A 54-year-old man comes to the emergency department due to increasing left flank pain, nausea, and hematuria for 5 days. The pain is dull, constant, and nonradiating. Yesterday, the patient also noticed swelling of the left testis. He was diagnosed with idiopathic membranous nephropathy 6 months ago. The diagnosis was confirmed by kidney biopsy and is medically managed. Temperature is 37 C (98.6 F), blood pressure is 130/70 mm Hg, and pulse is 90/min. Examination reveals left flank tenderness. Dilated and tortuous veins are noted in the left scrotum. Bilateral 1+ pitting edema is also present. Which of the following most likely underlies this patient's acute presentation?

Question

A 54-year-old man comes to the emergency department due to increasing left flank pain, nausea, and hematuria for 5 days.  The pain is dull, constant, and nonradiating.  Yesterday, the patient also noticed swelling of the left testis.  He was diagnosed with idiopathic membranous nephropathy 6 months ago. The diagnosis was confirmed by kidney biopsy and is medically managed.  Temperature is 37 C (98.6 F), blood pressure is 130/70 mm Hg, and pulse is 90/min.  Examination reveals left flank tenderness.  Dilated and tortuous veins are noted in the left scrotum.  Bilateral 1+ pitting edema is also present.  Which of the following most likely underlies this patient's acute presentation?

Quizplus · Accepted Answer

This patient with membranous nephropathy, a common cause of nephrotic syndrome, shows evidence of an acute left renal vein thrombosis (RVT). Occlusion of the left renal vein markedly increases glomerular pressure and causes hematuria and left-sided flank pain. Because the left gonadal vein drains into the left renal vein, obstruction also causes left gonadal vein dilatation. Risk factors for RVT include nephrotic syndrome (especially membranous nephropathy), renal malignancy, and trauma. Nephrotic syndrome, which is characterized by proteinuria (>3.5 g/day), hypoalbuminemia (<3 g/dL), peripheral edema, and hypercholesterolemia, is also associated with hypercoagulability. As a consequence, patients who have nephrotic syndrome are at increased risk for deep vein thrombosis, pulmonary embolism, and RVT. Patients with hypoalbuminemia can become hypercoagulable as they also lose protein C, protein S, plasminogen, and antithrombin III in their urine. In addition, nephrotic syndrome is associated with increased platelet activation and circulating levels of fibrinogen among other hemostatic abnormalities. Patients with RVT and acute kidney injury should undergo urgent clot removal (eg, thrombolysis). Otherwise, anticoagulation alone is appropriate. (Choice A) Although patients with nephrotic syndrome and hypoalbuminemia are at increased risk for thrombosis, it is the loss of anticoagulant proteins in their urine that is more important to the pathogenesis. Reduced serum albumin (with subsequently diminished oncotic pressure) is a marker for the loss of these other proteins rather than the pathophysiologic mechanism. (Choice C) Patients prone to nephrolithiasis are often found to have elevated urinary calcium excretion. Nephrolithiasis causes acute flank pain and macroscopic hematuria; however, this patient's edema and left testicular swelling would not be expected. (Choice D) Renal cell carcinomas (RCC) can cause gross hematuria, flank pain, and subacute to chronic development of testicular swelling due to infiltration of the collecting system and obstruction of the renal vein. However, these symptoms do not commonly present acutely, and most patients with symptomatic RCC have preceding anemia, cachexia, or other evidence of malignancy. (Choice E) Urinary tract infections typically cause dysuria and urinary hesitancy and frequency, although microscopic or macroscopic hematuria and flank pain may be seen, depending on the severity of infection. The absence of fevers and the presence of dilated scrotal veins make this diagnosis less likely. Educational objective: Renal vein thrombosis, which can present with hematuria, flank pain, and scrotal edema (in men), is an important complication of nephrotic syndrome. Nephrotic syndrome, and membranous nephropathy in particular, is associated with the urinary loss of several endogenous anticoagulant proteins, resulting in hypercoagulability. References: The forgotten urinalysis: an integral part of unmasking thrombophilia (http://www.ncbi.nlm.nih.gov/pubmed/30788075) Adult idiopathic renal vein thrombosis mimicking acute pyelonephritis. (http://www.ncbi.nlm.nih.gov/pubmed/27790518)

A 54-Year-Old Man Comes to the Emergency Department Due to Increasing