Conjunto de datos “Pima Diabetes”

C

^hemistry

43 [email protected]

Biological fluids

125. Changes in urine after 2 hours include:

a. ↑bilirubin.

b. ↑ketones.

c. ↑nitrite level d. ↓pH

Probable answer: ↑nitrite

Changes of urine when it's decomposed

Constituent Result Reason

Physical Odour Offensive (ammonical)

Bacteria growth → breakdown of urea to ammoia

Aspect ↑ turbiity  ↑bacteria

 Crystal formation

 Precipitation of a. crystals (phosphate)

Reaction ↑ pH Breakdown of urea to ammonia by bacteria Chemical Glucose False -ve Utilized by bacteria

Ketones Fase –ve  Volatalization of acetone

 Breakdown of acetoacetate y bactera Bilirubin False –ve  Destroyed by light

 Oxidized to bilivirdin Urobilinogen False –ve Destroyed by light

Nitrite False +ve Produced by bacteria after specimen is voided Microsco

py Bacteria ↑ bacteruria Bacteria multiply in voided sample

Cells & asts Disintegration of cells & casts

Unstable environment especiall when urine is alkaline

&/or hypotonic

126. A vegetable meal changes urine pH to:

a. Alkaline b. Acidic c. Neutral d. No change

Probable answer: Alkaline

 Urine pH is an indicator of dietary acid-base load.

Acidic foods: include meats, beans, legumes, grains, nuts, milk and cheeses → acidic urine.

Alkaline foods: → alkaline urine: this include:

Most fruits are acid-neutralizing, due in part to the high amounts of alkaline minerals, including potassium, calcium and magnesium.

Most vegetables are alkaline due to their high concentration of alkaline minerals.

 A more alkaline diet, high fruit and vegetable intake and lower consumption of meat is significantly associated with a more alkaline urine.

127. Difference between urine and other biological fluids:

a. Creatinine >50mg/dl and urea

>600mg/dl.

b. Urobilinogen.

c. Na and K concentration.

d. pH

Probable answer: Creatinine >50mg/dl and urea >600mg/dl.

Explanation:

Occasionally following abdominal or pelvic surgery, drainage fluid is submitted to the laboratory for identification as urine. After centrifugation, the supernatant may be tested for urea, creatinine, sodium and chloride. These analytes are usually sufficiently concentrated in urine, and this differentiates urine from plasma or serous exudate (Dr Ola Demerdash).

128. All cause urine turbidity except:

a) Amorphous urate.

b) Amorphous phosphate.

c) Ca oxalate d) Ca carbonate.

Propable answer: Ca Oxalate.

Transparency (Clarity) of urine⁹:

 Urine is normally clear when voided.

 Assessment of transparency:

- Should be assessed on a well-mixed urine specimen

- Looking through the specimen in an optically clear container.

- Degrees of transparency:

1. Clear 2. Hazy

9Dr Ola Demerdash.

Biological Fluids

C

^hemistry

44 [email protected]

3. Cloudy 4. Turbid.

 Causes of turbidity:

Generally Normal Possibly Pathologic

On standing, urine often becomes

cloudy Amorphous

phosphates.

Normal crystals Epithelial cells (squamous, transitional) Bacteria (old urine) Mucus

Sperms, prostatic fluid

Amorphous urates (also normal) Abnormal crystals Red blood cells White blood cells (pus) Casts Fat (lipids) Epithelial cells (renal, transitional, malignant) Bacteria (fresh urine) Chyluria Fecal matter (from fistula)

Precipitation of amorphous crystals (urates in acid urine, phosphates in alkaline urine).

Mucus.

Growth of bacteria

 Calcium oxalate crystals:

- typically are colorless squares resembling an envelope.

- The most frequently observed crystals in urine, - 75% of renal calculi have calcium oxalate.

- Can form at any pH and have various microscopic morphologies.

- Half of the oxalate in urine comes from ascorbic acid.

- Also associated with ethylene glycol ingestion.

 Calcium carbonate crystals:

- Can be found as small granular crystals in alkaline urine.

- Not common in urine but when present can be mistaken for bacteria.(differentiated by adding acetic acid to the sample→

crystals release CO2 →effervescence.

