DIG Exam 3 Lopez Small Bowel, Colon, Anus

Esophagus, stomach, duodenum proximal to opening of the bile duct, liver, hepatic ducts, gallbladder, bile ducts and pancreas

Foregut

Foregut arterial supply?

Celiac trunk

Distal of bile duct duodenum, ileum, jejunum, cecum, appendix, ascending colon, right 1/2-1/3 of the transverse colon

Mid gut

Midgut arterial supply?

SMA

Left 1/3-1/2 of the transverse colon, descending colon, sigmoid colon, rectum, superior part of anal canal. epithelium of urinary bladder, and most of the urethra

Hindgut

Hindgut arterial supply?

IMA

Herniation of midgut loop

rotation of midgut loop

retraction of intestinal loops

fixation of intestines

Midgut formation steps

Midgut is attached to the?

umbilical cord

Midgut elongates forming U shaped loop of intestine which communicates with the umbilical vesicle through omphalocentric duct

Herniation of midgut loop

Why does herniation of the midgut loop happen?

There is not enough space in the abdominal cavity for the rapid growth

The __________ limb of the midgut grows rapidly and forms small intestinal loops

cranial

The _______ limb develops the cecal swelling (diverticulum), the primordium of the cecum, and appendix

Caudal

While the midgut is inside of the umbilical cord, it rotates ___ degrees counterclockwise around the axis of the SMA

90

The first rotation of the midgut loop brings the _____ limb of the midgut loop to the right and the ____ limb to the left.

Cranial (small intestine)

Caudal (large intestine)

Intestines return to the abdomen. Small intestine returns first passing _____ to the SMA and occupies the central part of the abdomen.

posterior

The large intestine returns, it undergoes a ____ degree counterclockwise rotation

180

Intestines returning to the abdomen

Retraction of intestinal loops

As the intestine returns to the abdomen, it makes __ rotations and becomes __ into its normal position with the small bowel centrally located in the abdomen and the colon draping around the top and sides of the small intestine

2; fixed (fixation of intestines)

Congenital anomaly that occurs due to an abnormal rotation and fixation of the intestines during development. This process is interrupted or does not occur

Midgut malrotation

Intestines may only rotate 90 or 180 degrees

SI being on the right side of the abdomen and cecum displaces to abnormal location

Incomplete rotation

Abnormal fibrous bands leading to obstruction

Ladd’s bands

Abnormal positioning and fixation. prone to rotation and necrosis.

Volvulus

Malrotation of the midgut

SI on the right and colon on the left

Malrotation of the midgut

180 rotation did not happen

may be asymptomatic or have obstruction

Persistence of the herniation of abdominal contents usually intestines sometimes liver into the proximal part of the umbilical cord

Congenital omphalocele

Herniation of intestines into cord 1/5000 live births

Herniation of liver and intestines 1/10,000 births

Up to 50% associated with chromosomal abnormalities

Epidemiology and prevalence of congenital omphalocele

Congenital omphalocele

Congenital anomaly resulting in incomplete obliteration of the omphalomesenteric duct (vitelline duct)

Meckel’s diverticulum

Male to female 2:1

Epidemiology of Meckel’s diverticulum

Presence of ectopic tissue with Meckel’s’ diverticulum. Gastric or pancreatic tissue within the diverticulum increases the risk of complications like _____ or ________

bleeding or perforation

Painless rectal bleeding

Abdominal pain

Intestinal obstruction

Perforation

Complications: inflammation can mimic appendicitis, perforation, can cause obstruction through intussusception or volvulus

Clinical pictures of Meckel’s diverticulum

2 year-old male with history of constipation presented with one episode of painless hematochezia that occurred 1 hour prior to arrival. He had a benign abdominal exam. POCUS revealed a focal fluid collection in the RLQ with a bowel wall appearance containing a hyperechoic focus

Meckel’s diverticulum

Congenital disorder characterized by failure of neural crest cell formation

Absence of ganglion cells in myenteric and submucosal plexuses in the distal colon

Result is lack of peristalsis in affected segment

Hirschsprung disease

Hirschsprung disease

Delayed passage of meconium within first 48 hours of life

Progressive abdominal distension

Bilious vomiting

FTT

Enterocolitis

Clinical presentation of Hirschsprung disease

20-30 cm C shaped predominantly on the left side of the vertebral column

Duodenum

How many segments does the duodenum have?

4

What vertebral level is the duodenum positioned?

