small and large intestine applied anatomy.pptx

This ppt is all about anatomy of small intestine and large intestine , it gives clear differentiation of small and large bowel both grossly and radiographically

1. APPLIED ANATOMY AND PHYSIOLOGY OF SMALL AND LARGE INTESTINE Dr.K.V.V.Naga Santosh Assistant professor GMC/GGH, GUNTUR

2. TOPICS COVERED: Applied anatomy of small intestine( jejunum,ileum ) Histology of small intestine Physiology of small intestinal motility Applied anatomy of large intestine( caecum, colon) Histology of large intestine Physiology of large intestinal motility

3. APPLIED ANATOMY OF SMALL INTESTINE Although duodenum is indistinguishable from small intestine it is dealt along with stomach for convinence in surgical terms. Small intestine lies between duodeno jejunal flexure and ileo caecal valve. Length varies widely between subjects, however ranges between 300-850 cms . Proximal 40% is jejunum and distal 60% is ileum .(no clear demarcation between jejunum and ileum as small intestine character changes gradually from proximal to distal).

4. Layers of small intestine: Serosa- toughest layer Muscularis propria - outer longitudinal, inner circular layers Submucosa Muscularis muscosa Muscosa - lamina propria and Columnar epithelium. The columnar epithelium dips down to form glands ( the crypts of Lieberkuhn ) and thrown up between the gland openings into villi . Some of the villous cells are mucous secreting goblet cells; others are enterocytes or absorbing cells. Both these cells are renewed every few days from progenitors in the crypts. Crypts have various neuroendocrine cells, granular paneth cells, chromaffin cells and other cells. Terminal ileum has groups of lymphoid follicles in mucosa forming Peyer’s patches.

5. Neuroendocrine cells are responsible for the production of intestinal hormones, including secretin, somatostatin and CCK. Paneth cells secrete lysozyme. A fold of mucous membrane that passes across 2/3 rds of the bowel Circumference in small intestine are called Valvulae conniventes or Plicae circularis . Muscularis mucosa is sparse or even absent in jejunum and there are no glands in Submucosa. JEJUNUM ILEUM

6. JEJUNUM Vs ILEUM

7. Blood supply: Artery– Superior mesenteric artery (direct branch of aorta) Vein – Superior mesenteric vein ( drains into portal vein) Lymphatics – along arterial supply Nerve supply: SI has autonomic innervation arising from splanchnic nerves, which contribute a dense network of sympathetic fibres around SMA and it’s branches. Pain from small intestine is usually referred to peri umbilical region( T10)

8. PHYSIOLOGY OF SMALL INTESTINE JEJUNUM is the principal site for digestion and absorption of fluid, electrolytes, iron, folate, fat, protein and carbohydrate. Absorption of bile salts and vit B12 only occurs in the terminal ileum. Ileum can take up the function of jejunum if jejunum is respected, but if terminal ileum is respected it will result in vit B12, A, D, E and K deficeincies . Ileum also plays an important role in water absorption therefore it’s significant resection results in trouble some diarrhoea. Small intestine is the main site of synthesis of HDL, LDL, VLDL. And also for GLP-1 and 2, peptide YY and motilin which interact with enteric nervous system to modulate intestinal function , growth and differentiation.

9. Small intestinal motility: The seminal experiments of Bayliss and Starling led to the adoption of term ‘ peristalsis’ in 1899. In the small intestine, fasting motility can be described by the three phases of the migratory motor complex(MMC)

10. The intestine, like heart, is autonomous in generating its own rythmical electrical activity And therefore local motor activity by intrinsic pacemaker activity generated by small fibroblast like cells called the interstitial cells of Cajal . ( In Muscularis propria ) This activity is affected by a hierarchy of external control systems, mainly enteric nervous system ( myenteric plexus and submucosal plexus) Myenteric plexus has major role in motor functions while submucosal plexus has roles in sensing, mucosal blood flow regulation and secretion .