- Horse urine is normally markedly turbid because of calcium carbonate

Ca oxalate Amorphous Ca carbonate

129. Urine contains:

a. Vitamins, b. Na, c. K,

d. all of the above

Propable answer: All of the above

 Vitamins are excreted in urine: although fat soluble vitamins are not excreted in urine, yet water soluble vitamins i.e. Vit B and Vit C are excreted → excess vitamin B causes Yellowing/light orange urine and excess vitamin C causes ca oxalate crystals.

 Clinical applications of urine electrolytes:

Na⁺  To assess volume status

 Differential diagnosis of hyponatremia

 Differential diagnosis of AKI

 To assess salt intake in patients with hypertension

 To evaluate calcium and uric acid excretion in stone-formers

 To calculate electrolyte-free-water clearance Cl⁻  Differential diagnosis of metabolic alkalosis K⁺  Differential diagnosis of hypokalemia

 To calculate electrolyte-free-water reabsorption

 To calculate transtubular K+ gradient

Biological Fluids

C

^hemistry

45 [email protected]

130. Fructose test in semen:

a. Used to investigate prostatic causes of infertility.

b. Used to investigate seminal vesicles.

c. Gives red color when negative.

d. Negative with azoospermia.

Answer: b. seminal vesicles

Lesion Sperm conc. pH Vol Fructose

Bilateral Epididymal obstruction

Azoospermia N N N

Congenital absence of Vas deferens

Azoospermia N or ↓ ↓ Absent

Ejacuatory duct obstruction

Azoospermia N or ↓ ↓ Absent

Polyzoospermia Azoospermia N N ↓

Fructose Test:

 Fructose is produced in semen by the seminal vesicles.

 ↓fructose in semen is caused by:

- Agenesis: Congenital absence of the seminal vesicles, a common

anomaly often

associated with absence of vasa deferentia,

- Infection: Obliteration of seminal vesicular secretion by infection,

►►

- ↓ fructose in semen, - ↓ motility of sperms.

- ↓seminal volume (seminal vesicles contribute > ½ total volume of semen.

- ↓pH

- No coagulation - No characteristic semen

odour.

 Preanalytical variables: As the semen sample ages, the fructose level will fall due to utilization by spermatozoa. The more sperms in the ejaculate, the greater the fall in fructose concentration.

 Methods:

Resorcinol test of Seliwanoff:

Principle:

HCl resorcinol

Fructose furfuraldehyde Condensation product (red)

H2O

- Hydrochloric acid forms a derivative of furfuraldehyde which acts on fructose: This furfuraldehyde gives a red coloured compound when linked with resorcinol.

a. Seliwanoff's reagent:

Dissolve 5.0 mg of resorcinol in 33 mL of concentrated HCl, and dilute to 100 rnL with water.

Procedure:

- Add few drops of semen to 5 mL of reagent.

- Bring to boil (20 - 30 seconds) → fructose gives a red colour within half a minute after boiling.

- Control:

Compare with normal semen sample.

Fructose solution (0.5 g%).

b. Other tests:

Secretory capacity of prostate: measured by the contents of zinc, citric acid and acid phosphatase in semen.

Secretory capacity of the epididymis: monitored by L-carnitine and neutral a-glucosidase.

131. Morning urine specific gravity never exceeds:

b. 1035 c. 1040 d. 1020 e. 1025

Probable answer: a.1.035 Specific gravity:

Definition:

- Specific gravity is the ratio of the density (mass per unit volume) of a solution compared with the density of an equal volume of pure, solute-free water at a constant temperature.

- Specific gravity is a measure of dissolved substances present in urine, primarily urea and NaCl; however, any substance dissolved in urine will contribute to the specific gravity.

Biological Fluids

C

^hemistry

46 [email protected]

Significance: The specific gravity indicates the concentrating ability of the kidney and state of hydration of the patient

Expected values:

 Normal kidney:

o Specific gravity ranges from 1.003 to 1.035.

o Urine of low specific gravity is called hyposthenuric (<1.007) o Urine of fixed specific gravity of about 1.010 is known as

isothenuric

o First morning sample after fluid deprivation for 10 hours should have a specific gravity> 1.020 if the kidney is functioning normally.

o In infants, the range for specific gravity is less because of kidney immaturity.

o After a major surgery, increased secretion of ADH causes fluid retention within the vascular space. As stress after surgery decreases, ADH and other hormones. This increases urine volume a few days after surgery is sometimes referred to as a surgical diuresis.