L1-L3

Segments of the duodenum

superior: intraperitoneal first 2-3 cm

Descending

horizontal

Ascending

Main vessels supplying the duodenum superior and inferior ________ arteries.

pancreaticoduodenal

Superior pancreaticoduodenal arteries branch from the ______ artery

celiac trunk → common hepatic → gastroduodenal

(foregut portion of duodenum)

The inferior pancreaticoduodenal arteries branch from the _____ artery.

SMA

(midgut portion of duodenum)

_______ branches supply the intraperitoneal portion of the duodenum

Duodenal

Duodenum

Brunner glands in submucosa

•Mucosa [shaped as villi]

• Surface epithelium

• Absorptive Cells [Enterocytes] Simple Columnar Cells with microvilli

• Goblet cells

• Crypts

• Lamina propria

• Muscularis mucosae

•Submucosa

• Brunner glands

•Muscularis Externa

•Adventitia

Layers of the duodenum

Brunner glands

Only seen in duodenum. Secrete alkaline mucus to protect duodenum from stomach acid and lubricates the digestive tract

More distal you go down GI tract, the more _____ cells

goblet

Jejunum

roller coaster appearance

Plicae circularis [valves of Kerckring]

Only in jejunum

•Mucosa- form villi

• Surface epithelium: Enterocytes- simple columnar cells with microvilli with goblet cells

• Lamina propria

• Muscularis mucosae

•Submucosa [no glands]

•Muscularis externa

•Adventitia

Layers of jejunum

Intraperitoneal organs have ____

serosa

Retroperitoneal does not have _____

serosa

Ileum

Peyer’s patches in lamina propria GALT

Lymphoid tissue, either as loose infiltrations or nodules are found _________ gastrointestinal tract (GALT or gut-associated lymphoid tissue).

throughout

•Mucosa- form villi, crypts

• Surface epithelium: Enterocytes- simple columnar cells with microvilli with goblet cells

• Lamina propria: Peyer's Patches - or of lymphatic tissue found in the intestinal wall (GALT).

• Muscularis mucosae

•Submucosa: connective tissue with permanent folds that circle the inner surface of the intestinal lumen to form (circular folds, folds of Kerckring)

•Muscularis externa

•Adventitia

Layers of ileum

Jejunum location is on the ___ side

left

Ileum location is ____ abdomen to the _____ side

lower, right

DJI

Connivant valves are

valves of Kircking

The feathery appearance of the small intestine is due to the circular folds and is most prominent in the _____.

jejunum

Orange- Cecum

Blue- ascending colon

Green- descending colon

Yellow- sigmoid colon

Sigmoid colon is normally towards the ____ side

left

Colon

No villi

Crypts of Lieberkühn

Tinea coli (3 bundles of smooth muscle outer longitudinal)

Lots of goblet cells

•Mucosa- villi are absent

• Surface epithelium: Enterocytes- simple columnar cells with microvilli with goblet cells

• Crypts of Lieberkuhn

• Lamina propria 

• Muscularis mucosae

• Submucosa 

•Muscularis externa

• Outer Longitudinal Layer - consolidated into three distinct bundles of smooth muscle (tinea coli).

Layers of the colon

Tinea coli (3 distinct bundles of smooth muscle outer longitudinal layer)

Colon

Peyer’s patches

Only in ileum

Recto-anal junction

Red circle sebaceous gland

other gland is apocrine/circumanal glands

Skeletal muscle with peripheral nuclei

The anal canal is the site where there is a transition from the simple columnar epithelium of the colon to the stratified squamous epithelium of skin

The pectinate line

•Colorectal Zone: left side of the specimen.

• Anal Glands: secrete mucus into the anal canal.

• Absorptive Cells (or Enterocytes) - simple columnar cells with microvilli (or brush border).

• Goblet Cells - very abundant and secrete mucus

• Pectinate Line: (Anal Transition Zone) - junction between the simple columnar epithelium of the colon and the stratified squamous epithelium of the skin. [stratified columnar]

• Smooth muscle

•Squamous Zone

• External anal sphincter

• Circumanal glands [apocrine]

• Sebaceous glands

• Skeletal muscle

Recto-Anal junction

Jejunal arteries branches from

SMA

Ileal arteries branches from

SMA

Vasa recta in ______ is longer than the vasa recta in ________

Jejunum; ileum

Ileocolic artery branches from _____

• Ileal branch

• Colic branch
  Appendicular branch

SMA

Right colic artery branches from ____ supplies mostly the ______

SMA; ascending colon

Middle colic artery branches from supplies some of the ______

SMA; transverse colon

Left colic artery branches from _____

• ascending branch

• descending branch

IMA

Sigmoidal arteries branch from ____

IMA

Superior rectal artery branches from _____ and supplies the ____ part of the rectum

