Small Bowel Obstruction PDF

Definition: Bowel obstruction is when the normal flow of contents moving through the intestines is interrupted. Sub-classification: ◦ Mechanical. ‣ Caused by actual blockages in the large or small intestine, and it can be defined as: Pa...

Definition: Bowel obstruction is when the normal flow of contents moving through the intestines is interrupted. Sub-classification: ◦ Mechanical. ‣ Caused by actual blockages in the large or small intestine, and it can be defined as: Partial: ◦ Gas and liquid stool can pass Complete: ◦ Nothing can pass ◦ Functional (AKA: ileus). ‣ Functional causes disrupt peristalsis, which are the waves of contraction that move through the smooth muscles of the bowel wall that pushes food through the intestines. Etiology: Mechanical obstruction: ◦ Small intestine Most common cause: ‣ Postoperative adhesions. ◦ Large intestine Most common cause: ‣ Volvulus ◦ Common causes of mechanical obstruction both small and large intestine: ‣ Inflammatory bowel disease. Cause strictures and adhesions ‣ Ingestion of a foreign body. ‣ intussusception. Most common cause of bowel obstruction in children under the age of 2. Functional causes: ◦ Causes include anything that decreases smooth muscle contractility. ◦ Most common cause: ‣ Postoperative ileus Causes Related to surgery: ◦ Most common cause of BO in pt with previous surgery: ‣ Adhesions ◦ Most common cause of BO in pt without previous surgery: ‣ Hernias Intrinsic vs. Extrinsic causes of bowel obstructions: Etiology from Step-up to surgery: Pathophysiology: Grossly: When obstruction happens, regardless of the cause, the gas and stool distal (after) the obstruction will get passed, meanwhile proximal (before) the obstruction the bowel contents will start to accumulate. --> Over time, the gas and stool causes pressure inside the bowel lumen to increase, so the intestinal contents push towards the intestinal wall, compressing the mucosal blood and lymphatic vessels. --> Since the walls of veins and lymphatics are weaker and easier to compress compared to arteries, venous and lymphatic drainage are the first ones to get blocked. --> The pressure pushes the water in these vessels into the surrounding tissue, leading to mucosal edema. --> If pressure inside the lumen gets even higher, it also compresses mucosal arteries, leading to ischemia or reduced blood flow to the intestinal wall. --> In turn, ischemia causes hypoxia, or low oxygen supply. At the cellular level: This is accompanied by the production of reactive oxygen species; which can damage DNA, RNA, and proteins of the cells in the epithelial layer and lamina propria of the mucosa, leading to cell death, or mucosal infarction. --> So, when the mucosa becomes damaged and capillary blood vessels in the lamina propria rupture, blood enters the bowel lumen. --> All this stool and blood in the lumen becomes a nutritious feast for bacteria that normally reside in the intestines, and they start growing out of control. --> These bacteria can then get into the intestinal wall, where they get attacked by macrophages rushing into the mucosa. --> These macrophages then release inflammatory cytokines like tumor necrosis factor-alpha, which cause blood vessels to become more permeable to fluid and to more immune cells, further increasing mucosal edema, inflammation, and damage. --> The overall result is the compromised ability of the mucosa to absorb food and water, which may lead to dehydration and loss of electrolytes, like sodium, potassium and chloride. --> Now, as all these lumen contents continues to build up, intraluminal pressure rises even higher, making the problem even worse if not corrected. --> And if this pressure becomes high enough, even larger arteries get compressed, meaning that the arterial supply to more layers of the bowel wall is compromised. --> In other words, bowel ischemia and infarction extend from just the mucosa to all layers bowel wall, known as a transmural infarction. --> This may result in perforation, so there’s basically a hole in the bowel wall that connects the lumen to the peritoneal cavity. And all the bacteria that have been accumulating inside the lumen, can now easily leak