Digestive System: Anatomy of the Small and Large Intestines PDF

CBS II: BLOCK V, MODULE 1, CASE 3 DIGESTIVE SYSTEM ​ The mucosa is the innermost layer and it consists of three ANATOMY OF THE SMALL AND LARGE INTESTINES...

CBS II: BLOCK V, MODULE 1, CASE 3 DIGESTIVE SYSTEM ​ The mucosa is the innermost layer and it consists of three ANATOMY OF THE SMALL AND LARGE INTESTINES layers: epithelium, lamina propria, and muscularis GROSS ANATOMY mucosae. Schwartz Principles of Surgery, 11th Ed., Chapter 28 ○​ The epithelium is exposed to the intestinal lumen Gross Anatomy of the Small Intestine and is the surface through which absorption from and ​ The small intestine is a tubular structure that extends from secretion into the lumen occurs. the pylorus to the cecum. The estimated length varies ○​ The lamina propria is located immediately external depending on whether radiologic, surgical, or autopsy to the epithelium and consists of connective tissue measurements are made. and a heterogeneous population of cells. ​ In the living, it is thought to measure 4 to 6 meters. The ​ It is demarcated from the more external small intestine consists of three segments lying in series: submucosa by the muscularis mucosae, a the duodenum, the jejunum, and the ileum. thin sheet of smooth muscle cells. ○​ The duodenum, the most proximal segment, lies in ○​ The mucosa is organized into villi and crypts (crypts the retroperitoneum immediately adjacent to the of Lieberkuhn). Villi are finger-like projections of head and inferior border of the body of the pancreas. epithelium and underlying lamina propria that contain ​ The duodenum is demarcated from the blood and lymphatic (lacteals) vessels that extend stomach by the pylorus and from the jejunum into the intestinal lumen. by the ligament of Treitz. ​ Intestinal, epithelial cellular proliferation is confined to the ○​ The jejunum and ileum lie within the peritoneal crypts, each of which carries 250 to 300 cells. cavity and are tethered to the retroperitoneum by a ○​ All epithelial cells in each crypt are derived from an broad-based mesentery. unknown number of multipotent stem cells located at ​ No distinct anatomical landmark demarcates or near the crypt’s base. the jejunum from the ileum; the proximal 40% ○​ Our understanding of these crypt cells is rapidly of the jejunoileal segment is arbitrarily defined expanding. It appears that there are two subgroups as the jejunum and the distal 60% as the of intestinal stem cells, with specific cell markers. ileum. ○​ Bmi1-positive cells are usually quiescent, ○​ The ileum is demarcated from the cecum by the radiation-resistant cells that are induced by injury, ileocecal valve. while LGR5-positive cells facilitate homeostatic vs. ​ The small intestine contains internal mucosal folds known injury-induced regeneration and are radiation as plicae circulares or valvulae conniventes that are sensitive. visible upon gross inspection. ​ The stem cells can differentiate along one of four ○​ These folds are also visible radiographically and help pathways that ultimately yield enterocytes and goblet, in the distinction between small intestine and colon, enteroendocrine, and Paneth cells. which does not contain them, on abdominal ○​ Except for Paneth cells, these lineages complete radiographs. their terminal differentiation during an upward ○​ These folds are more prominent in the proximal migration from each crypt to adjacent villi. intestine than in the distal small intestine. ○​ The journey from the crypt to the villus tip is ○​ Other features evident on gross inspection that are completed in 2 to 5 days and terminates with cells more characteristic of the proximal than distal small being removed by apoptosis and/or exfoliation. intestine include larger circumference, thicker wall, ​ Thus, the small-intestinal epithelium undergoes less fatty mesentery, and longer vasa recta (Fig. continuous renewal, making it one of the body’s most 28-1). dynamic tissues. ​ Gross examination of the small-intestinal mucosa also ​ The high cellular turnover rate contributes to mucosal reveals aggregates of lymphoid follicles. resiliency but also makes the intestine uniquely ○​ Those follicles, located in the ileum, are the most susceptible to certain forms of injury such as that induced prominent and are designated Peyer’s