< 1.016 1.025 Causes of false high Sp.

Gr - Compulsive

polydipsia.

- Diabetes insipidus.

- Glomerulonephritis.

- Pyelonephritis.

- Arteriosclerotic kidney.

- Sever dehydration.

- Nephrotic syndrome (presence of protein) - Diabetes mellitus

(presence of glucose) - SIADH

- Adrenal insufficiency (presence of Na+) - Congestive heart

failure.

- Hepatic disease.

- Excessive loss of water due to sweating, fever, vomiting and diarrhea.

- Dextran

- Radiopaque contrast media.used in X-rays of the UT

- Urine removed from the refrigerator.

 Dysfunctional kidney loses its ability to concentrate and dilute urine, and the urine specific gravity will be fixed at about 1.010.

Further clinical points¹⁰:

 Relationship of specific gravity to urine volume: Generally, the greater the volume of urine excreted, the lower the specific gravity.

a. In a normal kidney, specific gravity varies inversely with the volume of urine (600 to 1600 mL per day).

b. In some renal diseases such as glomerulonephritis, pyelonephritis, a combination of low specific gravity, and low urine volume results since the renal epithelium is unable to either excrete normal amounts of water or concentrate waste products.

c. In DI, there is loss of the concentrating ability resulting in extremely large volumes of urine with very low specific gravity, ranging from 1.001 to 1.003.

 Relationship of Specific Gravity and Osmolality

 Specific gravity is proportional both to the number and weight of solute particles present.

 Osmolality is determined only by the number of solute particles present (more accurate).

 Osmolality vs. SG:

- Relationship is relatively predictable in normal subjects¹¹ (urine primarily contains urea and sodium potassium and ammonium salts);

10Nice information collected from multiple sources for more understanding.

Biological Fluids

C

^hemistry

47 [email protected]

 Urine osmolality of 300 mOsm/kg – similar to that of plasma – is equivalent to a specific gravity of 1.008 to 1.010.

 After a marked water load, urine osmolality can be as low as 50 to 100 mOsm/Kg with specific gravity 1.002 to 1.003.

 With dehytdration, urine osmolality may reach 1000 to 1400 mOsm/Kg with specific gravity of 1.030 to 1.040.

- Disproportionate relationship occurs when larger solutes are present, e.g. glucose (MW 180) and radiocontrast media (MW 550) where specific gravity can exceed 1.030 to 1.040 while osmolality may be only 300 mOsm/Kg.

 Maximal concentrating ability of the kidney:

 The human kidney can produce a maximal urine concentration of 1200 to 1400 mOsm/L, 4 to5 times the osmolarity of plasma.

 The obligatory water loss:

- The minimal amount of fluid loss from the body that can occur to remove various solutes from the body.

- Determines the minimal amount of fluid intake that is required to maintain total water balance.

 A typical daily solute load of 600 mOsms in a patient with a maximum urinary concentrating ability of 1200 mOsm/kg will require a minimum urine volume of 500ml/day to excrete it.

 Unavailability of this obligatory volume leads to:

- Dehydration.

- Renal failure (solutes accumulate).

 Ill or elderly patients are typically not able to achieve urine osmolality of 1200 mOsm/kg so the obligatory minimum urine volume is much higher than 500 ml.

11Urine osmolality can be roughly estimated from SG using the equation: Uosm = (SG-1000)x 42.5

C

^hemistry GIT

48 [email protected]

GIT

132. Normal D-xylose test in a case of steatorrhea occurs in:

a. Acute gastroententeritis.

b. Bacterial overgrowth.

c. Biliary tract disease.

d. Gluten Sensitive Enteropathy.

e. Lactose intolerance f. Tropical sprue.

Probable answer: Biliary Tract Disease.

Steatorrhea: Possible causes include lack of bile acids (due to liver damage, hypolipidemic drugs, cholecystectomy, pancreatic insufficiency, and defective mucosal cells.

