Colon

The appendix: extends from the cecum approximately 3 cm below the ileocecal valve as a blind-ending elongated tube,

- 8 to 10 cm in length.

- Location:

• retrocecal (65%)
• pelvic (31%)
• subcecal (2.3%),
• preileal (1.0%)
• retroileal (0.4%)

- Anatomic Markers

• Convergence of the taeniae coli
• Fold of Treves: only antimesenteric epiploic appendage normally found on the small intestine which marks the junction of the cecum and ileum

The cecum is a capacious sac-like segment of the

proximal colon, with an average diameter of 7.5 cm and length of 10 cm.

- Greater than 12 cm can lead to ischemic necrosis

Ascending Colon:

- Length

• 15 cm

- Peritoneal locations

• Anterior and Lateral portion: Intraperitoneal
• Posterior portion: secondary retroperitoneal

- White Line of Toldt

• Represents the fusion of the mesentery with the posterior peritoneum
• Used in surgical mobilization

Transverse colon is

- Length: approximately 45 cm.

- Peritoneal location: Intraperitoneal

- Ligamentous Attachments

• Nephrocolic: secures the hepatic flexure and directly overlies the right kidney, duodenum, and porta hepatis
• Phrenocolic: lies ventral to the spleen and fixes the splenic flexure in the left upper quadrant
• Greater Omentum: Attached to the superior aspect of the transverse colon. A fused double layer of visceral and parietal peritoneum (four total layers)
• Gastrocolic: Contination of the omentum superiorly

Descending colon:

- Course:

• lies ventral to the left kidney and extends downward from the splenic flexure for approximately 25 cm.

Characteristics:

• Smaller in diameter than the ascending colon. At the level of the pelvic brim, there is a transition between the relatively thin walled, fixed, descending colon and the thicker, mobile sigmoid colon.

Sigmoid colon:

- Length:

• Variable
• 15 to 50 cm (average, 38 cm)

- Characteristics:

• Small diameter, muscular tube
• Long floppy mesentery that often forms an omega loop in the pelvis

- Intersigmoid Fossa

• Small recess in the mesentery created by mesosigmoid attachment to the left pelvic side wall
• Surgical landmark for the underlying left ureter.

Endopelvic fascia

- Thick layer of parietal peritoneum that lines the walls and floor of the pelvis.

- Presacral fascia:

• Closely applied to the periosteum of the anterior sacrum

- Fascia Propria:

• Closely applied to the periosteum of the anterior sacrum
• Help create the lateral rectal stalks or ligaments

- Lateral rectal stalks or ligaments

• Anterolateral structures containing the middle rectal artery.
• Close to the mixed autonomic nerves, containing sympathic and parasympathetic nerves, and division of these structures close to the pelvic sidewall may injure these nerves, resulting in impotence and bladder dysfunction

- Rectosacral fascia, or Waldeyer fascia

• Thick condensation of endopelvic fascia connecting the presacral fascia to the fascia propria at the level of S4 that extends to the anorectal ring.
• Waldeyer fascia is an important surgical landmark, and its division during dissection from an abdominal approach provides entry to the deep retrorectal pelvis.
• Dissection between the fascia propria and presacral fascia follows the principles of surgical oncology and minimizes the risk for vascular or neural injuries

Anatomists consider the dentate line the distal extent of the rectum, whereas surgeons typically view this union of columnar and squamous epithelium as existing within the anal canal and

consider the end of the rectum to be the proximal border of the anal sphincter complex.

Superior Mesenteric Artery

- supplies the entire small bowel, giving off 12 to 20 jejunal and ileal branches to the left and upto three main colonic branches to the right.

