Alimentary Tract - Small Intestine Flashcards
(93 cards)
1
Q
What is the most common location for Crohn disease?
A
Terminal ileum
15% to 20% of patients can present with colonic Crohn disease
2
Q
In regards to Crohn’s, what other anatomic location can be diseased in up to 30% of patients with terminal ileal disease and in more than 50% of patients with colonic involvement?
What are examples of disease processes in this area?
A
Perianal disease
Including anal fissures, fistulas, skin tags, strictures, and ulceration
3
Q
What are gross histologic features of Crohn’s disease?
A
creeping fat; skip areas of involvement; thickened mesentery; enlarged lymph nodes; long, deep, linear, aphthous ulcers in the mucosa; ulcerations; and cobblestoning
4
Q
What are microscopic features of Crohn’s disease?
A
Chronic inflammatory infiltrate that extends transmurally through the mucosa and submucosa
It is often characterized by noncaseating granulomas and Langerhans giant cells
5
Q
What is the most common primary surgical disease of the small bowel?
A
Crohn disease
6
Q
Identify the incidence and age distribution of Crohn disease and recognize the strong familial association.
A
The incidence is 50 of 100,000 individuals in the general population
Bimodal distribution of cases: majority presenting between the ages of 15 to 25 years and a second peak between the ages of 55 to 65 years
Strong familial association: risk of development of disease increased approximately 30-fold in siblings and 15-fold in all first-degree relatives
7
Q
Crohn’s disease presents with…
A
…chronic recurring episodes of abdominal pain (most common symptom), diarrhea (second most common symptom), and weight loss. Patients may also have isolated perianal disease.
Patients may initially present with fulminant/severe disease or alternatively may have quiescent disease that remains asymptomatic or minimally symptomatic for years. These patients may have more insidious symptoms such as failure to thrive and weight loss.
8
Q
Extraintestinal manifestations may occur in 30% of patients with Crohn’s. What are some examples?
A
skin lesions such as erythema nodosum and pyoderma gangrenosum, arthritis and arthralgias, uveitis and iritis, hepatitis, primary sclerosing cholangitis (PSC), and aphthous stomatitis
9
Q
What extraintestinal symptoms of Crohn disease do not correlate with intestinal disease activity (ie will not improve after resection of the diseased portion of bowel)?
A
Most extraintestinal manifestations improve after resection of the diseased portion of bowel. However, PSC and ankylosing spondylitis symptoms often do not correlate with intestinal disease activity.
10
Q
Compare/contrast CT vs MRI in the diagnostic workup of Crohn’s disease?
A
Magnetic resonance imaging (MRI) and computed tomography (CT) are equivalent in identifying gross disease activity and extent of bowel involvement. However, MRI may be superior in differentiating active inflammatory strictures from chronic fibrostenotic strictures as well as intestinal wall enhancement that correlates with active disease.
11
Q
What is the Vienna classification’s role in the management of Crohn’s disease?
A
Uses three characteristics to divide patients into groups used to predict remission, relapse, and response to therapy:
- Age at diagnosis (less than or greater than 40 years)
- Behavior (inflammatory, stricturing, or penetrating)
- Location (terminal ileum, colon, ileocolonic, upper gastrointestinal tract, anorectal)
12
Q
What serologic markers can be useful to assess for inflammation and the presence of active disease in IBD?
A
erythrocyte sedimentation rate, C-reactive protein, perinuclear antineutrophil cytoplasmic antibody, and antisaccharomyces cerevisiae antibody. Stool lactoferrin and calprotectin also show some promise in predicting clinical recurrence after resection
13
Q
What non-IBD disease must be excluded in the diagnostic workup of Crohn’s disease (ie a patient that presents w/ episodic diarrhea and abdominal pain)?
A
Bacterial (Salmonella, Shigella, Campylobacter, Yersinia, Clostridium difficile) and protozoal infections (amebiasis)
In immunocompromised individuals, mycobacterial disease and cytomegalovirus should be considered.
14
Q
How can you distinguish Crohn’s from UC?
A
From 5% to 10% of patients will have indeterminate colitis.
In general, ulcerative colitis involves the rectum and extends proximally in a continuous fashion.
In contrast, Crohn disease is segmental and more likely to result in fistulas and strictures, may have perianal involvement, and often spares the rectum.
15
Q
Approximately of patients with the disease require resection within 15 years of diagnosis in Crohn disease. Surgical recurrence rates after resection are 24% at 5 years and 35% at 10 years.
A
70%
Understand that surgery for Crohn disease is not curative and it is therefore necessary to minimize the extent of small bowel resection.
16
Q
most common indication for surgery in patients with Crohn disease
A
Obstruction
17
Q
Surgical management of Crohn’s disease:
Partial obstruction
A
Partial obstruction may respond to a trial of conservative management (bowel rest, parenteral nutrition, steroids) provided that the patient is not toxic and has a reassuring abdominal examination.
18
Q
Surgical management of Crohn’s disease:
Small bowel stricture
A
For small bowel stricture, interventions include endoscopic dilation, stricturoplasty (Heineke-Mikulicz, Finney, Michelassi), or segmental resection with stoma or primary anastomosis.
