Small Intestine

What does the cranial limb of the midgut loop develop into?

• Distal duodenum, jejunum, and proximal ilium

What does the caudal limb of the midgut loop develop into?

• Distal ilium and proximal two-thirds of the transverse colon

What structure joins the yolk sac to the juncture of the cranial and caudal limbs of the midgut loop?

• The vitelline duct

What is a persistent vitelline duct otherwise known as?

• Meckel diverticulum

How much does midgut loop rotate during normal physiologic herniation of bowel?

• 270° counterclockwise rotation

How long is the entire small intestine, from the pylorus to the cecum?

• ~6 m (20 ft)

How long is the duodenum?

• 26 cm (9.8 in.)

How long is the jejunum?

• 2.5 m (8.2 ft)

How long is the ileum?

• 3.5 m (11.5 ft)

What peritoneal fold supports the duodenojejunal angle, which marks where the duodenum ends and the jejunum begin?

• Ligament of Treitz

What are plicae circulares?

• Circular folds of mucosa in the small bowel lumen (also known as valvulae conniventes)

Excluding the proximal duodenum, what artery supplies the entire blood supply of the small bowel?

• Except for the proximal duodenum that is supplied by branches of the celiac axis, the supply comes entirely from the superior mesenteric artery (SMA).

Where is the parasympathetic innervation of the small bowel derived from?

• Parasympathetic fibers are derived from the vagus, which traverse the celiac ganglion to supply the small bowel.

Where is the sympathetic innervation of the small bowel derived from?

• Sympathetic fibers originate from 3 sets of splanchnic nerves; ganglion cells found in a plexus around base of SMA.

Describe the lymphatic drainage of the small intestine:

• From mucosa through wall of the bowel

• Mesenteric lymph nodes adjacent to the bowel

• Regional nodes adjacent to the mesenteric arterial arcades

• Group of lymph nodes at the base of the superior mesentery vessels

• Cisterna chyli

• Thoracic ducts

• Return to venous system

What are the 4 layers of the small bowel? From out to in:

• Serosa

• Muscularis propria

• Submucosa

• Mucosa

The muscularis propria comprises what 2 muscle layers?

• Thin outer longitudinal layer; thicker inner circular layer (with myenteric [Auerbach] plexus between the muscle layers)

The strongest layer of the small bowel:

• Submucosa

What extensive plexus of nerve fibers and ganglion cells are found in the submucosa of the small bowel?

• Meissner plexus

What 3 layers comprise the mucosa of the small bowel?

• Muscularis mucosae (thin layer of muscle that separates mucosa from submucosa)

• Lamina propria (connective tissue layer between epithelial cells and muscularis mucosae)

• Epithelial layer (continual sheet of epithelial cells covering villi and lining crypts)

Which layer of small bowel mucosa is responsible for combating microorganisms that penetrate the overlying small bowel epithelium?

• Lamina propria (contains a rich supply of immune cells)

What are the 4 main cell types found in the small bowel mucosal layer?

• Absorptive enterocytes

• Goblet cells (secretes mucus)

• Paneth cells (secrete lysozyme, tumor necrosis factor)

• Enteroendocrine cells (produce gastrointestinal hormones)

Term for the fuzzy coat of glycoprotein that covers the microvilli to further increase absorption:

• Glycocalyx

The portions of the duodenum that are retroperitoneal:

• Second portion (descending), third portion (transverse)

The vascular supply of the duodenum is:

• Anterosuperior pancreaticoduodenal and posterosuperior pancreaticoduodenal arteries (from gastroduodenal artery) and anteroinferior pancreaticoduodenal and posteroinferior pancreaticoduodenal arteries (from SMA)

What is the first branch off of the SMA?

• Anteroinferior pancreaticoduodenal and posteroinferior pancreaticoduodenal arteries

What is the primary responsibility of the small bowel?

• The absorption of carbohydrates, proteins, fats, ions, vitamins, and water

What does the terminal ileum absorb?

• Fatty acids; bile salts; vitamin B₁₂

What enzymes involved in carbohydrate digestion are contained in the brush border of the small intestine?

• Lactase; maltase; sucrase-isomaltase; trehalase

Name the substrate and the product for lactase, located in the brush border of the small intestine:

• Substrate: lactose

• Product: glucose, galactose

What brush border enzyme in the duodenum activates pancreatic trypsinogen that is secreted into the intestine?