out, causing peritonitis. --> Now, since the layers of the peritoneum are very rich in blood vessels, large numbers of bacteria from the peritoneal cavity can sneak into the bloodstream, triggering a massive inflammatory response called sepsis. --> In sepsis, blood vessels throughout the body can get leaky, letting the water in blood escape into the interstitial space. --> If too much fluid is lost, blood volume drops and so does the blood pressure. This leads to a decrease in the amount of blood reaching vital organs to deliver oxygen and we call this shock. Ultimately, this can cause organ failure and death. Clinical features: Cardinal signs: ◦ The cardinal signs of mechanical bowel obstruction regardless of the underlying etiology are: ‣ Abdominal pain, Vomiting, constipation, Abdominal distention, and decreased bowel sounds ◦ Difference between complete and partial obstruction: ‣ Complete bowel obstruction: Can be associated with obstipation (complete inability to pass stool or gas) ‣ Partial bowel obstruction: Can be associated with the intermittent passage of flatus and overflow diarrhea Cause of colicky pain: ◦ ↑ Peristaltic activity that attempts to overcome the obstruction Cause of diarrhea in SBO: ◦ Since the ↑ motility is not localized, patients with SBO can present with diarrhea. Cause of nausea and vomiting: ◦ Distention stretches visceral peritoneum, resulting in autonomic stimulation with progressive nausea and emesis. Progression and Complications: Depending on the onset and progression of clinical features, mechanical bowel obstruction can be classified as simple or complicated and acute or subacute. ◦ Simple bowel obstruction: ‣ Bowel obstruction with no evidence of complications (i.e., no features of bowel ischemia, bowel perforation, or red flags for complicated bowel obstruction). ◦ Complicated bowel obstruction: ‣ Bowel obstruction associated with Strangulation Ischemic necrosis Perforation. ◦ Red flags for complicated bowel obstruction: ‣ Pain out of proportion ‣ Peritoneal signs ‣ Signs of systemic toxicity, e.g., SIRS (Systemic inflammatory response syndrome) ‣ Hemodynamic instability ‣ Laboratory abnormalities: e.g., significant leukocytosis, metabolic acidosis, ↑ lactate. Diagnosis: General principles ◦ Imaging is required to: ‣ Confirm mechanical bowel obstruction ‣ Identify the site and assess the severity of the obstruction ‣ Identify complications and the underlying etiology of the obstruction ‣ Guide treatment planning ◦ No reliable physical finding or serum laboratory for: ‣ Distinguishes ileus from mechanical obstruction ‣ Rules out strangulated obstruction. ◦ Laboratory studies provide supportive evidence to help assess the severity of the obstruction. History is critical. ◦ 1. Prior abdominal  surgery ◦ 2. Signs of infection or peritonitis ◦ 3. Prior history of obstructions ◦ 4. History of malignancy or inflammatory bowel disease ◦ 5. History of abdominal trauma ‣ a. Splenosis ‣ b. Diaphragmatic hernia ◦ 6. History of endometriosis Imaging: ◦ Abdominal X-ray (AXR): ‣ Indication: Most appropriate initial test in hemodynamically unstable patients or in resource-poor centers. ‣ Findings Proximal bowel dilatation Minimal or no intraluminal air distal to the obstruction Stepladder sign (best seen on an upright view): multiple air-fluid levels and stacked dilated loops of small bowel Chest x-ray : Air under the diaphragm is an indicator of bowel perforation. ◦ CT abdomen and pelvis (GOLD STANDARD) ‣ indication: With IV contrast: most appropriate initial test in hemodynamically stable patients with ‣ Findings: Transition point: sudden narrowing of the bowel lumen at the site of obstruction Similar to those in abdominal X-ray ◦ Abdominal ultrasound: ‣ Indication: Hemodynamically unstable patients (may be preferred over abdominal x-ray) ‣ Findings: Most Specific sign: Multiple fluid-filled dilated bowel loops > 2.5 cm in diameter adjacent to collapsed bowel loops. Thickened bowel wall Prominent plicae circulares of dilated small bowel loops (sometimes referred to as the keyboard sign) ◦ Barium enema or water-soluble contrast enema. ‣ what is is it: X-ray of the colon and rectum after rectal administration of a