patches. by radiation and chemotherapy. ​ Most of the duodenum derives its arterial blood from ​ Enterocytes are the predominant absorptive cell of the branches of both the celiac and the superior mesenteric intestinal epithelium. Their apical (lumen-facing) cell arteries. membrane contains specialized digestive enzymes, ○​ The distal duodenum, the jejunum, and the ileum transporter mechanisms, and microvilli that are estimated derive their arterial blood from the superior to increase the absorptive surface area of the small mesenteric artery. intestine by up to 40-fold. ​ Their venous drainage occurs via the superior mesenteric ​ Goblet cells produce mucin believed to play a role in vein. mucosal defense against pathogens. ​ Lymph drainage occurs through lymphatic vessels ​ Enteroendocrine cells are characterized by secretory coursing parallel to corresponding arteries. granules containing regulatory agents and are discussed ○​ This lymph drains through mesenteric lymph nodes in greater detail in the “Endocrine Function” section. to the cisterna chyli, then through the thoracic duct, ​ Paneth cells are located at the base of the crypt and and ultimately into the left subclavian vein. contain secretory granules containing growth factors, ​ The parasympathetic and sympathetic innervation of the digestive enzymes, and antimicrobial peptides, through small intestine is derived from the vagus and splanchnic which they control the host-microbe interaction and nerves, respectively. influence the intestinal microbiome. ​ In addition, the intestinal epithelium contains M cells and intraepithelial lymphocytes. These two components of the immune system are discussed in this chapter. ​ The submucosa consists of dense connective tissue and a heterogeneous population of cells, including leukocytes and fibroblasts. ○​ The submucosa also contains an extensive network of vascular and lymphatic vessels, nerve fibers, and ganglion cells of the submucosal (Meissner’s) Histology plexus. ​ The wall of the small intestine consists of four distinct ​ The muscularis propria consists of an outer, layers: mucosa, submucosa, muscularis propria, and longitudinally-oriented layer and an inner, serosa (Fig. 28-2). circularly-oriented layer of smooth muscle fibers. 1  ○​ Located at the interface between these two layers COLON VASCULAR SUPPLY are ganglion cells of the myenteric (Auerbach’s) plexus. ​ The serosa consists of a single layer of mesothelial cells and is a component of the visceral peritoneum. ​ The arterial supply to the colon is highly variable. In general, the superior mesenteric artery branches into: Gross Anatomy of the Large Intestine ○​ the ileocolic artery (absent in up to 20% of people), Schwartz Principles of Surgery, 11th Ed., Chapter 29 which supplies blood flow to the terminal ileum and ​ The large intestine extends from the ileocecal valve to the proximal ascending colon; anus. It is divided anatomically and functionally into the ○​ the right colic artery, which supplies the ascending colon, rectum, and anal canal. colon; and ​ The wall of the colon and rectum comprise four distinct ○​ the middle colic artery, which supplies the layers: mucosa, submucosa, muscularis propria (inner transverse colon. circular muscle, outer longitudinal muscle), and serosa. ​ The inferior mesenteric artery branches into: ​ In the colon, the outer longitudinal muscle is separated ○​ the left colic artery, which supplies the descending into three teniae coli, which converge proximally at the colon; appendix and distally at the rectum, where the outer ○​ several sigmoidal branches, which supply the longitudinal muscle layer is circumferential. sigmoid colon; and ​ In the distal rectum, the inner smooth muscle layer ○​ the superior rectal artery, which supplies the proximal coalesces to form the internal anal sphincter. rectum. ​ The intraperitoneal colon and proximal one-third of the ​ The terminal branches of each artery form anastomoses rectum are covered by serosa; the mid and lower rectum with the terminal branches of the adjacent artery and lack serosa. communicate via the marginal artery of Drummon. ○​ This arcade is complete in only 15 to 20% of people. COLON LANDMARKS ​ Except for the inferior mesenteric vein, the veins of the ​ The colon begins at the junction of the terminal ileum and colon