• Enterokinase

What 3 principal pancreatic proteases comprise the endopeptidases?

• Trypsin

• Chymotrypsin

• Elastase

What 2 principal pancreatic proteases comprise the exopeptidases?

• Carboxypeptidase A

• Carboxypeptidase B

What is the primary action of trypsin?

• Forms products with basic amino acids at carboxyl-terminal end by attacking peptide bonds involving basic amino acids.

What is the primary action of chymotrypsin?

• Forms peptide products with aromatic amino acids, leucine, glutamine, and methionine at carboxyl-terminal ends by attacking peptide bonds involving aromatic amino acids, leucine, glutamine, and methionine.

What is the primary action of elastase?

• Forms products with neutral amino acids at carboxyl-terminal end by attacking peptide bonds involving neutral aliphatic amino acids.

What is the primary action of carboxypeptidase A?

• Attacks peptides with aromatic and neutral aliphatic amino acids at carboxyl-terminal end

What is the primary action of carboxypeptidase B?

• Attacks peptides with basic amino acids at carboxyl-terminal end

Normally, what percentage of digestion and absorption of protein is completed in the jejunum?

• 80% to 90%

Describe the process of the fat digestion in the small bowel:

• Fat globules from the diet are emulsified with the help of bile

• Pancreatic lipase splits triglycerides into free fatty acids and 2-monoglycerides

• Bile salts form micelles with the monoglycerides and free fatty acids (dissolved in central hydrophobic portion of micelles) formed from lipolysis

• Micelles carry the products of fat hydrolysis to brush border where absorption occurs

What is a micelle?

• A small spherical globule with a lipophilic sterol nucleus and a polar hydrophilic group that projects outward and is composed of 20 to 40 molecules of bile salts

What kind of fatty acids are absorbed directly into the portal blood?

• Short- and medium-chain fatty acids

What kind of fatty acid is absorbed via chylomicrons passing from the epithelial cells into lacteals, which pass through the lymphatics into the venous system?

• Long-chain fatty acids

What is the composition of a chylomicron?

• ~90% triacylglycerol; ~10% phospholipid; cholesterol; protein

What percentage of fat absorption occurs by way of the thoracic lymphatics?

• 80% to 90%

What percentage of bile salts are reabsorbed?

• 95%

How are unconjugated bile acids absorbed into the jejunum?

• Passive diffusion

Only location of the small bowel where conjugated bile is absorbed:

• Terminal ileum

What is bile conjugated to?

• Glycine and taurine

What are the primary bile acids?

• Chenodeoxycholic; cholic

What are the secondary bile acids?

• Dexoycholic; lithocholic

How much is the total bile salt pool in humans?

• 2 to 3 g

Approximately how much bile is lost in the stool in 1 day?

• 0.5 g

Number of times the bile recirculates in 24 hours (enterohepatic circulation):

• ~6 times

In the ileal enterocyte, what binds and transports free vitamin B₁₂ into the portal circulation?

• Transcobalamin II

What are the 3 areas of the small bowel where gut-associated lymphoid tissue can be found?

• Intraepithelial; lamina propria; Peyer patches

What cells contained within the follicle-associated epithelium of the small bowel serve as a site for the selective sampling of intraluminal antigens?

• M cells (microfold cells)

What is the most important hormone in the migrating motor complex?

• Motilin

During which phase of the migrating motor complex is motilin found at its peak plasma levels?

• Phase III

What happens during Phase I of the migrating motor complex?

• Rest

What happens during Phase II of the migrating motor complex?

• Acceleration and gallbladder contraction

What happens during Phase III of the migrating motor complex?

• Peristalsis

What happens during Phase IV of the migrating motor complex?

• Deceleration

What is the primary effect of the hormone gastrin?

• Stimulates gastric mucosal growth; stimulates acid and pepsinogen secretion

Location of the cells that release the hormone gastrin:

• G cells in the duodenum; antrum

What are the major stimulants for the release of the hormone gastrin?

• Amino acids; peptides; antral distention; gastrin-releasing peptide (bombesin); vagal and adrenergic stimulation

What is the primary effect of the hormone cholecystokinin?

