The following changes occur in urinary system in pregnancy except :
URINARY SYSTEM: Kidney--There is dilatation of the ureter, renal pelvis and the calyces. The kidneys enlarge in length by 1 cm. RBF is increased by 50-75%, maximum by the 16 weeks and is maintained until 34 weeks. Thereafter it falls by 25%. Glomerular filtration rate (GFR) is increased by 50% all throughout pregnancy. Increased GFR causes reduction in maternal plasma levels of creatinine, blood urea nitrogen (BUN) and uric acid. Renal tubules fail to reabsorb glucose, uric acid, amino acids, water soluble vitamins and other substances completely. Ureter: Ureters become atonic due to high progesterone level. Dilatation of the ureter above the pelvic brim with stasis is marked on the right side specially in primigravidae. It is due to dextrorotation of the uterus pressing the right ureter against the pelvic brim and also due to pressure by the right ovarian vein which crosses the right ureter at right angle. The stasis is marked between 20-24 weeks. There is marked hyperophy of the muscle and the sheath of the ureter specially the pelvic pa probably due to estrogen. There is elongation, kinking and outward displacement of the ureters. Bladder: There is marked congestion with hyper-trophy of the muscles and elastic tissues of the wall. In late pregnancy, the bladder mucosa becomes edematous due to venous and lymphatic obstruction especially in primigravidae following early engagement. Increased frequency of micturition is noticed at 6-8 weeks of pregnancy which subsides after 12 weeks. It may be due to resetting of osmoregulation causing increased water intake and polyuria. In late pregnancy, frequency of micturition once more reappears due to pressure on the bladder as the presenting pa descends down the pelvis. Stress incontinence may be observed in late pregnancy due to urethral sphincter weakness. Reference: Dutta's Textbook of Obstetrics 7th edition page 54
Increased GFR
Increased RBF
Hyperophy of bladder musculature
Increased activity of ureters
General obstetrics