parallel their corresponding arteries and bear the cecum and extends 3 to 5 feet to the rectum. same terminology. ​ The rectosigmoid junction is found at approximately the ​ The inferior mesenteric vein ascends in the level of the sacral promontory and is arbitrarily described retroperitoneal plane over the psoas muscle and as the point at which the three teniae coli coalesce to form continues posterior to the pancreas to join the splenic the outer longitudinal smooth muscle layer of the rectum. vein. ​ The cecum is the widest diameter portion of the colon ○​ During a colectomy, this vein is often mobilized (normally 7.5–8.5 cm) and has the thinnest muscular wall. independently and ligated at the inferior edge of the ○​ As a result, the cecum is most vulnerable to pancreas. perforation and least vulnerable to obstruction. ​ The ascending colon is usually fixed to the COLON LYMPHATIC DRAINAGE retroperitoneum. ​ The lymphatic drainage of the colon originates in a ○​ The hepatic flexure marks the transition to the network of lymphatics in the muscularis mucosa. transverse colon. ○​ Lymphatic vessels and lymph nodes follow the ​ The intraperitoneal transverse colon is relatively mobile, regional arteries. but is tethered by the gastrocolic ligament and colonic ​ Lymph nodes are found on the bowel wall (epicolic), along mesentery. the inner margin of the bowel adjacent to the arterial ○​ The greater omentum is attached to the arcades (paracolic), around the named mesenteric anterior/superior edge of the transverse colon. vessels (intermediate), and at the origin of the superior ○​ These attachments explain the characteristic and inferior mesenteric arteries (main). triangular appearance of the transverse colon ​ The sentinel lymph nodes are the first one to four lymph observed during colonoscopy. nodes to drain a specific segment of the colon, and are ​ The splenic flexure marks the transition from the thought to be the first site of metastasis in colon cancer. transverse colon to the descending colon. ○​ The use of sentinel lymph node dissection and ○​ The attachments between the splenic flexure and the analysis in colon cancer remains controversial spleen (the lienocolic ligament) can be short and dense, making mobilization of this flexure during colectomy challenging. COLON NERVE SUPPLY ​ The descending colon is relatively fixed to the retroperitoneum. ​ The sigmoid colon is the narrowest part of the large intestine and is extremely mobile. ○​ Although the sigmoid colon is usually located in the left lower quadrant, redundancy and mobility can result in a portion of the sigmoid colon residing in the right lower quadrant. ○​ This mobility explains why volvulus is most common in the sigmoid colon and why diseases affecting the sigmoid colon, such as diverticulitis, may occasionally present as right-sided abdominal pain. ​ The colon is innervated by both sympathetic (inhibitory) ○​ The narrow caliber of the sigmoid colon makes this and parasympathetic (stimulatory) nerves, which parallel segment of the large intestine the most vulnerable to the course of the arteries. obstruction. ​ Sympathetic nerves arise from T6-T12 and L1-L3. 2  ​ The parasympathetic innervation to the right and ANATOMY AND PATHOPHYSIOLOGY transverse colon is from the vagus nerve; the Harrison’ 21st Ed. Chapter 329. Pp. 2506 parasympathetic nerves to the left colon arise from sacral nerves S2-S4 to form the nervi erigentes. MELENA & HEMATOCHEZIA Melena ​ Black, tarry, foul-smelling stool Hematochezia ​ The passage of bright red or maroon blood from the rectum DISEASES WITH LOWER GASTROINTESTINAL BLEEDING MESENTERIC ISCHEMIA ​ The blood supply to the intestines is supplied by the celiac INCIDENCE AND EPIDEMIOLOGY artery, SMA, and inferior mesenteric artery (IMA) (Fig. 329-1). Harrison’ 21st Ed. Chapter 329. Pp. 2506 ​ Extensive collateralization occurs between major ​ Intestinal ischemia occurs when splanchnic perfusion fails mesenteric trunks and branches of the mesenteric to meet the metabolic demands of the intestines, resulting arcades. in ischemic tissue injury. ○​ Collateral vessels within the small bowel are ​ Mesenteric ischemia affects 2–3 people per 100,000, with numerous and meet within the duodenum and the bed of an increasing incidence in the aging population. Mortality the pancreas. with