19
Q
Surgical management of Crohn’s disease:
Colonic stricture
A
For colonic strictures, if associated with an anastomosis, endoscopic dilation can be attempted. Otherwise, surgical resection is used because there is a higher risk of underlying malignancy in colonic strictures and thus stricturoplasty is not indicated.
20
Q
Management of intestinal fistulas in Crohn’s
A
Up to 35% of patients with Crohn disease develop intestinal fistulas. Most involve other small bowel, colon, abdominal wall and skin, or other surrounding viscera (bladder, gynecologic structures). Fistulous disease may respond to anticytokine therapy. If this fails, treatment is segmental resection. Involved organs such as bladder may be primarily repaired.
21
Q
Management of perforation and abscess in Crohn’s:
Free perforation with minimal contamination
A
Penetrating disease is usually associated with localized abscess but can occasionally result in free perforation into the abdominal cavity. If minimal contamination is present, a primary anastomosis can be performed after resection of the diseased portion of bowel.
22
Q
Management of perforation and abscess in Crohn’s:
generalized peritonitis
A
However, if generalized peritonitis is present, it is generally safer to perform a diverting enterostomy with delayed reconstruction.
23
Q
Management of perforation and abscess in Crohn’s:
abscess
A
Most abscesses can be controlled initially via percutaneous drain placement, antibiotics, and interval resection of the involved bowel segment with a delay of at least 4 to 6 weeks to allow inflammation to resolve.
If the segment is left unresected, at least 30% of patients will develop recurrent abscesses.
24
Q
What is considered failure of medical management in a patient with Crohn’s disease?
A
Failure to adequately control symptoms, side effects of medications that may prohibit their use, and patient noncompliance with medical management are all considered failure of medical management.
25
What are some general concepts behind excessive bleeding management in Crohn's disease?
Most bleeding associated with Crohn disease is chronic blood loss and its associated anemia. However, life-threatening hemorrhage may occur; this is associated more with colonic disease. Arteriography, CT angiography, or tagged red blood cell scanning can all be used to localize the segment of diseased bowel prior to resection. If bleeding is associated with duodenal disease, endoscopic intervention can be used for control of bleeding.
26
What is the disease history of GI cancer in a Crohn's patient?
There is an increased incidence of cancer in patients with long-standing Crohn disease, particularly colon cancer. Seven percent of colonic strictures in patients with Crohn disease can harbor malignancy. Patients with chronic active disease require persistent surveillance, and the presence of high-grade dysplasia or inability to rule out a malignancy is an indication for colectomy.
27
Patient with Crohn's presents with high fever, severe abdominal pain and distention, hemodynamic instability, and leukocytosis. What is on the differential?
Toxic colitis
Free perforation
28
Management of toxic colitis in Crohn's disease
If peritonitis is present, this mandates emergent surgery; otherwise aggressive nonoperative management and serial abdominal examinations may be appropriate for 24 to 36 hours, with surgery necessary if there is no improvement. The radiographic presence of a “megacolon” is not mandatory for the diagnosis of toxic colitis but is often seen. This syndrome mandates emergent total abdominal colectomy with end ileostomy and occurs more commonly in ulcerative colitis.
29
General surgical principles in perianal disease in Crohn's disease
minimizing tissue loss and sphincter injury with drainage catheters and noncutting setons to control perianal abscesses and fistulas
30
What does literature show in regards to safety/efficacy in minimally invasive procedures for Crohn's disease?
Laparoscopic surgery has been shown to be both safe and feasible. In studies, minimally invasive procedures have been associated with shorter operative times, decreased blood loss, shorter hospital stays, and decreased postoperative ileus. The conversion rate of laparoscopic to open procedures is estimated at approximately 10%.
31
What is the goal of segmental resection?
With segmental resection, the goal is only to remove grossly inflamed tissue. Frozen sections are an unreliable way to identify microscopic disease and not predictive of postoperative recurrence. The decision to use primary anastomosis versus diversion depends on many factors, including the extent of intra-abdominal contamination, nutritional status, steroid use, and overall clinical stability.
32
What kind of operation should be done for a patient who is septic secondary to colonic Crohn disease?
Subtotal/total colectomy is indicated for patients with sepsis due to colonic Crohn disease requiring emergency operation, in which case an end ileostomy is indicated. Also, this may be indicated for patients with multiple sites of colonic Crohn disease. Ileorectal anastomosis may be appropriate if the bowel appears healthy.
33
What is the role of ileal-pouch anastomosis in Crohn's disease?
Ileal-pouch anastomosis is not indicated given the high rate of pouchitis and recurrence of Crohn disease in the pouch.
34
What is the role of proctectomy in Crohn's disease?
Proctectomy or total proctocolectomy with end (Brooke) ileostomy may be warranted. In patients with extensive perianal and rectal disease that is refractory to medical management, removal of the rectum (and possibly the entire colon, based on disease distribution) can aid in symptom control. Proctectomy is very rarely indicated in the emergent setting given its high risk of complications.
