Pathologies of the Small Intestine

The Anatomy of the Small Intestine 

The small intestine is a six to seven-meter long organ located in the abdominal region, and comprising three distinct parts; the duodenum, Jejunum, and the ileum. The duodenum is the uppermost part of the small intestine, which is connected to the liver by the hepatoduodenal ligament, and it descends and wraps around the pancreas (Li et al., 2016). The superior mesenteric and the gastroduodenal arteries supply blood to the duodenum while the superior mesenteric vein drains blood from this part of the small intestine. The Brunner’s Gland, which produces mucus that neutralizes the acidic chime from the stomach and the Crypts of Lieberkühn that is lined with goblet cells and enterocytes responsible for the production of cholecystokinin and secretin hormones for the regulation of digestion are the primary parts of the duodenum.

Brunner’s Glands (DG), Ducts of Brunner’s glands that empty into Crypts of Lieberkühn in mucosa (D), and muscularis mucosae (MM) 

The jejunum is the middle part of the small intestine that is characterized by simple squamous epithelia that can turn into villi and, which is continuous with the Crypts of Lieberkühn. Literature suggests that the lamina propria is the small intestine is the primary part of the villi, and it surrounds the Crypts of Lieberkühn (Li et al., 2016). The same cited literature indicates that goblet cells of the jejunum contain mucin-secreting cells that protect and lubricate the whole of the small intestine and the rest of the gastrointestinal tract while the plicae criculares are foldings within the jejunum that increase its surface for enzymatic activity and the absorption of dietary lipids, carbohydrates, phosphate, and some folate, especially in the mucosal and submucosal folds. To enable its functioning, the jejunum is supplied with blood by the superior mesenteric artery while the superior mesenteric vein empties blood from it. 

The ileum is the lower part of the small intestine, which is made up of the mucus-secreting goblet cells, cup cells, and Peyer’s Patches. This region of the small intestines is supplied with blood by the superior mesenteric artery while the superior mesenteric vein drains blood back to the he heart for oxygenation. The ileum is a site for the absorption of cobalamin (B12), which binds to receptors before entering the enterocyte.

Physiology and Function 

Enzymes secreted into the small intestine by the pancreas and the liver complete much of the chemical digestion on this part of the gastrointestinal tract. Furthermore, the small intestine is responsible for the absorption of digested nutrients, which is enabled by the numerous villi found lining the intestinal walls. The villi has enterocytes lining the lumen of the intestine and having microvilli that increase the surface area for absorption of nutrients and lacteals, which are highly permeable and containing fenestrated capillaries (Li et al., 2016). Notably, the food that remains undigested and unabsorbed is passed into the large intestine. 

Diseases of the Small Intestine 

Whipple’s Disease 

Whipple’s Disease is an uncommon systematic infection affecting the digestive system and joints. The disease interferes with the normal digestion of food in the body through impairing food breakdown, which hampers the ability of the body to absorb digested food nutrients. The disease was first discovered in 1907, and ninety percent of cases discovered so far involve Caucasian men aged between forty and fifty years and farmers or outdoor workers (Fenollar, Puéchal, & Raoult, 2007). 

The etiology of the disease indicates that it is a bacterial infection by T. whipplei, which is found within the environment and healthy carriers. The bacteria causes immune deficiencies that result in the inability of the white blood cells to digest bacteria. On its diagnosis, literature indicates that the disease is characterized by possible thickening of the gastrointestinal walls, the infiltration of mesenteric fact, or retroperitoneal adenopathy (Fenollar, Puéchal, & Raoult, 2007). The clinical manifestations of Whipple’s Disease considers the gastrointestinal dominance of symptoms could migrate symmetrically, and that such migration could cause delays in diagnosis. The disease is also manifested by non-erosive polyarthritis in the wrists, ankles, and knees (Fenollar, Puéchal, & Raoult, 2007). The cited literature reports further that neurotically involvement could occur in between twenty-one and forty-three percent of the reported cases. At the time of diagnosis, eighty-five percent of the patients had sweats, fever, lymphadenopathy, weight loss, and diarrhea. The symptoms could be managed by antibiotic treatment, and the absence of proper treatment could be fatal. 

Celiac Disease 

The disease is a genetic autoimmune condition that elicits both an innate and adaptive response to the digestion of gluten. The inflammatory responses result in damaged mucosa, which leads to intraepithelial lymphocytosis as well as villi atrophy (Green & Cellier, 2007). On the pathogenesis of the disease, it is reported that it causes gliadin to pass through the epithelium as well as the production of macrophages that react and present the antigen on the surfaces of their cells. The latter cited literature indicates further that CD4 T cells react with gliadin. The disease also raises the rate of attack on the mucosa of the intestinal walls by cytokines and the production of B-Cells that target gliadin and tissue transglutaminase. The disease’s symptoms could be both intestinal and extra-intestinal, including vomiting, abdominal pain, diarrhea, anemia, arthritis, increase liver enzyme levels, and neurologic abnormalities among others. Biopsy and blood smears are two of the described tests that could be done in the diagnosis of the disease. Genetic factors, including mutation, ingestion of gluten, and environmental factors, such as viral infections and feeding, affect the etiology of the disease. Children and women of European descent are identified in the literature as the high-risk groups for the disease. 

