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
This post was last modified on 08 April 2022