- Branches:

• Ileocolic artery: Supplies terminal ileum, cecum, and appendix
• Right colic artery: supplies ascending colon and hepatic flexure

- Communicates with Middle colic artery through marginal artery

- May aries from SMA, ICA, or MCA

- Absent in 2% to 18% of specimens

• Middle Colic artery: Proximal branches of the SMA and divides into right and left branches which supply proximal and distal transverse colon

Inferior Mesenteric Artery

- Origin: originates from the aorta at the level of L2 to L3, approximately 3 cm above the aortic bifurcation

- Branches

• Left colic artery: most proximal branch, supplying the distal transverse colon, splenic flexure, and descending colon
• Sigmoid Arteries: Multiple branches
• Superior rectal artery: which courses behind the rectum in the mesorectum, branching and then entering the rectal submucosa

Wastershed area:

- The left branch of the middle colic artery may supply territory also supplied by the left colic artery through the collateral channel of the marginal artery.

- This collateral circulation in the area of the splenic flexure is the most inconsistent of the entire colon and has been referred to as a watershed area, vulnerable to ischemia in the presence of hypotension.

The Sudeck point refers to a specific location in the arterial supply of the rectosigmoid junction, namely the origin of the last sigmoid arterial branch from the IMA

• This arterial branch usually forms an anstomosis with a branch of the superior rectal artery. The anastomosis is small and often only singular. Sudeck point has particular relevance in colorectal surgery and also forms a site of watershed rectal wall that is susceptible to ischaemic colitis.

Ulcerative Colitis

Epidemiology

Developed Countries

Incidence

- 4 to 6 cases/100,00 white

adults

Prevalance

- 40 to 100/100,000c cases

Age and Race

-All ages are susceptible,but it more commonly affects patients younger than 30 years.

- A small secondary peak in the incidence occurs in the sixth decade.

- Both genders are equally affected, but the condition is more common in whites, Ashkenazi Jews, and persons of northern European ancestry.

Smoking

- Protective against

development

- Therapeutic

- Reports of nicotine induced

remission

Family history

- Strong correlation

- Gentitic alleles

• HLA
• DR2
• DR1501 = benign course
• DR1502 = Virulent course

Pathologic Features

Gross Features:

- Mucosa and Submucosa

- Hyperemic mucosa

- Rectal involment = Hallmark

- Diagnostic characteistic

• Uniterrupted inflmation of

colonic mucosa

• Extending from the rectum to

variable proximal distance

- "Backwash" Ileitis

Strictures

- Location: colon

- Occurs in 5% to 12% of people

with chronic UC

- Caused by hypertrophy of muscularis

- Needs to be diffentiated from malignancy

• Occurs later in the course of UC
• Proximal to splenic flexure
• Causing large bowel obstruction

Histologic Appearance

- Inflmmation of mucosa and submucosa

- Charteristic Lesion

• Crypt abscess
• Neutrophils fill and expand in Crypts of Lieberkuhn

- Presence of perinuclear antineutrophil cytoplasmic Ab

Clinical Presentation

- Presents similarly to Crohn's

• Diarrhea
• passage of blood and mucous
• Weight loss

- Increased urgency 2/2 to distal

proctitis

Perianal disease is

an uncommon finding

Disease Severity

• Most patients with ulcerative colitis present with an attack of mild severity at presentation, approximately 27 percent of patients have moderate disease, and 1 percent have severe disease at presentation

Mild – Patients with mild clinical disease have four or fewer stools per day with or without blood, no signs of systemic toxicity, and a normal erythrocyte sedimentation rate (ESR). Mild crampy pain, tenesmus, and periods of constipation are also common, but severe abdominal pain, profuse bleeding, fever, and weight loss are not part of the spectrum of mild disease.

Moderate – Patients with moderate clinical disease have frequent loose, bloody stools (>4 per day), mild anemia not requiring blood transfusions, and abdominal pain that is not severe. Patients have minimal signs of systemic toxicity, including a low-grade fever. Adequate nutrition is usually maintained, and weight loss is not associated with moderate clinical disease.

Severe – Patients with a severe clinical presentation typically have frequent loose, bloody stools (≥6 per day) with severe cramps and evidence of systemic toxicity as demonstrated by a fever (temperature ≥37.5°C), tachycardia (HR ≥90 beats/minute), anemia (hemoglobin <10.5 g/dL), or an elevated ESR (≥30 mm/hour). Patients may have rapid weight loss.