contrast agent. ‣ Indication: Suspected distal LBO if CT is unavailable. ‣ Findings. Tapering of the bowel lumen at the site of obstruction ◦ Complete bowel obstruction: ‣ Contrast not visible beyond the obstruction ◦ Partial bowel obstruction: ‣ Small amount of contrast visible beyond the obstruction Bird beak sign: in volvulus Apple core sign: in colonic malignancy Management: BO is an emergency and should be detected and managed early to minimize the risk of bowel perforation and strangulation, and the subsequent development of sepsis. The initial management of bowel obstruction is similar to that of undifferentiated acute abdomen. Approach: ◦ ABCDE approach: ‣ Evaluate vital signs, volume status, and the need for invasive monitoring. ◦ Initial management ‣ NPO status Term used to indicate that nothing (e.g., medications, food) should be taken by mouth) ‣ Obtain IV access with two large-bore peripheral IVs; Simultaneously draw blood for urgent laboratory studies. ‣ IV fluid resuscitation Patients with bowel obstruction are likely to be hypovolemic due to dehydration from recurrent vomiting and/or third-spacing due to bowel dilation. ‣ Electrolyte repletion as needed ‣ Insert a nasogastric tube in patients with recurrent vomiting and/or significant abdominal distention. ◦ Administer supportive care as needed. ‣ Parenteral analgesics ‣ Parenteral antiemetics ‣ Empiric antibiotics for intra-abdominal infections (not routinely recommended for simple bowel obstruction) If fever and/or leukocytosis are present For strangulated or perforated bowel obstruction Treatment: Interventional management ◦ Surgery: ‣ Indication: Complicated bowel obstruction (i.e., signs of ischemia, perforation, or clinical deterioration) ‣ Procedure: Exploratory Laparotomy ◦ Management of the obstruction (e.g., adhesiolysis, hernia reduction, cecopexy, tumor resection) ◦ Resection of gangrenous bowel with restoration of intestinal transit or creation of a stoma ◦ Endoscopic intervention: ‣ Considered for bowel obstruction with no signs of Strangulation or Perforation. ‣ Indications: Sigmoid volvulus Intraluminal bowel obstruction that is within reach of an endoscope, ◦ For the removal or fragmentation of foreign objects that are within reach of an endoscope ◦ Stool evacuation ‣ Indication: simple bowel obstruction caused by fecal impaction Nonoperative management: ◦ Indictions: ‣ Early postoperative bowel obstruction (i.e., within 6 weeks of abdominal surgery). ‣ Partial bowel obstruction with no evidence of complications ‣ Consider in patients with complete SBO and no evidence of complications. ◦ Contraindications: ‣ Complicated bowel obstruction (e.g, peritoneal signs, signs of strangulation) ‣ Refractory metabolic acidosis ‣ Significant leukocytosis (> 18,000/mm3) ‣ Significant cecal dilation ◦ Initial measures: ‣ Bowel Rest (NPO) ‣ Supportive care ‣ NG tube (Bowel decompression) in (persisting vomiting) ◦ Duration: ‣ Not more than 72 hours. Complications: Important complication: ◦ Bowel ischemia ◦ Bowel perforation ◦ Peritonitis Hint on an accruing complication: ◦ A change in the character of pain (colicky pain becoming continuous), rebound tenderness on examination, and/or signs of sepsis in a patient with bowel obstruction indicate the onset of complications and necessitate emergency surgical intervention. Define and propose management plan for paralytic ileus and colonic pseudo-obstruction: Management: ◦ Conservative management (Most of the time) ‣ is indicated in all patients without signs of infectious causes or complications of paralytic ileus. ◦ Surgery (Rarely): ‣ Not routinely indicated, except in the following situations: Treatment of the underlying cause, e.g., appendicitis Treatment of complications, (e.g., intestinal ischemia or perforation (rare in paralytic ileus)  General Surgery [SMALL BOWEL] Introduction The main point in dealing with the bowel is to decide if there’s a youcanassessthat bytapingonapositionontheirbellythat need to operate or if we can can watch and wait. If someone is it if dose hurts herefers the to a reat hatd osethat'sparitonitis ever peritoneal (rebound tenderness, involuntary guarding) they commoninperitonitis go to surgery. Beyond