Anterior Resection

"𝗧𝗬𝗣𝗘𝗦 𝗢𝗙 𝗔𝗡𝗧𝗘𝗥𝗜𝗢𝗥 𝗥𝗘𝗦𝗘𝗖𝗧𝗜𝗢𝗡" 

  

Anterior resection is the general term used to describe resection of the rectum from an abdominal approach to the pelvis with no need for a perineal, sacral incisions.

𝗧𝘆𝗽𝗲𝘀;

𝗜-High Anterior Resection:

It's resection of the distal sigmoid colon and upper rectum and is the appropriate operation for benign lesions and disease at rectosigmoid junction such as diverticulitis. Upper rectum is mobilized, but the pelvic peritoneum is not divided and the rectum is not mobilized fully from the concavity of the sacrum. 

𝗜𝗜- Low Anterior Resection:

It used to remove lesions in the upper and mid rectum. The rectosigmoid is mobilized, the pelvic peritoneum is opened, and the inferior. Rectum is mobilized from the sacrum by sharp dissection (TME) under direct view within the endopelvic fascial plane. The dissection may be performed distally to the anorectal ring, extending posteriorly through the rectosacral fascia to the coccyx and anteriorly through Denonvilliers’ fascia to the vagina in women or the seminal vesicles and prostate in men.Coloanal anastomosis done by hand sewenor staple.

𝗜𝗜𝗜-Extended or ultra Low Anterior Resection;

 This resection is necessary to remove lesions located in the distal or mid/lower third rectum, but lower margin of tumor should be 2cm proximal to anorectal junction or anal sphincter.  Rectum is fully mobilized to the level of the 𝗹𝗲𝘃𝗮𝘁𝗼𝗿 𝗮𝗻𝗶 muscle just as for a low anterior resection, but the anterior dissection is extended along the rectovaginal septum in women and distal to the seminal vesicles and prostate in men. After resection at this level, coloanal anastomosis can be done by stapled or hand sewn technique. 

🌏"LATEST ADVANCES INTERSPHINCTERIC RESECTION (ISR)";

It's mobilization of the rectum to the levator ani, with total mesorectal excision via the abdominal route like ultra low AR but resection of the internal anal sphincter also done via the anal route to obtain maximum distal resectional margin.

🙄"This technique avoid 𝗔𝗣𝗥 (Abdominperineal resection)"

The most common indication for ISR is a tumor with T1–3 categories and a tumor located at 10–50 mm from the anal verge.

Lymphatic Drainage of the Rectum and Anal Canal (two, four, eight):

•The lymph channels of the rectum and anal canal form two extramural plexuses, one above and one below the pectinate line. The upper  plexus drains through the posterior rectal nodes to a chain of nodes along the superior rectal artery to the pelvic nodes (Fig. 12.19). Some drainage follows the middle and inferior rectal arteries to the hypogastric nodes. Below the pectinate line, the plexus drains to the inguinal nodes.

•The “𝘄𝗮𝘁𝗲𝗿𝘀𝗵𝗲𝗱” of the extramural lymphatic vessels is at the pectinate line. The watershed for the intramural lymphatics is higher, at the level of the middle rectal valve (Fig. 12.20).These two landmarks may be kept in mind by the 𝗺𝗻𝗲𝗺𝗼𝗻𝗶𝗰m “two, four, eight,” meaning:

• 2 cm = anal verge to pectinate line

• 4 cm = surgical anal canal (above and below the pectinate line)

• 8 cm = anal verge to middle rectal valve

Downward spread of lesions of the rectum is rare;perhaps only 2% may spread downward. A margin of 2–3 cm distal to the tumor should be allowed in anterior resection.

𝗧𝘂𝗺𝗼𝗿 𝗽𝗼𝘀𝗶𝘁𝗶𝗼𝗻 𝗿𝗲𝗹𝗮𝘁𝗶𝘃𝗲 𝘁𝗼 𝘁𝗵𝗲 𝗱𝗲𝗻𝘁𝗮𝘁𝗲 𝗹𝗶𝗻𝗲 𝗮𝗳𝘁𝗲𝗿 𝗺𝗼𝗯𝗶𝗹𝗶𝘇𝗮𝘁𝗶𝗼𝗻 𝗼𝗳 𝗿𝗲𝗰𝘁𝘂𝗺:

•For middle to low #rectal cancers, TME involves removing the entire mesorectum with its enveloping fascia as an intact unit. For tumors in the upper rectum (>10 cm from the anal verge), TME is extended to 5 to 6 cm below the level of the tumor, dividing the rectum and mesorectum at the same level. 

