Diagnostic Tests for Diarrheagenic Escherichia coli
Diarrheagenic Escherichia coli Tests: Book Excerpts
Home Diagnostic Testing
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Diarrheagenic Escherichia coli Diagnosis: Book Excerpts
Diagnostic Tests for Diarrheagenic Escherichia coli: Online Medical Books
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DIARRHEA, ACUTE:
DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)
The first thing to do is a stool for occult blood. This will help distinguish those patients who are having obvious infectious disease of the large intestine or maybe even the small intestine. It will also make one suspicious of ulcerative colitis. All patients need a stool culture and stool for ova and parasites. A stool for
Giardia
antigen can also be done. Serologic studies will not be of much help in the acute condition, but they may help later on in cases of salmonellosis and amebiasis. The clinician himself should do a methylene blue smear for leukocytes and examine a wet saline preparation of the stool. If there is a history of antibiotic uses, a stool should be tested for
Clostridium difficile
toxin B. Leukocytes on a smear suggest bacterial cause and a culture should be done. The laboratory should be alerted if
Campylobacter
or
Yersinia
are suspected because special culture media are needed. If the diarrhea persists or if there is blood, sigmoidoscopy or colonoscopy should be performed. It is always important to examine the rectum for hemorrhoids and anal fissures that may be causing the positive stool for occult blood. When the diarrhea persists and becomes chronic, the diagnostic workup should include the studies that are listed under chronic diarrhea.
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Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
DIARRHEA, CHRONIC:
DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)
Most patients will be diagnosed by a stool culture, stool for occult blood, and stool for ovum and parasites, along with a sigmoidoscopy and barium enema. Giardiasis may be best diagnosed by the finding of
Giardia
antigen in the stool. In patients who have been on antibiotics, the stool should be tested for
C. difficile
toxin B. If a systemic disease is suspected, CBC, sedimentation rate, chemistry panel, and thyroid profile should be done. An HIV antibody test may be indicated depending on the history. A urine test for 5-HIAA will uncover a carcinoid syndrome. A serum gastrin will usually reveal a gastrinoma. If these tests do not provide a diagnosis, the most cost-effective approach at this point is to refer the patient to a gastroenterologist, who will undoubtedly perform a colonoscopy as part of the workup. Small bowel aspiration and biopsy will be useful in diagnosing
Giardia
infection or celiac sprue; angiography will confirm mesenteric ischemia or infarcts.
If a gastroenterologist is not available, the clinician may proceed with a quantitative 24-hr stool analysis for fat. If there is 10 g or more of fat in the stool in a day, then steatorrhea can be diagnosed and one can proceed with the workup of steatorrhea. If there is less than 7 g of fat per day in the stool, the stool volume after fasting should be done. If it is large and we have ruled out surreptitious laxative abuse, a polypeptide-secreting tumor should be considered. Here again, it would be best to refer the patient to a gastroenterologist. If the volume after a fast is small, the problem is most likely lactose or other food intolerance or an irritable bowel syndrome. Occasionally, the problem is dysfunction of the anal sphincter. Once again, a GI specialist is probably best consulted for workup of a dysfunctional anal sphincter.
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Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
Diarrhea:
History and physical examination
(Handbook of Signs & Symptoms (Third Edition))
If the patient isn't in shock, proceed with a physical examination. Evaluate hydration, check skin turgor and mucous membranes, and take blood pressure with the patient lying, sitting, and standing. Inspect the abdomen for distention, and palpate for tenderness. Auscultate bowel sounds. Check for tympany over the abdomen. Take the patient's temperature, and note any chills. Also, look for a rash. Conduct a rectal examination and a pelvic examination if indicated.
Explore signs and symptoms associated with diarrhea. Does the patient have abdominal pain and cramps? Difficulty breathing? Is he weak or fatigued? Find out his drug history. Has he had GI surgery or radiation therapy recently? Ask the patient to briefly describe his diet. Does he have any known food allergies? Last, find out if he's under unusual stress.
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Source: Handbook of Signs & Symptoms (Third Edition), 2006
Fecal incontinence:
History and physical examination
(Handbook of Signs & Symptoms (Third Edition))
Ask the patient with fecal incontinence about its onset, duration, and severity and about any discernible pattern — for example, does it occur at night or only with episodes of diarrhea? Note the frequency, consistency, and volume of stools passed within the past 24 hours and obtain a stool sample. Focus your history taking on GI, neurologic, and psychological disorders.