• Stimulates gallbladder contraction; relaxes sphincter of Oddi; stimulates pancreatic enzyme secretion; inhibits gastric emptying

Location of the cells that release the hormone cholecystokinin:

• Duodenum; jejunum (I cells)

What are the major stimulants for the release of the hormone cholecystokinin?

• Amino acids; peptides; fats

What is the primary effect of the hormone secretin?

• Stimulates flow/alkalinity of bile and release of water and bicarbonate from pancreatic ductal cells; inhibits gastrin releases and gastric acid secretion and motility

Location of the cells that release the hormone secretin:

• Duodenum; jejunum (S cells)

What are the major stimulants for the release of the hormone secretin?

• Bile salts; fatty acids; luminal acidity

What is the primary effect of the hormone somatostatin?

• Inhibits gastric acid secretion, release of gastrointestinal hormones, small bowel water and electrolyte secretion, and secretion of pancreatic hormones (universal "off" switch)

Location of the cells that release the hormone somatostatin:

• Pancreatic islets (D cells); antrum; duodenum

What are the major stimulants for the release of the hormone somatostatin?

• Pancreas: amino acids, cholecystokinin, and glucose;

• Gut: acid, fat, protein, and other hormones (gastrin, cholecystokinin)

What is the primary effect of the hormone gastrin-releasing peptide?

• Stimulates release of all gastrointestinal hormones (except secretin), gastric acid secretion and release of antral gastrin, gastrointestinal secretion and motility, and growth of intestinal mucosa and pancreas (universal "on" switch)

Location of the cells that release the hormone gastrin-releasing peptide:

• Small bowel

What are the major stimulants for the release of the hormone gastrin-releasing peptide?

• Vagal stimulation

What is the primary effect of the hormone gastric inhibitory peptide?

• Stimulates pancreatic insulin release in response to hyperglycemia and inhibits gastric acid and pepsin secretion

Location of the cells that release the hormone gastric inhibitory peptide:

• Duodenum; jejunum (K cells)

What are the major stimulants for the release of the hormone gastric inhibitory peptide?

• Adrenergic stimulation

• Glucose

• Fat

• Protein

What is the primary effect of the hormone motilin?

• Stimulates upper gastrointestinal tract motility (may initiate migrating motor complex)

Location of the cells that release the hormone motilin:

• Duodenum; jejunum

What are the major stimulants for the release of the hormone motilin?

• Gastric distention; fat

What is the primary effect of the hormone vasoactive intestinal peptide?

• Potent vasodilator; stimulates pancreatic and intestinal secretion and inhibits gastric acid secretion (primarily functions as a neuropeptide)

Location of the cells that release the hormone vasoactive intestinal peptide:

• Neurons throughout the gastrointestinal tract

What are the major stimulants for the release of the hormone vasoactive intestinal peptide?

• Vagal stimulation

What is the primary effect of the hormone neurotensin?

• Stimulates growth of small and large bowel mucosa

Location of the cells that release the hormone neurotensin:

• Small bowel (N cells)

What are the major stimulants for the release of the hormone neurotensin?

• Fat

What is the primary effect of the hormone enteroglucagon?

• Glucagon-like peptide-1: stimulates insulin release and inhibits pancreatic glucagon release

• Glucagon-like peptide 2: potent enterotrophic factor

Location of the cells that release the hormone enteroglucagon:

• Small bowel (L cells)

What are the major stimulants for the release of the hormone enteroglucagon?

• Glucose; fat

What is the primary effect of peptide YY?

• Inhibits gastric and pancreatic secretion and gallbladder contraction

Location of the cells that release peptide YY:

• Distal small bowel; colon

What are the major stimulants for the release of peptide YY?

• Cholecystokinin; fatty acids

What are the 3 categories for the causes of small bowel obstruction?

• Extraluminal cause of obstruction

• Intraluminal cause of obstruction

• Obstruction intrinsic to the bowel wall

What is the #1 cause of small bowel obstruction in the world?

• Hernia

What is the #1 cause of small bowel obstruction in children?

• Hernia

What is the #1 cause of small bowel obstruction in adults?

• Postoperative adhesions

Why can diarrhea accompany early partial or even complete small bowel obstruction?

• Intestinal motility and contraction increase both above and below the obstruction in an effort to propel luminal contents past the obstruction

What are the cardinal symptoms of intestinal obstruction?

