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GI III: Small Intestine & Colon Cheat Sheet by



Increased frequency or volume of stool (eg 3+ liquid­/se­misolid stools daily for at least 2-3 consec­utive days)
Infect­ions, toxic, dietary (laxative use), other GI disease
Pertinent Patient History
All current meds, illnesses among others who may have shared meals with pt.
Clinical Features: Secretory Diarrhea
Large volume w/o inflam­mation (pancr­eativ insuff­ici­ency, ingestion of preformed bacterial toxins, laxative use)
Clinical Features: Inflam­matory Diarrhea
Bloody diarrhea + fever (invasive organisms or IBD)
Clinical Features: Antibi­oti­c-A­sso­ciated Diarrhea
Clostr­idium dificile (causes pseudo­men­branous colitis in the most severe cases)
Lab Findings
WBCs in the stool = inflam­matory process, and get cultures
Supportive therapy, antibi­otics for pts with severe diarrhea and systemic sx (C. diff, Shigella, Campyl­oba­cter)

Celiac Disease (celiac sprue)

Inflam­mation of the small bowel with the ingestion of gluten­-co­nta­ining foods (wheat, rye, barley) leading to malabs­orption
Multif­act­orial inheri­tance
Among the most common genetic conditions in Europe and USA
Clinical Presen­tation
Diarrhea, steato­rrhea, flatul­ence, weight loss, weakness, abdominal distension (infan­ts/kids - failure to thrive) (older pts - iron defici­ency, coagul­opathy, hypoca­lcemia)
Serologic screening tests: IgA antien­dom­ysial and antitisuue transg­lut­aminase antibodies
Gluten­-free dieat, should see nutrit­ionist possibly lactos­e-free diet, supple­men­tation, prednisone

IBS (Irritable Bowel Syndrome)

A functional disorder without a known pathology - thought to be a combin­ation of altered motility, hypers­ens­itivity to intestinal disten­tion, and psycho­logical distress, W>>M and can occur with menses­/st­ress. A dx of exclusion.
Most common cause of...
chronic or recurrent abdominal pain the the US. Usually an interm­itt­ent­/li­fetime problem.
Lactose intole­rance, cholec­yst­itis, chronic pancre­atitis, intestinal obstru­ction, chronic perito­nitis, carcinoma of pancre­as/­stomach
Clinical features
Abdominal pain (worsened with ingestion, relieved with defeca­tion), pain may be associated with bowel distention from accumu­lation of gas and associated spasm of smooth muscle; postpr­andial urgency common, changes in stool freque­ncy­/ch­ara­cter, dyspepsia, urinary freque­ncy­/ur­gency in women
Lab Findings
Generally normal - test stool for blood, bacteria, parasites, lactose intole­rance. R/O other pathology with colono­sco­py/­barium enema/­US.CT, and endoscopic studies in pts with persisten sx or weight loss/b­leeding
Avoid triggers, high-fiber diet, bulking agents, and symptom control (antis­pas­modics, antidi­arr­heals, prokin­etics, antide­pre­ssants)

Colonic Polyps

Fleshy growth on lining of colon/­rectum; common and can be benign or malignant. Removal can reduce the occurence of colon cancer
Familial Polyposis Syndrome
Genetic predis­pos­ition to multiple colonic poolups with a near-100% risk of developing colon cancer (evaluate q1-2 yrs beginning at age 10)
Clinical Features
Asympt­omatic, Can get contip­ation, flatul­ence, rectal bleeding, or iron deficiency anemia
Lab Findings
Heme-p­ositive stool, detected by colono­scopy, and must get histologic evaluation to determine dysplasia
Removal and FU


A decrease in stool volume and increase in stool firmness accomp­anied by straining (normal BM ranges 3/day-­3/wk)
Red Flag
Patients >50 yo with new-onset consti­pation --> evaluate for colon cancer!
Basic Treatm­ent­/Li­festyle modifi­cations
Increase fiber (10-20­g/day), increase fluid intake (1.5-2­L/day), increased exercise
Treatment if consti­pation lasts > 2wks or if refractory to lifestyle modifi­cations
Invest­igate and treat underlying cause

Bowel Obstru­ction

Etiology: small bowel obstru­ction (SBO)
Adhesions or hernias, neoplasm, IBD, volvulus
Etiology: large bowel obstru­ction
Neoplasm, strict­ures, hernias, volvulus, intuss­usc­eption, fecal impaction
Complete strang­ulation of bowel tissue can lead to
Infarc­tion, necrosis, perito­nitis, death
Clinical Features
Andominal pain, disten­tion, vomiting, obstip­ation, high-p­itc­hed­/ru­shing bowel sounds, more severe cases pts can be febril­e/t­ach­yca­rdic, in shock
Lab Findings
Dehydr­ation, electr­olyte imbalance, upright radiog­raphs showing air-fluid levels
NPO, NG suctio­ning, IV fluids, monitoring (surgery likely, esp. with large bowel obstru­ction)

Crohn's Disease (aka regional enteritis)

