Diverticulosis pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Seyedmahdi Pahlavani, M.D. [2]
Overview
The development of colonic diverticuli is the result of weakening in the muscular layer of the colonic wall. Additional factors that may be critical in the development of diverticulosis include increased motility and increased cooncentration of VIP.[1][2][3][4][5][6]
Pathogenesis
Weakening of Colonic Muscular Layer
- The development of colonic diverticuli is the result of weakening in the muscular layer of the colonic wall.
- The most common colonic sites of diverticula development are regions of muscular weakness, which correspond to locations where the vasa recta penetrate the circular muscle layer of the colon[7][1].
- The development of diverticula in the sigmoid colon may be explained by Laplace’s law: pressure (P) is proportional to wall tension (T) and is inversely proportional to bowel radius (R), where k is a conversion factor (P = kT ÷ R). Since the sigmoid colon is the segment of the colon with the smallest diameter, it is the site of the highest pressure during segmentation of the colon.[8]
- A typical colonic diverticulum is a "false" or pulsion diverticulum, in which the mucosa and submucosa herniate through the muscle layer, covered only by serosa (shown below).
Abnormal Colonic Motility
- Abnormal colonic motility is an important predisposing factor in the development diverticula.
- Patients with diverticulosis have exaggerated segmentation contractions in which segmental muscular contractions separate the lumen into chambers.
- It is hypothesized that the increase in intraluminal pressure predisposes to herniation of mucosa and submucosa.[2][3][4][5]
Additional Factors
- Increased level of chemical mediators such as vasoactive intestinal peptide (VIP) is also thought to play a critical role in the development of colonic diverticula.[6]
Pathogenesis of Complicated Diverticulosis
Diverticular bleeding
- As a diverticulum herniates, the penetrating vessel responsible for the wall blood blood supply weakness and is draped over the dome of the diverticulum, separated only from the bowel lumen by mucosa.[7][1]
- Over time, the vasa recta is exposed to injury along its luminal aspect, leading to eccentric intimal thickening and thinning of the media.
- These changes may result in segmental weakness of the artery, predisposing to rupture into the lumen.[7][1]
Diverticulitis
The primary process is thought to be an erosion of the diverticular wall by increased intraluminal pressure or inspissated food particles.
- Inflammation and focal necrosis ensue, resulting in perforation and inflammation.[9]
References
- ↑ 1.0 1.1 1.2 1.3 Meyers MA, Volberg F, Katzen B, Alonso D, Abbott G (1973). "The angioarchitecture of colonic diverticula. Significance in bleeding diverticulosis". Radiology. 108 (2): 249–61. doi:10.1148/108.2.249. PMID 4541643.
- ↑ 2.0 2.1 MORSON BC (1963). "THE MUSCLE ABNORMALITY IN DIVERTICULAR DISEASE OF THE COLON". Proc. R. Soc. Med. 56: 798–800. PMC 1897181. PMID 14080071.
- ↑ 3.0 3.1 Chia JG, Wilde CC, Ngoi SS, Goh PM, Ong CL (1991). "Trends of diverticular disease of the large bowel in a newly developed country". Dis. Colon Rectum. 34 (6): 498–501. PMID 1645247.
- ↑ 4.0 4.1 Trotman IF, Misiewicz JJ (1988). "Sigmoid motility in diverticular disease and the irritable bowel syndrome". Gut. 29 (2): 218–22. PMC 1433293. PMID 3345933.
- ↑ 5.0 5.1 Bassotti G, Battaglia E, Spinozzi F, Pelli MA, Tonini M (2001). "Twenty-four hour recordings of colonic motility in patients with diverticular disease: evidence for abnormal motility and propulsive activity". Dis. Colon Rectum. 44 (12): 1814–20. PMID 11742167.
- ↑ 6.0 6.1 Milner P, Crowe R, Kamm MA, Lennard-Jones JE, Burnstock G (1990). "Vasoactive intestinal polypeptide levels in sigmoid colon in idiopathic constipation and diverticular disease". Gastroenterology. 99 (3): 666–75. PMID 1696228.
- ↑ 7.0 7.1 7.2 Meyers MA, Alonso DR, Baer JW (1976). "Pathogenesis of massively bleeding colonic diverticulosis: new observations". AJR Am J Roentgenol. 127 (6): 901–8. doi:10.2214/ajr.127.6.901. PMID 1087123.
- ↑ PAINTER NS, TRUELOVE SC, ARDRAN GM, TUCKEY M (1965). "SEGMENTATION AND THE LOCALIZATION OF INTRALUMINAL PRESSURES IN THE HUMAN COLON, WITH SPECIAL REFERENCE TO THE PATHOGENESIS OF COLONIC DIVERTICULA". Gastroenterology. 49: 169–77. PMID 14323727.
- ↑ Rege RV, Nahrwold DL (1989). "Diverticular disease". Curr Probl Surg. 26 (3): 133–89. PMID 2651018.