Diagnosis

History

- Rule out other forms of colitis

- Recent travel

- Antibiotic use

- Risk for althersclerotic disease

- Sexually transmitted disease

- Immunocompromised

- History of pelvic radiation

Laboratory Values

- CBC

- BMP

- Albumin

- ESR

- CRP

Endoscopy and Biopsy

- Acute phase:

• Proctosigmoidoscopy

- Long term:

• Will need completion colonoscopy

- Findings:

• Confluent and symmetrical disease from the dentate line and proximal
• Loss of normal vessel pattern 2/2 edema
• Pseudopolyps
• Frank ulceration

Differential Diagnosis

• Crohn disease

• Infectious colitis

• Radiation colitis

• Diversion colitis

• Solitary rectal ulcer syndrome

• Graft versus host disease

• Diverticular colitis

• Medication-associated colitis

Indications for Surgery

Adults

- Fulminant colitis

• with Toxic megacolon

- Massive bleeding

- Intractable disease

- Dysplasia or Carcinoma

Pediatrics

- Growth retardation

Fulminant colitis and toxic megacolon

- Severe Ulcerative Colitis

• Fulminant colitis refers to a subgroup of patients with severe ulcerative colitis who have more than 10 stools per day, continuous bleeding, abdominal pain, distension, and acute, severe toxic symptoms including fever and anorexia. Such patients are at risk of progressing to toxic megacolon and bowel perforation

- Toxic Megacolon

• Radiographic evidence of colonic distension( diameter ≥6 cm or cecum >9 cm and systemic toxicity)
• PLUS at least three of the following:

Fever >38ºC

Heart rate >120 beats/min

Neutrophilic leukocytosis >10,500/microL

Anemia

• PLUS at least one of the following:

Dehydration

Altered sensorium

Electrolyte disturbances

Hypotension

- Procedure

• Total abdominal colectomy with Brooke ileostomy

Massive Hemorrhage

- Uncommon

• Less than 5% of patient requiring operation

- Procedure

• Sub-total Colectomy
• Bleeding continues = proctectomy

Intractability

- Debilitating symptoms refractory to medical management

• Abdominal pain, frequent bowel movements, anemia, etc

- Complications of long-term steriod therapy

• Diabetes, cataracts, avascular necrosis of femoral head, osteoprosis etc
• Life long dependence of steroids = Medical failure

- Procedure:

• Elective
• Resortative Protocolectomy with ileal pouch-anal anastomosis

Surgical Techniques

General considerations

- Elective:

• Total Protocolectomy with ileal pouch-anal anastamosis

- Emergent

• Total abdominal colectomy with Brooke ileostomy.

- Rare

• Abdominal colectomy wiht ileorectal anastamosis
• Rectum is almost always involved and recurrent disease leads to intractable diahrrea

- Contraindicated

• Segmental Colectomy
• Recurrence of disease in a short time

Total Protocolectomy with ileal pouch-anal anastamosis

- Overview

• Near-total proctocolectomy
• Preservation of the anal sphincter complex
• Single-chambered pouch is fashioned from the distal 30 cm of the ileum
• Connected to the anus using a double-stapled technique

Controversy:

- Mucosectomy

• Double-stapling technique may leave a small remnant of rectal mucosa at the anastomosis, which may be at risk for development of dysplasia and cancer.
• Avoiding the mucosectomy preserves the anal transition zone, which contains nerve endings involved in differentiating liquid and solid stool from gas, and is thus thought to provide superior postoperative continence.

- Fecal diversion

• High risk vs Low risk

Complications

- Pouchitis

• Inflammation of the mucosa of the ileal pouch, or pouchitis,occurs in 7% to 33% of patients with ulcerative colitis treated by IPAA.
• Pouchitis typically is manifested with increased stool frequency, fever, bleeding, cramps, and dehydration.
• Cause is unknown but may be related to bacterial overgrowth, mucosal ischemia, or other local factors.
• Episodes usually respond to rehydration and oral antibiotics, usually metronidazole or ciprofloxacin.
• Probiotics have been reported to provide dramatic resolution in some cases of pouchitis resistant to antibiotic therapy.
• The diagnosis of Crohn’s disease must also be entertained in patients with significant pouchitis that does not respond to medical treatment.