D-Xylose absorption test:

133. Diagnoses malabsorption due to defects in integrity of GI mucosa.

134. D-Xylose does not require enzymes for digestion. Its absorption requires an intact mucosa only.

Interpretation:

 In normal individuals, 25 g oral dose of D-xylose will be absorbed and excreted in the urine at approximately 4.5 g in 5 hours.

 ↓urinary excretion of D-xylose → conditions involving the GI mucosa e.g. small intestinal bacterial overgrowth and Whipple's disease.

 In cases of bacterial overgrowth, absorption returns normal after treatment with antibiotics.

 If urinary excretion is normal, the problem is mostly non-mucosal.

Disorders leading to malabsorption are either:

A. Disorders of intraluminal digestion

1. Gastric .e.g. Zolinger Ellison's syndrome (gastrin-secreting tumor of the pancreas).

2. Pancreatic e.g. cystic fibrosis (sever AR disorder associated with pancreatic insufficiency)→ affects absorption of the three elements.

3. Biliary disease, resection of terminal ileum, small bowel bacterial overgrowth → affects absorption of fat and vitamin B12 B. Disorders of transport into the mucosal cell:

1. Generalized →↓ absorptive surface area e.g.

Celiac Disease (=Gluten Sensitive Enteropathy): Autoimmune malabsorption of gluten.

Tropical sprue: commonly found in the tropical regions, with abnormal flattening of the villi and inflammation of the lining of the small intestine.

2. Specific disorders: e.g. Disaccharidase deficiency: either congenital lactase deficiency or adult type hypolactesia (more common than congenital)

C. Disorders of transport out of mucosal cell:

1. Lymphatic Blockage e.g. abdominal lymphoma 2. α-β-Iipoproteinemia.

Hormones

C

^hemistry

49 [email protected]

Hormones

d. Pituitary

135. In diabetes insipidus there is:

a. ↑ Plasma osmolality>290 mosmol/Kg.

b. ++ vasopressin.

c. ↓ sodium.

d. Sp.G >1030

e. Thirst center abnormality.

Probable answer: Plasma osmolality>290mosmol/Kg DI = (deficient ADH) can result from

1. ADH deficiency.

2. ADH resistance:

Renal tubular disease.

Nephrogenic DI

3. Central (hypothalamic, neurogenic, cranial DI ) Any destructive hypothalamic or infundibular lesion (80 % of ADH secreting neurones )

DI is characterized by:

- Polyuria >2.5L/day

- Low urine Sp. Gr.(1^st morning sample) <1018 - Low Urinary osmolality (<800 mOsm/Kg).

- High serum osmolality (>290 mOsm/Kg) - Hypernatremia.

136. In panhypopituitrism the following is decreased:

a. Aldosterone b. Cortisol c. Estrogen d. TSH e. ADH

Probable answer: TSH or cortisol.

Panhypopituitarism is a condition of inadequate or absent production of the anterior pituitary hormones.

Insufficient Hormones

 Insufficient levels of gonadotropins.

 Insufficient levels of growth hormone.

 Insufficient levels of thyroid-stimulating hormones.

 Insufficient corticotrophic levels.

 Excessive prolactin levels.

e. Reproduction

137. A hormone decreased in woman pregnant with a fetus having Down syndrome

a. E3

b. E2

c. hCG

d. Progesterone

Probable answer: Estriol (E3)

A number of tests can be used for screening pregnant women for fetus with Down syndrome with varying levels of accuracy and invasiveness.

Maternal serum AFP and E3 and pregnancy-associated plasma protein-A (PAPP-A) are lower in Down syndrome than in unaffected pregnancies while CG is increased about twice as high.

While E3 is only produced in significant amounts during pregnancy as it is made by the placenta, estradiol (E2) is produced by the ovaries and is used to measure primarily the activity of the ovaries.

Hormones

C

^hemistry

51 [email protected]

First and second trimester screening Screen Weeks

gestation Description

Combined

test 10–13.5 wks

- US to measure nuchal translucency (NT) - Free or total β-hCG

- APP-A.

Quad

screen 15–20 wks AFP

Unconjugated estriol, hCG,

Inhibin-A.