acute presentation remains high, between 50 and ○​ Collateral vessels within the colon meet at the 80%, and early diagnosis with prompt intervention is splenic flexure and descending/sigmoid colon. crucial in improving clinical outcomes. ○​ These areas, which are inherently at risk for ​ Intestinal ischemia is further classified as chronic decreased blood flow, are known as Griffiths’ point mesenteric ischemia (CMI) or acute mesenteric ischemic and Sudeck’s point, respectively, and are the most (AMI). common locations for colonic ischemia (Fig. 329-1, ○​ CMI is secondary to multiple major visceral shaded areas). arterio-occlusive disease, with involvement of the ​ The splanchnic circulation can receive up to 30% of the superior mesenteric artery (SMA) most worrisome. cardiac output. Protective responses to prevent intestinal ○​ AMI is most commonly associated with ischemia include abundant collateralization, ​ (1) arterio-occlusive mesenteric ischemia, autoregulation of blood flow, and the ability to increase ​ (2) nonocclusive mesenteric ischemia, and oxygen extraction from the blood. ​ (3) mesenteric venous thrombosis. ​ Occlusive ischemia is a result of disruption of blood flow ​ CMI is the failure to achieve normal postprandial by an embolus or progressive thrombosis in a major artery hyperemic intestinal blood flow. This occurs due to an supplying the intestine. imbalance between the supply and demand of oxygen ○​ In >75% of cases, emboli originate from the heart metabolites to the intestinal tract similar to cardiac angina. and preferentially lodge in the SMA just distal to the ○​ CMI occurs due to significant atherosclerotic disease origin of the middle colicartery. leading to the narrowing of the SMA and/or celiac ○​ Progressive thrombosis of typically two of the major artery origins. vessels supplying the intestine is required for the ​ AMI is the occurrence of an abrupt cessation of development of chronic intestinal angina. mesenteric blood flow, usually embolic or thrombotic in ○​ The involvement of the SMA is most worrisome. nature. Approximately 50% of AMI is due to embolus to ​ Nonocclusive ischemia is disproportionate mesenteric the mid to distal SMA. vasoconstriction (arteriolar vasospasm) in response to ○​ Embolus etiology includes atrial fibrillation, recent severe physiologic stress such as shock. myocardial infarction, soft atherosclerotic plaque, ○​ If left untreated, early mucosal stress ulceration will infective endocarditis, valvular heart disease, and progress to full-thickness injury. recent cardiac or vascular catheterization. ○​ Approximately 25–30% of cases are characterized by an acute-on-chronic thrombosis in patients with PRESENTATION, EVALUATION, AND MANAGEMENT preexisting mesenteric atherosclerosis. Harrison’ 21st Ed. Chapter 329 ○​ Thrombotic occlusion most commonly occurs in ​ Patients with CMI typically present with insidious onset of areas of severe atherosclerotic narrowing at the SMA symptoms and classically with recurrent episodes of and celiac artery. acute, dull, crampy, post-prandial epigastric pain, which ​ Nonocclusive mesenteric ischemia represents 20% of the has also been referred to as “intestinal angina.” cases and is secondary to intestinal ischemia when ○​ Weight loss and chronic diarrhea may also be noted. subjected to acute hemodynamic instability. ○​ Duration of symptoms is typically 6–12 months. ○​ Hypovolemia, shock, and the use of vasoconstrictive ​ Physical examination often reveals a malnourished patient agents (digoxin, α-adrenergic agonists, cocaine) can with other manifestations of atherosclerosis. precipitate ischemia in these patients. ​ Duplex ultrasound has gained popularity as a screening ○​ It is the most prevalent gastrointestinal disease tool for the evaluation of the mesenteric vessels due to complicating cardiovascular surgery. high sensitivity and specificity. ​ The incidence of ischemic colitis following elective aortic ○​ Mesenteric duplex scan demonstrating a high peak repair is 5–9%, and the incidence triples in patients velocity of flow in the SMA is associated with an following emergent repair. ~80% positive predictive value of mesenteric ​ Mesenteric venous thrombosis accounts for 50%. period. The most significant indicator of survival is the timeliness ​ After revascularization, peristalsis