11. APPLIED ANATOMY OF LARGE INTESTINE: Large intestine begins at ileo caecal valve and extends to anus Approximately 1.5 metre long. Distinguishing features: taenia coli – longitudinal muscle layer condenses to form 3 that run from the appendix base to rectosigmoid junction. haustrations – taenia coli pull the bowel into sacculated state, producing haustrations which are visible even on abdominal radiograph appendices epiploicae – fat filled peritoneal tags found principally on the left side of colon

12. Divided into caecum, ascending colon, hepatic flexure, transverse colon, spleenic flexure , descending colon , sigmoid colon, rectum and anal canal CAECUM : Completely covered with peritoneum and possess considerable amount of mobility. Blood supply: 1)anterior and posterior caecal arteries which arise from ileocolic artery, a branch of Superior mesenteric artery. 2)venous drainage follows arteries into SMV. 3) Lymphatics drain into several mesenteric lymph nodes which finally drain into superior mesenteric nodes Nerve supply: sympathetics and parasympathetics ( vagus ) form superior superior mesenteric plexus

13. ASCENDING COLON : Retroperitoneal organ covered by peritoneum on anterior, medial and lateral sides. Blood supply: ileocolic and right colic arteries, branches of SMA. Venous drainage, Lymphatics and nerve supply are same as caecum Important structures in relation to caecum and ascending colon are right ureter, iliac vessels, gonadal vessels, femoral nerve which should be preserved carefully during surgery.

14. TRANSVERSE COLON: Transverse mesocolon suspends the transverse colon from pancreas and attached to superior border of transverse colon and greater omentum is attached at the inferior border. Related to duodenum and head of pancreas posteriorly ,should be taken care during surgery proximal 2/3rds distal 1/3rd Blood supply: middle colic artery, branch left colic artery, branch of of SMA. IMA veins drain into SMV Veins drain into IMV Lymphatics drain into Lymphatics drain into colic colic nodes and then nodes and then into IMN into SMN. Nerve supply: Superior mesenteric plexus Inferior mesenteric plexus.

15. SPLEENIC FLEXURE: Gives attachment to phrenicocolic ligament. “Watershed area” of spleenic flexure representing the embryological junction of midgut and hindgut may have tenous blood supply. Sudden occlusion of inferior mesenteric artery leads to ishceamic colitis of spleenic flexure. DESCENDING COLON : Retroperitoneal organ same as ascending colon Blood supply: left colic artery and sigmoid branches of IMA venous drainage into IMV lymphatics drain into colic nodes and then into IMN around the origin of IMA Nerve supply: inferior mesenteric plexus

16. SIGMOID COLON: Blood supply: sigmoid branches of IMA veins drain into IMV Nerve supply: from inferior hypogastric plexus. Inferior and superior mesenteric veins joins the portal venous system Pain from the territory of superior mesenteric plexus is referred to periumbilical region same as that of small intestine, where as from the part of colon distal to that is referred to suprapubic region Peripheral branches of superior and inferior mesenteric arteries anatomose and form “ Marginal artery of Drummond” resulting in a continuous vascular supply along the colon. Anatomy of rectum and anal canal are dealt in detail separately.

17. HISTOLOGY OF LARGE INTESTINE: Similar to small intestine except- 1) absence of villi and Plicae circularis 2) more number of crypts of Lieberkuhn with goblet cells secreting mucus 3) Epithelium overlying lymphatic follicles contains M cells.

18. PHYSIOLOGY OF LARGE INTESTINE: Principal function: absorption of water, approximately 1000ml of ileal content enters caecum every 24hrs of which only 200ml is excreted. Sodium absorption is accomplished by an active transport system while water and chloride by passive transport. Fermentation of dietary fibre by normal colonic microflora generate short chain fatty acids which are an important substrate for colonic mucosa ( diversion of faecal stream denying the mucosa of this nutrition leads to inflammatory changes in colon downstream- diversion colitis) Colonic motility is variable, in general faecal residue reached caecum 4hrs after a meal and rectum after 24 hrs.

