2.6. Renal System

Question 1

Give the 5 principle functions of the kidney

Answer 1

1. Excretion of toxins, metabolic waste and excess ions in urine
2. Regulation of volume and chemical make up of blood
3. Maintenance of balance between water and salts, acids and bases
4. Hormone production. RENIN- Helps regulate blood pressure. ERYTHROPOIETIN- stimulates red blood cell production in bone marrow
5. Activation of Vit D

Question 2

What 4 things change to the kidney and associated organs during pregnancy?

Answer 2

1. Increase in blood flow and enlargement in size of kidney
2. Increase in filtration rate
3. Increase in bladder capacity with decrease in tone
4. Increased urinary excretion of protein (proteinuria) and glucose (glucosuria)

Question 3

Explain urine formation

Answer 3

1. Blood flows through the glomerulus from the afferent arteriole to the efferent arteriole. At the glomerulus, sodium; amino acids; glucose and water leak out and are collected in the Bowman’s Capsule. Proteins and cells cannot filter through.
2. The glomerular filtrate passes to the proximal convoluted tubule where ions, amino acids, glucose and water are reabsorbed.
3. Countercurrent multiplication occurs at the loop of Henle. The descending limb reabsorbs water passively and the ascending limb reabsorbs sodium, chloride and potassium actively.
4. The distal convoluted tubule reabsorbs sodium and chloride.
5. Water and urea is collected in the collecting tubule and sent to the renal calyces to become urine.
6. The efferent arteriole branches into peritubular capillaries which collect the reabsorbed nutrients across the nephron and the renal vein takes nutrients back to rest of body.

Question 4

What influence might the growing uterus have on renal system?

Answer 4

Urinary frequency and urgency increase early in pregnancy as the growing uterus puts pressure on the bladder- decreased bladder capacity and increased micturition.
In 3rd trimester the presenting part will have same result.
Nocturia- unusually frequent need to urinate at night

Question 5

Increase in circulating blood volume by 30-50%- impact on renal system

Answer 5

Increase in renal blood flow by end of 1st trimester by 60%.
Increased glomerular filtration rate by 50% beginning soon after conception and peaking at 9-16 weeks. This causes increased excretion and reduced blood levels of serum creatinine, urea and uric acid.

Question 6

Relaxin and progesterone- impact on renal system

Answer 6

Ureters become atonic and dilated with an increase in capacity. This may result in urinary stasis and increase risk of infection.
Progesterone causes bladder tone to decrease- capacity increases.

Question 7

Why may women have glucosuria and proteinuria?

Why is it important to monitor these?

Answer 7

Glucosuria:
Women may become insulin resistant in later pregnancy which leads to an increase in blood glucose. There is a resulting increase in glucose concentration in the filtrate. This, combined with increased tubular flow rate means that maximum capacity for glucose reabsorption in the tubules is exceeded, causing glucosuria.
Can be an indicator of GDM
Proteinuria:
due to increased excretion of amino acids. Alongside hypertension, may indicate preeclampsia.

Question 8

Why are pregnant women more prone to UTIs?

Why is it important to diagnose?

Answer 8

The walls of the bladder become more oedematous and hyperaemic. The lax walls of the bladder may lead to incomplete emptying of the urine. The urine is richer in glucose and amino acids, meaning that the usually harmless bacteria reach pathological levels. (Also due to immunosuppression)

Diagnosis and treatment important so that UTI doesn’t lead to pyelonephritis (kidney infection)

Question 9

How long do the changes persist after birth?

Answer 9

6-8 weeks postpartum, although could be up to 3 months