PA 534 - Week 8-10: GI I-III

Hiatal hernia definition

Herniation of stomach or abdominal contents into mediastinum through esophageal hiatus

Most common type of hiatal hernia

Type I: Sliding hiatal hernia

Type I sliding hernia anatomy

GE junction and gastric cardia slide upward into thorax

Cause of Type I sliding hernia

Weak phrenoesophageal ligament and widened diaphragmatic hiatus

Risk factors for sliding hernia

Obesity, pregnancy, chronic straining

Clinical significance of Type I hernia

Commonly associated with GERD

Type II hiatal hernia

Pure paraesophageal hernia

Anatomy of Type II hernia

Gastric fundus herniates; GE junction stays in normal position

Complications of paraesophageal hernia

Gastric volvulus, obstruction, strangulation

Type III hiatal hernia

Mixed sliding and paraesophageal hernia

Type IV hiatal hernia

Stomach + other organs (e.g., colon, small bowel) herniate into chest

Management of Type II–IV hernias

Surgical repair if large or symptomatic

Definition of ventral hernia

Hernia due to defect in anterior abdominal wall

Types of ventral hernias

Epigastric, umbilical, incisional, hypogastric

Cause of umbilical hernia in children

Failure of umbilical ring to fuse properly

Umbilical hernia management in kids

Observe until age 4 unless complications arise

Adult umbilical hernia characteristics

Rarely close spontaneously; increase in size

Contents of adult umbilical hernia

Usually preperitoneal fat or omentum; sometimes bowel

Risk factors for adult umbilical hernia

Multiple pregnancies, ascites, obesity, tumors

Incisional hernia definition

Herniation through a prior surgical site

Rate of incisional hernias post-surgery

Occurs in 10–30% of abdominal surgeries

Main risk factor for incisional hernia

Wound infection (increases risk up to 80%)

Obesity and hernia risk

Increases intra-abdominal pressure and poor wound healing

Other incisional hernia risk factors

Diabetes, smoking, age, coughing, collagen defects

Surgical factors increasing hernia risk

Small fascial bites, tight closures, poor technique

Most common hernia location

Inguinal region (75% of all hernias)

Most common type of inguinal hernia

Indirect inguinal hernia

Anatomy of indirect hernia

Passes through internal ring, canal, and external ring

Cause of indirect inguinal hernia

Patent processus vaginalis (congenital)

Direct inguinal hernia anatomy

Through weakness in transversalis fascia, within Hesselbach’s triangle

Borders of Hesselbach's triangle

Medial: rectus abdominis; Lateral: inferior epigastric vessels; Inferior: inguinal ligament

Diagnosis of inguinal hernia

Physical exam or ultrasound (100% sensitivity

Diaphragmatic hernia definition

Abdominal contents herniate into thorax via diaphragm defect

Types of diaphragmatic hernia

Congenital (CDH) and traumatic (TDH)

Most common CDH location

Left posterolateral (Bochdalek)

CDH complications

Pulmonary hypoplasia, PPHN, GER, cardiac dysfunction

Eventration

Ballooning of thin

Diagnosis of CDH

Prenatal ultrasound or postnatal imaging

TDH cause

Penetrating trauma > blunt trauma (e.g., MVA)

TDH presentation

Delayed chest

Tension enterothorax

Bowel herniates into thorax → ischemia and lung compression

IBS definition

Functional GI disorder with abdominal pain and altered bowel habits

IBS-D

Diarrhea-predominant irritable bowel syndrome

IBS-C

Constipation-predominant IBS

IBS-M

Mixed diarrhea and constipation IBS

IBS pathophysiology

Visceral hypersensitivity, altered motility, dysbiosis, ENS dysfunction

Psychosocial role in IBS

Stress, anxiety, depression worsen symptoms

IBD definition

Chronic GI inflammation due to immune dysregulation

Forms of IBD

Crohn’s disease and ulcerative colitis

Crohn’s features

Transmural, granulomatous inflammation; any GI segment

UC features

Mucosal inflammation; limited to colon

Crohn’s cytokines

↑ Th1, Th17; TNF-α central; IL-10 deficiency

UC immune dysregulation

T-cell dysregulation (e.g., IL-2 involvement)