An IBD for which there is some genetic predis­pos­ition, but the cause is unknown. Must be differ­ent­iated from ulcerative colitis (other IBD)
Anatomical Involv­ement
Skip lesions, Terminal ileum and right colon most common, can also be in small and large bowels, mouth, esophagus, stomach (rectum frequently spared)
Fistula, abscesses, aphthous ulcers, renal stones, predis­pos­ition to colonic cancer
Clinical Features
Abdominal cramps and diarrhea in pts <40yo (can also get low-grade fever, polyar­thr­algia, anemia, fatigue, bloody stool)
Lab Findings
Colono­scopy, bx to reveal involv­ement (will often see granul­omas), blood tests (anemia, decreased ESR, electr­olyte imbala­nces)
Acute tx: Prednisone +/e aminos­ali­cylates (add metron­idazole or cipro if perianal dz/fis­sur­es/­fis­tula. Chronic manage­ment: Mesala­mine, also smoking cessation


The invagi­nation of a proximal segment of bowel into the portion just distal to it (95% of the time occurs in children, following a viral infx. If in adults d/t neoplasm)
Clinical Features
Severe colicky pain, stool will contain mucus/blod (currant jelly stools), and sausag­e-s­haped mass felt on palpation
Lab Findings
Barium or air enema - diagnostic and therap­eutic (plain­-films, CT, surgery for adults)
Hospit­ali­zation, and barium/air enema for kids (surgery if that doesn't help or for all adults)

Toxic Megacolon

Extreme dilatation and immobility of the colon, Emergency!
Etiology: Newborn
Hirsch­spr­ung's Disease = Congenital agangl­ionosis of the colon, leading to functional obstru­ction in the neworn
Etiology: Adults
Occurs as a compli­cation of UC, Crohn's colitis, pseudo­men­branous colitis, and specific infectious causes (Shigella, C. diff)
Clinical Features
Fever, prostr­ation, severe cramps, abdominal disten­sion, and rigid abdomen and abdominal tenderness on exam
Lab Findings
Abdominal plain films will show colonic dilatation
Decomp­ression (sometimes colostomy or complete colonic resection may be necessary)


The twisting of any portion of bowel on itself (most commonly the sigmoid or cecal area)-­->r­equires emergent decomp­ression to avoid ischemic injury!
Clinical Features
Cramping abdominal pai, disten­tion, N/V, obstip­ation
Ischemia from volvulus can lead to
Gangrene, perito­nitis, sepsis
Signs/­sym­ptoms of Bowel Ischemia
Abdominal tympany, tachyc­ardia, fever, severe pain
Diagnosis confirmed by
Abdominal plain film--­>sh­owing colonic distention
Endoscopic decomp­res­sion, surgery if unresolved by non-su­rgical means


May involve a single nutrient (like Vit B12 in pernicious anemia) or lactase deficiency (lactose), or it may be global (celiac disease, AIDS)
Problems in digestion, absorp­tion, impaired blood/­lymph flow
Clinical Features
Diarrhea +/- bloating and discom­fort, weight loss, edema, steato­rrhea (othersL bone demine­ral­iza­tion, tetany, bleeding, anemia)
Lab Findings
If 72-hr fecal fat test is normal, consider specific defects (ie pancreatic insuff­ici­ency), and specific tests can detect defici­encies like B12/ca­lci­u/a­lbumin
Therap­eutic trials to help in dx/tx
Lactos­e-free diet, gluten­-free diet, pancreatic enzyme, antibi­otics in certain cases

Ulcerative Colitis

An IBD with ulcerated lesions in the colon, starts distally at the rectum and progresses proxim­ally, continuous (NO skip lesions)
Clinical Features - most common
Tenesmus (feeling of constantly needing to pass BM despite empty colon) and bloody­/pu­s-f­illed diarrhea
Less common features
LLQ pain, weight loss, malaise, fevere, might see toxic megacolon and malignancy seen more in UC than Crohn's (smoking actually protective in UC)
Lab Findings
Anemia, increased ESR, decreased serum albumin, abdominal plain film--­>co­lonic disten­sion. Sigmoi­doscopy or colono­scopy best to establish diagnosis
What to AVOID in pts with possible acute UC
Colono­scopy and barium enema - risk of perfor­ation and toxic megacolon!
Aminos­ali­cyates + Cortic­ost­eroids (surgery can be curative, total protoc­ole­ctomy most common type)

Divert­icular Disease

Divert­icu­losis (def.)
Large outpou­chings of the mucosa of the colon
Divert­icu­litis (def.)
Inflam­mation of the divert­icula caused by obstru­cting matter
In pts. with divert­icu­losis, can prevent divert­icu­litis with...
High-fiber diet and avoidance of obstru­cti­ng/­con­sti­pating foods (seeds, etc.)
Clinical Features (diver­tic­ulitis)
Sudden­-onset LLQ/su­pra­pubic pain +/- fever, altered BM, N/V
Divert­icular bleeding presen­tation
Sudden­-onset, large-­volume hemato­chezia (resolves sponta­neo­usly)
Lab Findings
Plain films + Ct: to r/o other causes of abdominal pain or tos how areas of edema/­dil­ata­tion. Colono­scopy: best to evaluate for ischemia,
Surgical revasc­ula­riz­ation (+ hydration)

Colorectal Cancer

Risk Factors
Hereditary nonpol­yposis colorectal cancer
3rd leading cause of cancer death in USA, >50yo, good prognosis if caught early
Clinical Features
Slow growing and no sx at first, Abdominal pain, change in bowel habits, occult bleeding, intestinal obstru­ction, anemia (fatigue, weakness), frank blood in stool, change in stool size/s­hape.
Lab Findings
Occult blood in stool, colono­scopy
Surgical resection + chemo (stage III and higher)


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