Subtotal colectomy for severe-to-fulminant CUC:

- Procedure

• Mobilize the colon from the lateral peritoneal reflection starting at the cecum with identification of the right ureter and right gonadal vessels as to avoid injury. The duodenum should also be visualized to avoid injury.
• Avoid excessive traction especially in areas like the splenic flexure as to avoid tearing the splenic capsule.
• The descending colon is then taken from its lateral peritoneal attachments from the sigmoid up with early identification of the left ureter and left gonadal vessels.
• A long rectal stump should be left to avoid injury to the pelvic plexus of nerves and vessels, which is of greater likelihood in the emergent setting.
• The retained rectum should be monitored endoscopically for malignancy. Strong consideration for removal of the remaining rectum should be evaluated once the patient has completely healed from the total abdominal colectomy.

Crohn's Disease

Crohn’s disease is a non-

specific IBD that may affect any segment of the GI tract.

15% have disease limited to the

colon.

Epidemiology

The incidence of Crohn’s disease varies between 1 and 10/100,000, depending on the geographic location, with the highest incidence in Scandinavian countries and Scotland, followed by England and North America.

Bimodal age distribution, with peaks between the

ages of 15 and 30 years and a second smaller peak between 55 and 80 years of age.

Common among

patients of Jewish descent and occurs more frequently in urban

residents.

Smoking appears to be

a risk factor for Crohn’s disease, and after intestinal resection, the

risk of recurrence is greatly increased in smokers.

Genetic Factors

NOD2/CARD15 gene, located on chromosome 16, has been shown to be involved in the activation of nuclear factor kappa-beta, a transcription factor that plays a significant role in Crohn’s disease.

Pathological Features

Gross appearance:

- Transmural, predominantly submucosal inflammation characterized by a thickened colonic wall.

• Cobblestone appearance
• Creeping fat of the mesentery
• Strictures may develop in the small and large intestines.
• The mucosa may demonstrate long, deep linear ulcers that resemble railroad tracks or bear claws
• Normal mucosa may intervene between areas of inflammation, causing skip areas characteristic of the disease.

Histologic appearance:

- Crohn’s disease is characterized microscopically by transmural inflammation, submucosal edema, lymphoid aggregation, and, ultimately, fibrosis.

- Pathognomonic histologic feature of Crohn’s disease is the noncaseating granuloma

• a localized, well formed aggregate of epithelioid histocytes surrounded by lymphocytes and giant cells
• Granulomas are found in 50% of specimens resected in Crohn’s disease

Clinical Presentation

Triad of Symptoms

- Abdominal pain

- Weight loss

- Diarrhea

Secondary Symptoms

- Anorexia

- recurrent oral aphthous ulcers

- Fevers

Rectal Disease

- Present in 60% of patients

Colonic disease:

- Entire colon involved in 2/3 of patients

Anal disease

Anal fistulas fissures, strictures, edematous, skin tags

Diagnosis

The diagnosis of Crohn’s colitis is made by a combination of clinical, endoscopic, and radiologic features.

The Vienna Classification:

- Divides all patients into 24 distinct categories based Age, Behavior, and Location:

• Age of onset: before or after the age of 40 years
• Disease behavior

1. Nonstricturing/nonpenetrating,

2. Stricturing

3. Penetrating

• Disease site: terminal ileum, colon, ileocolonic, upper gastrointestinal tract.

- This classification was developed to provide

a reproducible staging of the disease, to help predict remission and relapse, and to direct therapy.

Indications of Surgery

Intractability:

- Patients who fail to respond to optimal medical

therapy for Crohn’s disease and remain symptomatic are referred for surgical consultation.