Let the history guide your physical examination. If you suspect a brain or spinal cord lesion, perform a complete neurologic examination. (See
Neurologic control of defecation.) If a GI disturbance seems likely, inspect the abdomen for distention, auscultate for bowel sounds, and percuss and palpate for a mass. Inspect the anal area for signs of excoriation or infection. If not contraindicated, check for fecal impaction, which may be associated with incontinence.
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Source: Handbook of Signs & Symptoms (Third Edition), 2006
Diarrhea:
History and physical examination
(Professional Guide to Signs & Symptoms (Fifth Edition))
If the patient isn’t in shock, proceed with a brief physical examination. Evaluate hydration, check skin turgor and mucous membranes, and take blood pressure with the patient lying, sitting, and standing. Inspect the abdomen for distention, and palpate for tenderness. Auscultate bowel sounds. Check for tympany over the abdomen. Take the patient’s temperature, and note any chills. Also, look for a rash. Conduct a rectal examination and a pelvic examination if indicated.
Explore signs and symptoms associated with diarrhea. Does the patient have abdominal pain and cramps? Difficulty breathing? Is he weak or fatigued? Find out his drug history. Has he had GI surgery or radiation therapy recently? Ask the patient to briefly describe his diet. Does he have any known food allergies? Lastly, find out if he’s under unusual stress.
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Source: Professional Guide to Signs & Symptoms (Fifth Edition), 2006
Fecal incontinence:
History and physical examination
(Professional Guide to Signs & Symptoms (Fifth Edition))
Ask the patient with fecal incontinence about its onset, duration, and severity and about any discernible pattern—for example, at night or with diarrhea. Note the frequency, consistency, and volume of stools passed within the last 24 hours and obtain a stool specimen. Focus your history taking on GI, neurologic, and psychological disorders.
Let the history guide your physical examination. If you suspect a brain or spinal cord lesion, perform a complete neurologic examination. (See Neurologic control of defecation, page 334.) If a GI disturbance seems likely, inspect the abdomen for distention, auscultate for bowel sounds, and percuss and palpate for a mass. Inspect the anal area for signs of excoriation or infection. If not contraindicated, check for fecal impaction, which may be associated with incontinence.
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Source: Professional Guide to Signs & Symptoms (Fifth Edition), 2006
Diarrhea:
Physical examination
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
A. Focused physical examination. Obtain vital signs (notably temperature) and include orthostatic blood pressure measurements. Assess the patient’s weight and general nutritional status. The abdomen should be examined for bowel sounds, localized tenderness, and organomegaly. A rectal examination may demonstrate a fistula or abscess that can be a clue to Crohn’s disease. Occult or gross blood can indicate an invasive inflammatory diarrheal illness, diverticular disease, or an ischemic bowel.
B. Additional physical examination. The history may lead to a more specific examination (e.g., thyroid for thyrotoxicosis) or a search for lymphadenopathy in an immunocompromised patient.
Testing (5)
A. Acute diarrhea. Laboratory testing should be reserved for those patients with severe symptoms (e.g., fever, bloody diarrhea, abdominal pain, and dehydration, or symptoms not improving after 5 days) or a comorbid condition. Examination of the stool sample is the most important laboratory test. A single specimen should be submitted for a Wright’s stain for leukocytes, occult blood, Sudan stain for fat, and selected bacterial cultures (Salmonella, Shigella, Campylobacter, and Yersinia organisms). Large numbers of white cells are consistent with inflammatory causes, whereas isolated occult or gross blood may suggest amebiasis, neoplastic disease, vascular disease, or intestinal ischemia. If excess fat is present, malabsorption should be considered (e.g., celiac sprue). Clostridium difficile toxin should be obtained in the elderly and in those with a recent antibiotic history. Tests for ova and parasites on three consecutive specimens should be done in patients with diarrhea that persists for more than 7 to 10 days. In patients where ova and parasite testing is negative and clinical suspicion is high, an enzyme-linked immunosorbent assay test for the Giardia antigen should be considered as well as a wet mount examination of the stool for amebiasis. Sigmoidoscopy is warranted acutely in patients with symptoms of severe proctitis and in patients with suspected C. difficile colitis who appear ill. Rectal swabs for Chlamydia, herpes simplex virus, and gonorrhea may additionally be warranted in sexually active patients with severe proctitis.