35
Medical management is frequently first-line therapy for patients with Crohn disease. What are the options?
The different classes of drugs used are...
* corticosteroids
* tumor necrosis factor alpha antagonists such as infliximab, adalimumab, and certolizumab
* aminosalicylates such as sulfasalazine and mesalamine
* immunosuppressives such as azathioprine, 6-mercaptopurine, methotrexate, and tacrolimus
* novel agents such as vedolizumab and ustekinumab.
36
What are the general approaches to medical management for Crohn's disease?
There is a top-down versus a step-up approach to starting medications. This entails starting with a biologic agent versus starting with aminosalicylates, respectively. The top-down approach is used more frequently in patients with severe Crohn disease.
37
Understand that long-term follow-up is key to monitoring for recurrence of Crohn disease as well as early diagnosis and management of possible oncologic complications of the disease.
Endoscopic recurrence as high as 80% at 1 year after resection for Crohn colitis.
Long-standing Crohn disease is associated with significant risk of cancer of the small intestine and colon. Surveillance should start 8 years after disease diagnosis or at the time of diagnosis of PSC and be performed every 1 to 3 years. A random biopsy protocol mandates four biopsies every 10 cm from the cecum to the rectum. Chromoendoscopy uses indigo carmine or methylene blue to enhance mucosal irregularities. Patients with a Hartmann pouch and residual rectum should undergo surveillance of the rectum every 1 to 3 years.
There is an increased risk of squamous cell carcinoma of the vulva and anal canal and Hodgkin and non-Hodgkin lymphomas in patients using immunomodulators for medical treatment.
38
A 21-year-old man presents to the emergency department with acute right lower quadrant abdominal pain, diarrhea, fever, and chills. He reports a 10-lb weight loss over the past month. What is your plan for workup and management of this patient?
* Realize that evaluation of this patient should include a thorough history to assess for family history of inflammatory bowel disease, review of systems to cover possible extraintestinal manifestations of Crohn disease, and CT scan of the abdomen and pelvis to evaluate for acute appendicitis versus signs of Crohn disease such as terminal ileitis, bowel wall thickening or enhancement, mesenteric abscesses, or phlegmon formation.
* Recognize that the differential diagnosis should include infectious diarrhea and acute appendicitis.
* Understand that postoperatively the patient would require referral to gastroenterology for further workup and induction medical therapy.
39
A woman with known stricturing intestinal Crohn disease presents with abdominal pain, nausea, and vomiting that started 4 days ago. She is still passing flatus but notes decreased frequency of bowel movements. She has had a previous stricturoplasty of a segment of small bowel. She is found on CT to have dilated loops of small bowel with a possible transition point in the right lower quadrant. What are your diagnostic and management options for this patient?
* Likely partially obstructed
* Trial of conservative management: NGT, NPO, IVF, serial abd exams
* Consider CT or MR enterography - evaluate for strictures - obsx
* If fails - OR. Surgical plan based on intraoperative findings.
* It is necessary to assess the safety and viability of performing stricturoplasty versus resection if stricture is found.
* Heineke-Mikulicz - strictures 5 - 7 cm, requires pliable mesentery so tissues can be approximated in a transverse fashion.
* Finney stricturoplasty - strictures 10 - 15 cm, allows maximum retention of bowel length. However, it can result in the creation of bypassed diseased segment that may contain stagnant bowel
* Michelassi stricturoplasty - long-segment diseased bowel and mesentery, requires careful division of potentially very fibrotic mesentery. Ideal for pts with long areas of strictures at high risk for short bowel syndrome.
* Recognize that if resection is performed, the goal is grossly normal tissue; no role for frozen assessment
40
A man with Crohn disease presents to the emergency department with abdominal pain, nausea, vomiting, fever, leukocytosis (white blood count of 18,000/µL), and tachycardia. He is found on CT of the abdomen and pelvis to have mixed-density free fluid in the pelvis with fat stranding and a thickened right colonic wall. How do you proceed with management of this patient?
* Recognize the need for prompt initiation of broad-spectrum intravenous antibiotics, intravenous fluid resuscitation, and operative intervention.
* It is possible to perform a delayed proctectomy given that the patient is too sick now.
* Understand that diversion is preferred in the setting of intra-abdominal sepsis.
41
Findings on XR of SBO?
* air-fluid levels
* gastric and small bowel distention
* "coin stacking"
42
What is a "transition point" on CT scan (in reference to SBO dx)?
sudden change from proximal distention to distal decompression
43
How does gallstone ileus occur? Where is the obstruction?
large stone causes fistula b/w gallbladder and GI
obstruction usually at ileocecal valve
44
The most common electrolyte abnormality associated with a bowel obstruction is...
a hypokalemic, hypochloremic metabolic alkalosis.
* Vomiting causes depletion of hydrochloric acid, resulting in a loss of both hydrogen and chloride.
* In an attempt to normalize the developing alkalosis, the renal system attempts to retain hydrogen ions while excreting potassium.
