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Chapter 17 - GI

Congenital abnormalities

Agenesis very rare, can occur anywhere in GI tract

Atresia more common, most common near tracheal bifurcation, causes mechanical obstruction; esophageal atresia is

associated with cardiac defects, neurological disease, genitourinary malformations

Stenosis smaller, but sometimes patent opening, can cause obstruction and difficulities with swallowing; most

common in esophagus and duodenum, imperforate anus is most common (caused by failure of the cloacal diaphragmto involude)

Duodenal atresia double bubble sign on xray, associated with Downs syndrome

Fistulae occur in trachea and esophagus in esophageal atresia; can lead to aspiration, suffocation, pneumonia, and severe

electrolyte imbalances

Duplications congenital duplication cysts contain redundant musclular layers, can be present in esophagus, small intestine or

colon

Diaphragmatic hernia can cause hypoplastic lungs; caused by incomplete formation of the thoracic diaphragm

Omphalocele ventral wall defect, intestines covered in peritoneum, usually associated with other defects (CDH, etc)

Gastroschisis ventral wall defect, intestines not covered in peritoneum

Ectopic tissues (developmental rests)

Ectopic gastric mucosa aka inlet patch - located in upper third of esophagus; usually asymptomatic, can cause

dysphagia, esophagitis, Barret esophagus, adenocarcinoma

Ectopic pancreatic tissue usually in esophagus or stomach, usually asymptomatic, can cause local inflammation and

damage that can lead to scarring and obstruction; can mimic invasive cancer

Gastric heteropia small patches of ectopic gastric mucosa in the small intestine or colon, can lead to occult blood loss

due to peptic ulceration

Diverticulum blind outpouching of the intestine lined by mucosa that communicates with the lumen, includes all three layers

of the bowel wall

Meckel diverticulum Rule of 2s: 2 feet from ileocecal valve (in ileum), 2% of the population, 2 inches long,

symptomatic by age 2; caused by failure of involution of the vitelline duct; may be associated with peptic

ulceration/occult bleeding and abdominal pain

Pyloric hyperplastic stenosis males>females, high concordance in twins, associated with Turner syndrome and trisomy 18,

usually presents in 2nd-3rd week of life with new-onset regurgitation, projectile, nonbilious vomiting, hyperperistalsis and

ovoid mass (from hyperplastic muscularis propria); surgical splitting is curative; can be acquired in adults due to peptic

ulceration and cancer causing an obstruction

Hirshprungs Disease aka congenital aganglionic megacolon usually isolated, sometimes associated with downs syndrome,

due to failure of neural crest cells to migrate, lack of both GI plexuses; genetic component (heterozygous loss of functionmutation in RET), males>females in incidence but females>males in severity, diagnosis by biopsy (H&E morphology and

immuno stains for acetylcholinesterase which will be increased1), rectum is always affected (sometimes sigmoid or entire

1Normal nerves do not stain for AChE, but increased AChE expression is associated with the hypertrophied extrinsic nerve fibres of the aganglionic segment in HSCR. False

negative results are primarily related to age, and an absence of AChE reaction does not exclude HSCR in neonates within the first 3 weeks after birth. The presence of fine

AChE neurofibrils in the ganglionated segment has contributed to the debate surrounding intestinal neuronal dysplasia. Quantitative assay of cholinesterase activity confirms

the pattern of histochemical staining. AChE is particularly increased in relation to butrylcholinesterase, with one molecular form, the G4 tetrameric form, predominating. It is

likely that the raised levels of AChE in aganglionic tissue are the transcriptional consequence of the abnormalities in signalling molecules that characterize HSCR. Evidence

suggests that this AChE is functioning in a nonenzymatic capacity to promote cell adhesion and differentiation and that the hypertrophied nerves and neurofibrils may be the

result of this increased AChE expression.

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colon), proximal colon may be dilated (megacolon) and distal will be contracted; clinically presents as neonate without

meconium and obstructive constipation (occasional passage of stool in mild cases), major complications are enterocolitis,

electrolyte disturbances, perforation, peritonitis; tx: surgical resection and anastamosis (may take years to be normal)

Acquired megacolon Chagas disease (actually has loss of ganglia), neoplasm obstruction, inflammatory stricture

Toxic megacolon complicates ulcerative colitis, visceral myopathy, or psychosomatic

Esophagus

Nutcracker esophagus periodic, short-lived esophageal obstruction

Diffuse esophageal spasm can result in functional obstruction and pseudo diverticulae (lack muscularis)

Zenker diverticulum (pharyngoesophageal diverticulum) located above UES, can be large and accumulate food, which causes

regurgitation

Traction diverticulum midpoint in esophagus

Epiphrenic diverticulum above LES

Stenosis can impede food passage, most often due to inflammation and scarring from GERD, irradiation, caustic injury;

progressive dysphagia (solids first, then liquids pts may prefer softer foods without realizing)

Esophageal mucosal webs ledge-like protrusions that can cause obstruction, usually women>40, associated w GERD, chronicGvH, blistering skin diseases; composed of connective tissue and epithelium; sx: dysphagia with incompletely chewed food

Paterson-Brown-Kelly or Plummer-Vinson syndromes associated with upper esophageal webs, iron-deficiency

anemia, glossitis, and chelosis

Esophageal rings (Shatzki rings) more circumferential and thicker than webs, include mucosa, submucosa, and sometimes

hypertrophic muscularis propria; A and B types (depending on location)

Achalasia Triad: increased tone of LES, imcomplete smooth muscle relaxation in LES2, and aperistalsis; causes obstruction;

primary caused by failure of distal esophageal inhibitory neurons in vagus nerve or dorsal motor nucleus of the vagus;

secondary caused by Chagas disease (dystruction of myenteric plexus, failure of peristalsis, and esophageal diliation

(megaesophagus)) (can also affect other areas of GI tract; tx: laproscopic myotomy and pneumatic balloon dilitation and Botox

injections to inhibit LES cholinergic neurons

Acalasia-like disease caused by diabetic autonomic neuropathy, malignancy, amyloidosis, sarcoidosis, lesions of dorsal motor

nuclei (polio, surgical ablation)

Esophagitis p 768

2Release of nitric oxide and vasoactive intestinal polypeptide from inhibitory neurons, along with interruption of normalcholinergic signaling, allows the LES to relax during swallowing.