and return of pink color of diagnosis and treatment. of the bowel wall should be observed. Palpation of major ​ An overview of diagnosis and management of each form arterial mesenteric vessels can be performed, as well as of intestinal ischemia is given in Table 329-1. applying a Doppler flowmeter to the antimesenteric border of the bowel wall, but neither is a definitive indicator of viability. ​ In the assessment of acute-on-chronic mesenteric ischemia, typically involvement of the orifice of the SMA is seen. Therefore, the entire small bowel is compromised. ○​ Revascularization using an endovascular, open, and/or hybrid approach should be individualized based on the patient’s critical status, comorbidities, and anatomy. ○​ Endovascular stenting, suction thrombectomy, and/or thrombolysis catheter should be considered for ​ AMI resulting from an arterial embolus or thrombosis intervention. presentation is nonspecific and requires a high index of ○​ The bowel should be evaluated for viability, typically suspicion for diagnosis. via an exploratory laparotomy. ○​ Severe, acute, unremitting abdominal pain strikingly ​ Nonocclusive or vasospastic mesenteric ischemia out of proportion to the physical findings is the most presents with Disorders of the Gastrointestinal System common complaint (95%). This may be associated generalized abdominal pain, anorexia, bloody stools, and with nausea (44%), vomiting (35%), diarrhea (35%), abdominal distention. and blood per rectum (16%). ○​ Often these patients are obtunded, and physical ○​ Later findings will demonstrate peritonitis and findings may not assist in the diagnosis or may be cardiovascular collapse. obscured by the underlying etiology. ​ Specific clinical features can help differentiate the ○​ The presence of leukocytosis, metabolic acidosis, underlying etiology, whether embolic or thrombotic. and/or lactic acidosis is useful in support of the ​ Patients with embolic ischemia are typically older adults diagnosis of advanced intestinal ischemia; however, with an underlying condition that predisposes to embolism these markers may not be indicative of either such as atrial fibrillation, prior embolic event, or recent reversible ischemia or frank necrosis. infective endocarditis. ​ Emergent admission to a monitored bed or intensive care ​ Thrombotic ischemia typically presents as an acute unit is recommended for resuscitation, broad-spectrum occlusion in patients with the underlying atherosclerotic antibiotics, and further evaluation. disease who may have been previously diagnosed with ○​ Anticoagulation is not recommended as the goal of CMI. resuscitation is to maintain hemodynamics. ​ AMI is a surgical emergency, and emergent admission ​ For select patients, intramesenteric infusion of to a monitored bed or intensive care unit is recommended vasodilators such as papaverine, prostaglandins, and for resuscitation with fluids and administration of nitroglycerin for reversal of mesenteric ischemia can be broad-spectrum antibiotics in addition to further used, but resuscitation and the treatment of the underlying evaluation. pathology should be the priority. ​ If the diagnosis of intestinal ischemia is being considered, ​ If ischemic colitis is a concern, colonoscopy should be consultation with a surgical service is necessary. considered to assess the integrity of the colon mucosa. ○​ Often the decision to operate is made on a high ○​ Ischemia of the colonic mucosa is graded as mild index of suspicion from the history and physical with minimal mucosal erythema or as moderate with exam despite normal laboratory findings. pale mucosal ulcerations and evidence of extension ​ In patients with suspected AMI, CT angiography with a to the muscular layer of the bowel wall. 1-mm or thinner cut should be used to detect mesenteric ○​ Severe ischemic colitis presents with severe arterial occlusive disease most likely due to embolic or ulcerations resulting in black or green discoloration of thrombotic etiology and is the gold standard. 