Negrated

test 15-20 wks Quad screen + PAPP-A, and NT

138. In post menopausal women continual elevation of:

Probable answer: FSH Menopause

Definition: the permanent cessation of menstruation resulting from loss of ovarian follicular activity.

Hormonal changes:

 Oestrogen and FSH:

- The ovaries fail to produce adequate amounts of estrogen and inhibin → ↑gonadotropin production to stimulate the ovary.

- Perimenenopausal changes: Hormonal changes begin about 5 years before the actual menopause, as the response of the ovary to gonadotropins begins to decrease, and menstrual cycles become increasingly irregular. This transition phase has been observed to last from 2 to 8 years.' At this time, FSH concentrations increase and estradiol concentrations decrease.

 β-CG concentrations: It has been occasionally observed that postmenopausal women have slightly elevated β-CG

concentrations (typically >5 but <25 IU/L). These results may cause confusion when the concentrations are above the detection limit defined for a positive pregnancy test. Although this phenomenon is not associated with pregnancy, these results are not false positives as they are routinely confirmed by alternate methods.

139. Male with increased FSH and LH and decreased testosterone:

a. hypergonadotrophic b. hypogonadism c. hypogonadotrophic d. a and b

e. b and c

Probable answer: d. hypergonadotrophic hyponadism Male Hypogonadism:

Definition: A condition caused by a decreased function of the testes leading to retardation of sexual development if manifested early in life.

Classification: The disorder is classified as hypogonadotropic or hypergonadotropic depending on whether the pituitary gonadotropic hormones (LH and FSH) are decreased or increased.

A. Male hypogonadotropic Hypogonadism:

Pathogenesis: Defects in the hypothalamus or pituitary prevent normal gonadal stimulation.

Causative factors: include

(1) congenital or acquired panhypopituitarism, (2) hypothalamic syndromes,

(3) GnRH deficiency, (4) hyperprolactinemia, (5) malnutrition or anorexia, (6) iatrogenic causes.

Hormonal abnormalities: ↓testosterone and gonadotropin concentrations.

Kallmann syndrome:

- The most common form of hypogonadotropic

Hormones

C

^hemistry

51 [email protected]

hypogonadism and results from a deficiency of GnRH in the hypothalamus during embryonic development.

- Five times more common in men.

- Characterized by hypogonadism and anosmia (loss of the sense of smell) in male or female patients;

B. Hypergonadotropic Hypogonadism

 Pathogenesis: Primary testicular failure = gonadal dysfunction.

 Hormonal abnormalities: ↑LH and FSH and ↓ testosterone.

 Causes for primary hypogonadism include:

(1) testicular damage, such as from irradiation, disease, or drugs;

(2) chromosomal defects;

(3) enzymatic defects in androgen synthesis;

(4) testicular agenesis;

(5) seminiferous tubular disease

Aging is also associated with gonadal failure, which occurs in about 20% of men older than 60 years of age (andropause)

b. Thyroid

140. Thyroid hormones storage form a. TBG

b. Tetraiodothyronin c. Thyroglobulin d. Thyroxin e. rT3

f. Thyroxin albumin complex g. Thyroxin binding

pre-albumin.

h. Triiodothyroinin

Probable answer: Thyroglobulin Explanations:

 Thyroxin (=T4=tetraiodothyronin): secreted from thyroid gland only.

 Tri-iodothyronine (T3): secreted from liver, kidney, muscles.

 rT3 (reversed T3): inactive part of the hormone.

 Thyroglobulin: Thyroid hormones are stored extracellularly in the colloid inside the follicle in the form of ioidinated thyroglobulin.

 Thyroid binding globulin (TBG): binds to 70% of T4 & 80% of T3.

 Thyroxin binding pre-albumin (TBPAL).

 Thyroxin binding albumin (TBAL).

141. Antithyroglobulin antibodies are found in which disease?

a. Hashimoto's thyroiditis b. Multinodular goiter c. Non-toxic thyroiditis d. Thyroid adenomas

Probable answer: Hashimoto’s thyroiditis or Graves’ disease Anti-thyroglobulin antibodies are often found mainly in patients with Hashimoto's thyroiditis or Graves' disease.

