A 31-year-old woman, gravida 2 para 1, at 30 weeks gestation comes to the emergency department due to increased swelling in her face and lower extremities. She has noticed a sudden onset of swelling and a 2.72-kg (6-lb) weight gain in the last day. The patient has not urinated in the last 12 hours despite an increase in fluid intake. She has a twin pregnancy and no chronic medical conditions. Blood pressure is 154/98 mm Hg, and pulse is 98/min. Bladder catheterization yields a total of 10 mL of dark urine. Urinalysis shows no red blood cells. Which of the following pathologic factors is the most likely cause of this patient's decreased urine output?

Question

A 31-year-old woman, gravida 2 para 1, at 30 weeks gestation comes to the emergency department due to increased swelling in her face and lower extremities.  She has noticed a sudden onset of swelling and a 2.72-kg (6-lb) weight gain in the last day.  The patient has not urinated in the last 12 hours despite an increase in fluid intake.  She has a twin pregnancy and no chronic medical conditions.  Blood pressure is 154/98 mm Hg, and pulse is 98/min.  Bladder catheterization yields a total of 10 mL of dark urine.  Urinalysis shows no red blood cells.  Which of the following pathologic factors is the most likely cause of this patient's decreased urine output?

Quizplus · Accepted Answer

11ec160b_3b20_f6ed_9249_5bbd026b04c7_MD0001_00 This patient at 30 weeks gestation has oliguria, or decreased urine output (<500 mL/24 hr), likely due to preeclampsia. Preeclampsia is defined as new-onset hypertension (systolic ≥140 mm Hg or diastolic ≥90 mm Hg) at ≥20 weeks gestation plus proteinuria and/or signs of end-organ dysfunction (eg, renal failure). Preeclampsia is thought to be caused by abnormal placentation and poorly developed uterine spiral arteries, which lead to placental ischemia. Twin gestations are at increased risk, likely due to increased placental mass. In preeclampsia, the ischemic placenta releases antiangiogenic factors that cause widespread maternal endothelial cell damage. The resulting capillary leakage is responsible for third spacing of fluid (eg, facial edema, weight gain) and leakage of protein into the urine (ie, proteinuria). In addition, disrupted endothelial control of vascular tone causes hypertension and widespread vasospasm, resulting in end-organ hypoperfusion. In the kidneys, vasospasm causes decreased renal blood flow and glomerular filtration rate, leading to minimal, concentrated urine (ie, high specific gravity) and increased serum creatinine levels. Gradual recovery of renal function typically occurs following delivery of the placenta, which is curative for preeclampsia. (Choices A and B) Inflammation of the glomeruli (ie, glomerulonephritis) can occur as a result of glomerular immune complex deposition, such as with anti-glomerular basement membrane (Goodpasture) disease (ie, basement membrane IgG deposits) and IgA nephropathy (ie, mesangial IgA deposits). Although these conditions can cause nephritic syndrome (eg, hypertension, mild to moderate proteinuria and edema, oliguria), red blood cells and casts would be expected on urinalysis. (Choice C) Inflammation of the renal interstitium (eg, acute interstitial nephritis) can cause oliguria but is typically drug related (eg, nonsteroidal anti-inflammatory drugs, beta-lactam antibiotics) and associated with rash and fever, which are not seen in this patient. (Choice D) A stone within the renal calyx (eg, staghorn calculus) may decrease the urine output of the affected kidney due to obstruction; however, overall urine output is typically preserved due to normal functioning of the contralateral kidney. In addition, renal stones typically cause hematuria. Educational objective: Preeclampsia is new-onset hypertension at ≥20 weeks gestation plus proteinuria and/or signs of end-organ damage. Preeclampsia is caused by widespread maternal endothelial cell damage due to release of antiangiogenic factors from an ischemic placenta. The result is widespread capillary leakage (proteinuria, edema) and vasospasm (hypertension, end-organ hypoperfusion [eg, renal failure]). __________ References: Preeclampsia: novel mechanisms and potential therapeutic approaches. (http://www.ncbi.nlm.nih.gov/pubmed/30090069) Pathophysiology of hypertension during preeclampsia: linking placental ischemia with endothelial dysfunction. (http://www.ncbi.nlm.nih.gov/pubmed/18055511)

A 31-Year-Old Woman, Gravida 2 Para 1, at 30 Weeks