Pocket Medicine: The Massachusetts General Hospital Handbook of Internal Medicine (42 page)

• “Intestinal angina”: postprandial abd pain, early satiety, & ↓ wt from gastric vascular “steal”; may occur wks to mos before onset of acute pain in Pts w/ chronic mesenteric ischemia
Physical exam

• May be unremarkable, or may only show abdominal distention;
FOBT ~75% of Pts

• Bowel infarction suggested by peritoneal signs (diffuse tenderness, rebound, guarding)
Diagnostic studies

• Dx relies on high level of suspicion; rapid dx essential to avoid infarction (occurs w/in h) • Laboratory: often nl; ~75% ↑ WBC; ↑ amylase, LDH, phosphate, D-dimer; ~50% acidosis w/ ↑ lactate (late) • KUB: nl early before infarct; “thumbprinting,” ileus, pneumatosis in later stages

•
CT angiography
(arterial phase imaging): noninvasive test of choice; can detect thrombi in mesenteric vessels, colonic dilatation, bowel wall thickening, pneumatosis/ portal venous gas;
venous
phase imaging for dx of mesenteric vein thrombosis •
Angiography
: gold standard; potentially therapeutic; indicated if vasc occlusion suspected
Treatment

• Fluid resuscitation,
optimize hemodynamics
(minimize pressors); broad-spectrum abx • Emergent surgery for prompt resection of necrotic bowel if evidence of peritonitis

•
Anticoagulation
for arterial & venous thrombosis and embolic disease •
Papaverine
(vasodilator) catheter-directed infusion into SMA, typically in nonocclu-sive ischemia when spasm is considered the primary cause of the ischemia •
SMA embolism
: consider fibrinolytic; if no quick improvement → surgical embolectomy if possible, o/w aortomesenteric bypass •
SMA thrombosis
: percutaneous or surgical revascularization (
J Vasc Surg
2009;50:341) •
Nonocclusive
: correct underlying cause (esp. cardiac)

• Consider angioplasty/stent vs. surg revasc in cases of
chronic
mesenteric ischemia if: ≥2 vessels or occl SMA, supportive clinical hx, & other etiologies for abd pain excluded
Prognosis

• Mortality 20 to >70% if bowel infarcted; dx prior to infarction strongest predictor of survival

ISCHEMIC COLITIS (75%)

Definition & pathophysiology

• Nonocclusive disease 2° to Ds in systemic circulation or anatomic/fxnal Ds in local mesenteric vasculature; often underlying etiology unknown, frequently seen in elderly •
“Watershed”
areas (splenic flexure & rectosigmoid) most susceptible, 25% involve R side
Clinical manifestations, diagnosis, & treatment

• Disease spectrum: reversible colopathy (35%), transient colitis (15%), chronic ulcerating colitis (20%), resulting stricture (10%), gangrene (15%), fulminant colitis (<5%) • Usually p/w
cramping LLQ pain w/
overtly bloody stool; fever and peritoneal signs should raise clinical suspicion for infarction •
Dx: r/o infectious colitis; consider flex sig/colonoscopy
if sx persist and no alternative etiology identified (only if peritonitis not present, o/w avoid overdistention of colon) •
Treatment: bowel rest, IV fluids, broad-spectrum abx
, serial abd exams; surgery for infarction, fulminant colitis, hemorrhage, failure of med Rx, recurrent sepsis, stricture • Resolution w/in 48 h w/ conservative measures occurs in >50% of cases

PANCREATITIS

Pathogenesis

• Acinar injury via direct or indirect toxicity → release or impaired secretion (ie, duct obstruction) of enzymes → autodigestion → fat necrosis • Profound acute inflammatory response
Etiologies

•
Gallstones
(40%):
>
, usually small stones (<5 mm) or microlithiasis •
Alcohol
(30%):
>
, usually chronic, w/ acute flares • Drugs (via hypersens, toxic metab or direct toxicity): furosemide, thiazides, sulfa, ddI, ? DPP-4 inhib, asparaginase, estrogen, 6-MP/AZA, ACEI, dapsone, 5-ASA, valproic acid • Obstructive: panc/ampullary tumors, mets (breast, lung), annular pancreas, divisum w/ concurrent minor papilla stenosis and ascaris • Metabolic: hypertriglyceridemia (TG >1000 and usually ~4500; seen w/ types I, IV, & V familial hyperlipidemia), hypercalcemia • Infections: coxsackie, mumps, EBV, CMV, HAV, HBV, mycoplasma, TB, candida/toxo/crypto • Autoimmune: can p/w chronic disease or panc mass; ↑ IgG4,
ANA, duct abnl • Ischemia: vasculitis, cholesterol emboli, hypovolemic shock, cardiopulmonary bypass • Post ERCP: ~5% w/ clinical, overt pancreatitis; 35–70% with asx ↑ amylase; prevent w/ indomethacin 100 mg PR immediately after ERCP (
NEJM
2012;366:1414) • Post trauma: blunt abd trauma, pancreatic/biliary surgery • Familial: autosomal dominant w/ variable penetrance (
PRSS1
,
CFTR
,
SPINK1
genes) • Scorpion sting (in Trinidad): mechanism believed to be hyperstimulation of pancreas
Clinical manifestations

•
Epigastric abdominal pain
, radiating to back, constant, some relief w/ leaning forward • Nausea and vomiting • Ddx: acute cholecystitis, perforated viscus such as DU, intestinal obstruction, mesen-teric ischemia, IMI, AAA leak, distal aortic dissection, ruptured ectopic pregnancy
Physical exam

•
Abdominal tenderness and guarding
, ↓ bowel sounds (adynamic ileus) ± palpable abdominal mass; ± jaundice if biliary obstruction • Signs of retroperitoneal hemorrhage (Cullen’s = periumbilical; Grey Turner’s = flank) rare • Fever, tachycardia, hypotension ± shock
Diagnostic studies
(
Gastro
2007;132:2022)
• Laboratory

↑ amylase
: levels >3× ULN suggestive of pancreatitis; level ≠ severity

 false
: acute on chronic (eg, alcoholic); hypertriglyceridemia (↓ amylase activity)

 false
: other abd or salivary gland process, acidemia, renal failure, macroamylasemia  (amylase binds to other proteins in serum, cannot be filtered by kidneys)