B. Chronic diarrhea. Additional tests to be considered include complete blood count, serum electrolytes, liver function tests, calcium, phosphate, albumin, B12, folate, and iron studies to rule out significant abnormalities secondary to the diarrhea, nutritional abnormalities, or hepatobiliary disease. Thyroid studies, serum gastrin, and vasoactive intestinal peptide should be ordered if clinically indicated. Sigmoidoscopy, which allows direct visualization for biopsy and culture, may be helpful in detecting inflammatory bowel disease. Barium studies of the small and large bowel can identify Crohn’s disease, blind loops, celiac sprue, fistulae, and tumors. The stool specimen can be alkalinized for phenolphthalein, consistent with laxative abuse. The presence of steatorrhea warrants a 72-hour collection of stool fat (Chapter 9.12). A gastroenterologist can pursue additional specialized testing, including upper endoscopy with biopsy, breath testing for malabsorption, and pancreatic function testing.
Diagnostic assessment
A careful history helps to classify the diarrhea, provides clinical clues for selected diagnostic testing, and aids in risk stratifying the patient. Comorbid diseases and associated symptoms increase the urgency for diagnostic workup and management (e.g., fever, symptoms > 5 days, bloody diarrhea, known exposures, weight loss). Abnormal vital signs or bloody diarrhea identify patients at higher risk who require early therapeutic intervention. Although most diarrhea is benign and self-limited, a thorough history, focused physical examination, and directed laboratory testing will identify those cases requiring early diagnostic evaluation, aggressive management, or referral.
References
1. Kroser JA, Metz DC. Evaluation of the adult patient with diarrhea. Primary Care 1996;23(3):629–647.
2. Blacklow NR, Greenberg HB. Viral gastroenteritis. N Engl J Med 1991;325(4):
252–264.
3. Donowitz M, Kokke FT, Saidi R. Evaluation of patients with chronic diarrhea. N Engl J Med 1995;332(11):725–729.
4. Norris TE. Lower gastrointestinal problems. Monograph, edition No. 198. Home Study Self-Assessment program. Kansas City, Mo: American Academy of Family Physicians, November 1995.
5. Kearney DJ, McQuaid KR. Approach to the patient with gastrointestinal disorders. In: Grendell JH, ed. Current diagnosis and treatment in gastroenterology. Norwalk, CT: Appleton & Lange, 1996.
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Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
Acute Diarrhea:
Diagnostic Approach
(Field Guide to Bedside Diagnosis)
Most cases of acute diarrhea are self-limited. Red flags to prompt further evaluation include: profuse watery diarrhea with dehydration; passage of blood or mucous; temperature .38.5˚C, duration .48 hours; severe abdominal pain in a patient over 50; or an immunocompromised patient.
Symptoms that begin within 6 hours of eating suspect food suggest a preformed toxin of Staph aureus or Bacillus cereus, at 8 to 14 hours Clostridium perfringens, and over 14 hours from viral agents or bacterial contamination of food with E. coli.
Secretory diarrhea is characterized by the absence of fever and prominent nausea/vomiting with watery stools that persist when fasting. It is caused by a toxin (Staph, E. coli, Vibrio cholera), gastrin (pancreatic cancer), calcitonin (medullary carcinoma of the thyroid), or vasoactive intestinal peptide
(VIP). Invasive infection with exudative diarrhea is associated with systemic
symptoms, fever, chills, and blood, pus, and proteinaceous material in
the stools. It is most commonly found with infections such as Salmonella, Shigella, Campylobacter, or enterohemorrhagic E. coli. Bloody diarrhea usually indicates invasive infection, but the differential also includes superior mesenteric artery thrombosis, inflammatory bowel disease, and drug-induced or ischemic colitis.
Small bowel diarrhea is characterized by passage of large loose stools, and with periumbilical pain. Large bowel diarrhea has frequent passage of small stools, with tenesmus.
Common pathogens in HIV-associated diarrhea are cytomegalovirus, Cryptosporidia, Isospora, Salmonella, and Giardia.
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Source: Field Guide to Bedside Diagnosis, 2007
Chronic Diarrhea:
Diagnostic Approach
(Field Guide to Bedside Diagnosis)
Symptoms of inflammatory diarrhea are fever, abdominal tenderness, blood in the stool, or extraintestinal manifestations such as arthritis, erythema nodosum, pyoderma gangrenosum, or iritis. Osmotic diarrhea is suggested by steatorrhea or carbohydrate malabsorption. It improves with fasting. Secretory diarrhea is evidenced by large volume and watery stools, which persist at night and with fasting. Voluminous watery diarrhea is more likely with small bowel disorders, while small-volume frequent diarrhea occurs with colon disorders.