Microbiome and IBD

Dysbiosis alters immune response to commensal microbes

Diverticulosis

Outpouching of mucosa

MC location of diverticula

Sigmoid colon

Risk factors for diverticulosis

Low fiber, constipation, aging, connective tissue disorders

Diverticular bleeding

Painless bleeding from vasa recta rupture; MC cause of painless GI bleeding in elderly

Diverticulitis

Inflamed diverticulum; LLQ pain + fever; may mimic appendicitis

Diverticulitis complications

Abscess, perforation, fistula, obstruction

Opioids in diverticulosis

Contraindicated due to ↑ intraluminal pressure

Volvulus definition

Twisting of bowel around mesentery causing obstruction

MC site of volvulus

Sigmoid colon (~90%)

Sigmoid volvulus x-ray sign

“Coffee bean” sign; apex toward RUQ

Sigmoid volvulus enema finding

“Bird’s beak” sign

Cecal volvulus cause

Nonfixation of cecum and ascending colon

Cecal volvulus imaging

Kidney-shaped loop in LUQ on x-ray

Volvulus risk factors

Chronic constipation, megacolon, narrow mesenteric base

Benign esophageal tumors are most often what type?

Leiomyoma (smooth muscle origin) is the most common.

Where does esophageal squamous cell carcinoma typically arise?

Middle third of the esophagus.

Major risk factors for squamous cell carcinoma of the esophagus?

Smoking, alcohol, poor nutrition, low fruit & vegetable intake.

Histologic hallmark of esophageal SCC?

Invasive nests of atypical squamous cells with keratin pearls.

Most common esophageal cancer in the US?

Adenocarcinoma.

Where does esophageal adenocarcinoma most commonly arise?

Gastroesophageal (GE) junction.

Main risk factor for esophageal adenocarcinoma?

Barrett's esophagus (due to chronic GERD).

Microscopic appearance of esophageal adenocarcinoma?

Invasive atypical glands with bizarre nuclei, mitoses, apoptotic debris.

Two histologic types of gastric adenocarcinoma?

Intestinal type and diffuse type.

What infection is intestinal-type gastric adenocarcinoma associated with?

Chronic Helicobacter pylori infection.

Histology of diffuse-type gastric adenocarcinoma?

Signet ring cells with mucin-pushed nuclei and no gland formation.

Which type of gastric adenocarcinoma is more common in younger patients?

Diffuse type.

What is a gastrointestinal stromal tumor (GIST) derived from?

Interstitial Cells of Cajal.

Most common gene mutations in GISTs?

c-KIT or PDGFRA.

Immunohistochemistry marker for GISTs?

CD117 (c-KIT).

Main predictor of metastasis in GISTs?

Tumor size >10 cm.

Origin of gastric MALT lymphoma?

Mucosa-associated lymphoid tissue (B-cell origin).

Strongest risk factor for gastric MALT lymphoma?

Chronic H. pylori infection.

Histologic hallmark of MALT lymphoma?

Lymphoepithelial lesions and diffuse lymphoid infiltration.

Aberrant immunohistochemistry marker in MALT lymphoma?

CD43 on B-cells.

Most common malignancy of the small intestine?

Adenocarcinoma.

Most common site of small intestine adenocarcinoma?

Duodenum (esp. ampulla of Vater).

Histologic features of small bowel adenocarcinoma?

Glandular structures with varying differentiation.

Common presentation of small intestine adenocarcinoma?

Obstruction, anemia, weight loss.

Main type of NET in distal small bowel?

Serotonin-producing carcinoid (enterochromaffin cells).

Histologic hallmark of carcinoid tumors?

Salt-and-pepper chromatin, bland nuclei.

Markers for neuroendocrine tumors?

Chromogranin, synaptophysin.

Definition of colon polyp?

Visible mucosal protrusion in the colon.

Which polyp histology has highest malignancy risk?

Villous > tubulovillous > tubular.

What gene is mutated first in colon cancer adenoma-carcinoma sequence?

APC gene (tumor suppressor).

What gene mutations occur in progression of colon cancer?

KRAS

Microsatellite instability (MSI) is associated with which syndrome?

Lynch syndrome (HNPCC).