* The result is a hypochloremic, hypokalemic metabolic alkalosis.
45
Most common causes of SBO
* post-surgical adhesions
* hernia
* cancer
46
For intussusception, what are the most common etiologies?
* malignancy
* polyps
* benign masses
47
What is the presentation of an SBO?
* nausea
* vomiting
* cramping pain
* lack of bowel function
* distention
48
In a patient with signs and symptoms of SBO and currant jelly stools, what should be included in the top of differential?
intussusception
49
What are findings on CT for a closed loop obstruction?
* mesenteric swirling
* pneumatosis intestinalis
* portal venous gas
50
What are findings on CT for an intussusception?
"target sign" - lumen within a lumen
51
In a patient w/ SBO, what are the findings (imaging or exam) warranting OR?
* peritonitis
* mesenteric swirling
* free air
* internal hernia
* evidence of bowel compromise
52
In a patient w/ SBO, when is non-op management and a Gastrografin study warranted?
* stable patient
* no peritonitis or bowel compromise
* no closed loop obstruction or internal hernia
* hx of surgery indicating adhesive disease
* this is both therapeutic and diagnostic
53
Describe the anatomy of an intussusception, specifically the process and structures that are involved.
* The intussusceptum is the innermost segment of bowel, ie, the proximal segment that has prolapsed into the more distal segment.
* The intussuscipiens is the outermost, distal segment that receives the inner prolapsing segment.
* Adults: vast majority (\> 90%) of intussusceptions have a pathologic lead point that pulls the intussusceptum into the intussuscipiens.
* Adults: leads points are typically a neoplasm (polyp, other benign mass, or cancer).
54
Discuss the possible etiologies for a radiographically-diagnosed intussusception.
* Benign masses such as hamartomas
* Polyps such as hyper plastic polyps, inflammatory polyps, adenomas
* Cancers such as GI lymphoma, adenocarcinoma, or GIST
55
Identify the radiographic testing modalities that are used to diagnose intussusception
* In general, in order to make the diagnosis preoperatively, cross-sectional imaging is required.
* Plain x-ray films and ultrasound may occasionally, if not rarely, make the diagnosis, but more often than not, only provide non-specific findings. That being said, these imaging modalities may rule-out competing pathologies (perforation in a child w/ severe abdominal pain)
* If a surgeon has a high-index of suspicion, then he/she should proceed to cross-sectional imaging (typically CT scan) or proceed directly to diagnostic laparoscopy.
56
Name the clear operative indications for intussusception.
* Peritonitis, bowel obstruction, GI bleeding
* Radiographic presence of a lead point even if asymptomatic
57
Explain the general operative strategy in managing a patient with bowel obstruction found to be due to intussusception.
* Exploration with diagnostic laparoscopy (ideally) or exploratory laparotomy
* Exploration of all four quadrants and the pelvis
* En-bloc resection of the intussusception
* May consider careful reduction (outside of the peritoneal cavity) in select cases. This is typically not recommended unless an exceptionally long segment of small bowel is affected as a) the lead point must be resected, and b) reduction may result in exposure of compromised, infarcted bowel, resulting in gross fecal contamination and an increase surgical site infection rate including intra-abdominal abscess and subsequent anastomotic leakage.
58
Contrast the management of intussusception in pediatric and adult patients.
* Pediatric patients are much more likely to harbor a benign lead point, typically lymphoid hyperplasia, than in adults in whom the lead point is typically a neoplasm.
* Thus, in pediatric patients, resectional therapy is reserved for those who have peritonitis or failure to reduce with hydrostatic water-soluble contrast enema.
59
A 56-year-old woman presents with a sudden onset of right lower quadrant pain, vomiting, and palpable abdominal mass. Laboratory evaluation reveals a mild leukocytosis. CT scan evaluation reveals a target sign consistent with intussusception. What are the most common causes of intussusception in adults, and how will you manage this patient?
The most common etiology for adult intussusception is a benign or malignant tumor (\> 65% to 90% of cases). In patients with a previous operation, etiologies may include adhesions or the suture line as the lead point.
The management for this patient is surgical exploration with diagnostic laparoscopy or exploratory laparotomy. If any signs of inflammation, ischemia, or malignancy are present, en-bloc resection is recommended. Reduction of the intussusceptum without resection is controversial, but is advocated by some in uncomplicated cases.
60
Five days after undergoing a colectomy, a 60-year-old man presents with acute onset of abdominal distention, severe abdominal pain, obstipation, and fever. Plain abdominal radiography shows a dilated cecum and a soft tissue mass surrounded by two strips of air. How would you manage this patient? If this patient had a partial obstruction and a more benign exam, would this change your management?
* Given the patient's clinical deterioration and radiographic signs (mass), he needs urgent exploration and resection.
* In the event that plain films do not suggest a specific etiology, evaluation of a partially obstructed postoperative patient without a mass would include...
* CT to evaluate for abscess, hematoma, or anastomotic stricture.
* Small bowel follow-through and Gastrografin enema can further exclude stricture, intussusception, or internal hernia.