-As with ulcerative colitis, this represents

the most common indication for operative treatment of Crohn’s

disease.

Intestinal obstruction

- Intestinal obstruction in Crohn’s disease may be caused by active inflammation, a fibrotic (fibroste-

nosis) stricture from chronic disease, or an abscess or phlegmon causing a mass effect.

- Obstruction typically involves the small intestine, although large bowel obstruction from strictures

• Initial treatment includes bowel rest, nasogastric decompression, IV fluids, and anti-inflammatory medications (usually steroids).
• Resection with diversion is typically the appropriate operation if the obstruction involves the colon or terminal ileum.
• Primary anastomosis is generally done in proximal small bowel obstructions.

Intra-abdominal abscess:

- An intra-abdominal abscess in Crohn’s disease is the result of intestinal perforation caused by transmural inflammation.

• Diagnosed by CT and can often be managed nonoperatively
• CT guided Drainage
• If fails Drainage and IV antibiotics then surgical drainage indicated

Fistulas:

- Fistulas may develop between the intestine and any

other intra-abdominal organ, including the bladder, bowel, uterus,

vagina, and stomach.

• Up to 35% of patients with Crohn’s disease develop fistulas, most of which involve the small intestine.

- Common fistula is ileosigmoid fistula

• Ileal disease with secondary involvement of the sigmoid.
• Symptomatic patients should undergo resection of the terminal ileum
• Extesive sigmoid disease = Sigmoidectomy

- Colovesical and colovaginal fistulas require surgical intervention

• Resctoion of disease bowel
• Closure of related organ with omental patch/position

- Enterocutaneous fistulas develop spontaneously

• Common Location: Ileum or anastomic breakdown site
• Conservative and medicinal treatment
• May require surgical intervention

Surgical Techniques

- Ileocecal Resection

- Total proctocolectomy with end ileostomy.

- Total abdominal colectomy with ileorectal anastomosis.

- Segmental colon resection.

Ileocecal resection

- Indications: Obstruction or perforation

- Overview of Procedure:

• Resection of approximately 6 to 12 inches of the terminal ileum and cecum
• Anastomosis created between the ileum and ascending colon.
• The terminal ileum is transected 2 cm proximal to grossly apparent Crohn’s disease.
• Stricturoplasty is not indicated for disease of the terminal ileum.
• Recurrence rate: Approx. 50%

- Appendicitis like presentation

• Traditional approach: Perform appendectomy and treat terminal ileitis medcinally
• Future complication requring ileocecal resection

Strictureplasty

- Indication:

• Complete obstruction 2/2 single or multiple strictures
• Parital obsturction that fails medical management

-Goal: Effectively widens the lumen but avoids intestinal resection.

- Overview: Heineke-Mikulicz

• Longitudinal incision is made through the narrowed intestine
• Closure in a transverse manner

- Longer diseased segments (>10 cm),

• Finney Technique
• Side-to-side isoperistaltic strictureplasty

-Utilization:

• Multiple areas of stricture over long segments of inestine
• History of previous small bowe resections
• Narrowing 2/2 to firbrous obstruction instead of acute inflammation

- Cancer risk

• Increased risk of cancer at chronically strictured segments
• full-thicknessbiopsy with frozen section of the stricture site has been advocated at the time of surgery

Colon/Small bowel

Video Resources

Anatomy

The arc of Riolan is a collateral artery, that directly connects the proximal SMA with the proximal IMA and may serve as a vital conduit when one or the other of these arteries is occluded

The colon and rectum constitute a tube of variable diameter

approximately 150 cm in length.

Internal Illiac Artery

- Branches

• Middle Rectal artery: It is variable in size and enters the rectum anterolaterally, passing alongside and slightly anterior to the lateral rectal stalks. It has been reported to be absent in 40% to 80% of specimens studied
• Inferior Rectal artery: branch f the pudendal artery, which itself is a more distal branch of the internal iliac

- From the obturator canal, it traverses the obturator fascia, ischiorectal fossa, and external anal sphincter to reach the anal canal

- This vessel is encountered during the perineal dissection of an abdominoperineal resection

.

