Download MBBS Surgery Presentations 9 Bowel Lecture Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) 1st Year, 2nd Year, 3rd Year and Final year Surgery 9 Bowel PPT-Powerpoint Presentations and lecture notes

Bowel

Anatomy

Atresia, Volvulus,

Meckel's diverticulum

Anatomy

? Smal intestine: 6 meters
? Large intestine: 1.5 meters.
? The first 25 cm of the smal intestine (duodenum) is retroperitoneal
? Jejunum marks the entry of the smal intestine into the peritoneal

cavity, terminates where the ileum enters the colon at the ileocecal

valve

? Large intestine is subdivided into cecum, ascending, transverse, &

descending colon.

? Sigmoid colon begins at the pelvic brim and loops within the peritoneal

cavity

? Rectum begins at about the level of the third sacral vertebra.
? Reflection of the peritoneum from the rectum over the pelvic floor

creates a cul de sac known as the pouch of douglas




Vasculature

? Superior mesenteric artery: proximal jejunum to hepatic flexure of colon

? Inferior mesenteric artery: remainder of colon to the level of rectum

? Superior hemorrhoidal branch of the inferior mesenteric artery: upper

rectum

? Hemorrhoidal branches of the internal iliac or internal pudendal artery:

lower rectum




? venous drainage follows essential y the same distribution

? connected by an anastomotic capil ary bed between the superior and

inferior hemorrhoidal veins, providing a connection between the

portal and systemic venous systems.

? Since the colon is a retroperitoneal organ in the ascending and

descending portions, it derives considerable accessory arterial blood

supply and lymphatic drainage from a wide area of the posterior

abdominal wal .




Smal Intestinal Mucosa

? The most distinctive feature of the smal intestine is its mucosal lining,

which is studded with innumerable vil i

? Vil i: site for terminal digestion and absorption of foodstuffs
? Between the bases of the vil i are the pit like crypts of Lieberk?hn
? Crypts of Lieberk?hn: contain stem cel s that replenish and

regenerate the epithelium

? In normal individuals, the vil us-to-crypt height ratio is about 4 to 5:1.
? Within the duodenum are abundant submucosal mucous glands,

termed Brunner glands.

? Brunner glands: secrete bicarbonate ions, glycoproteins, and

pepsinogen I and are virtual y indistinguishable from the pyloric

mucous glands.




Colonic Mucosa

? The function of the colon is to reclaim luminal water and electrolytes.
? Colonic mucosa has no vil i and is flat.
? Mucosa is punctuated by numerous straight tubular crypts
? Crypts contain abundant goblet cel s, endocrine cel s, and stem cel s.
? Paneth cel s are occasional y present at base of crypts in the cecum&

ascending colon

? The regenerative capacity of the intestinal epithelium is remarkable.
? Cel ular proliferation is confined to the crypts
? Turnover of the colonic surface epithelium takes 3 to 8 days

Atresia




Incidence of Atresia

? Duodenum : 35%

? Jejunum : 15%

? Ileum : 25%

? Colon : 10%

? Multiple sites : 15%

Duodenal Atresia

? Failure of vacuolization of duodenum from it's solid cord stage

at 8-10th week gestation

? Types :

? Duodenal stenosis
? Mucosal web
? Gap separated by fibrous cord
? Complete gap




Associated anomalies

? Down Syndrome (30%)

? Malrotation

? Annular pancreas

? Biliary atresia

? Congenital heart disease

? Anorectal malformations

Clinical features

? Presents in first 24hrs of life.

? 85% distal to ampulla of vater

? Characterized by bilious emesis

? Abdominal distension is absent

? Visible gastric peristalsis




Imaging

? Check for patent anus/anorectal anomalies

? Abdominal x-ray: Double Bubble sign:

? Air in the stomach, and 1st and 2nd portions of duodenum.
? If there is no distal air, the diagnosis is secure.
? If there is distal air, and urgent UGI contrast study is

needed to rule out midgut volvulus.

"Double Bubble" Sign




Management

? Nasogastric decompression

? Duodenoduodenostomy

? Duodenojejunostomy

Types of jejunoileal atresia




Jejuno-ileal atresia

? Type I:

? Mesenteric development and
intestinal length are normal
? Mucosa and submucosa forms a web or membrane
within the intestinal lumen
? Windsock Effect

Increased pressure proximal to the obstruction causes
the web to prolapse, pushing the web through the bowel

distally

Jejuno-ileal atresia

? Type II:

? Mesenteric development and
overall intestinal length is normal
? Small bowel lumen is not continuous
? Proximal small bowel ends in bulbous blind pouch
? Distal small bowel is flattened
? Proximal and distal small bowel connected by fibrous cord.




Jejuno-ileal atresia

? Type II a:

? Similar to Type II
? Small V-shaped mesenteric defect
is present, bowel length is shortened
? Proximal blind end is markedly dilated & aperistaltic
? No fibrous cord connects the proximal & distal small bowel

Jejuno-ileal atresia

? Type II b:

? Similar to Type II a
? Significant mesenteric defect is present

Superior mesenteric artery is largely absent
Small bowel supplied by a single ileocolic or right colic

artery

? Known as Christmas tree or apple peel deformity

Bowel wraps around a single perfusing artery




Jejuno-ileal atresia

? Type IV:

? Multiple JIAs of any
combination Types I ? II

Appears as a string of sausages due to multiple lesions

? Likely result of multiple ischemic insults or
inflammatory process

Pathophysiology

JIA is usually a vascular insult versus failure to recanalization of

Duodenal Atresia

Intrauterine vascular accident Necrosis of bowel segment in a

sterile environment Resorption and disappearnce of tissue

Malrotation, Volvulus (abnormal twisting of SMA),

Gastroschisis, Omphalocele

All result in blood supply / gut segment separation




symptoms, physical exam findings.