• Abdominal distension; colicky abdominal pain; nausea; vomiting; failure to pass flatus and stool (obstipation)

What must you remember to do on physical exam in a patient with a small bowel obstruction?

• Note previous surgical scars; auscultate and palpate the abdomen; perform a careful examination to rule out incarcerated inguinal hernias, femoral hernias, and obturator hernia; perform a rectal exam to assess for intraluminal masses and occult blood

What is the characteristic appearance of a small bowel obstruction on upright abdominal x-ray?

• Dilated loops of small bowel with multiple air-fluid levels (often layer in stepwise pattern)

What percentage of plain abdominal radiographs accurately make the diagnosis of small intestinal obstruction?

• ~60%

What is the usual treatment for a patient with a small bowel obstruction?

• Make patient NPO; aggressive intravenous fluid replacement with isotonic solution; monitor urine output with a Foley catheter; decompress with nasogastric suction; follow serial electrolyte measurements and complete blood cell count; perform serial abdominal exams

Reported percentage of patients with small bowel obstruction whose symptoms resolve and get discharged from the hospital without the need for surgery:

• 60% to 85%

What are the classic signs of intestinal strangulation from obstruction?

• Constant, noncramping abdominal pain

• Fever

• Leukocytosis

• Tachycardia

Name CT findings associated with the late stages of irreversible intestinal ischemia:

• Pneumatosis intestinalis; portal venous gas

What clinical parameters lower the threshold to operate on a patient with a small bowel obstruction?

• Worsening abdominal pain

• Fever

• Increasing leukocytosis

• Tachycardia/tachypnea

Indications for surgery in a patient with a small bowel obstruction:

• Fever

• Progressive pain

• Failure to resolve

• Worsening leukocytosis

• Signs of strangulation/perforation

• Peritoneal signs

What are absolute indications to operate on a patient with a partial small bowel obstruction?

• Free air on x-ray; peritoneal signs

What is the usual operative management in a patient with a small bowel obstruction secondary to an adhesive band without evidence of strangulation?

• Lysis of adhesions

What is the usual operative management in a patient with a small bowel obstruction secondary to an incarcerated hernia without evidence of strangulation?

• Manual reduction of herniated segment of bowel and closure of the defect

What is the usual operative management in a patient with a small bowel obstruction secondary to Crohn disease without evidence of strangulation?

• If acute, try conservative management; if chronic fibrotic stricture, perform strictureplasty versus bowel resection (try to conserve bowel if possible)

What is the usual operative management in a patient with a small bowel obstruction secondary to intra-abdominal abscess without evidence of strangulation?

• Percutaneous drainage of the abscess (may be sufficient to relieve obstruction)

What is the usual operative management in a patient with a small bowel obstruction secondary to radiation enteropathy without evidence of strangulation?

• If acute, try nonoperative management with tube decompression ± corticosteroids; if chronic, will likely require laparotomy with possible resection of the irradiated bowel or bypass.

How can you evaluate the viability of bowel after the release of a strangulation?

• Place released bowel in warm, saline-moistened sponge for 15 to 20 minutes and re-examine (normal color and peristalsis indicate viability); Doppler probe; administration of fluorescein and evaluating fluorescence; second-look laparotomy 18 to 24 hours after the initial procedure

What is the most effective means of limiting the number of adhesions?

• Good surgical technique: avoidance of unnecessary dissection; adequate irrigation and removal of infectious/ischemic debris; exclusion of foreign material from the peritoneal cavity

What is an ileus?

• Slowing/absence of the intestinal passage of luminal contents and distention without a demonstrable mechanical obstruction.

What are the causes of ileus?

• Postoperative; drugs (opiates, psychotropics, anticholinergics); intra-abdominal inflammation; intestinal ischemia; metabolic and electrolyte derangements; retroperitoneal hemorrhage/inflammation; systemic sepsis

What is the treatment for ileus?

• Correction of the underlying cause (correction of any metabolic/electrolyte abnormalities, treatment of sepsis, discontinuation of possible ileus-producing medications) and supportive with nasogastric decompression and IV fluids

What is the most common primary surgical disease of the small bowel?

• Crohn disease

What is the most common reason to operate on a patient with Crohn disease?

• Small bowel obstruction

What are the most common sites of occurrence of Crohn disease?