* In a patient with a clinically partial small bowel obstruction, initial conservative management with a nasogastric tube is appropriate.
61
What criteria would you use to manage nonoperatively a patient with radiographic intussusception?
* Incidental intussusception that is found on abdominal CT evaluation for unrelated causes with no signs or symptoms of bowel obstruction
* In a minimally symptomatic, stable patient with abdominal CT findings that include short length/narrow diameter intussusception and those without a clear lead point
62
On mesenteric angiography and/or CT of the abdomen with IV contrast, identify the major and minor vessels that supply the abdominal viscera.
* SMA provides the blood supply for the small bowel, except for the proximal duodenum (celiac).
* inferior pancreaticoduodenal artery
* ileal and jejunal branches
* the ileocolic, right colic, and middle colic arteries
* The IMA provides blood supply to the large intestine from the distal transverse colon to the rectum.
* left colic and sigmoid arteries and superior rectal artery.
* The venous system parallels the arterial system and drains into the portal vein.
63
How do the SMA and IMA communicate?
What is pathologically important about this location?
The SMA and IMA communicate via the marginal artery of Drummond and the meandering mesenteric artery (Arc of Riolan). The marginal artery runs adjacent to the colonic wall along the entire length of the colon.
Watershed areas: The splenic flexure (Griffiths’ point) and rectosigmoid junction (Sudeck’s point) are areas prone to ischemia, as they are supplied by the terminal branches of the SMA and IMA.
64
Oftentimes, the embolic vs thrombotic mesenteric ischemia can be identified on CT scan. How?
* In embolic mesenteric ischemia, the occlusion of the SMA is just distal to its takeoff from the aorta without associated mural calcifications.
* In thrombotic mesenteric ischemia the occlusion is at the takeoff rather than distal to it and there are associated calcifications along the SMA and likely other vessels.
65
Acute ARTERIAL mesenteric ischemia. What is the physiological mechanism? Etiology?
* Underlying Mechanism: An abrupt decrease or cessation of arterial inflow to the mesenteric vessels.
* This can be caused by an embolism (most frequently a thrombus broken off from the left atrium, ventricle, heart valves, or proximal aorta) or a mesenteric arterial thrombus.
66
In embolic mesenteric ischemia, the embolism usually affects the SMA. Why?
Is presentation chronic or abrupt? Why?
How is this different from acute thrombus?
The embolism usually affects the SMA as it is wide at the origin with a narrow take-off angle. It lodges 3–10 cm distal to the origin where it tapers, usually distal to the takeoff of the middle colic artery, sparing the proximal jejunal branches.
Presentation can be very abrupt as collaterals have not had a chance to form.
An acute thrombus usually occurs at the origin of the celiac axis or SMA in the setting of chronic mesenteric ischemia, which has allowed time for collaterals to form.
67
Acute VENOUS mesenteric ischemia usually involves which vessles? What portions of the bowel are commonly affected?
Venous occlusion usually involves the SMV and most commonly affects the ileum and jejunum followed by the colon and duodenum.
68
Acute VENOUS mesenteric ischemia Underlying Mechanism
* A combination of venous stasis, vascular injury, and hypercoagulability (Virchow’s triad) leads to thrombosis of the mesenteric veins. This leads to increased venous pressure and bowel wall edema, causing submucosal hemorrhage and damage to the vasa recta which leads to ischemic bowel.
* Sequestration of large amounts of fluid in the bowel wall can lead to hypotension and decreased arterial flow which exacerbates the ischemia.
69
Acute NONOCCLUSIVE mesenteric ischemia mechanism? Primarily affects what vessel?
* Underlying Mechanism: Acute onset of decreased arterial blood flow to the intestines.
* Usually due to vasoconstriction during a low flow state.
* Primarily affects the SMA.
70
All conditions causing acute mesenteric ischemia present with
* Acute onset abdominal pain
* Minimal findings on abdominal exam – "pain out of portion to exam"
* Metabolic acidosis
71
Acute Arterial Mesenteric Ischemia Presentation and Risk Factors
* May have a history of chronic mesenteric ischemia – pain after meals and weight loss. Fear of food causing weight loss. May have nausea, emesis, bowel emptying. Bloody bowel movement are less common and indicate advanced ischemia.
* Risk Factors: Any risk factors for embolism or atherosclerosis: Cardiac arrhythmias, valvular disease, infective endocarditis, recent MI, ventricular or aortic aneurysm, smoking, HTN, diabetes, hyperlipidemia. Thrombotic risk factors include PAD, advanced age, low cardiac output states, and traumatic injury to the vessels.
72
Venous Mesenteric Ischemia Presentation, Risk Factors
* Less sudden than arterial mesenteric ischemia. 75% have pain over 2 days.
* Factors leading to a low flow state (venous stasis), vascular injury, or hypercoagulability (Virchow’s triad) contribute to the risk of venous mesenteric ischemia. This can include intra-abdominal inflammation (pancreatitis, diverticulitis, inflammatory bowel disease), abdominal mass causing venous compression, acquired or inherited thrombophilia (malignancy, OCP use, Factor V Leiden, protein S or C deficiency, ATIII deficiency, antiphospholipic syndrome), portal hypertension, personal or family history of VTE.
