Diagnostic Tests for Gastrointestinal Anthrax
Gastrointestinal Anthrax Tests: Book Excerpts
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Gastrointestinal Anthrax Diagnosis: Book Excerpts
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Introduction: Gastrointestinal Disorders:
Accurate assessment vital
(Professional Guide to Diseases (Eighth Edition))
Your assessment of the patient with suspected GI disease must begin with a careful history that includes occupation, family history, and recent travel. The medical history should include previous hospital admissions; surgical procedures (including recent tooth extraction); family history of ulcers, colitis, or cancer; and current medications, whether prescribed, over-the-counter, or herbal remedies, with particular attention to aspirin, steroids, or anticoagulants.
Have the patient describe his chief complaint in his own words. Does he have abdominal pain, indigestion, heartburn, or rectal bleeding? How long has he had it? What relieves these symptoms or makes them worse? Has he experienced nosebleeds or difficulty in swallowing recently? Has he had recent weight loss or gain? Is he on a special diet? Does he drink alcoholic beverages or smoke? If yes to either, how much and how often? Ask about bowel habits. Does he regularly use laxatives or enemas? If he experiences nausea and vomiting, what does the vomitus look like? Does changing his position relieve nausea?
Next, try to define and locate any pain. Ask the patient to describe the pain. Is it dull, sharp, burning, aching, spasmodic, or intermittent? Where is it located? Does it radiate? How long does it last? When does it occur? What triggers it? What relieves it?
Visual assessment
Observe how the patient looks and note appropriateness of behavior. Changes in fluid and electrolyte balance, severe infection, drug toxicity, and hepatic disease may cause abnormal behavior. Your visual examination should check:
❑ Skin: loss of turgor, jaundice, cyanosis, pallor, diaphoresis, petechiae, bruises, edema, and texture (dry or oily)
❑ Head: color of sclerae, sunken eyes, dentures, caries, lesions, tongue (color, swelling, dryness), and breath odor
❑ Chest: shape (asymmetrical, barrel, or sunken)
❑ Lungs: rate, rhythm, and quality of respirations
❑ Abdomen: size and shape (distention, contour, visible masses, and protrusions), abdominal scars or fistulae, excessive skin folds (may indicate wasting), and abnormal respiratory movements (inflammation of diaphragm).
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Source: Professional Guide to Diseases (Eighth Edition), 2005
Gastrointestinal Bleeding:
Physical examination
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
A. Vital signs. The single most important aspect of the initial physical examination is determining the patient’s hemodynamic stability. Unstable patients should be managed as trauma patients. Placement of a nasogastric (NG) tube is considered the “fifth vital sign” in patients with acute GI bleeding (2).
B. Focused physical examination. After ensuring hemodynamic stability, the initial physical examination should eliminate a nasal or oropharyngeal source of bleeding. Examine the skin and abdomen carefully for clues to an underlying cause. A rectal examination is mandatory.
1. Skin examination. Ecchymoses, petechiae, and varices should be noted. Conjunctival pallor is a sign of chronic anemia. Numerous mucosal telangiectasias can point to an underlying vascular abnormality.
2. Abdominal examination. Look for stigmata of chronic liver disease (hepatosplenomegaly, spider angiomata, ascites, palmar erythema, caput medusae, gynecomastia, and testicular atrophy) (Chapter 9.9).
3. Rectal examination. Rectal varices, hemorrhoids, and fissures should be noted.
Laboratory evaluation
A. Basic laboratory studies should include a complete blood count with particular attention to the hematocrit, coagulation studies [prothrombin time (PT) and partial thromboplastin time (PTT)], liver function tests (LFTs), serum chemistries (blood urea nitrogen is elevated disproportionately to creatinine in patients with GI blood loss), electrocardiogram (ECG), and NG aspirate analysis. Acutely, the hematocrit is a poor indicator of blood loss; however, serial hematocrits can be useful in assessing ongoing blood loss. A prolonged PT or PTT suggests an underlying coagulopathy. Elevated LFTs suggest underlying liver disease. An ECG is important, especially in elderly patients, to search for evidence of cardiac ischemia. Finally, the NG aspirate is essential. If the aspirate is bright red, or “coffee grounds” in appearance, an upper GI source is likely.
