patho sheet # 8 - h.h. Ibrahim al omari

Acute gastric ulceration :
Focal, acutely developing gastric mucosal defects that may appear after severe physiologic stress are called stress ulcers .
Generally there are many lesions located mainly in the stomach and occasionally the duodenum
Stressulcers are most commonly encountered in
1-severe trauma(major surgery , sepsis, and shock )
2-chonic exposure to gastric irritant drugs (NSAIDS , steroids )
3- extensive burns ( which is called carling ulcers 0 these carry a high risk of pe)
4- traumatic or surgical injury to the CNS (cushing ulcers ) these carry a high risk of perforation
The pathogenesis of these lesions is uncertain and may vary with the setting .
NSAIDS-induced ulsers are linked to decreased prostaglandin synthesis. The systemic acidosis that can accompany severe trauma and burns may contribute to mucosal injury which is rendered hypoxic by impaired mucosal blood flow with cranial lesions , direct stimulation of the vagal nuclei by increased intracranial pressure may cause gastric acid hypersecretion.
Acute stress ulcers are usually multiple located throughout the stomach and duodenum , they are small , circular and brown in color (why brown ?? bcz of te reaction between the acids and the blood)they vary in depth from erosion to those involving full mucosal thickness (true ulceration )
Clinically a high percentage of persons admitted to hospitals "I.C.U." with sepsis , severe burns or trauma develop stress ulcers.
These can be of no significance or can be life threatening .
Although prophylactic antacid regimens and blood transfusion may blunt the impact of stress ulcers , the single most important determinant of clinical outcome is the ability to correct the underlying condition . The gastric mucosa can recover completely if the person does not die from the primary disease .



GASTRIC TUMERS
*Gastric polyps:
The term polyp is applied to any nodule or mass that projects above the level of the surrounding mucosa.
Occasionally a lipoma or a lieomyoma arising in the wall of the stomach may protrude from under the mucosa to produce and apparent polypoid lesion . However , the use of the term polyp in the G.I.T is generally restricted to mass lesions arising in the mucosa .
Gastric polyps are uncommon and are found in about 0.4% of adults autopsies, as compared with colonic polyps , which are seen in 25%-50% of older persons .
In the stomach these are most frequently
1-hyperplastic polyps 80% - 85%
2-fundic gland polyps ~ 10%
3- adenomatous polyps ~ 5%
All three types arise in the setting of chronic gastritis and so are seen in the same potent population .
Hyperplastic polyps and fundic gland polyps are essentially innocuous .In contrast , these is a definite risk of an adenomatous poly harboring adenocarcinoma , which increases with polp signs .
Because the different types of gastric polyps cannot be reliably distinguished by endoscopy ,histological examination is mandatory .
Morphologically , hyperplastic polyps arise from an exuberant reparative response to chronic mucosal damage and have are composed of hyperplastic epithelium and inflamed edematous struma , they are not true neoplasm .
Fundic glands polyps are small collections of dilated corpus type gland thought be small hamartomes .
The less common adenomas contain dysplastic epithelium , and are true neoplasms.
Gastric Carcinoma :
Among the malignant tumors that occur in the stomach carcinomas is overwhelming the most important and the most common (90-95%) . next in frequency are lymphatic (4%) , carcinoids (3%) , and stomach tumors (2%).
Gastric Carcinoma is the second leading cause of cancer-related deaths in the world with a widely varying geographic induced with a 5 years survival rate less than 20% .
Gastric cancers share two 2 morphologic types , called intestinal and diffuse . the intestinal type is thought to arise from gastric mucus cells that have undergone intestinal metaplasia in the setting of chronic gastritis .
This patterns of cancers tends be better differentiated and is the more common type in high-risk populations . The diffuse variant is thought to arise de novo from native gastric mucosa cells , is not associated with chronic gastritis and tends to be poorly differentiated
Chronic gastritis associated with H.pylori infection constitutes a major risk factor for gastric carcinoma . The risk is particularly high in individual with chronic gastritis to the gastric pylorus and antrum .Gastritis is generally accompanied by sever gastritis atrophy and intestinal metaplasia , which are ultimately followed by dysplasia and cancers . chronic inflammation induced by H.pylori may release reactive oxygen species , which eventually cause DNA damage , leading to an imbalance between cell proliferation and apoptosis , practically in areas of tissue repair .
Notably , individual with H.pylori-associated duodenal ulcers are largely protected from developing gastric cancers(they don’t develop gastric cancers) .
*diffuse adenocarcinoma
The risk factor for this type of cancer remain undefined .mutations in E-cadherin, which are not detectable in intestinal-type cancers , are present in 50% of diffused cancers . A subset of patients may have a hereditary form of diffused gastric cancer, caused by germ-line mutation in E-cadherin . Mutations in FGFR2 ,a member of the fibroblast growth factor receptors family , and increased expression of metalloproteinases are present in about one-third of cases , but are absent in intestinal-type.
The location of gastric carcinomas within the stomach is as follows : pylorus and antrum , 50% to 60% ; carda,25% : and the reminder in the body and fundus .The lesser curvature is involved in about 40% and the greater curvature in 12% . Thus , a favored location is the lesser curvature of the antropyloric region.
Early gastric carcinoma is defined as a lesion confined to the mucosa and submucosa , regardless of the presence or absence of perigastric lymph node metastases .
Advanced gastric carcinoma is a neoplasm that has extended below the submucosa into the muscular wall.
The intestinal variant is composed of malignant cells forming neoplastic intestinal glands resembling those of colonic adenocarcinomas .The diffuse variant is composed of gastric-type mucosa cells that generally do not form glands but rather permeates the mucosa and wall as scattered individual "signet –ring" cells.
For obscure reasons , the earliest lymph node metastasis may sometimes involve a supraclavicular lymph node ( Virchow node) . Another somewhat unusual mode of intraperitoneal spread in females is to both the ovaries , giving rise to the so called Krikenberg tumor .
`Clinical futures
Both intestinal-type and diffuse gastric carcinoma are generally asymptomatic and can be discovered only by repeated endoscopic examination in persons at high risk. Advanced carcinoma also may be asymptomatic , but it often first comes to light because of abdominal discomfort or weight loss. Uncommonly , these neoplasms cause dysphagia when they are located in the cardia or obstructive symptomatic when they arise in the pyloric canal. The only hope for cure is early detection and surgical removal , because the most important prognostic indicator is stage of the tumor at the time of resection.

