Maximum voluntary pressure is the highest pressure recorded above the baseline (zero) at any level of the anal canal during maximum squeeze effort by the patient.

Squeeze pressure is the pressure increment above resting pressure after voluntary squeeze contraction and is a calculated value that is the difference between the maximum voluntary pressure and the resting pressure at the same level of the anal canal.

Cough pressure is the pressure increment above resting pressure after a cough and is a calculated value that is the difference between the maximum pressure recorded during cough and the resting pressure at the same level in the anal canal.

Sphincter endurance is the length of time the patient can maintain a squeeze pressure above the resting pressure.

Enterocele

An enterocele is a protrusion of the peritoneum between the rectum and vagina containing small intestine. Enteroceles are classified by the position of the lowest loop of the small bowel during evacuation effort on defecography. A first-degree enterocele is above the pubococcygeal line. A second-degree enterocele is below the pubococcygeal line but is above the ischiococcygeal line, and a third-degree enterocele is below the ischiococcygeal line.

Sigmoidocele

A sigmoidocele is a protrusion of the peritoneum between the rectum and vagina that contains sigmoid colon. Sigmoidoceles are classified by the position of the lowest loop of sigmoid during evacuatory effort on defecography. A first-degree sigmoidocele is above the pubococcygeal line, a second-degree sigmoidocele is below the pubococcygeal line but is above the ischiococcygeal line, and a third-degree sigmoidocele is below the ischiococcygeal line.

Peritoneocele

A peritoneocele is a protrusion of the peritoneum between the rectum and vagina that does not contain any abdominal viscera as seen on peritoneography.

Rectocele

A rectocele is a bulging of the rectum into the posterior wall of the vagina. At this time there is insufficient data to endorse a classification system. Possible relevant features include anatomic features, clinical symptoms, and defecographic findings.

Nonrelaxation of the Puborectalis (Anismus, Paradoxical Contraction of the Puborectalis)

This nonrelaxation is the failure of the levator and external sphincter muscles to relax during straining. It can be demonstrated on anal EMG and/or defecography.

Rectal Prolapse

Rectal prolapse is a circumferential full-thickness intussusception of the rectal wall with protrusion beyond the anal canal.

Internal Prolapse (Intussusception)

Internal prolapse is a full-thickness intussusception of the rectal wall without protrusion beyond the anal canal, demonstrated on defecography.

Mucosal Prolapse

Mucosal prolapse is a protrusion of rectal mucosa into or beyond the anal canal.

Abdominoperineal Resection

A complete removal of the rectum and anus via a combined abdominal and perineal approach.

Anterior Resection

High anterior resection of the rectum is a colorectal resection with anastomosis of the colon to intraperitoneal rectum.

Low anterior resection of the rectum is a colorectal resection with anastomosis of the colon to extraperitoneal rectum.

Low anterior resection of the rectum with coloanal anastomosis is a colorectal resection with anastomosis of colon to the anal canal circumferentially.

Anal Canal (Surgical)

The surgical anal canal is the terminal portion of the intestinal tract that extends from the anorectal ring to the anal verge.

Anal Verge

The anal verge is the junction between the anoderm and skin (the distal end of the anal canal).

Anorectal Ring

The anorectal ring is the palpable muscular band corresponding to the proximal shelf of the anal canal.

Anus

The anus is the distal orifice of the intestinal tract.

Resection Margins

ProximalMargin is the portion of the resected specimen proximal to the tumor that is grossly free of tumor.

Distal Margin.
Surgical Distal Margin is the portion of the resected specimen distal to the tumor that is grossly free of tumor as measured in the fresh, unpinned specimen.

Pathologic Distal Margin is the portion of the resected specimen distal to the tumor that is free of tumor as measured after fixation. There should be a statement as to whether the specimen was pinned to fixation.

Circumferential Margin is the least distance between the radial extent of the tumor and the circumferential resection margin measured microscopically.

High Ligation of the Inferior Mesenteric Artery

High ligation is division and ligation of the inferior mesenteric artery at its origin at the aorta.

Low Ligation of the Inferior Mesenteric Artery

Low ligation is division and ligation of the inferior mesenteric artery distal to the branching of the left colic artery.

Tumor Location in the Rectum

Tumor location in the rectum is the distance from the anal verge to the lowest margin of the tumor in the rectum measured with a rigid proctosigmoidoscope. The description should include the quadrant(s) involved by the tumor.

Mesorectum

The mesorectum is the perirectal tissue composed of fat, lymphatics, and blood vessels contained within the endopelvic visceral fascia and extending the length of the rectum.

Rectosigmoid Junction

The rectosigmoid junction is the zone overlying the sacral promontory that begins with the divergence of the teniae coli proximally and ends when they coalesce to become the continuous outer longitudinal muscular layer of the rectum.

Rectum

The rectum is the portion of the intestinal tract extending from the rectosigmoid junction to the anorectal ring. The rectum can be divided into intraperitoneal and extraperitoneal components.

Total Mesorectal Excision

Total mesorectal excision is the complete excision of the visceral mesorectal tissue to the level of the levators.

Tumor-Specific Mesorectal Excision

Tumor-specific mesorectal excision is the precise perpendicular and circumferential excision of the mesorectum to the level of an appropriate distal resection margin.

Wide Pelvic Lymphadenectomy

Wide pelvic lymphadenectomy is performed en bloc with excision of the rectum and its mesorectum to include the nodes caudad to the aortocaval bifurcation inclusive of the nodes along the common iliac arteries and veins and internal iliac and middle hemorrhoidal branches.

Radical Lymphadenectomy

Complete lymphadenectomy begins just below the duodenum and extends caudally to include the adventitial surface of the aorta and the vena cava (the ureters mark the lateral extent of dissection in the abdomen and the pelvis) with ligation of the inferior mesenteric vein just inferior to the duodenum and ligation of the inferior mesenteric artery flush with the aorta. The lymphadenectomy is extended beyond the aortocaval bifurcation into the pelvis onto the common iliac arteries with the lateral dissection to include all the adipose and lymphatic tissue along the external and internal iliac vessels, the superior vesicle, superior gluteal and obturator arteries, as well as the obturator foramen. The rectum is fully mobilized to the levators and is resected with the lateral ligaments and its entire mesorectum.

1. Morgan CN, Thompson HR. Surgical anatomy of the anal canal with special reference to the surgical importance of the internal sphincter and conjoint longitudinal muscle. Ann R Coll Surg Engl 1956:1988-114.

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