73
Non-occlusive Mesenteric Ischemia Presentation, Risk Factors
* Presentation: Usually critically ill with severe cardiovascular disease.
* Risk Factors: Factors leading to hypotension or vasoconstriction include heart failure or cardiogenic shock, peripheral artery disease, aortic insufficiency, septic shock, cardiac arrhythmias, recent CABG, dialysis, or medications causing vasoconstriction such as digoxin, alpha-adrenergic agonists, or drugs of abuse such as cocaine.
74
Diagnosis of acute mesenteric ischemia
* The classic triad of an older patient with atrial fibrillation and pain out of portion to exam is present in less than 50% of patients with acute embolic occlusion.
* Any patient that presents with acute onset abdominal pain, pain out of proportion to the abdominal exam findings, and metabolic acidosis should be assumed to have intestinal ischemia.
* Once intestinal ischemia is suspected, workup should be initiated immediately to obtain CT scan with IV contrast or contrast angiography the evaluate the mesenteric vasculature.
75
Nonoperative Management, including Alternative and Adjuvant Treatments of Mesenteric Ischemia
* Resuscitation: optimize cardiac function, correct hypovolemia and metabolic acidosis, assess and correct any cardiac arrhythmias.
* Bowel rest with NPO and NGT decompression
* Broad-spectrum antibiotics.
* Systemic anticoagulation for mesenteric arterial & venous thrombosis (but not NOMI)
* Correct the underlying cause of hypoperfusion and reverse any exacerbating factors, if possible, including limitation of vasoconstrictive medications such as vasopressors.
* Anticoagulation with heparin to limit arterial thrombosis.
76
In a patient with acute mesenteric ischemia and peritonitis, formulate an operative management plan
* Perioperative mortality is high, 30-60%.
* Laparotomy with inspection of the entire bowel.
* If possible, blood flow is restored through embolectomy and/or bypass.
* Non-viable bowel should be resected.
* Use of intraoperative doppler ultrasound, fluorescein dye, and other perfusion mapping technologies can be helpful.
* Review the possibility of a second-look laparotomy to assess viability.
77
Management principles if extensive mesenteric ischemia has occurred.
* If a large amount of ischemic bowel is present with questionable viability, a second-look laparotomy should be planned within 12–48 hours to allow for reevaluation of the bowel after a period of improved perfusion.
* The goal in this setting is to preserve as much bowel as possible.
* Extensive ischemia with resection of large amount of intestine can lead to short gut syndrome, long-term TPN dependence, or may not be compatible with life.
78
You are seeing a patient in the medical intensive care unit for suspected mesenteric ischemia. What history or physical findings can be used to suggest the possible causes of bowel ischemia?
* For nonocclusive ischemia, look for use of alpha-adrenergic pressors or periods of hypotension during hospitalization.
* For arterial occlusive disease, check for calcifications on plain abdominal film and history of vascular disease. For embolus, look for atrial fibrillation.
* For mesenteric venous thrombosis, look for a history of hypercoagulability or for any disease that would lead to this process. Evaluate for cirrhosis or chronic pancreatitis.
79
You plan to operate on a patient with acute superior mesenteric artery occlusion and signs of bowel ischemia. How do you expose the superior mesenteric artery?
In cases of acute embolic occlusion, the anterior approach at the base of the transverse mesocolon is appropriate for rapid exposure (NOTE: retrograde bypasses from the infrarenal aorta cannot be routed to the anteriorly exposed SMA without crossing the duodenum. In these cases, lateral approach craniad to 4th portion of duodenum is necessary).
* Elevate the transverse colon and omentum, wrap intestines in moist lap pads, and retract to right.
* Make a horizontal incision in the peritoneum at the base of the transverse mesocolon extending from the duodenal-jejunal junction toward the patient’s right.
* Identify the SMV/autonomic/nerves/lymphatics—the SMA will be to the patient’s left of the SMV (similar orientation as the aorta and IVC). The middle colic artery can be traced proximally to identify the superior mesenteric artery.
* Isolate the middle and right colic branches as well as the jejunal branches. Can expose more proximal segments by cephalad retraction of the inferior pancreatic border.
80
You are operating on a patient with acute mesenteric ischemia. Having removed a superior mesenteric artery (SMA) embolus, you find four feet of frankly necrotic bowel and a second area of two feet of questionable bowel. What is your plan?
* Resect the necrotic area, consider bringing out the stoma or leaving the stapled bowel in the abdomen, perform a temporary abdominal closure, and re-explore the patient in 12 to 24 hours to examine areas where bowel viability is questionable.
* If the two areas are close together, you can resect both together and perform an end stoma or re-anastomose (but only if the bowel at the margins looks very healthy).
81
In a patient with acute SMA occlusion, you cannot perform an antegrade bypass to the SMA because of previous upper abdominal surgery and dense scarring. What will you do?
