Basic Science: Small Bowel

Grace Kim, MD

June 6, 2007

Basic Anatomy

• 270-290 cm from pylorus to cecum– Duo 20 cm– Jejunum 100 cm– Ileum 150 cm

Studying the SB

• UGI and SB follow-through

• Enteroclysis

• CT

• Enteroscopy– Push enteroscopy (up to 100 cm past LOT)– Double balloon enteroscopy (to TI ideally)

• Capsule endoscopy (beware: obstruction)

Pathology

• Case: 72 yo man no prior history of abdominal operations presents with nausea, vomiting, and abdominal distention x 5 days. Last BM and flatus 2 days ago. AXR as shown on next slide.

• DDx?

• Management?

Small bowel obstruction

• Etiology– Extrinsic

• Adhesions (#1)• Hernias (#3)• Abscess• Mass

– Intrinsic• Mass (#2)• Foreign body (bezoar, gallstone)

Pathophysiology

• Hyperperistalsis

• Bowel dilatation

• Third-spacing

• Decrease in mucosal blood flow

• Bacterial translocation

Presentation

• Crampy abdominal pain

• Nausea

• Vomiting

• Obstipation

• PE: Vitals; Abdominal exam – scars, hernias, bowel sounds, tenderness, peritonitis; Rectal exam

Imaging/Labs

• AXR

• +/- CT scan

• Chem, CBC, lactate

Treatment

• Suspicion for strangulation or bowel compromise– Resuscitate and operate

• Simple obstruction– Conservative management (NGT decompression,

resuscitate, serial exams)– Failure or decompensation

• Operate

• Operation: Adhesiolysis +/- bowel resection

• Case: During a laparotomy for a small bowel volvulus secondary to adhesions, you lyse the adhesions and detorse the small bowel. It appears congested and ischemic immediately after devolvulizing. Should this bowel be resected?

Is the bowel viable?

• Warm saline-soaked lap pads

• Time and patience

• Doppler

• Fluorescein fluorescence

• Planned second look

• Case: 70 yo woman POD#5 from an exploratory laparotomy and lysis of adhesions for SBO secondary to adhesions c/o abdominal distention. She does not tolerate advancement of diet. She has had one flatus since surgery. Labs significant for WBC 13K, K 3.2. She remains on Dilaudid IV PCA and has been minimally ambulatory.

• Management?

Diverticular Disease

• Duodenal diverticula– Asymptomatic – no treatment– Symptomatic (biliary obstruction, hemorrhage,

perforation, diverticulitis, blind loop) – choledochoduodenostomy or choledochojejunostomy vs. resection or duodenal diverticulization

• Jejunoileal diverticuli– Resect if symptomatic (bleeding, perf)

Meckel’s

• True diverticulum• Rule of 2’s: 2% population, symptomatic in

2%, 2 years of life, 2 feet from ICV• Rx:

– Bleeding: Small bowel resection– Diverticulitis: ?SBR vs. diverticulectomy– Incidental finding in child: Diverticulectomy– Incidental finding in adult: Diverticulectomy if

low risk

• Case: You are performing a diagnostic laparoscopy for a presumed acute appendicitis in a 20 yo woman. You find thickened, inflamed ileum with extensive fat creeping. The cecum is uninvolved, and the appendix is normal.

• Diagnosis and management?

Crohn’s Disease

• Can involve GI tract from mouth to anus– 40% ileocolic, 30% SB only, 30% colon or

anorectum only

• Transmural inflammation, non-caseating granuloma formation

• Skip lesions

• Usually spares rectum

• Medical and surgical treatment is palliative

• 3-7/100,000

• Highest incidence in N. America and Europe

• Bimodal distribution (20-30s and 60s)

• Etiology unclear

• Increased risk of developing SB adenocarcinoma (100x)

Presentation

• Relapsing/remitting abdominal pain and diarrhea with weight loss

• Extra-intestinal manifestations (30%)– Skin lesions (erythema nodosum and

pyoderma gangrenosum)– Arthritis and arthralgias – Uveitis and iritis– Hepatitis and pericholangitis– Aphthous stomatitis

Diagnosis

• Barium study of small bowel (linear ulcers, transverse sinuses, and clefts)

• Endoscopy (discrete ulcers,cobblestoning, skip lesions

• Adjunctive labs: ASCA positive/pANCA negative

Medical Management

• Aminosalicylates (Pentasa, Asacol)

• Antibiotics (Flagyl, cipro)

• Corticosteroids

• Immunosuppresive drugs (6-MP, aza)

• Anti-TNFα (Infliximab)

Surgery

• Reserved for complications and failures of medical management (75%)

• Indications– 1 – Obstruction– 2 – Fistula– 3 – Perforation/Abscess– 4 – Perianal disease– 5 – Toxic megacolon

• “Operative treatment of a complication should be limited to that segment of bowel involved with the complication and no attempt should be made to resect more bowel even though grossly evident disease may be apparent.”

