Case study- Urinary system anatomy

Question 1

A 6 1 -year male ba n ker, Tom J ones, was in good health until he lost control of his car, hit a light pole, and suffered
head trauma. Wh ile hospital ized in the i ntensive ca re unit during
recovery, he developed hospital-acquired pneumon ia. During his long hospita l ization, Tom began to show signs of depression and was treated with a selective serotonin reu ptake inhibitor. His
depression was not lessened in 2 weeks and the dosage of the antidepressa nt was increased. Six days after his dosage increase, his nurse noted the patient exh ibited confusion and l etha rgy. Tom ‘s
blood pressure was slightly elevated . His basic blood work showed
the following:

Serum sodium: 121 mEq/L, decreased
Blood u rea n itrogen: 9 mg/dl, decreased
Serum chloride: 85 mEq/L, decreased
Serum uric acid: 2.2 mg/dl, decreased

The rest of his electrolytes and chemistry panel blood tests were normal, in add ition to his thyroid and cortisol tests all being
in normal range.
Tom ‘s physician then ordered a serum and a urine osmola rity
and a urine sodium l evel. He was sta rted on a water restriction
regimen and was g iven a sa line IV and sa line PEG tube fl ushes were
begun. The serum osmola rity was l ow, while the u rine osmola rity
was elevated and the urine sodium was elevated .

1. What condition has hypotonic plasma, with lower serum osmolarity and higher urine osmolarity and an elevated urine sodium level with a lower plasma sodium level?
2. What other disorder is associated with ADH?
3. What conditions does the patient have that are associated
   with SIADH?
4. How does ADH affect the body?

Answer 1

1. What condition has hypotonic plasma, with lower serum osmolarity and higher urine osmolarity and an elevated urine sodium level with a lower plasma sodium level?
   - The syndrome of inappropriate antidiuretic hormone
   (SIADH).
2. What other disorder is associated with ADH?
   - Diabetes insipidus.
3. What conditions does the patient have that are associated with SIADH?
   - SIADH can be a complication of brain injury, pneumonia, tumor growth, and certain medications such as SSRis for depression.
4. How does ADH affect the body?
   - When the body needs to conserve water, ADH is excreted and the walls of the distal and collecting tubules are made very permeable to water by ADH,
   thereby allowing water to be reabsorbed back into the body. If the body has excess water, less ADH is produced, and the walls of the tubules become less permeable, and the volume of excreted urine increases.

Question 2

A 61 -year-old C a ucasian woman with no significant medical history has routine laboratory tests done as part of her
annual physical exami nation. She weighs 1 3 5 lb (6 1 . 2 kg) and is 64 in ( 1 63 cm) tall. Her serum creati nine l evel is 1.1 mg/dl; her estimated GFR is 53 m Umin/1 .73 m2 A urina lysis dipstick is normal
for protein and blood .
1. How does age affect GFR?
2. What is the difference between creatinine clearance and
GFR?
3. Is this patient’s GFR normal?

Answer 2

1. How does age affect GFR?
   - SFR decreases normally with age although the amount of the decrease can vary due to various conditions such as atherosclerosis.
2. What is the difference between creatinine clearance and
   GFR?
   - Both measure glomerular filtration, but while creatinine clearance approximates GFR, it overestimates due to the fact that creatinine is secreted by the proximal tubule as well as filtered by the glomerulus. GFR can be measured from serum creatinine and creatinine excretion or estimated from serum creatinine using estimating equations. Measurement of creatinine clearance requires collection serum and of a timed urine sample, which is inconvenient and frequently inaccurate as well. Creatinine clearance levels are normally slightly higher than the GFR
3. Is this patient’s GFR normal?
   - No, this patient’s GFR is in stage 3A, indicating moderate chronic kidney disease.