19. Large intestinal motility is more complicated and still poorly understood with some features akin to the MMC but also specific phenomena such as retrograde movements ( presumed to allow greater resident time and therefore fluid and electrolyte absorption).

20. MOTILITY REFLEXES Gastroileal reflex: . Distension of stomach with food----- stimulation of vagus ------ relaxation of ileocaecal sphincter. Intestinointestinal reflex: Over distension of one segment of bowel leads to reflex relaxation of smooth muscle of entire intestine. Gastrocolic reflex: Colon has increased motility in response to distension of stomach with ingestion of food.

21. Defaecation reflex: . 1) Intrinsic defeacation reflex : Enteric nervous system– myenteric plexus Weak reflex ; fortified by Parasympathetic defaecation reflex

22. 2) Parasympathetic defaecation reflex: Parasympathetic system—autonomic fibres of pelvic nerves

23. FUNCTIONAL DISORDERS OF INTESTINE Dr.K.V.V.Naga Santosh Assistant professor GMC/GGH,GUNTUR

24. Topics dealt: Tests for intestinal function Functional intestinal diseases.

25. Tests for intestinal function:

26. SMALL BOWEL CONTRAST STUDIES: Generally available Eg : barium follow through Has poor sensitivity for detecting other than visceral or grossly retarded transit. Hence superseded by axial imaging with CT or MRI BREATH HYDROGEN TESTING: Easily available Using lactulose or lactose 13C-ureide. Assess the presence of carbohydrate malabsorption , an indirect measure of transit It’s utility in reliably measuring transit or detecting bacterial overgrowth is limited by issues of reproducibility TESTS FOR SMALL INTESTINE FUNCTION:

27. WIRELESS MOTILITY CAPSULES SMALL BOWEL TRANSIT STUDY: Adopted by some highly funded health systems. Wireless motility capsule measures pH, temperature and pressure as it traverses the whole gastrointestinal tract; changes in these variables can be used to determine timings. Advantageous above current techniques with respect to patient tolerability, safety and standardisation. ANTRDUODENAL MANOMETRY: Shows phases of MMC. These findings have issues of specificity Available only in a small number of centres worldwide DYNAMIC MRI STUDIES: Currently a research tool but may well represent the future.

28. TESTS FOR COLONIC FUNCTION: RADIO OPAQUE MARKER STUDIES: Generally available Mainstay of evaluation of colonic transit Patient abstains from laxatives for the duration of the study. ISOTOPE SCINTIGRAPHY AND WIRELESS MOTILITY CAPSULE WHOLE GUT TRANSIT STUDY: Restricted to a very small number of specialist centres worldwide

29. Functional intestinal diseases Diagnosis is usually made when routine investigations fail to find any easy explanation (e.g. A structural or biochemical cause) for a combination of typical symptoms. CLASSIFICATION: ACUTE CHRONIC DILATED BOWEL NORMAL BOWEL CONSTIPATION IRRITABLE BOWEL SYNDROME DILATED BOWEL Small intestine Large intestine Small intestine Large intestine Ieus ( Including post operative ileus ) Acute colonic pseudo obstruction Intestinal pseudo obstruction Megacolon

30. ILEUS: acute adynamic neuromuscular states of small intestine with dilatation DEFINITION: a disruption of the normal propulsive ability of the intestine due to a malfunction of contractile activity in the absence of mechanical obstruction. Certain older terms like “meconium ileus” and “ gallstone ileus” are misnomers and differ from ileus The term “paralytic ileus” is not entirely correct as the motor activity is not abolished but rather dysregulated . PATHOPHYSIOLOGY: concept 1- Reflex inhibition of intestinal motility caused by deranged ANS inputs. ‘ fight and flight’ concept of increased sympathetic signalling and parasympathetic withdrawal during trauma or other stressful situation concept 2- ‘two phase response’ an immediate stress response mediated by spinal reflexes and HPA axis activation followed by more prolonged inflammatory response in bowel wall itself.