SMALL AND LARGE INTESTINES
Developmental anomalies:
Atresia , the complete failure of development of the intestinal lumen , and stenosis , narrowing of the intestinal lumen with incomplete obstruction , may affect any segment of the small intestine , but duodenal atresia is common.
Duplication usually takes the form of well-formed saccular to tubular cystic structure , which may or may not communicate with the lumen of the small intestine .
Meckel diverticulum is the most common and innocuous of the anomalies . it result from failure of involution of the omphalomesentric duct , leaving a persistent blind-ended tubular protrusion as long as 5 to 6 cm. the diameter is vareiable , sometimes approximating that of the small intestine itself. Such diverticula are usually in the ileum, about 80 cm proximal to the ileocecal valve.
Rarely , pancreatic rests are found in a Meckel diverticulum , and in about half of the cases there are heterotopic islands of functioning gastric mucosa. Peptic ulceration in the adjacent intestinal mucosa sometimes is responsible for mysterious intestinal bleeding or symptoms resembling acute appendicitis.
Omphaloceleis a congenital defect of the periumbilical abdominal musculature that creates a membranous sac , into which the intestines herniate.
Hirschsprung disease : ( congenital megacolon)
Distention of the colon to greater than 6 or 7 cm in diameter (megacolon) occurs as a congenital and as an acquired disorder . Hischsprung disease result when ,during development , the migration of neural crest-derived cells along the alimentary tract arrest at some point before reaching the anus . Hence , an aganglionic segment is formed that lack both the Meissner submucosal and Auerbach myenteric plexuses .This cause functional obstruction and progressive distention of the colon proximal to the affected segment . Ganglia are absent from the muscle wall and submucosa of the constricted segment but may be present in the dilated portion.
Genetically , hischsprung disease is heterogeneous , approximately 50% of familial cases result from mutation in RET gene and RET ligands , because this signal pathway is required for development of the myoenteric nerve plexus and provides direction to migrating neural crest cells. Many of the remaining cases arise from mutation in endothelin 3 and endothelin receptors . Hischsprung disease occurs in approximately 1 in 5000 to 8000 live bithths
Clinical features : in most cases a delay occurs in the initial passage of meconium which is followed by vomiting in 48 to 72 hours . when a very short distal segment of the rectum alone is involved , the obstruction may not be complete and may not produe manifestations until later in infancy.
The principal threat to life is superimposed enterocolitis with fluid and electrolyte disturbances . More rarely , the distended colon perforates, usually in the thin-walled cecum. The diagnosis is established by documenting the absent of ganglion cells in the nondistended bowel segment .


Patho sheet number :9
Done by : h.h. Ibrahim al omari