Surgical options

• Small bowel resection

• Ileocolic resection

• Strictureplasty– Take mucosal bx first

Small Bowel Tumors

• Represent 2% of all GI malignancies

• Presentation: intermittent or partial SBO, bleeding, pain, perforation, weight loss– Malignant lesions usually will cause sx –

based on tumor infiltration– Benign lesions may/may not cause sx –

based on intussusception

• Dx: SBFT, enteroclysis, CT, enteroscopy

Benign Lesions

• Adenomas

• Lipomas

• Hemangiomas

• Hamartoma

• Usually asymptomatic

• Should be excised or resected

Malignant Tumors

• Metastatic Disease (cervix, ovaries, renal, stomach, colon pancreas, melanoma)

• Adenocarcinoma

• Carcinoids

• Malignant GIST

• Lymphoma

Adenocarcinoma

• 50% SB tumors

• More frequently proximal SB

• Treatment: Wide resection with 10-cm margins, ?adjuvant

• Prognosis poor – usually late stage when diagnosed

Carcinoids

• From Kulchitsky cells – enterochromaffin cells• Produce 5-HIAA, chromogranins, neuropeptide

K, substance P• 80% found within 2’ of TI

– AIR: Appendix (45%), Ileum (28%), Rectum (16%) • 10% have carcinoid syndrome (diarrhea,

blushing, bronchospasm, hypotension, endocardial fibrosis – R heart failure)– Metastatic carcinoid or tumors that bypass the portal

system• Fibrotic, desmoplastic reaction in mesentery

• Dx: high index of suspicion, urine 5-HIAA, CT (mesenteric shortening), SBFT, octreotide scan

• Case: You are operating on a 70 yo woman with a SBO presumably from a carcinoid tumor. During induction of general anesthesia, she develops SVT, hypotension, and elevated peak airway pressures.

• Management?

Carcinoids

• Treatment: Segmental resection• Beware: Carcinoid crisis with general anesthesia

(Rx: somatostatin, hydrocortisone, antihistamine) prep all patient with preoperative octreotide

• Adjuvant: doxo, 5-FU, streptozocin, chemoembolization bulky liver disease

• Palliative for carcinoid syndrome: octreotide• Experimental: radionuclide somatostatin

agonists “smart bomb”

Last two…

• Lymphoma– Ileum– Risk factors: immunodeficiency, celiac

disease– Rx: Wide resection with nodes

• GIST– Jejunum/ileum– Segmental resection

Vascular

Acute Mesenteric Ischemia

• Acute-onset pain, out of proportion to exam, fever, Heme (+) stool

• MI, A-fib, mural thrombus, mitral valve disease

• Dx: CT scan (good for bowel, large vessels), angiogram, MRA

• Embolus– Acute onset without

antecedent sx– Lodge distal to middle

colic and jejunal branches of SMA

• Sparing of proximal jejunum and R colon

• Thrombus– Antecedent intestinal

angina– Origin of vessel

• Entire SB and R colon affected

Nonocclusive Mesenteric Ischemia (NOMI)

• Optimize fluid resuscitation

• Improve CO

• Eliminate vasopressors

• Selective vasodilatory injection (papaverine)

• Bowel resection for frankly necrotic bowel

Mesenteric Embolic Disease

• Surgical embolectomy– Exposure of SMA– Transverse or longitudinal arteriotomy (vein

patch)– 3 and 4-Fr Fogarty embolectomy

Acute Mesenteric Thrombotic Disease

• Bypass– Antegrade or retrograde– Conduit: autologous greater saphenous vein

(acute situation)– Inflow: supraceliac aorta, infrarenal aorta, iliac

artery

Outcome

• Perioperative mortality 62%– MODS, ischemia/reperfusion insult

• Long-term TPN 31%

Chronic Mesenteric Ischemia

• Chronic post-prandial abdominal pain in a vasculopath

• Dx: Duplex, angiogram

Management

• Visceral Bypass– One or two-vessel bypass– Inflow: supraceliac, infrarenal– Conduit: Vein or PTFE/Dacron

• Endovascular– PTA

– *not many studies supporting management

Outcome

• Mortality 8%, morbidity 30% (includes acute)

• Primary patency 89% at 72 months

• 5-yr survival 64%, 3-yr symptom-free rate 81%

• Endovascular approaches promising – more recent studies: similar symptom-free rate with lower morbidity and mortality

• Case: You perform a small bowel resection in a 80-yo woman who presented with an SBO secondary to a strangulated incisional hernia. She is slow to regain bowel function. On POD#6, her wound appears erythemaous. You open it at the bedside, and purulent, feculant material is returned.

Enterocutaneous Fistula

• Prevention: preoperative nutritional status, good technique, perioperative hemodynamics, bowel prep

• Disability– Electrolyte imbalance– Malnutrition– Sepsis

• Low-output <200cc/ 24 hr versus high >200 cc/24 hr

Initial Management

• Resuscitate

• Imaging

• Consider abx

• Nutritional support

• Control of fistula drainage

• Skin care

• Consider somatostatin

Impediments to closure

• High output (>500 mL/24 hr) • Severe disruption of intestinal continuity (>50% of bowel

circumference) • Active inflammatory bowel disease of bowel segment • Cancer • Radiation enteritis • Distal obstruction • Undrained abscess cavity • Foreign body in the fistula tract • Fistula tract <2.5 cm in length • Epithelialization of fistula tract

Secondary Management

• Fistulogram (one week later)– Define anatomy– Rule out distal obstruction

• Failure of conservative management– Operate: small bowel resection

Short Gut

Short bowel

• Less than 200 cm healthy small intestine

• Downside of TPN– Liver failure– Cholelithiasis– Line sepsis– Venous thrombosis

• Adaptive response: 1-2 years

Medical Therapy

• Diarrhea: Immodium, lomotil, opiods• Bile salt-induced diarrhea: cholestyramine• Electrolyte losses: replete IV/PO• Hypergastrinemia: H2 blocker or PPI• Vitamin/Mineral deficiencies: Monitor and

replete• Bacterial overgrowth: Flagyl, tetracycline• Enteral nutrition with supplemental TPN

Surgical Therapy

• Reanastomose

• Gastrostomy over jej

• Intestinal valves (iatrogenic intussusception

• Reversed segment

• Tapering enteroplasty (Bianchi procedure)

• Intestinal tranplantation