4  the mucosa, consistent with full-thickness bowel-wall ○​ The type of diverticulum most commonly affecting the necrosis. colon is the pseudodiverticulum. ○​ Laparoscopy can also be employed for assessment. ​ The diverticula occurs at the point where the nutrient Ischemic colitis is optimally treated with resection of artery, or vasa recta, penetrates through the muscularis the ischemic bowel and the formation of a proximal propria, resulting in a break in the integrity of the colonic stoma. wall. ​ Onset of mesenteric venous thrombosis can be acute or ○​ This anatomic restriction may be a result of the subacute based on the location of thrombosis in the relative high-pressure zone within the muscular splanchnic circulation. sigmoid colon. ○​ Patients often present with vague abdominal pain ○​ Thus, higher-amplitude contractions combined with associated with nausea and vomiting. constipated, high-fat-content stool within the sigmoid ○​ Physical examination findings include abdominal lumen in an area of weakness in the colonic wall distention with mild to moderate tenderness and result in the creation of these diverticula. signs of dehydration. ○​ Consequently, the vasa recta is either compressed or ○​ Findings on CT venous phase include diffuse eroded, leading to either perforation or bleeding. bowel-wall thickening and thrombus within the ​ Diverticula commonly affects the left and sigmoid colon; splanchnic system. the rectum is always spared. However, in Asian ​ IV therapeutic anticoagulation, broad-spectrum antibiotics, populations, 70% of diverticula are seen in the right colon and correction of electrolyte abnormalities should be and cecum as well. performed. ○​ Yamanda et al. found right- sided colonic ○​ Surgical intervention is not performed unless there is diverticulosis in 22% of Japanese patients evidence of peritonitis and/or bowel perforation. undergoing colonoscopy. ​ If there is evidence of bowel compromise, an exploratory ​ Diverticulitis is inflammation of a diverticulum. Previous laparotomy should be performed with resection of understanding of the pathogenesis of diverticulosis compromised bowel. attributed a low-fiber diet as the sole culprit, and onset of ○​ Second-look laparotomy after 24–48 h should be diverticulitis would occur acutely when these diverticula attempted as anticoagulation can help prevent become obstructed. resection of viable bowel. ​ However, evidence now suggests that the pathogenesis is ​ Hypercoagulability testing should be performed, and if more complex and multifactorial. underlying inherited disorders are diagnosed, lifelong ​ Better understanding of the gut microbiota suggests that anticoagulation is recommended. dysbiosis is an important aspect of disease. ○​ Chronic low-grade inflammation is thought to play a DIVERTICULAR DISEASE key role in neuronal degeneration, leading to dysmotility and high intraluminal pressure. EPIDEMIOLOGY ○​ As a consequence, pockets or outpouchings develop Harrisons’s 21st Ed. Chapter 328 in the colonic wall where it is weakest. ​ In the United States, diverticulosis affects one-third of the population aged >60 years, and in most instances, there PRESENTATION, EVALUATION, AND MANAGEMENT OF are no associated symptoms. DIVERTICULAR BLEEDING ○​ However, 10–25% of individuals with diverticulosis ​ Hemorrhage from a colonic diverticulum is the most will develop acute diverticular disease. common cause of hematochezia in patients >60 years, yet ○​ In addition, 10–25% of individuals with diverticular only 20% of patients with diverticulosis will have disease will experience recurrent symptoms, and up gastrointestinal bleeding. to 10% will develop complications leading to surgery. ​ Patients at increased risk for bleeding tend to be ​ Diverticular disease has become the fifth most costly hypertensive, have atherosclerosis, and regularly use gastrointestinal disorder in the United States and is the antithrombotic therapy and nonsteroidal anti-inflammatory leading indication for elective colon resection. agents. ​ The incidence of diverticular disease is on the rise, ○​ Additional risk factors include obesity and a history of especially among individuals 2 per year), multimorbidity, obesity, and as fistula or obstruction, removing the diseased colonic smoking. segment, and restoring intestinal continuity. ​ Prevention strategies may include smoking cessation and ○​ These goals must be obtained while minimizing weight loss. morbidity rate, length of hospitalization, and cost in ​ Diverticular disease is now considered a functional bowel addition to maximizing survival and quality of life. disorder