• Small intestine; colon

What percentage of Crohn patients present with small bowel involvement alone?

• 30%

The decreasing frequency of malignant neoplasms of the small bowel:

• Adenocarcinoma; carcinoid tumor; malignant GIST; lymphoma

What is the surgical treatment of an adenoma of the small bowel?

• Wide resection including regional lymph nodes (may need Whipple for duodenal lesions); if surgical resection for cure is impossible, perform palliative resection or bypass of the involved segment.

What is the surgical treatment of a lymphoma of the small bowel?

• Wide resection including regional lymph nodes (may need Whipple for duodenal lesions) with adjuvant chemotherapy and radiation; if surgical resection for cure is impossible, perform palliative resection or bypass of the involved segment.

What are the most common benign small bowel lesions that produce symptoms?

• GISTs

What is the eponym for an intestinal pacemaker cell of mesodermal descent?

• Interstitial cell of Cajal

What is the surgical treatment of GIST tumor of the small bowel?

• Segmental bowel resection

What cells do carcinoids of the small bowel arise from?

• Enterochromaffin cells (Kulchitsky cells/argentaffin cells)

Where can enterochromaffin cells (Kulchitsky cells/argentaffin cells) be found?

• The crypts of Lieberkühn

Second most common affected site in the gastrointestinal tract by carcinoid:

• Small intestine (ileum 28%)

What percentage of ileal carcinoids metastasize?

• ~35%

What percentage of small bowel carcinoids are multicentric?

• 20% to 30%

What procedure would you perform for a patient with a primary small bowel carcinoid tumor <1 cm in diameter without evidence of regional lymph node metastasis?

• Segmental intestinal resection

What procedure would you perform for a patient with a primary small bowel carcinoid tumor >1 cm or multiple small bowel carcinoid tumors or primary small bowel carcinoid tumor with regional lymph node metastasis?

• Search the abdomen thoroughly for multicentric lesions; perform wide excision of bowel and mesentery; right hemicolectomy for lesions of the terminal ileum; local excision of small duodenal tumors versus pancreaticoduodenectomy for more extensive lesions

What would you do if you find a hepatic metastasis from a primary small bowel carcinoid tumor during abdominal exploration?

• Perform surgical debulking (wedge resection, formal hepatic lobectomy)

What is the most common extra-abdominal malignancy to metastasize to the small intestine?

• Cutaneous melanoma

What is the most common benign tumor of the small bowel?

• Leiomyoma

What are the 3 primary types of small bowel adenomas?

• True adenoma; villous adenoma; Brunner gland adenoma

What is the most common site of cancer in a patient with Peutz-Jeghers syndrome?

• The small intestine

What are the most common acquired diverticula of the small bowel?

• Duodenal diverticula

Where are most duodenal diverticulum found?

• Within a 2 cm radius from the ampulla (periampullary)

What is the most common true congenital diverticulum of the small bowel?

• Meckel diverticulum

What are the major complications of duodenal diverticula?

• Cholangitis from obstruction of the biliary duct; pancreatitis from obstruction of the pancreatic duct; hemorrhage; perforation; blind loop syndrome

Which border of the small bowel are jejunoileal diverticula usually found?

• Mesenteric border

What is the treatment of choice for perforated jejunoileal diverticula?

• Resection with reanastomosis (simple closure, excision, invagination associated with greater mortality/morbidity); if diffuse peritonitis, may require enterostomies.

What are your surgical options for treating an obstruction caused by a dislodged enterolith formed in a jejunal diverticulum?

• Enterotomy and removal of the enterolith; can try to milk the enterolith distally into the cecum; if enterolith causes obstruction at the level of the diverticulum, perform bowel resection with reanastomosis.

What is a Meckel diverticulum?

• A remnant of the omphalomesenteric duct (vitelline duct)

What border of the intestine is a Meckel diverticulum found?

• Antimesenteric border

What is the most common heterotopic tissue found within a Meckel diverticulum?

• Gastric mucosa (50% of all Meckel diverticula)

What percentage of Meckel diverticula contain heterotopic pancreatic tissue?

• ~5%

What is the most common clinical presentation of Meckel diverticulum?

• Gastrointestinal bleeding (accounts for half of all lower GI bleeding in patients <2 years old)

What is the most common complication from a Meckel diverticulitis in an adult?