Fat malabsorption is characterized by increased stool bulk with foul-smelling stools. Stools are difficult to flush and leave oil in the bowl. Weight loss occurs despite adequate appetite and intake. Increased flatulence occurs with carbohydrate malabsorption. Protein-losing enteropathy is associated with peripheral edema and ascites. Malabsorption of fat-soluble vitamins may cause specific deficiencies, such as vitamin A (night blindness and dry eyes), vitamin D (paresthesias and cramps), or vitamin K (easy bruising) deficiencies.
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Source: Field Guide to Bedside Diagnosis, 2007
Diarrhea:
Physical assessment
(Signs & Symptoms: A 2-in-1 Reference for Nurses)
If the patient isn’t in shock, proceed with a brief physical examination. Evaluate hydration, check skin turgor and mucous membranes, and take blood pressure with the patient lying, sitting, and standing. Inspect the abdomen for distention, and palpate for tenderness. Auscultate bowel sounds. Check for tympany over the abdomen. Take the patient’s temperature, and note any chills. Also, look for a rash. Conduct a rectal examination and a pelvic examination if indicated.
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Source: Signs & Symptoms: A 2-in-1 Reference for Nurses, 2007
Diarrhea:
Diagnostic Approach: Acute Diarrhea
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)
Most commoncause of acute diarrhea is infection with rotavirus. Common bacterial pathogensinclude Salmonella species, Shigella species, and C. jejuni.Presence of fever and blood or pusin stool suggests bacterial infection, and bacterial stool cultureshould be performed.Stool toxin assay for C. difficileshould be considered whenever diarrhea persists during or followingantibiotic therapy.Cow milk or soy protein sensitivityis likely when diarrhea occurs after ingestion of these productsand no evidence of infection or antibiotic usage exists.Intussusception and HUS also shouldbe considered in children with bloody diarrhea.
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Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006
Fecal Incontinence:
Diagnostic Approach
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)
In childwith normal physical exam, most common causes of fecal incontinenceare maturational delay, developmental conflict, stress-related factors,and constipation. If primary psychologic disturbance exists, furtherevaluation should be performed by clinical psychologist or psychiatrist.History and physical exam can screenfor a neurologic disorder. Relaxed anal sphincter tone, decreasedperianal sensation, lower extremity weakness, and urinary incontinencesuggest spinal cord lesion. Combination of spine radiography, CT,and MRI is usually diagnostic.
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Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006
Diarrhea:
History and physical examination
(Nursing: Interpreting Signs and Symptoms)
If the patient isn't in shock, proceed with a physical examination. Evaluate hydration, check skin turgor and mucous membranes, and take blood pressure with the patient lying, sitting, and standing. Inspect the abdomen for distention, and palpate for tenderness. Auscultate bowel sounds. Check for tympany over the abdomen. Take the patient's temperature, and note any chills. Also, look for a rash. Conduct a rectal examination and a pelvic examination if indicated.
Explore signs and symptoms associated with diarrhea. Does the patient have abdominal pain and cramps? Difficulty breathing? Is he weak or fatigued? Find out his drug history. Has he had GI surgery or radiation therapy recently? Ask the patient to briefly describe his diet. Does he have any known food allergies? Last, find out if he's under unusual stress.
» READ BOOK EXCERPT ONLINE »
Source: Nursing: Interpreting Signs and Symptoms, 2007
Fecal incontinence:
History and physical examination
(Nursing: Interpreting Signs and Symptoms)
Ask the patient with fecal incontinence about its onset, duration, and severity and about any discernible pattern—for example, does it occur at night or only with episodes of diarrhea? Note the frequency, consistency, and volume of stools passed within the past 24 hours and obtain a stool specimen. Focus your history taking on GI, neurologic, and psychological disorders.
Let the history guide your physical examination. If you suspect a brain or spinal cord lesion, perform a complete neurologic examination. (See Neurologic control of defecation.) If a GI disturbance seems likely, inspect the abdomen for distention, auscultate for bowel sounds, and percuss and palpate for a mass. Inspect the anal area for signs of excoriation or infection. If not contraindicated, check for fecal impaction, which may be associated with incontinence.
» READ BOOK EXCERPT ONLINE »
Source: Nursing: Interpreting Signs and Symptoms, 2007
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