that, it’s knowing when to go to surgery Colicky Abdominal Pain, and when to attempt conservative measures that defines Fever, Leukocytosis, Borborygmi, Constipation, questions of the small bowel. Peritoneal Findings Obstipation t he reachthe the obstruction p ainbut as peristalsis whenitpassitpains Small Bowel Obstruction KUB SBO is caused by either adhesions (most common with CT sasafollowup obstruction ji previous abdominal surgeries) or hernias (most common cause winner you Ø total block nowisobstruction without previous surgery). There will be colicky abdominal Barium is ispartial or pain with progressive distention of the abdomen. Early on, there complate will be gas/stool and a condition called borborygmi where Gas Complete Strangulated there are high-pitched, rapid, crescendo bowel sounds. Late, Obstruction the distal intestines decompress while the proximal bowel Incomplete Surgery Surgery Emergently swells. At this point, there are Ø bowel sounds and Ø gas or Obstruction 3-4d stool. Confirm what’s seen on an upright KUB (1st test, dilated ØΔ loops of bowl with air-fluid levels) with either a small bowel Wait for resolution devopspariton iti s series (ingested barium and serial x-rays) or a CT-Scan. If they Serial Abd Exams ifthe it are peritoneal or there’s a complete bowel obstruction, they go to Ex-Lap. If they have an incomplete obstruction do serial hernias exams and attempt conservative measures (fluids, potassium rateablecangoback incarceratedcan't back and NG tube decompression). ineducable go strangulated ischemic Hernias Hernias are just a wall defect that intestines can move through. Question is: When do Hernias go to OR? Direct hernias are groin hernias of adults that pass directly 1. Emergent = Black/Blue, Acute Abdomen, Sepsis through the transversalis fascia and are the “adult hernia”. 2. Urgent = Acutely irreducible or +SBO without Emergent Indirect hernias are groin hernias which pass through the 3. Elective = reducible hernia and Ø SBO and Ø Acute Abd inguinal ring, an embryonic defect, so are the “baby hernia”. Femoral hernias are groin hernias pass under the inguinal Question is: What type is it? ligament and are the “lady hernia.” Finally, the most common is ♀ = Femoral Hernia, under ligament Lady hernia femoral female a ventral hernia, caused by an incomplete closure after surgery ♂ adult = direct, through transversalis Adult hernia (i.e. iatrogenic) “surgery hernia”. Hernias aren’t a big deal so ♂ baby = indirect, through the inguinal ring Baby Hernia long as the hernia is reducible. If it becomes irreducible (that Surgery = Ventral, through abdominal wall Surgery hernia is, it becomes incarcerated) it can present with obstruction. rentsupinscrotum Reducible is considered elective, incarcerated urgent. If the incarcerated hernia turns strangulated, with obvious peritoneal signs and an affected hernia, it becomes a surgical emergency Reducible Elective Elective requiring emergent Ex-Lap. Abdominal Physical Irreducible Urgently Appendicitis (technically large bowel, I know) Incarcerated Bulge Exam Elective A patient who presents with a classic history doesn’t need diagnostic tests. Go straight to treatment (surgery). A patient Acute that presents with anorexia, then vague periumbilical pain that Strangulated Emergent Abdomen Ex-Lap resolves but comes back at McBurney’s Point (RLQ) with focal peritoneal findings is appendicitis. If unsure, get a CT Paritonial signs scan while preparing the OR. For the test, if the diagnosis is Periumbilical Pain obvious go straight to surgery. moved to McBurney’s point Appendicitis Emergent Carcinoid with Anorexia, N/V Ex-Lap Let’s briefly mention it. Carcinoid produces serotonin. Intestinal serotonin is degraded by the liver. With mets to the and peritoneal signs liver, serotonin goes to the R heart causing fibrosis, flushing, Negative ? wheezing, and diarrhea. The lungs degrade serotonin sparing Vague symptoms Physical the L heart, releasing 5-HIAA to be excreted into the urine; it is worrisome for Exam Inflammation used as a screening tool for the cancer. It must be staged and resected. Appendicitis Surgery Now Perforation Surgery + ICU © OnlineMedEd. http://www.onlinemeded.org