B. Endoscopy plays a central role in the diagnosis and management of GI bleeding. Fiberoptic endoscopy is 90% accurate in pinpointing the source of upper GI bleeding. In addition, the endoscope can also be used to deliver therapy directly.
C. Anoscopy can be used to identify the source of lower GI bleeding; however, the yield is poor (5). Often the site of bleeding cannot be directly visualized or the volume of bleeding is sufficiently heavy to obscure clear visualization.
D. Nuclear medicine studies are useful in grossly localizing bleeding sources to the small intestine, right colon, or left colon. Nuclear scanning is also useful in detecting Meckel’s diverticulae. These images can detect ongoing GI bleeding with a sensitivity of blood loss at 0.05 to 0.1 ml/minute.
E. Angiography can also identify the source of lower GI bleeding. It is not as sensitive as nuclear scanning, requiring a blood loss of more than 0.5 ml/minute.
Diagnostic assessment
The key to the successful approach to GI bleeding is ensuring the hemodynamic stability of the patient. Once done, a systematic search for the source of the bleeding should be undertaken. Although often unreliable, a careful patient history can provide valuable clues to factors that may predispose the patient to hemorrhage from a particular site within the GI tract. Physical examination (including placement of a NG tube) can further delineate whether an upper source or a lower source is most likely. The key diagnostic modality in GI bleeding is fiberoptic endoscopy. Following the clues provided by a careful history and physical examination, targeted endoscopy is then used to definitively identify the source of bleeding. In the rare cases where endoscopy is unable to adequately identify the source of GI bleeding, specialized nuclear medicine and angiographic studies can be used.
References
1. Zimmerman HM, Curfman K. Acute gastrointestinal bleeding. AACN Clin Issues 1997;8(3):449–458.
2. Laine L. Acute and chronic gastrointestinal bleeding. In: Feldman M, Sleisinger MH, Scharschmidt BF, eds: Gastrointestinal and liver disease: pathophysiology, diagnosis, and management. Philadelphia: WB Saunders, 1998:198–218.
3. McGuirk TD, Coyle WJ. Upper gastrointestinal tract bleeding. Emer Med Clin N Am 1996;14(3):523–545.
4. Zuccaro G. Management of the adult patient with acute lower gastrointestinal bleeding. Am J Gastroenterol 1998;93(8):1202–1208.
5. Bono MJ. Lower gastrointestinal bleeding. Emer Med Clin N Am 1996;14(3):547–556.
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Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
Gastrointestinal Bleeding:
DIagnostic Approach
(Field Guide to Bedside Diagnosis)
With overt bleeding, determining whether a source is proximal or distal to the ligament of Treitz is key to the further diagnostic evaluation. Hematemesis confirms an upper GI source, and suggests loss of more than a quarter of blood volume. Melena (black, tarry stool) also comes from an upper source unless the bleeding is brisk or large volume and transit is rapid. Melena without hematemesis usually results from a lesion distal to the pylorus (e.g., duodenal ulcer) or to slow bleeding. Tarry stools may be produced by as little as 100 mL of blood. Lower sources produce hematochezia (maroon or clots from the right colon and bright red from the left colon). A small amount of blood only on the toilet tissue nearly always comes from a bleeding hemorrhoid or fissure. Silver stool is said to arise from acholic stools combined with luminal bleeding in an ampullary cancer.
Determine the hemodynamic significance of the bleeding by looking for postural lightheadedness or changes in pulse or blood pressure. Early symptoms of thirst and lightheadedness occur with loss of more than 15% of intravascular volume. An orthostatic blood pressure drop of 10 mm Hg indicates a loss greater than or equal to 20% of volume. Shock with hypotension and pallor develops with 25% to 40% volume loss.
Stools may be falsely colored by ingestants such as bismuth subsalicylate, iron, licorice or charcoal, which turn it black, or beets, which turn it red. These stools are not sticky. A negative stool test for occult blood will usually resolve this.
Hemoccult screening detects blood loss down to 1 to 10 ml/day. Evaluation of a heme positive stool will reveal colon cancer in 5% to 14% of patients, and large adenomatous polyps in another 15% to 35%. Any single positive stool should be evaluated. Hemoccult screening reduces colon cancer mortality by 15% to 33%. An asymptomatic patient with a negative Hemoccult has only a 0.2% chance of having colon cancer (compared with 1.4% prevalence in this population). Using Hemoccult alone as a screening strategy will miss 50% to 60% of colon cancers.