IMA; proximal

Marginal arteries from SMA and IMA serve as

collaterals

3 arteries supply the rectum

Superior rectal artery

Middle rectal

Inferior rectal

Superior rectal artery is a branch of the

IMA

Middle rectal artery is a branch of the

left and right internal iliac arteries

Inferior rectal artery is a branch of the

internal pudendal artery

Referred pain from the appendix travels through _____ splanchnic nerves

lesser (T10)

Pain and the appendix

Atrial Fibrillation: Increases the risk of embolic events that can block the mesenteric arteries.

Advanced Age: More common in older adults due to age-related vascular changes.

Atherosclerosis: Patients with a history of coronary artery disease, peripheral artery disease, or cerebrovascular disease are at higher risk due to the potential for plaque rupture or thrombus formation.

Heart Failure: Reduced cardiac output can decrease mesenteric blood flow, increasing the risk of ischemia.

Recent Myocardial Infarction: Increases the risk of thromboembolism.

Hypercoagulable States: Conditions such as malignancy, thrombophilia, or recent surgery can predispose to thrombosis.

Risk factors for acute mesenteric ischemia

Atrial fibrillation

risk factor for acute mesenteric ischemia

The most common cause of acute mesenteric ischemia, where an embolus from the heart (often due to atrial fibrillation) lodges in the superior mesenteric artery (SMA), blocking blood flow.

Embolic occlusion

Acute mesenteric ischemia in patients with pre-existing atherosclerosis, where a thrombus forms at the site of atherosclerotic plaque, further narrowing or occluding the artery.

Thrombotic occlusion

Acute mesenteric ischemia in patients with severe hypotension or shock, where reduced blood flow leads to ischemia without a direct vascular occlusion

Non-occlusive mesenteric ischemia

Thrombosis of the mesenteric veins leads to impaired venous outflow, increasing intraluminal pressure, and leading to acute mesenteric ischemia.

Mesenteric venous thrombosis

Severe Abdominal Pain: Classically described as "pain out of proportion to the physical findings," meaning the intensity of pain is much greater than what is expected based on physical examination.

Nausea and Vomiting: Common symptoms, often accompanying the abdominal pain.

Diarrhea or Bloody Stools: May occur as the ischemia progresses, indicating mucosal injury and sloughing.

Abdominal Tenderness: Mild early on but can become more pronounced as ischemia leads to bowel infarction.

Systemic Signs: Fever, tachycardia, and signs of shock (e.g., hypotension) may develop as ischemia progresses to infarction and sepsis.

Clinical presentation of Acute mesenteric ischemia

Pain out of proportion to the physical findings, meaning the intensity of pain is much greater than what is expected based on physical examination.

Acute mesenteric ischemia

Age: More common in the elderly, particularly over the age of 60.

Chronic Constipation: Leads to increased colonic distension, which predisposes to ____.

Neuropsychiatric Disorders: Conditions like Parkinson's disease and dementia can lead to chronic constipation and immobility, increasing the risk.

Congenital Malformations: In children, malrotation of the intestines can predispose to _______.

History of Previous Volvulus: Increases the likelihood of recurrence.

High Fiber Diet: May contribute to large, bulky stools that increase colonic distension.

Risk factors for volvulus

Loop of intestine twists around itself and the mesentery that supports it, leading to a mechanical obstruction

Volvulus

Twisting of bowel → vascular compromise/edema → mechanical blockage → perforation/peritonitis

Progression of volvulus

Abdominal Pain

Abdominal Distension

Nausea and Vomiting

Constipation: obstipation

Shock

Clinical features of volvulus

Air within involved area

Coffee bean

dilated loop of colon. Apex points towards RUQ

Volvulus

Age: Most common in children between 6 months and 3 years old.

Male Gender: More common in boys than in girls.

Previous Viral Infection: Recent history of viral gastroenteritis or upper respiratory infection, which may lead to lymphoid hyperplasia.

Congenital Anomalies: Conditions like Meckel's diverticulum, polyps, or tumors can serve as a lead point for intussusception

Risk factors for intussusception

A segment of the intestine telescopes into an adjacent segment, leading to obstruction and potential ischemia.

typically involves the ileum telescoping into the colon at the ileocecal junction

Intussusception