•Several pathologic studies demonstrate that tumor spread within mesorectum rarely extends beyond 4 cm distal to the caudal edge of the tumor; usually most nodes or mesorectal implants are within 3 cm of the distal edge of the tumor. However, multiple studies have shown that a 1 to 2-cm margin is adequate on the mucosa. Fewer than 2% to 4% of tumors will have mucosal or submucosal spread beyond 2 cm distally.

•Rigid sigmoidoscopy may be used to identify the appropriate site for transection if the cancer is not palpable, especially after neoadjuvant therapy.

👉"Once the rectum has been mobilized (from lateral ligament or attachments), a tumor measured 𝗮𝘁 𝗳𝗶𝘃𝗲 𝗰𝗺 by rigid proctoscopy often may be 𝗺𝗼𝘃𝗲𝗱 𝘁𝗼 𝗲𝗶𝗴𝗵𝘁 𝗰𝗺 from the dentate line, a distance that permits an adequate resection margin and sphincter preservation (Fig.54-18).the rectum. This may permit a 𝘀𝗽𝗵𝗶𝗻𝗰𝘁𝗲𝗿 𝗽𝗿𝗲𝘀𝗲𝗿𝘃𝗶𝗻𝗴 𝗿𝗲𝘀𝗲𝗰𝘁𝗶𝗼𝗻𝘀".

"👉A sphincter-saving operation (anterior resection) is usually possible for tumours whose lower margin is ≥2 cm above the anorectal junction or 5 cm from anal verge as length of anal canal is about 3cm plus 2cm (3+2=5) of length below the lowest margin of rectal tumor.

Nervi erigentes injury during pelvic dissection:

•Thinner patients, the surgeon can visualize the nervi erigentes coursing laterally (see Fig. 17.5 ). These may be swept out of the way. The nerves are again seen running at the back of the lateral edge of the seminal vesicles, bladder neck, and prostate. Bleeding encountered here means one is too medial in the mesorectum or too lateral along the pelvic sidewall, and the plane should be reassessed. The lateral “ligaments” in fact represent only a minimal amount of connective tissue and do not contain the middle rectal artery, which courses much lower and out of reach of most dissections.

▪︎Nerve injury can be sympathetic, parasympathetic, or both. There are a number of locations where nerve injury is likely to occur, and care should be taken during dissection of these locations. The aortic plexus or subsequent hypogastric nerves contain sympathetic fi bers and can be damaged if in the wrong plane at the level of the pelvic brim. After removal of the rectum, the nerves appear as a wishbone, preserved under a thin layer of Toldt’s fascia. These nerves may also be damaged at any point during the posterior dissection if the surgeon dissects too far posterior. Injury here results in pure sympathetic injury, causing retrograde ejaculation. Along the lateral sidewalls,parasympathetic injury can occur, resulting in impotence and bladder dysfunction. The nervi 

erigentes course laterally around the lower part of the rectum from the pelvic plexus. They continue anteriorly near the lateral border of the seminal vesicles (in males) or the cardinal ligaments (in females). Anterior dissection to include Denonvilliers fascia in the extramesorectal plane can also 

damage these nerves. Injury at any point along this path can result in a mixed sympathetic and parasympathetic injury. Incidence of retrograde ejaculation was 33 %, and impotence rates averaged 12 % in male patients with attention to nerve preservation. This is higher with lateral wall lymphadenectomy and splanchnic nerve resection for locally advanced tumors (nerve dysfunction in 25–75 % of pts, with an average of 50 %). 

•The incidence of urinary dysfunction may be as high as 27% and includes difficulty emptying the bladder as well as urinary incontinence. Sexual dysfunction may also reach 11–55% after TME. For females, the inability to achieve orgasm, dyspareunia and reduction in vaginal lubrication may be distressing, even for some of the more elderly females. Many male surgeons do not realise that this is an important quality of life factor, especially for younger female patients. For males, nerve dysfunction may include erectile dysfunction, absence of ejaculation or retrograde ejaculation. The increased use of neoadjuvant and adjuvant radiotherapy is associated with poorer functional outcomes. When radiotherapy is indicated, however, it cannot be withheld just because of the fear of nerve dysfunction. One of the main risk factors, poor surgical technique with resultant iatrogenic sexual and urinary dysfunction, however, may be prevented by thorough and practical understanding of pelvic nerve anatomy.