31. CAUSES AND RISK FACTORS: . 10-20% of patients undergoing elective major abdominal surgeries develop post operative ileus and is usually defined as a failure to tolerate oral intake or pass stool 72 hrs after surgery.

32. CLINICAL FEATURES: abdominal distension, vomiting colicky pain is less of a feature O/E : distended, tympanic abdomen with reduced or absent bowel sounds DIAGNOSIS: CT scanning and blood tests ( hypokalemia )

33. MANAGEMENT: Nasogastric drainage and restriction of oral intake Fluid and electrolyte balance and nutrition Management of underlying drivers like abscess or peritonitis on their merits Prokinetics are not proved sufficiently effective Need for laparotomy becomes increasingly likely the longer the bowel inactivity persists, particularly if it lasts for >7days or if bowel activity recommences following surgery and then stops again. PREVENTION: Minimally invasive surgical approaches Enhanced recovery programme by avoidance of opioid containing drugs and suppression of the inflammatory response.

34. ACUTE COLONIC PESUDO-OBSTRUCTION: acute adynamic neuromuscular states of the large intestine with dilatation DEFINITION: Acute massive Dilatation of the colon with obstructive symptoms but in the absence of mechanical obstruction. First described by SIR WILLIAM OGILVIE, hence the eponym “ Ogilvie’s syndrome” Three common diagnoses in patients presenting with large bowel obstruction are 3 Ts : tumor , torsion and tired out. Toxic megacolon is the 4 th T. Colorectal Volvulus ACPO PATHOPHYSIOLOGY: same like ileus- both imbalanced extrinsic autonomic innervation and an inflammatory state.

35. RISK FACTORS: Majority of patients fall into 2 categories: 1) those that have a high background risk and a small acute event E.g.:an elderly patient with Parkinson’s disease and a UTI 2) those with little background risk and a large acute event. E.g.: major surgery / trauma

36. CLINICAL FEATURES: abdominal distension, absolute constipation and as later feature, vomiting colicky pain is less a feature P/A: grossly distended and tympanic abdomen . tenderness and especially any e/o peritonism indicate that massive colonic dilatation may have led to ischaemia +/- perforation. ( Occurs in 3-15% cases with advanced age and increased caecal diameter) DIAGNOSIS: plain abdmoninal radiography CT is definitive investigation DIFFERENTIAL DIAGNOSIS: Pseudo membranous colitis with toxic dilatation in hospitalised or . institutionalised patients due to Clostridium difficile infection.

37. MANAGEMENT: . Depends on whether complications are evident or considered imminent In caecal ischaemia or perforation: emergency surgery is required (Subtotal colectomy and end ileostomy) Majority of patients follow a more step wise approach

38. Caecal diameter >/=12 cm warrant rapid decompression Intravenous neostigmine- reserved for patients in whom supportive measures and colonic decompression have failed. S/E: salvation, bradycardia, bronchospasm, hypotension, abdominal cramps followed often by massive evacuation of flatus and faeces. C/I: renal insufficiency, recent MI, arrhythmias and asthma. Surgery is associated with high mortality and morbidity. PROGNOSIS: It is a life threatening condition. M ortality rates in patients undergoing surgery are 30-60% Recurrence is an issue in some patients with unmodifiable risk factors - they requires regular enemas, chronic modification of polypharmacy - Prokinetics may have a role but are not licensed for this indication.