Small Intestine Cancer 

Although cancer of this type is very rare, it has been growing in prevalence in recent years. Small intestine cancers develop from only 2.4% of gastrointestinal tumors. Notably, adenocarcinoma, a type of cancer of the small intestine, affects the duodenum, carcinoids, and lymphomas affect the ileum and jejunum while sarcomas are evenly distributed (Li et al., 2016). On the epidemiology of the disease, literature reports that only close to 5300 hundred cases out of which 1100 are fatal are reported annually (Li et al., 2016). The disease has notably higher incidence rates among ethnic Hawaiians, African Americans, and New Zealanders than other groups while it is rare in Romania and other nations in Eastern Europe. The risk factors for the disease include the intake of alcohol, smoking cigarettes, and dietary issues. Furthermore, the risk of contracting the disease increase with age. Only so much is known about the etiology of the disease with some studies reporting an association with gene mutations (Li et al., 2016). 

The signs and symptoms of the disease include jaundice, diarrhea, anemia, gastrointestinal bleeding, weight loss, vomiting, and abdominal pain. The diagnosis of the disease is difficult, which delays the onset of interventions to manage the condition. The diagnosis of the disease is done using computed tomography, bleeding scans and angiography, noninvasive barium studies, capsule endoscopy, and others. Radiations, chemotherapy, and surgery are the most common treatments given to people living with the disease. 

Crohn’s Disease 

Characterized by the inflammation of the lower or upper gastrointestinal tract, Crohn’s Disease is among the group of diseases that are referred to as Inflammatory Bowel Syndrome. The diagnosis of the disease is done using enteroscopy, MRI of the abdomen, capsule endoscopy, CT scans of the abdomen, colonoscopy, and barium enema. On its epidemiology, studies indicate that it could occur at an age, but mostly happens in persons aged between fifteen and thirty-five years. While its etiology is unknown, genetic factors and immune responses could lead to the disease ( Marks et al., 2010) . The signs and symptoms of the disease include abdominal pain, diarrhea, weight loss, fever, and blood in the stool. The common treatments for the disease include diet and nutrition, stress management, prescription medications, and surgery. 

References 

Fenollar, F., Puéchal, X., & Raoult, D. (2007). Whipple's disease.  New England Journal of Medicine ,  356 (1), 55-66. 

Green, P. H., & Cellier, C. (2007). Celiac disease.  New england journal of medicine ,  357 (17), 1731-1743. 

Irimia, R. E., & Gottschling, M. (2016). Taxonomic revision of Rochefortia Sw.(Ehretiaceae, Boraginales).  Biodiversity Data Journal , (4). 

Li, J., Wang, Z., Liu, N., Hao, J., & Xu, X. (2016). Small bowel adenocarcinoma of the jejunum: a case report and literature review.  World journal of surgical oncology ,  14 (1), 177. 

Marks, D. J. B., Rahman, F. Z., Sewell, G. W., & Segal, A. W. (2010). Crohn’s Disease an Immune Deficiency State. Clinical Reviews in Allergy & Immunology , 38 (1), 20–31. 

Part 2: Intestinal Transplantation 

Intestinal transplantation has evolved over the past years from what was an experimental procedure to its present consideration as the only long-lived treatment options for persons living with intestinal failure or those who have developed irreversible complications that are associated with prolonged usage of parenteral nutrition. The number of people who have had intestinal transplantation has risen sharply from only five in 1990 to more than one hundred and forty-six in 2016 in the US alone ( OPTN, 2019 ). Nevertheless, it is unfortunate that the mismatch between demand and supply of the organ has resulted in increased waiting times for people wishing to have the procedures done on them, especially for patients who are younger than a year (Middleton & Jamieson, 2015). 

Advancements in medical technologies over the years are accredited to the growing levels of success for intestinal transplants. For example, according to Okumura and Mester (2012) and Szor, Ursoline, and & Herman (2013), the graft and patient survival rates are presently comparable with those of the heart, liver, and lungs, which was never the case before the 70s when the calcineurin inhibitor was developed. Intestinal transplants have been found to improve the quality of lives of patients, and this measure of the success of such procedures has been improving over time, which is why it can be compared to that of patients who opt for the uncomplicated parenteral nutrition. The most recent findings of the utilization of more targeted immunosuppression with antibodies that deplete lymphocytes, as well as less potent immunosuppression maintenance, indicate that further improvements in one-year survival could reach ninety percent for some of the cases involving the procedure. 

As it is the case for most medical procedures, the timing of small intestine transplantation is critical for the survival and success rates of the patients, and they should always be referred for such assessments before they are debilitated and before they could develop inadequate venous access, which has the adverse implication of raising the risk that the procedure may not be successful (Carrel, 2001). 

References 

Carrel, A. (2001). The transplantation of organs: a preliminary communication. 1905 [classical article].  The Yale journal of biology and medicine ,  74 (4), 239. 

Middleton, S. J., & Jamieson, N. V. (2015). The current status of small bowel transplantation in the UK and Internationally.  Gut ,  54 (11), 1650-1657. 

Okumura, M., & Mester, M. (2012). Coming of age of small bowel transplantation a historical perspective. In  Transplantation proceedings  (Vol. 24, No. 3, pp. 1241-2). 

Organ Procurement and Transplantation Network - OPTN . (2019).  Optn.transplant.hrsa.gov . Retrieved 1 April 2019, from https://optn.transplant.hrsa.gov/ 

Szor, D., Ursoline, M., & Herman, P. (2013). Adenoma hepático.  ABCD. Arquivos Brasileiros De Cirurgia Digestiva (São Paulo) ,  26 (3), 219-222. doi:10.1590/s0102-67202013000300012