Physiology

The rectoprostatic fascia (Denonvilliers' fascia) is a membranous partition at the lowest part of the rectovesical pouch. It separates the prostate and urinary bladder from the rectum. It consists of a single fibromuscular structure with several layers that are fused together and covering the seminal vesicles.

Rectum:

- Function: Fecal reservoir

- Length: 12 to 15 cm

- Characteristics

• Lacks taeniae coli or epiploic appendices
• Occupies the curve of the sacrum in the true pelvis

- Peritoneal Attachments:

• Posterior surface: Extraperitoneal
• Anterior surface: Proximal third of the rectum is covered by visceral peritoneum

- Peritoneal reflections

• The peritoneal reflection is 7 to 9 cm from the anal verge in men and 5 to 7.5 cm in women

.

Occlusion of SMA

Occlusion of IMA

Houston valves

- 3 valves

- These valves are more

properly called folds because they have no specific function as impediments to flow.

- Lost during surgical mobilization of the rectum

• Provides 5 cm of additional length

It is also known as the meandering mesenteric artery and is highly variable in size. Flow can be forward (IMA stenosis) or retrograde (SMA stenosis), depending on the site of obstruction. Such obstruction results in increased size and tortuosity of this meandering artery, which may

be detected by arteriography; the presence of a large arc of Riolan thus suggests occlusion of one of the major mesenteric arteries

Embryology:

- Foregut

• Supplied Celiac Artery

- Midgut

• Supplied by SMA

- Hindgut

• Supplied IMA

Medical Therapy

Extraintestinal Manifesations

Vide0 Resources

High Yield

Inflammatory bowel disease

Dysplasia or Carcinoma

- Procedure is pending stage

and location of cancer

= Mural edema

In forming an ileostomy, the ileum is brought through the abdominal wall at a site selected before the operation to ensure

that the location is ideal for maintaining the seal of an appliance (i.e., away from natural abdominal wall creases, scars, hernias).

A disc of skin is excised, the dissection is carried longitudinally

through the center of the rectus muscle, and the posterior fascia

is divided

The abdominal wall aperture should be

approximately 2.5 cm in diameter, thus admitting two fingers. Sufficient length of well-vascularized ileum is brought through the abdominal wall to permit creation of a spigot hat will protrude well above skin level (Brooke configuration), allowing the ileal contents to pour into an appliance sealed to the adjacent skin

The abdominal wall aperture should be

approximately 2.5 cm in diameter, thus admitting two fingers. Sufficient length of well-vascularized ileum is brought through the abdominal wall to permit creation of a spigot

that will protrude well above skin level (Brooke configuration),

allowing the ileal contents to pour into an appliance sealed to the

adjacent skin (Fig. 51-20). The ileostomy is completed by approx-

imating the full thickness of the divided wall of the ileum to the

subcuticular tissue of the abdominal skin of the stoma site, placing

sutures in so as to maintain the everted configuration of the stoma

(Figs. 51-21 and 51-22).

The ileostomy is completed by approximating the full thickness of the divided wall of the ileum to the subcuticular tissue of the abdominal skin of the stoma site, placing

sutures in so as to maintain the everted configuration of the stoma

To achieve this length, we usually divide the remnant of the ileocolic artery close to its origin from the SMA

The peritoneum of the mesentery may be serially incised on its

anterior and posterior surfaces; these relaxing incisions can confer

an additional 1 or 2 cm of length and are especially beneficial if

the mesentery has been thickened by adhesions from previous

surgery

- Mobilize posterior attachment of the entire small bowel mesentery to the

third portion of the duodenum, exposing the inferior portion of

the head of the pancreas.

An estimate of the ease of the pouch

reaching the anus can be made by drawing the selected apex of the anticipated pouch over the symphysis pubis, with the expectation that it should extend 6 cm beyond the pubis to reach the

anal canal easily