Chapter 355 - Acute Intestinal Obstruction Flashcards
Morbidity and mortality from acute intestinal obstruction have been increasing over the past several decades.
True or False?
False.
How can one classify the extension of the mechanical obstruction? What does it correlate to?
“The extent of mechanical obstruction is typically described as partial, high-grade, or complete - generally correlating with the risk of complications and the urgency with which the underlying disease process must be addressed.”
What does characterize a “stragulated” obstruction?
Vascular insufficiency and intestinal ischemia.
How does one pathophysiologically differentiate a mechanical obstruction from a functional one?
“Acute intestinal obstruction occurs either mechanically from blockage or from intestinal dysmotility when there is no blockage. In the latter instance, the abnormality is described as being functional.”
“Functional obstruction, also known as ileus and pseudo-obstruction, is present when dysmotility prevents intestinal contents from being propelled distally and no mechanical blockage exists.”
Name all the common causes of acute intestinal obstruction. Organize them by categories.
- Extrinsic disease: adhesions (especially due to previous abdominal surgery), internal or external hernias, neoplasms (including carcinomatosis and extraintestinal malignancies, mostly commonly ovarian), endometriosis or intraperitoneal abcesses, and idiopathic sclerosis;
- Intrinsic disease: (1) congenital: e.g.: malrotation, atresia, stenosis, intestinal duplication, cyst formation, and congenital bands - the latter rarely in adults; (2) inflammation: e.g.: inflammatory bowel disease, especially Crohn’s disease but also diverticulitis, radiation, tuberculosis, lymphogranuloma venereum, and schistosomiasis); (3) Traumatic: e.g.: hematoma formation, anastomotic strictures; (4) other, including intussusception (where the lead point is typically a polyp or tumor in adults), volvulus, obstruction of duodenum by superior mesenteric artery, radiation or ischemic injury, and aganglionosis, which is Hirschprung’s disease.
- Intraluminal abnormalitis: bezoars, feces, foreign bodies including inspissated barium, gallstones (entering the lumen via a cholecystoenteric fistula), enteroliths.
Crohn’s disease is only associated with acute intestinal obstruction after surgery, due to the risk of adhesions and anastomotic strictures.
True or False?
False.
Although the risk is especially higher after surgery, Crohn’s disease might lead to adhesions due to the transmural inflammation of the intestinal wall.
State the percentage of cases due to acute intestinal obstruction for each of the following: (i) Hospitalizations; (ii) Emergent general surgery admissions; (iii) Involvement of the small and the large bowel; (iv) Significant ischemia due to small bowel obstruction; (v) Mortality rate before 24-30h and after.
(i) 1-3%
(ii) 1/4
(iii) 80% and 20%, respectively
(iv) 1/3
(v) 8% and its triple, respectively
Name the three most common causes extrinsic small bowel obstruction in the United States and Europe.
Postoperative adhesions (>50%), carcinomatosis, or herniation of the anterior abdominal wall.
Adhesions are responsible for >90% of cases of early postoperative obstruction that require intervention.
True or False?
True.
Name common and rare causes of carcinomatosis.
“Carcinomatosis most often originates from the ovary, pancreas, stomach, or colon, although rarely, metastasis from distant organs like the breast and skin can occur.”
Hernias are more common in developed countries as the cause of obstruction in comparison to neoplasias.
True or False?
False.
- Postoperative adhesions (50%)
- Neoplasms (20%)
- Hernias (10%)
- Inflammatory bowel disease, other inflammation (5%)
- Other (less than 15%)
Appendectomy has a small risk for adhesions.
True or False?
False.
Laparoscopic procedures have fewer cases of postoperative adhesions in comparison to open surgery, but the risk of obstruction is not eliminated.
True or False?
True.
Give one example of a risk procedure for internal herniation.
Roux-en-Y gastric bypass (either via open surgery and laparoscopically).
Successfully treated adhesive small-bowel obstruction might recur in the future. What is the rate of recorrence?
“The rate varies according to how patients were initially managed. Approximately 20% of patients who were treated conservatively and between 5 and 30% of patients who were managed operatively will require readmission within 10 years.”
What are the most common causes of colonic obstruction?
“Cancer of the descending colon and rectum is responsible for approximately two-thirds of all cases, followed by diverticulitis and volvulus.”
Explain the pathophysiology of colonic volvulus and cecal volvulus, as well as their frequency. What are the main risk factors for volvulization?
“Volvulus, which occurs when bowel twists on its mesenteric axis, can cause partial or complete obstruction and vascular insufficiency. The sigmoide colon is most commonly affected, accounting for approximately two-thirds of all cases of volvulus and 4% of all cases of large-bowel obstruction. The cecum and terminal ileum can also volvulize, or the cecum alone may be inveolved as a cecal bascule. Risk factors include institutionalization, the presence of neuropsychiatric conditions requiring psychotropic medication, chronic constipation, and aging”
Which countries and age groups are most affected by volvulus?
“patients typically present in their seventies or eighties. Colonic volvulus is more common in Eastern Europe, Russia, and Africa than it is in the United States.”
What are the other names for functional obstruction?
Ileus and pseudo-obstruction.
Name the most common causes of ileus of the intestine.
- Intraabdominal procedures, lumbar spinal injuries, or surgical procedures on the lumbar spine and pelvis
- Metabolic or electrolyte abnormalities, especially hypokalemia and hypomagnesemia, but also hyponatremia, uremia, and severe hyperglicemia
- Drugs such as opiates, antihistamines, and some psychotropic (e.g., haloperidol, tricyclic antidepressants) and anticholinergic agents
- Intestinal ischemia
- Intraabdominal or retroperitoneal inflammation or hemorrhage
- Lower lobe pneumonias
- Intraoperative radiation (likely due to muscle damage)
- Systemic sepsis
- Hyperparathyroidism
- Pseudo-obstruction (Ogilvie’s syndrome)
- Ileus secondary to hereditary or acquired visceral myopathies and neuropathies that disrupt myocellular neural coordination
- Some collagen vascular diseases such as lupus erythematosus or scleroderma
How does one explain the dilation proximal to the point of obstruction?
“Increased intestinal contractillity, which occurs proximally and distal to the obstruction, is a characteristic response. Subsequently, intestinal peristalsis slows as the intestine or stomach proximal to the point of obstruction dilates and fills with gastrointestinal secretions and swallowed air. Although swallowed air is the primary contributor to intestinal distension, intraluminal air may also accumulate from fermentation, local carbon dioxide production, and altered gaseous diffusion.”
Explain the pathophysiology of intestinal ischemia due to acute intestinal obstruction.
“Intraluminal dilation also increases intraluminal pressure. When luminal pressure exceeds venous pressure, venous and lymphatic drainage is impeded. Edema ensues, and the bowel wall proximal to the site of blockage may become hypoxemic. Epithelial necrosis can be identified within 12 h of obstruction. Ultimately, arterial blood supply may becomse so compromised that full-thickness ischemia, necrosis, and perforation result.”
What are the most common intraluminal bacteria? Where else would you expect to find them?
“The most commonly cultured intraluminal organisms are Eschericia coli, Streptococcus faecalis, and Klebsiella, which may also be recovered from mesenteric lymph nodes and other more distant sites.”