associated with low-grade inflammation. ​ Table 328-4 lists the operations most commonly indicated ○​ The use of anti-inflammatory medications based on the Hinchey classification and the predicted (mesalazine) in randomized clinical trials has shown postoperative outcomes. them to be beneficial at reducing symptoms and disease recurrence in patients with SUDD. ○​ However, when objective signs of inflammation such as C-reactive protein and computerized imaging are taken into consideration, no benefit for the use of mesalazine has been shown. ​ Treatment strategies targeting dysbiosis in diverticular disease, have also been evaluated using polymerase chain reaction (PCR) on stool specimens. ​ The current options for uncomplicated diverticular disease ○​ Stool samples from consumers of a high-fiber diet include an open or a laparoscopic resection of the have different bacterial content than stool samples diseased area with reanastomosis to the rectosigmoid. from consumers of a low-fiber, high-fat diet. ○​ Preservation of portions of the sigmoid colon may ​ Probiotics are increasingly used by gastroenterologists lead to early recurrence of the disease. for multiple bowel disorders and may prevent recurrence ​ The benefits of laparoscopic resection over open surgical of diverticulitis. techniques include early discharge (by at least 1 day), ○​ Specifically, probiotics containing Lactobacillus less narcotic use, less postoperative complications, and acidophilus and Bifidobacterium strains may be an earlier return to work. beneficial; however, a recent systematic review was ​ The options for the surgical management of complicated unable to show any benefit to the use of probiotics diverticular disease (Fig. 328-3) include the following open alone. or laparascopic procedures: ○​ The addition of fiber or mesalazine with probiotics ○​ (1) proximal diversion of the fecal stream with an has been shown to maintain remission. Rifaximin (a ileostomy or colostomy and sutured omental patch poorly absorbed broad-spectrum antibiotic), when with drainage compared to fiber alone for the treatment of SUDD, is ○​ (2) resection with colostomy and mucous fistula or associated with 30% less frequent recurrent closure of distal bowel with formation of a symptoms from uncomplicated diverticular disease. Hartmann’s pouch (Hartmann’smprocedure) ○​ (3) resection with anastomosis (coloproctostomy), or ○​ (4) resection with anastomosis and diversion (coloproctostomymwith loop ileostomy or colostomy). ○​ (5) Laparoscopic technique of washout and drainage without diversion has been described for Hinchey III patients; however, a threefold increased risk of recurrent peritonitis requiring reoperation with washout alone has been reported. 7  ​ Patients undergoing surgical resection for presumed diverticulitis and symptoms of chronic abdominal cramping and irregular loose bowel movements consistent with irritable bowel syndrome have poorer functional outcomes. HEMORRHOIDAL DISEASE INCIDENCE AND EPIDEMIOLOGY Harrisons’s 21st Ed. Chapter 328, Page 2503 ​ Symptomatic hemorrhoids affect >1 million individuals in the Western world per year. ​ The prevalence of hemorrhoidal disease is not selective for age or sex. ​ However, age is known to be a risk factor. ​ The prevalence of hemorrhoidal disease is less in underdeveloped countries. ​ The typical low-fiber, high-fat Western diet is associated ​ Patients with Hinchey stage Ia are managed with with constipation and straining and the development of antibiotic therapy only followed by resection with symptomatic hemorrhoids. anastomosis at 6 weeks. ​ Patients with Hinchey stages Ib and II disease are ANATOMY AND PATHOPHYSIOLOGY managed with percutaneous drainage followed by ​ Hemorrhoidal cushions are a normal part of the anal resection with anastomosis about 6 weeks later. canal. ​ Current guidelines put forth by the American Society of ​ The vascular structures contained within this tissue aid in Colon and Rectal Surgeons suggest, in addition to continence by preventing damage to the sphincter muscle. antibioticmtherapy, CT-guided percutaneous drainage of ​ Three main hemorrhoidal complexes traverse the anal diverticular abscesses that are >3 cm and have a canal— the left lateral, the right anterior, and the right well-defined wall. posterior. ○​ Abscesses that are