? Within the first day of life

? Depends on level of obstruction

Proximal
Distal

? Vomiting green bile
? Bowel sounds absent in distal small intestine
? No meconium
? Abdominal distention

Proximal gut dilatation




Imaging

? Prenatal y

? Ultrasonography wil likely show excess amniotic fluid

(polyhydramnios)

? First day of life

? Abdominal X-ray: Air Fluid level, Dilated proximal gut
? Water soluble contrast enema: exclude multiple

strictures, Flattened distal gut, Micro colon




Triple Bubble Presentation

Initial treatment

? Immediately a tube is placed orally into the stomach to evacuate

excess fluid and gasses

? Prevents vomiting and aspiration
? Relieves GI discomfort

? IV Fluids and Nutrients are provided until surgery is available

? Surgical intervention is necessary to repair the bowel obstruction

and blood supply




Surgical management

? Aim: Preserve as much bowel length as possible

? Dilated proximal part

? Resection and anastomosis
? Tapering enteroplasty if remaining bowel is short

? Multiple strictures:

? Multiple anastomosis over an endoluminal tube

Prognosis

? Types I, II, and II a have good prognosis

? Fairly normal small bowel length results in almost normal

bowel function

? Types II b, IV is associated with complications

? Shortened small bowel is associated with short gut

syndrome and malabsorption




Volvulus

? Volvulus occurs when an air-filled segment of the colon twists about its

mesentery.

? Sigmoid colon is involved in up to 90% of cases, but volvulus can involve the

cecum (<20%) or transverse colon.

? Volvulus may reduce spontaneously, but more commonly produces bowel

obstruction

? Chronic constipation may produce a large, redundant colon (chronic megacolon)

that predisposes to volvulus

? Symptoms: abdominal distention, nausea, and vomiting.

? Symptoms rapidly progress to generalized abdominal pain and tenderness.

? Fever and leucocytosis are heralds of gangrene and/or perforation.




Sigmoid volvulus

? Can often be differentiated from cecal or transverse colon volvulus

by the appearance of plain x-rays of the abdomen.

? Sigmoid volvulus produces a characteristic bent inner tube or

coffee bean appearance

? Gastrografin enema shows a narrowing at the site of the volvulus

and a pathognomonic bird's beak

Plain X ray showing coffee bean appearance




Gastrografin enema showing "bird-beak" sign (arrow)

Management

? Initial management: resuscitation followed by endoscopic detorsion

? Detorsion: by rigid proctoscope, but a flexible sigmoidoscope or

colonoscope might also be effective.

? Elective sigmoid colectomy should be performed after the patient has

been stabilized

? Surgical exploration: evidence of gangrene or perforation, presence of

necrotic mucosa, ulceration, or dark blood noted on endoscopy
examination

? If dead bowel is present at laparotomy, a sigmoid colectomy with end colostomy

(Hartmann procedure) may be the safest operation to perform.




Cecal Volvulus

? Nonfixation of the right colon.

? Rotation occurs around the ileocolic blood vessels and vascular impairment

occurs early.

? Plain x-rays of the abdomen show a characteristic kidney-shaped, air-filled

structure in the left upper quadrant (opposite the site of obstruction), and a
gastrografin enema confirms obstruction at the level of the volvulus.

? Cecal volvulus can almost never be detorsed endoscopically.

? Surgical exploration is necessary when the diagnosis is made.

? Right hemicolectomy with a primary ileocolic anastomosis can usually be

performed safely and prevents recurrence

Cecal Volvulus




Meckel's Diverticulum

? Failure of involution of the vitelline duct, which connects the lumen

of the developing gut to the yolk sac, produces a Meckel

diverticulum.

? True diverticulum: contains al three layers of the normal bowel

wall: mucosa, submucosa, and muscularis propria.

? It may be a small pouch or a blind segment having a lumen greater

in diameter than that of the ileum and a length of up to 6 cm.




Rule of 2's

? 2% of the population have one
? 1/2 of symptomatic lesions usually present before the age of 2

years old, others most commonly in the first 2 decades of life

? Diveriticuli in adult patients only become symptomatic in about 2%
? 2 times more common in males than females
? Usually found within 2 feet of the ileocecal valve
? Usually are about 2 inches in length
? 1/2 contain heterotrophic mucosa (usually gastric, occasionally

pancreatic)

Clinical Features:

? Lower GI bleeding
? Intestinal obstruction
? Local inflammation with or without perforation
? Rare presentations: Neoplasms

Diagnosis:

? Most accurate test, especially in children, is "Meckel's scan"- sodium
99-tc-pertechinetate, taken up by gastric mucosa
? Abdominal CT scan
? If CT is negative barium studies should be done
? If bleeding with a negative scan, angiography may be helpful


Treatment

? If symptomatic: prompt surgical intervention to resect the

diverticulum or segment of ileum containing the diverticulum.

? If not symptomatic: and found incidentally at surgery in children

under 2 y/o, resection is recommended.

? In asymptomatic adults, resection is controversial since only

about 2% of these patient's will become symptomatic and there

is about a 2% incidence of short or long term complications