UFC excretion reflects plasma unbound cortisol that is filtered and excreted by the kidney. This test is extremely sensitive for the diagnosis of Cushing's syndrome because, in 90% of affected patients, the initial UFC level is greater than 50 μg/24 hours when measured by HPLC or mass spectroscopy cortisol assays.
Patients with Cushing's disease usually have UFC levels between 100 and 500 μg/24 hours,
Whereas patients with the ectopic ACTH syndrome and cortisol-secreting adrenal adenomas or carcinomas frequently have UFC levels greater than 500 μg/24 hours.
The normal
The overnight dexamethasone suppression test can also be used as a screening test to evaluate patients suspected of having hypercortisolism. Dexamethasone, 1 mg, is given orally at
For these reasons, collection of urine for measurement of 24-hour UFC excretion is a better screening test.
In the dexamethasone suppression test (Liddle test), 0.5 mg of dexamethasone is given orally every 6 hours for 2 days, followed by 2 mg of dexamethasone every 6 hours for another 2 days. On the second day of the high dosage of dexamethasone, UFC is suppressed to less than 10% of that of the baseline collection in patients with pituitary adenomas but not in patients with the ectopic ACTH syndrome or adrenal cortisol-secreted tumors. Although the Liddle test is often helpful in establishing the etiology of Cushing's syndrome, it has some disadvantages. The test requires accurate measurement of urine collections, often necessitating inpatient hospitalization. In approximately 50% of patients with bronchial carcinoids causing ectopic ACTH production, cortisol secretion is suppressible by high-dose dexamethasone, which yields a false-positive result. In addition, because patients with Cushing's syndrome are often episodic secretors of corticosteroids, considerable variation in daily UFC excretion can occur and false results can be obtained. Therefore, the Liddle test should be interpreted cautiously and other confirmatory tests should be performed before a patient is sent to surgery.
An overnight high-dose dexamethasone suppression test is helpful in establishing the etiology of Cushing's syndrome. In this test, a baseline
دستگاه گوارش :
TABLE 35-2 Association between Pathobiology of Causative Agents and Clinical Features in Acute Infectious Diarrhea | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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توگسین از پیش ساخته شده و انتروتوکسین:
Preformed toxin: Bacillus cereus, Staphylococcus aureus, Clostridium perfringens |
Enterotoxin: Vibrio cholerae, enterotoxigenic Escherichia coli, Klebsiella pneumoniae, Aeromonas species |
اسهال + استفراغ شدید با یا بدون تب چند ساعت پس از مصرف غذا
اتصال به روده(انتروادهرنت):
Enteropathogenic and enteroadherent, E. coli, Giardia organisms, cryptosporidiosis, helminths |
استفراغ کمتر ، نفخ و کرامپ شکمی شدیدتر و تب بالاتر
سیتوتوکسین و تهاجم:
Clostridium difficile, Hemorrhagic E. coli |
هر د و نوع: تب بالا + درد شدید شکمی
باکتریهای مهاجم + آنتاموبا هیستولیتیکا:
Invasive organisms |
Minimal inflammation: Rotavirus and |
Variable inflammation: Salmonella, Campylobacter, and Aeromonas species, Vibrio parahaemolyticus, Yersinia |
Severe inflammation: Shigella species, enteroinvasive E. coli, Entamoeba histolytica |
دیسانتری
اسهال + تیروئیدیت اتوایمیون، پریکاردیت و گلومرولونفریت + علائم شبیه آپاندیسیت: یرسینیا
داروهای مسبب یبوست: کلسیم بلوکر، ضدافسردگی ها، آلومینیوم
داروهای مسبب کاهش وزن: آنتی بیوتیک ها ، SSRI ، NSAIDS، متفورمین، لوودوپا، ACEinh