Physiologic Changes in Pregnancy: Renal & Genitourinary
Pregnancy
↑ estrogen
↑ angiotensin synthesis in liver
Renin-angiotensin- aldosterone system activation
↑ aldosterone ↑ plasma volume
↑ glomerular filtration rate (GFR)
Mechanism unclear, possibly 1) ↑ circulating anti- angiogenic factorsà ↑ permeability of glomerular basement membrane, or 2) ↑ plasma volumeà↓ oncotic pressure of plasma at the glomerulus
Proteinuria
> 300 mg/day, abnormal in pregnancy
↑ hCG level
Dilation of renal vasculature
↑ renal vascular & interstitial volume
↑ filtration surface area
Overwhelming load of glucose to proximal tubule
↑ urine output
↑ relaxin secreted by placenta
Mechanism not well understood
↓ osmotic threshold for ADH release & thirst
↑ ADH secretion & ↑ oral hydration
Incomplete reabsorption of glucose
Glucosuria
Encourage bacterial growth in the urine
Urinary tract infection (e.g. cystitis, pyelonephritis)
↑ serum progesterone
Uterine rotation as uterus enlarge due to presence of large bowel
Ureter compression (R > L)
Ureterovesical reflux (back-flow of urine into the ureters/kidneys)
Dilatation of ureters (R > L) (hydroureter) & renal pelvis (hydronephrosis)
Progesterone competes with aldosterone
↓ sodium reabsorption
↓ plasma sodium concentration
Hyponatremia of pregnancy* (pathological if < 130 mEq/L) *Despite factors favoring sodium excretion, there is a net retention of sodium during pregnancy from adaptation of the renal tubules ↑ urinary stasis ↑ excretion of creatinine and urea in urine ↓ serum creatinine and urea ↓ ureteral toneà ↑potential for ureter dilation Mechanism not well understood ↓ peristalsis of ureters ↑ urinary frequency (voiding > 7x/day)
↑ nocturia (voiding ≥ 2x/night)
↓ oncotic pressure of plasma intra-vascularly àwater leaves blood, enters interstitial tissue, and stays there in gravity-dependent regions of the body
Pedal +/- ankle edema
Author: Simonne Horwitz Reviewers: Claire Lothian, Crystal Liu, Ronald Cusano*, Candace O’Quinn*, Yan Yu* * MD at time of publication
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published June 28, 2020 on www.thecalgaryguide.com