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Source: Field Guide to Bedside Diagnosis, 2007
Gastrointestinal Bleeding:
Diagnostic Approach
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)
Determination of Gastrointestinal Bleeding
Determinewhether reddish color of vomitus or stool is blood (e.g., raspberries,beets, and food colorings can give reddish color).Gastroccult (Smith Kline Diagnostics,San Jose, CA) test may be used to detect presence of blood in vomitusor gastric aspirate. Hemoccult test can be used to confirm presenceof blood in stool. Severity of Bleeding
If GI bleedingis obvious, most important task is to determine severity.Important to quantitate amount of bleeding:1–2 drops, 1 teaspoonful, 1 cupful, or massive bleedingwith clot formation. Passage of clots via rectum or vomiting of >1cupful of bright red blood is indicative of significant bleeding.In such cases, first note vital signsand perform any necessary resuscitation.Immediate fluid replacement is requiredto stabilize BP. Site of the Bleeding
Determinethe site of bleeding—whether it is from the upper or lowertract or both. Blood from nose or mouth can be swallowed and subsequentlyvomited or passed in stool. Retching from vomiting also can producesome blood-stained vomitus but is rarely severe.Except in these instances, NG tubeshould be placed to document level and rate of bleeding.Gastric aspirate that is positive forblood is highly specific for upper tract bleeding. Negative aspiratesuggests lower tract bleeding but does not totally preclude uppertract bleeding, especially from duodenum. Specific Diagnosis
Importantfactors to consider in diagnosis areAgeClinical findings (e.g., vomiting,diarrhea, fever, constipation, abdominal pain, hepatomegaly, splenomegaly,abdominal distension, weight loss, and jaundice)History of aspirin, NSAID, or alcoholingestionPresence of known diseases (e.g., IBDor liver disease) Diagnostic studies that may identifysource of acute bleeding include endoscopy, radionuclide scanning,and selective angiography.If upper tract bleeding has stoppedor is intermittent, upper endoscopy can be performed to diagnoseesophagitis, gastritis, gastric or duodenal ulcer, Mallory-Weisstear, and esophageal varices.If endoscopic exam is impossible to performbecause of continuous bleeding, radionuclide scan or selective angiographycan be performed. Technetium sulfur colloid scan can detect slow ongoingbleeding, whereas technetium red cell scan can detect slow intermittentbleeding. These techniques help localize site of bleeding, so thatother diagnostic studies can be performed.Sulfur colloid scan can detect bleedingat rate as low as 0.1 mL/min, but only if bleeding is occurringat time of injection because half-life of tracer is <2.5mins. Labeled red cells remain in blood for 24 hrs, so technetiumred cell scan can detect intermittent bleeding.If these scans fail to disclose siteof bleeding or bleeding is brisk, selective angiography should beperformed—angiography of celiac axis and superior mesentericartery for suspected upper tract bleeding, and superior mesentericand inferior mesenteric artery angiography for suspected lower tract bleeding.Another advantage of angiography isthat therapeutic measures (e.g., vasopressin infusion and embolization)can be used if necessary.If the bleeding is massive or uncontrolled,immediate surgery should be considered. In stable child with lower tract bleeding,anus should be examined for anal fissure and rectum for polyp.With bloodydiarrhea, bacterial stool culture should be performed, and examof stool for ova and parasites should be considered.Technetium 99m–pertechnetatescan to identify ectopic gastric mucosa in Meckel diverticulum orintestinal duplication also should be considered. If diagnosis remainsuncertain, proctosigmoidoscopy should be performed. This may befollowed by colonoscopy or contrast studies.Colonoscopy with biopsy may diagnosepolyps, colitis, IBD, hemangiomas, and malignant lesions. Air-contrastenema may diagnose intussusception. With persistent undefined bleeding,upper tract endoscopy may be useful to identify ulcer, esophagealor gastric varices, or vascular lesion.Upper GI radiographic series with smallbowel follow-through may diagnose lesions of esophagus, stomach,and duodenum as well as lesions of small bowel, including CrohndiseaseSelective angiography may not revealsite of bleeding if bleeding is too slow, but it may suggest angiodysplasticlesion or tumor by revealing abnormal vascular pattern. >
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Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006
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