Other causes for a positive test result include:

 Hypothyroidism

 Myxedema

 Systemic lupus erythematosus (SLE)

 Thyrotoxicosis

 Type 1 diabetes

 Pregnant women and relatives of patients with autoimmune thyroiditis may also test positive for these antibodies.

142. The earliest lab test helps in diagnosis of hypothyroidism a. Free T3 and free T4 b. Total T3

c. Total T4 d. TSH

Probable answer: TSH.

Primary hypothyroidism is diagnosed by:

1. Very high TSH (> 20 mIU/L): TSH elevation may precede the decrease of T4 & T3

2. Low free & total T4 3. Low free & total T3

Both may be just low normal (secreted by organs other than thyroid)

4. Low T3 uptake & FTI (Free Thyroid Index)

5. Positive antimicrosomal or antithyroglobulin antibodies in Hashimoto's thyroiditis.

Secondary hypothyroidism is diagnosed by:

1. Low TSH.

2. Low total & free T4.

3. Low total & free T3.

4. TRH (thyrotrophin) stimulation test: (give external TRH)

Hormones

C

^hemistry

52 [email protected]

- Delayed normal response: hypothalamic lesion.

- Blunt response: pituitary lesion.

Always remember that:

- Free thyroid hormones correlates better with thyroid status than total plasma thyroid hormones

- Total and free T3 and T4 may be near normal in hypothyroidism since they have other sources of production.

- Follow up of response to treatment of hypothyroidism is by T4 (increases within few days), and long term follow up is by TSH (returns normal within 6-8 wks). This also applies for 1ry

hyperthyroidism i.e. T4 is used for early follow up since TSH is still suppressed and is not reliable for longer period.

- The main use of rT3 is to differentiate between non thyroidal illness (elevated rT3 & decreased T3) & hyperthyroidism (both are elevated).

- T3 Resin uptake & free thyroxin index (= T4 x T3 resin uptake) are replaced by fT3 and fT4.

143. False increase in total T3 & T4 occurs in the following except:

a. pregnancy

b. contraceptive pills.

c. heroin addiction.

d. acute liver failure.

Probable answer: d. acute liver failure,

The given choices are causes of NTI (sick euthyroid syndrome) which result in false low (as with liver cell failure) or false low tT4 and tT3 (as in all other choices).

Remember: Non thyroidal illness (NTI) & the sick euthyroid syndrome:

Definition: Disturbances in TFTs (T3, T4, TSH), however, the patient is euthyroid requiring no treatment for thyroid status.

Causes of elevated TBG

= Causes of false high tT4 & tT3

Causes of decreased TBG

= Causes of false low tT4 & tT3 1. Pregnancy.

2. Estrogen therapy 1. Androgen therapy

3. Estrogen producing tumors 2. Testosterone producing tumors.

4. Viral hepatitis 3. Liver cirrhosis.

5. Heroin addiction.

6. Hereditary ↑ TBG or variants of albumin & pre-albumin

4. Nephrotic syndrome.

5. Malnutrition.

Clinical significance of this:

 Diagnosis of thyroid diseases in such cases must depend on the presence of clinical features & biochemical abnormalities.

 Reversed T3: it differentiates between non thyroidal illness (elevated rT3 & decreased T3) & hyperthyroidism (both ↑).

 Free T3 & T4: It can better discriminate between hypo-, hyper- &

eu- thyroid state and is not affected by TBG.

c. Adrenals

144. Most important regulation of aldosterone is by:

a. ↑extracellular fluid.

b. ↑Na.

c. ↑serum K.

d. Inhibition of renin-antiogentsin system.

Answer: Increased blood potassium Aldosterone production is affected by:

a) Angiotensin II (secreted in response to ↓renal perfusion pressure and ↓extracellular sodium concentration) and extracellular K (Primarily)

b) ACTH plays a small role.

 Expansion of extracellular, inhibition of the renin-antiogentsin and

↑extracellular sodium →↓ angiotensin.

 ↑blood potassium is a primary regulator of aldosterone.

 Hypertension is a result not a cause of hyperaldosteronism.

In document Trabajo Fin de Máster (página 122-0)