39. INTESTINAL PSEUDO OBSTRUCTION:chronic impairment of intestinal motility with dilatation of the small intestine: DEFINITION: A clinical syndrome caused by severe impairment of intestinal motility leading to small intestinal dilatation in the absence of a mechanical issue. IPO is a rare disease. Half of cases arise shortly after birth or in infancy. CAUSES : primary/ secondary/ idiopathic

40. CLINICAL FEATURES: pain, distension and vomiting DIAGNOSIS: clinical evaluation and plain radiology, a degree of suspicion Axial imaging Blood and imaging tests including MRI brain, skeletal muscle biopsies to identify secondary causes Full thickness tissue biopsy of bowel via laparoscopic or minilaparotomy approach Two examples of myopathy: a) hollow visceral myopathy (note the vacuolation of the smooth muscle), b) extra muscle layer in muscularis propria

41. MANAGEMENT: For most patients there is no cure. Small bowel (or multivisceral ) transplantation is an optionin selected patients. PROGNOSIS: POOR – sometimes considered motor neuron disease of the gut. Infantile forms have a mortality of approximately 50%. Adult forms may progress to type 2/3 intestinal failure with need for lifelong parenteral nutrition.

42. MEGACOLON AND MEGARECTUM: chronic impairment of intestinal motility with dilatation of the large intestine DEFINTION: Chronic dilatation in the absence of a mechanical obstructing cause focused in colon or rectum Toxic megacolon is an acute condition in which acute inflammation leads to a loss of compliance and rapid dilatation. CAUSES: . differ for megacolon and megarectum . HIRSCHSPRUNG’S DISEASE is the most common cause with incidence of 1 in 5000 live births.

43. HIRSCHSPRUNG’S DISEASE is histologically very difficult to diagnose with certainty and some challenge its existence at all. Patients with megarectum are divided into 2 groups by clinicians: first: those who had previous surgery for HIRSCHSPRUNG’S DISEASE or anorectal malformations in whom on going problems are common. second: idiopathic, predominantly male, with some form of psychobehavioural disorder( stool withholding in infancy or childhood leading to chronic distension and loss of compliance) PRESENTATION: mass per abdomen (the size of a full term baby) diagnosis is mainly radiological.

44. MANAGEMENT : . aim- “getting rectum empty” In some patients manual disimpaction is required under anaethesia Thereafter, high doses of regular osmotic and stimulant laxatives orally as well as regular enemas( or high volume transanal irrigation TAI) A variety of options exist for megarectum , a first step may be an anterograde colonic enema( ACE ). Procedure Surgery has an important role in patients who fail medical management MEGACOLON : colectomy or Subtotal colectomy MEGARECTUM: pull through procedures, low anterior resection, restorative proctocolectomy , and rectum reducing procedures e.g. Vertical reduction rectoplasty ( all these surgeries should be undertaken with covering loop ileostomy usually done 6months to 1 year prior to surgery)

45. There is a considerable overlap between constipation and constipation predominant IBS. CONSTIPATION DEFINITION: American College of Gastroenterologists– “ unsatisfactory defecation, characterized by infrequent stools, difficult stool passage or both for atleast 3 months” Chronic constipation – “ unsatisfactory defecation characterized by infrequent stools, difficult stool passage or both at least 6 months where this has proven unresponsive to lifestyle alterations and basic laxative therapy” CONSTIPATION AND IBS: chronic impairment of intestinal motility without dilatation

46. EPIDEMIOLOGY: Worldwide prevalence: 10% chronic constipation -0.5% Women: men in self reported constipation – 2:1 chronic constipation – 9:1 RISK FACTORS:

47. DIAGNOSIS: clinical history – specifically about frequency and consistency of bowel movements and the progress of such changes over time, other alarming symptoms like rectal bleeding and weight loss , family history, previous colon cancer screening and other gastrointestinal investigations In patients with chronic symptoms, Many patients attribute the start of symptoms to a major life event like hysterectomy,childbirth , trauma and other abdominal surgeries It may sometimes be necessary to tactfully seek a history of physical or sexual abuse Others will have no such triggers, having had symptoms from childhood and on occasion from infancy. (95% are female) ( This group are variable referred to in literature as idiopathic slow transit constipation or colonic inertia)

48. List in the patient’s record the presence or absence of several common symptoms The remaining history should document prescribed and self administered laxatives and therapeutic benefit thereof and also gain an impression of the quality of diet in respect to fluid intake and fibre intake.