Perform a retrograde bypass from the distal aorta or iliac arteries.
* All things being equal, will take the bypass off of the R CIA in a "lazy C" configuration. 2nd choices are L CIA and distal infrarenal aorta.
* Graft will lie better if it is a little longer; some advocate an end to end anastomosis to the SMA.
* If no spillage, can use 6–8 mm Dacron or ringed PTFE (Whether to use prosthetic depends on whether there has been spillage, etc). Consider using greater saphenous vein or femoral vein if there has been spillage.
* Consider an omental flap to cover the graft.
82
Given a patient with Crohn disease, discuss and highlight common anatomic patterns of disease distribution, as well as gross and histologic anatomic characteristics.
* Distribution: TI is MC location, but 15% to 20% present with colonic disease.
* Perianal dz: fissures, fistulas, skin tags, strictures, ulceration; \< 30% if TI dz, \> 50% if colonic dz.
* Histolo: creeping fat; skip; thickened mesentery; largeLN; long, deep, linear ulcers; cobblestoning.
* Micro: chronic inflammatory infiltrate, transmural, noncaseating granulomas, Langerhans giant cells.
83
Identify the incidence and age distribution of Crohn disease and recognize the strong familial association.
* Crohn disease is the most common primary surgical disease of the small bowel.
* The incidence is 50 of 100,000 individuals in the general population.
* There appears to be a bimodal distribution of cases, with the majority presenting between the ages of 15 to 25 years and a second peak between the ages of 55 to 65 years.
* There is a strong familial association, with the risk of development of disease increased approximately 30-fold in siblings and 15-fold in all first-degree relatives.
84
Understand that Crohn disease often has an episodic presentation and may be accompanied by a variety of extraintestinal manifestations. What are common and emergent presentations? What are some extraintestinal manifestations?
* Crohn disease should be considered in patients presenting with chronic _recurring episodes_ of _abdominal pain_ (most common symptom), _diarrhea_ (second most common symptom), and _weight loss_. Patients may also have isolated perianal disease.
* Patients may initially present with fulminant/severe disease or alternatively may have quiescent disease that remains asymptomatic or minimally symptomatic for years. These patients may have more insidious symptoms such as failure to thrive and weight loss.
* Extraintestinal manifestations may occur in 30% of patients. The most common symptoms are skin lesions such as **erythema nodosum** and **pyoderma gangrenosum**, **arthritis** and arthralgias, **uveitis** and iritis, hepatitis, primary sclerosing cholangitis (**PSC**), and aphthous stomatitis. Most extraintestinal manifestations improve after resection of the diseased portion of bowel. However, PSC and ankylosing spondylitis symptoms often do not correlate with intestinal disease activity.
85
Demonstrate competence with diagnostic workup, relevant imaging, serologic markers, and important diseases to exclude in the ddx of Crohn disease.
Diagnosis of Crohn disease: H&P, radiography, laboratory values, and colonoscopy and biopsy.
* Magnetic resonance imaging (**MRI**) and computed tomography (**CT**) are equivalent in identifying gross disease activity and extent of bowel involvement.
* MRI +/- superiority: active inflammatory strictures vs chronic fibrostenotic strictures.
* The Vienna classification predicts remission, relapse, and response to therapy:
* **Age** at diagnosis (less than or greater than 40 years)
* **Behavior** (inflammatory, _stricturing_, or penetrating)
* **Location** (terminal ileum, colon, ileocolonic, upper gastrointestinal tract, anorectal)
* Serologic markers: presence of active disease: **ESR**, **CRP**, **p-ANCA**, **ASCA**.
* **Stool lactoferrin/calprotectin** show promise in predicting clinical recurrence s/p resection.
* It is important to _exclude bacterial_ (Salmonella, Shigella, Campylobacter, Yersinia, Clostridium difficile) _and protozoal infections_ (amebiasis). In immunocompromised individuals, mycobacterial disease and cytomegalovirus should be considered.
* Get stool studies: **FOBT**, **fecal WBC**, **fecal cx**
* It can be difficult to _distinguish Crohn disease from UC_. 5% to 10% of patients will have indeterminate colitis. In general, ulcerative colitis involves the rectum and extends proximally in a continuous fashion. In contrast, Crohn disease is segmental and more likely to result in fistulas and strictures, may have perianal involvement, and often spares the rectum.
86
Crohn disease: percent requiring surgery from diagnosis, probability and timing of surgical disease recurrence
Approximately 70% of patients with the disease require resection within 15 years of diagnosis. Surgical recurrence rates after resection are 24% at 5 years and 35% at 10 years.
87
Presentation and management of toxic colitis in Crohns.
* presents with fever, severe abdominal pain, distention, hemodynamic instability, leukocytosis
* if peritonitis - emergent surgery
* otherwise, aggressive nonoperative management and serial abd exams may be appropriate for 24 to 36 hours
* surgery is necessary if there is no improvement
* radiographic presence of a "megacolon" is not mandatory for the diagnosis of toxic colitis but is often seen
* this mandates emergent total abdominal colectomy w/ end ileostomy - more common w/ UC
88
Approach to perianal dz in Crohn dz.
