Examples of short essay questions and answers on kidney physiology (12-2012) by Dr Khaled A Abulfadle

Admin عدد المساهمات : 9481 تاريخ التسجيل : 06/08/2009

Q: What are the possible causes of anemia in renal failure?

Possible causes of anemia in renal failure which include:

1-defect in red blood cell production which is largely explained by the inability of the failing kidneys to secrete the hormone erythropoietin

2-the accumulation of so-called uremic toxins, may play a role in depressing bone marrow function

3-Excess stores of aluminum may accumulate in the bone marrow of long term dialysis patients and can contribute to anemia as well

4-Blood 1oss and red blood cell destruction also frequently contribute to the anemia in patients with renal failure

5-Platelets, which are small constituents of blood which aid in blood clotting, do not work normally in uremia. The defective blood clotting seen in uremia makes bleeding more common

6-Excessive destruction of red blood cells is also seen in advanced renal failure. Normally, red blood cells survive for about four months before being destroyed. This life span is reduced in renal failure, probably because of chemical effects of uremia and decreased flexibility of the red blood cells

7-platelet dysfunction leading to an increased risk of gastrointestinal bleeding

8-In patients receiving dialysis and especially those on hemodialysis, chronic blood loss resulting from frequent phlebotomy for laboratory studies and loss of blood in the dialysis tubing and dialyzer after each hemodialysis treatment may also contribute to declining Hb values

9-malnutrition and deficiencies of iron, folate, and vitamin B12 have been found to cause a reduction in Hb concentrations

Admin عدد المساهمات : 9481 تاريخ التسجيل : 06/08/2009

Q: What are the conditions that could increase the renin release and cause Renal hypertension ?

Answer:

Active renin secretion is regulated principally by 4 interdependent factors:

(1) a renal baroreceptor mechanism in the afferent arteriole that senses changes in renal perfusion pressure.

(2) changes in delivery of NaCl (sensed as changes in Cl- concentration) to the macula densa cells of the distal tubule (which lie close to the JG cells and, together, form the “JG apparatus”).

(3) sympathetic nerve stimulation via beta-1 adrenergic receptors.

(4) negative feedback by a direct action of Ang II on the JG cells.

THUS,

The causes of renin dependent hypertension include:

1-Renin-secreting neoplasms: Primary hypersecretion of renin by renal hemangiopericytomas (“JG cell tumors”),
some Wilms’ tumors and renal and extrarenal carcinomas (ovary, pancreas, lung).

2-Renovascular hypertension: Hypersecretion of renin due to segmental, unilateral, or bilateral renal ischemia.

3-Malignant hypertension and other renal small vessel disease (e.g., polyarteritis, scleroderma, hemolytic uremic syndrome, lupus): Hypersecretion of renin due to generalized renal ischemia.

4-Pheochromocytoma and other catecholamine-secreting tumors: Hypersecretion of renin due to catecholamine excess.

Admin عدد المساهمات : 9481 تاريخ التسجيل : 06/08/2009

Q: What is the condition in which there is increased renin secretion but, the blood pressure is normal? explain?

Answer:

Bartter syndrome (secondary aldosteronism) in which there is chronic hyponatremia (due to inhibited reabsorption of sodium from the thick ascending limb of LH) with increased both renin and aldosterone but the blood pressure is normal due to aldosterone escape phenomenon i.e. increased aldosterone increases blood volume which increases ANP that causes natriuresis preventing increase in blood pressure

Admin عدد المساهمات : 9481 تاريخ التسجيل : 06/08/2009

Q: Discuss the role of angiotensin II in regulation of renal blood flow (RBF) and glomerular filtration rate

Answer

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