49. Clinical examination – nutritional status. abdominal examination for scars, significant abdominal distension, tenderness or masses. per rectal examination- for evidence of feacal incontinence that may indicate impaction and overflow ( marked soiling of the underwear is especially associated with the rarer diagnosis of megarectum ), scarring , sentinal pile, fissure, external haemorrhoids or prolapse, degrees of perineal descent on straining (>3cm Is generally considered . abnormal), impaction , a rough measure of anal tone at rest and on . Squeeze. . anoscopy and proctoscopy in rectal bleeding urogynaecological examination in patients with suspected pelvic multi organ prolapse Investigations – serum electrolytes , creatinine, calcium ,glucose, haemoglobin levels and thyroid function tests.

50. The commonest undiagnosed systemic disease is hypothroidism colonoscopy, radio opaque marker study for transit, rectal sensory testing and evacuation proctography .

51. MANAGEMENT: . follows a step wise progression from lifestyle changes through potentially to major surgery in a small minority of patients.

52. .Before resorting to specialist tests, it is possible to try and rationalise laxative therapy and provide a programme of nurse –led behavioural interventions. .In regard to laxatives, current advice is to stop current laxatives ( unless these are working well) and then titrate on oral osmotic laxative, e.g. polyethylene glycol(PEG), until stool form is soft or liquid. .If this is insufficient,then a stimulant laxative ( bisacodyl ) may be added. .If symptoms of obstructed defaecation predominate then rectal laxatives in the form of suppositories or enemas may be tried +/- continuation of oral laxatives. .Failures of these drugs should then prompt a trail of one of the newer prokinetics or secretagogue drugs. All drugs should be tried daily for a minimum of 4weeks before concluding that they are ineffective and reactionary use of laxatives should be strongly discouraged.

53. . Behavioural intervention: Most common form is described by the term ‘ habit training’ This includes – Optimising dietary patterns. Morning clustering of colonic high amplitude propagated contractions. Dietary advice to optimise intake of liquids and fibre Advice about frequency and length of toilet visits and posture. Instructions on basic gut anatomy and function. Simple pelvic floor and balloon expulsion exercises . Further rationalise and monitor laxative therapy.

54. . Instrument based biofeedback learning technique: Provide direct visual computer based biofeedback of pelvic floor activity. The aim is to restrain the patients to appropriately contract abdominal and relax pelvic floor muscles during defaecation. . Trans anal irrigation: Low volume – 50-100ml High volume – 500ml of irrigant fluid is administered into rectum, patients then sits on the toilet to evacuate the fluid and faecal material. . Surgical options : broadly divided into 3 groups as follows.

55. Essential requirements that should be undertaken before surgery: 1) pathophysiological findings from specialist tests concur with the symptomatology and findings on clinical examination. 2) conservative (non-surgical) treatment options have been tried. 3) the patient’s case has been reviewed at a multidisciplinary team( MDT) meeting and surgery recommended. 4) the patient has been consented in the very clear knowledge of the range of possible outcomes. 5) surgery is undertaken in a centre with expertise in managing functional conditions.

56. Anterograde colonic enema procedures: A conduit is formed to introduce irrigant into the colon Best established in children and in patients with neurological disease Caecum is accessed directly e.g. With a Chait tube caecostomy , or indirectly via the appendix ( appendicostomy ). Appendix can be reversed ( Malone anterograde continent enema technique) or used in its native orientation(much simpler) Has variable outcomes but is a good option in patients considering colectomy and stoma as the only alternative. Neuromodulation : Done at sacral plexus. No role for slow transit constipation but has a role in some patients with severe functional syndromes leading to obstructed defaecation .