Glycosuria occurs when the venous blood glucose exceeds?

RUHS, Jaipur, M.Sc Nursing Entrance Exam-2018

Applied Physiology

Easy

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2018

Explanation

Glycosuria is the excretion of glucose into the urine, which is not a normal finding.
This occurs when the amount of glucose filtered by the glomeruli exceeds the reabsorptive capacity of the renal tubules.
This reabsorptive limit is known as the renal threshold for glucose.
The standard physiological renal threshold for glucose is in the range of 170–180 mg/dL.
Therefore, when venous blood glucose exceeds this range, glucose begins to appear in the urine.

Option A: A blood glucose level of 140–150 mg/dL is below the typical renal threshold. At this concentration, the renal tubules are still able to reabsorb all the filtered glucose, so it does not spill into the urine.
Option B: This option is a duplicate of the first option. A blood glucose level of 140–150 mg/dL is below the normal renal threshold, and glycosuria would not be expected.
Option C: While approaching the threshold, a blood glucose level of 160–170 mg/dL is generally still within the reabsorptive capacity of the kidneys for most individuals.

Clinical Relevance

Nursing practice connection: Knowing Renal threshold for glucose and the pathophysiology of glycosuria helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Glycosuria is a cardinal sign of hyperglycemia and is most commonly associated with diabetes mellitus. A urine dipstick test is a quick, non-invasive screening tool for high blood sugar.
Nurses should be aware that glycosuria is not always due to diabetes. It can occur in pregnancy (gestational glycosuria) due to increased glomerular filtration rate and a lowered renal threshold, or in benign familial renal glycosuria.
Patient education is crucial. A patient with newly discovered glycosuria needs to be referred for further blood tests (fasting blood glucose, HbA1c) to confirm a diagnosis of diabetes and rule out other causes.

How to Approach the Question

First, identify the key term in the question: 'Glycosuria'. Understand that this means glucose in the urine.
Recall the physiological mechanism of how the kidneys handle glucose. Glucose is filtered and then reabsorbed.
Remember that there is a limit to this reabsorption, known as the 'renal threshold'.
The question is asking for the specific blood glucose value that exceeds this threshold.
Access your memory of key physiological values. The renal threshold for glucose is a standard value taught in nursing and medical physiology.
Compare the options to the known value (approx. 180 mg/dL). Select the option that best matches this physiological fact.

Concept Tested & Keywords

Concept Tested: Renal threshold for glucose and the pathophysiology of glycosuria.
Stem keywords: Glycosuria, venous blood glucose, exceeds
Lead-in keywords: exceeds

QgONslfkEqb1xibb6E940q

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 1 (pp 26-370 of 370) p. 188-190