• Obstruction (25%)

Regarding Meckel diverticulum, what is the "rule of twos"?

• 2% of patients are symptomatic; found ~2 ft from the ileocecal valve; found in 2% of the population; most symptoms occur before age 2; ectopic tissue is found in half of patients (50%); approximately 2 in long; 2:1 male:female ratio

Name the hernia associated with an incarcerated Meckel diverticulum:

• Littre hernia

What is the single most accurate diagnostic test for Meckel diverticula in children?

• Scintigraphy with sodium 99mTc-pertechnetate (Meckel scan)

What are the reported diagnostic sensitivity, accuracy, and specificity for a Meckel scan in the pediatric age group?

• 85%; 90%; 95%

What drugs can be given to improve the sensitivity and specificity of 99mTc-pertechnetate scanning in an adult (less accurate secondary to reduced prevalence of ectopic gastric mucosa)?

• Pentagastrin (indirectly increases metabolism of mucous-producing cells); glucagon (inhibits peristaltic dilution/washout of intraluminal radionuclide); cimetidine (histamine-2 [H₂]-receptor antagonists result in higher radionuclide concentrations in the wall of the diverticulum)

What is the treatment for a symptomatic Meckel diverticulum?

• Diverticulectomy by hand-sewn technique versus stapling at the base of the diverticulum in a diagonal/transverse line (avoid narrowing) versus segmental resection of ileum bearing the diverticulum and reanastomosis

Why is segmental intestinal resection usually required for treatment of patients with a bleeding Meckel diverticulum?

• Bleeding site is usually in the ileum adjacent to the diverticulum

What is the general recommendation for an asymptomatic Meckel diverticula found in a child versus an adult?

• Child: asymptomatic Meckel diverticula found in children should be resected

• Adult: controversial (earlier thought that morbidity > potential for prevention of disease); recent studies suggest prophylactic Meckel diverticulectomy in select asymptomatic adult patients may be beneficial and safer than originally reported.

What does the HIS FRIEND mnemonic regarding the spontaneous closure of an enterocutaneous fistula stand for?

• High output (>500 mL/24 h); intestinal disruption (>50% of bowel circumference); short fistula tract (<2.5 cm long); foreign body in the fistula tract; radiation enteritis; inflammatory bowel disease/infection; epithelialization of fistula tract; neoplasm; distal obstruction

How much output must there be for an enterocutaneous fistula to be considered low output?

• <200 mL/24 h

What are the major complications associated with small bowel fistulas?

• Sepsis; fluid/electrolyte depletion; skin necrosis at the site of external drainage; malnutrition

What does the successful management of a patient with an enterocutaneous fistula entail?

• Establishment of controlled drainage; management of sepsis; prevention of fluid/electrolyte depletion; skin protection; adequate nutrition

What is the optimal time period to follow a conservative course in the management of an enterocutaneous fistula before surgical management should be considered?

• 4 to 6 weeks; if no closure has been obtained, consider surgical management (has been shown that when sepsis was controlled, >90% closed within 1 month, <10% closed after 2 months, none closed spontaneously after 3 months)

What is the preferred operation in the management of an enterocutaneous fistula?

• Tract excision and segmental resection of the involved segment of intestine and reanastomosis; if primary anastomosis unsafe (unexpected abscess; long, rigid, distended bowel wall), perform exteriorization of both intestinal ends.

What radiologic studies can be performed to define the precise location of the fistula, possibly surrounding abscess cavity, or disruption of the bowel wall?

• Fistulogram; can consider CT scan

What is the most common site for pneumatosis intestinalis?

• Jejunum

What is the second most common site for pneumatosis intestinalis?

• Ileocecal region

What are the causes of pneumatosis intestinalis?

• COPD; immunocompromised patients (AIDS; chemotherapy/corticosteroids; transplant patients; patients with leukemia, lymphoma, vasculitis, or collagen vascular disease); inflammatory/obstructive/infectious conditions of the intestine; iatrogenic conditions (endoscopy, jejunostomy placement); ischemia; extraintestinal diseases (diabetes); primary pneumatosis (not associated with any of the aforementioned)

What is the most common cause of small bowel bleeding?

• Small bowel angiodysplasia

What study can be performed to further work up a patient with guaiac positive stools and negative upper and lower endoscopy?

