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سه‌شنبه 6 شهریور‌ماه سال 1386
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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 8:00 am plasma cortisol level ranges between 8 and 25 μg/dL and declines throughout the day. By 11:00 pm, the values are usually less than 5 μg/dL. Most patients with Cushing's syndrome lack this diurnal variation. Thus, although their morning cortisol levels may be normal, their afternoon or evening concentrations are markedly higher.

 

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 11:00 pm, and plasma cortisol is measured the following morning at 8:00 am. A morning plasma cortisol level greater than 3 μg/dL suggests hypercortisolism. This test is easy and can be performed in an outpatient setting. The test is fairly sensitive, although some pituitary adenomas are very sensitive to dexamethasone and can suppress cortisol production readily in this test. However, the test produces a significant number of false-positive results, especially in obese and depressed patients.

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 8:00 am cortisol level is measured, and then 8 mg of dexamethasone is given orally at 11:00 pm. At 8:00 am the following morning, a plasma cortisol measurement is obtained. Suppression, which would occur in patients with pituitary Cushing's disease, is defined as a decrease in plasma cortisol to less than 50% of the baseline level. Few patients with bronchial carcinoid have been examined, so the suppressibility of these tumors by high-dose overnight dexamethasone is not well established.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

دستگاه گوارش :

 

TABLE 35-2 Association between Pathobiology of Causative Agents and Clinical Features in Acute Infectious Diarrhea

Pathobiology/Agents

Incubation Period

Vomiting

Abdominal Pain

Fever

Diarrhea

Toxin producers

 

 

 

 

 

  Preformed toxin

 

 

 

 

 

    Bacillus cereus, Staphylococcus aureus, Clostridium perfringens

1–8 h
8–24 h

3–4+

1–2+

0–1+

3–4+, watery

  Enterotoxin

 

 

 

 

 

    Vibrio cholerae, enterotoxigenic Escherichia coli, Klebsiella pneumoniae, Aeromonas species

8–72 h

2–4+

1–2+

0–1+

3–4+, watery

Enteroadherent

 

 

 

 

 

  Enteropathogenic and enteroadherent, E. coli, Giardia organisms, cryptosporidiosis, helminths

1–8 d

0–1+

1–3+

1–2+

1–2+, watery

Cytotoxin-producers

 

 

 

 

 

  Clostridium difficile

1–3 d

0–1+

3–4+

1–2+

1–3+, usually watery, occasionally bloody

  Hemorrhagic E. coli

12–72 h

0–1+

3–4+

1–2+

1–3+, initially watery, quickly bloody

Invasive organisms

 

 

 

 

 

  Minimal inflammation

 

 

 

 

 

    Rotavirus and Norwalk agent

1–3 d

1–2+

2–3+

3–4+

1–3+, watery

  Variable inflammation

 

 

 

 

 

    Salmonella, Campylobacter, and Aeromonas species, Vibrio parahaemolyticus, Yersinia

12 h–11 d

0–3+

2–4+

3–4+

1–4+, watery or bloody

  Severe inflammation

 

 

 

 

 

    Shigella species, enteroinvasive E. coli, Entamoeba histolytica

12 h–8 d

0–1+

3–4+

3–4+

1–2+, bloody

 

توگسین از پیش ساخته شده  و انتروتوکسین:

   Preformed toxinBacillus 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 Norwalk agent

  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

 


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