The general surgical principle is minimizing tissue loss and sphincter injury with drainage catheters and noncutting setons to control perianal abscesses and fistulas.
89
Identify the different options for surgical intervention in Crohn disease.
* Laparoscopic surgery - shown to be both safe and feasible
* shorter op times, dec blood loss, shorter hospital stays, and dec ileus.
* conversion rate of laparoscopic to open procedures is estimated at 10%
* Segmental resection - goal is only to remove grossly inflamed tissue
* Frozen sections - unreliable way to ID microscopic dz, not predictive of recurrence
* Anastomosis vs diversion - depends on intra-abdominal contamx, nutx status, steroids, HDS
* Subtotal colectomy - sepsis d/t Crohn disease (end ileostomy); multiple sites of colonicdz
* Ileorectal anastomosis may be appropriate if the bowel appears healthy
* Ileal-pouch anastomosis - not indicated given the high rate of pouchitis and recurrence
* Proctectomy or total proctocolectomy with end (Brooke) ileostomy - extensive perianal and rectal disease refractory to medical mgmt, removal of the rectum (and possibly the entire colon, based on disease distribution) can aid in sx control.
* Proctectomy is rarely indicated in emergent setting d/t high risk of complications.
90
Give a brief overview of different classes of medical therapy and an approach to how they are prescribed for Crohn dz
* Medical management is frequently first-line therapy for patients with Crohn disease. The different classes of drugs used are corticosteroids; tumor necrosis factor alpha antagonists such as infliximab, adalimumab, and certolizumab; aminosalicylates such as sulfasalazine and mesalamine; immunosuppressives such as azathioprine, 6-mercaptopurine, methotrexate, and tacrolimus; and novel agents such as vedolizumab and ustekinumab.
* There is a top-down versus a step-up approach to starting medications. This entails starting with a biologic agent versus starting with aminosalicylates, respectively. The top-down approach is used more frequently in patients with severe Crohn disease.
91
Understand that long-term follow-up is key to monitoring for recurrence of Crohn disease as well as early diagnosis and management of possible oncologic complications of the disease.
* When does endoscopic recurrence of Crohn's disease occur?
* What is long-standing Crohn's associated with?
* When should surveillance start?
* What cancer are patients on immunomodulators at increased risk for?
* Endoscopic recurrence can be as high as 80% at 1 year after resection for Crohn colitis.
* Long-standing Crohn dz is associated with inc risk of cancer of the small intestine and colon.
* Surveillance should start 8 years after disease dx or at the time of dx of PSC and be performed every 1 to 3 years. A random biopsy protocol mandates four biopsies every 10 cm from the cecum to the rectum. Chromoendoscopy uses indigo carmine or methylene blue to enhance mucosal irregularities.
* Hartmann pouch/residual rectum - surveillance of the rectum every 1 to 3 yrs
* There is an increased risk of squamous cell carcinoma of the vulva and anal canal and Hodgkin and non-Hodgkin lymphomas in patients using immunomodulators for medical treatment.
92
A woman with known stricturing intestinal Crohn disease presents with abdominal pain, nausea, and vomiting that started 4 days ago. She is still passing flatus but notes decreased frequency of bowel movements. She has had a previous stricturoplasty of a segment of small bowel. She is found on CT to have dilated loops of small bowel with a possible transition point in the right lower quadrant. What are your diagnostic and management options for this patient?
* Pt is partially obstructed - trial of conservative management: NGT, NPO, IVF, lytes, exams
* CT enterography or magnetic resonance enterography - eval for stricturing dz
* If med mgmt fails, surgical intervention will be required.
* Formulation of the surgical plan should be based on intraoperative findings.
* Assess safety and viability of stricturoplasty versus resection if small bowel stricture.
* Heineke-Mikulicz - strictures 5 to 7 cm in length, the procedure requires pliable mesentery so the tissues can be approximated in a transverse fashion.
* Finney - strictures 10 to 15 cm in length and that the procedure allows maximum retention of bowel length.
* Can result in the creation of bypassed diseased segment that may contain stagnant bowel.
* Michelassi - addresses long-segment diseased bowel and mesentery but requires careful division of potentially very fibrotic mesentery. This is ideal for patients with long strictures at high risk for short bowel syndrome.
* Recognize that if resection is performed, the goal is grossly normal tissue; there is no role for frozen intraoperative assessment of margins.
93
A man with Crohn disease presents to the emergency department with abdominal pain, nausea, vomiting, fever, leukocytosis (white blood count of 18,000/µL), and tachycardia. He is found on CT of the abdomen and pelvis to have mixed-density free fluid in the pelvis with fat stranding and a thickened right colonic wall. How do you proceed with management of this patient?
* Prompt BS IV ABX, IVF resuscitation, operative intervention
* Segmentectomy vs TAC - delayed proctectomy if necessary (pt too sick)
* Anastomosis vs diverting or permanent ostomy - diversion preferred d/t intra-abdominal sepsis