• Capsule study; small bowel contrast study (enteroclysis)

How does blind loop syndrome manifest?

• Abdominal pain; diarrhea; steatorrhea; weight loss; neurologic disorders; megaloblastic anemia; deficiencies of the fat-soluble vitamins (A, D, E, and K)

What tests can be used to diagnose the bacterial overgrowth with blind loop syndrome?

• Cultures obtained through an intestinal tube; 14C-xylose or 14C-cholylglycine breath tests

How can blind loop syndrome be differentiated from pernicious anemia with a Schilling test (57Co-labeled vitamin B₁₂ absorption)?

• A course of broad-spectrum antibiotic (tetracycline) will return vitamin B₁₂ absorption to normal and intrinsic factors will have no effect in a patient with the blind loop syndrome.

What is the treatment for patients with blind loop syndrome?

• Parenteral vitamin B₁₂ therapy and broad-spectrum antibiotics usually for 7 to 10 days (most commonly tetracycline or amoxicillin-clavulanate potassium [Augmentin]; alternative is combination of a cephalosporin [cephalexin {Keflex}] and metronidazole; if ineffective then chloramphenicol); surgery is indicated in those patients who require multiple rounds of antibiotics or are on continuous therapy

What is the treatment of acute noncomplicated radiation enteritis?

• Symptom control: antispasmodics/analgesics for abdominal pain and cramping; opiates/antidiarrheal agents for diarrhea; dietary manipulation; ± corticosteroids (questionable benefit)

What are indications for surgery in a patient with radiation enteritis?

• Obstruction; fistula formation; perforation; bleeding

What is the most common presentation of radiation enteritis?

• Obstruction

What are the surgical options for the treatment of radiation enteritis?

• Obstruction: bypass or resection with reanastomosis

• Perforation: resection and reanastomosis, if reanastomosis unsafe, exteriorize intestinal ends

What is the most common cause of short bowel syndrome in a pediatric patient?

• Bowel resection secondary to necrotizing enterocolitis

What are the clinical hallmarks of short bowel syndrome?

• Diarrhea; fluid and electrolyte deficiency; malnutrition (can also see gallstones from disruption of enterohepatic circulation and nephrolithiasis from hyperoxaluria)

How many centimeters of intestine do you need to survive off of TPN with short gut syndrome without an ileocecal valve?

• 75 cm

How many centimeters of intestine do you need to survive off of TPN with short gut syndrome with an ileocecal valve?

• 50 cm (can resect up to 70% of the small bowel if terminal ileum/ileocecal valve intact)

What is the usual treatment of short gut syndrome?

• Supplementation with TPN; lomotil/codeine/diphenoxylate/cholestyramine/octreotide for diarrhea; H₂ blockers for acid reduction; reduce fat with resumption of diet

What surgical strategies are used to treat patients with short bowel syndrome on chronic TPN?

• Procedures to delay intestinal transit time (construction of valves and sphincters; antiperistaltic jejunal segment); procedures to increase absorptive area (intestinal tapering and lengthening procedure); small bowel transplantation

What syndrome is characterized by vascular compression of the duodenum?

• Wilkie syndrome (SMA syndrome)

What portion of the duodenum is compressed by the SMA with Wilkie syndrome (SMA syndrome)?

• Third portion of the duodenum

What studies can be ordered to make the diagnosis of Wilkie syndrome (SMA syndrome)?

• Barium upper gastrointestinal series; hypotonic duodenography; CT scan

What is the operative treatment of choice for patients with Wilkie syndrome refractory to conservative management?

• Duodenojejunostomy

What organism is responsible for typhoid enteritis?

• Salmonella typhosa

How is the diagnosis of typhoid fever confirmed?

• Isolating Salmonella typhosa from blood, bone marrow, and stool cultures; finding of high titers of agglutinins against the O and H antigens

What is the usual treatment for uncomplicated typhoid enteritis?

• Antibiotics (chloramphenicol, ampicillin, amoxicillin, trimethoprim-sulfamethoxazole)

Most common site of protozoal infection (Cryptosporidium, Isospora, Microsporidium) causing diarrhea in a patient with AIDS?

• The small bowel

Most common site of intestinal involvement with Mycobacterium tuberculosis:

• Distal ileum and cecum (85%–90%)